Some standard content:
Military Standard of the Electronic Industry of the People's Republic of China FL0180
SJ20818\u20142002
Metal plating and chemical treatment for electronic equipment equipment
Published on January 31, 2002
Implementation on May 1, 2002
Approved by the Ministry of Information Industry of the People's Republic of China 1 Scope,
2 Reference documents
3 Definition.
4 General requirements
4.1 Main factors to be considered in the selection of metal plating and chemical treatment, 4.2 Properties of base materials
4.3 Use environment and working conditions
4.4 Properties of metal plating and chemical coatings 4.5 Processability of plated parts design.
4.6 Quality requirements for plated parts before plating,
4.7 Selection of metal contact pairs
4.8 Treatment conditions after plating.
5 Detailed requirements,
5.1 Selection and marking of metal plating and chemical treatment on the surface (indoor) of type II electronic equipment. 5.2 Selection and marking of metal plating and chemical treatment on the surface of type I electronic equipment (outdoor) 5.3 Technical conditions and inspection methods for metal plating and chemical treatment layers Appendix A Representation method for metal plating and chemical treatment (supplement) A1 Representation method
A2 Representation symbol
A3 Color representation symbol
A4 Symbol for name of independent processing operation
Appendix B Selection and marking of metal plating and chemical treatment for electrical connectors and electronic circuits (reference) B1 Design elements for selection of electrical contact layer
B2 Selection and marking of commonly used electrical contact layers for electronic equipment B3 Guidelines for compatibility of electrical contact layers
Appendix C Comparison table of commonly used new and old coating marks (reference) iiKAoNiKAca=
1 Scope
Military Standards for Electronic Industry of the People's Republic of China Metal plating and chemical treatment for electronic equipment 1.1 Subject content This standard specifies the selection and marking methods of general chemical treatment for various types of electronic equipment. 1.2 Scope of application This standard applies to the selection and marking of general chemical treatment for electronic equipment used in indoor environments.
Selection of plating such as electrochemical treatment and electrochemical treatment
Referenced documents
GB/T3138
GB/T6801
GB/T8013
GB/T8923
GB/T9793
GB/T9797-
GB/T9798-
GB/T9799-
Metallic sugars and chemical treatment
And related process terms
Technical conditions for phosphorus treatment of steel parts before painting Electroplating, chemical plating, chemical treatment
4986
General specification for anodized film of aluminum and aluminum alloys 19871
Rust grade and rust removal grade of steel surface before painting T981|| tt||GB/T9800\u20141988
GB/T11376\u20141997
GB/T11379\u20141989
GB/T12304--1990
Metallic and other inorganic coatings
Hot spray line
Zinc, aluminum and
Metal coatings Nickel + chromium and copper + nickel + chromium electrodeposition yellow Joint coating - Electrodeposition coating
MATION
Tail coating Zinc electroplating on steel
Chromate conversion coating of cast and electroplated coating
Phosphate conversion coating of metal coating room
Engineering electroplating coating
International Science and Technology Electric Design Co., Ltd.
Metal covering layer
GB/ T12305.1\u20141990
GB/T12305.2\u20141990
GB/T12305.3\u20141990
GB/T12305.4\u20141990
GB/T12305.5\u2014-1990
GB/T12305.6\u20141997
Metallic coating
Metallic coating
Metallic coating
Image test
Metallic coating
Test methods for gold and alloy electroplated coatings Part 1: Determination of coating thickness Test methods for gold and gold alloy electroplated coatings Part 2: Environmental testing Test methods for gold and gold alloy electroplated coatings Part 3: Electrodeposition of porosity Test methods for gold and gold alloy electroplated coatings Part 4: Gold content Tests for metallic coatings
Test methods for gold and gold alloy electroplated coatings Part 5: Determination of bonding strength Metallic coatings
Test methods for gold and gold alloy electroplated coatings
GB/T12306\u20141990 Metallic coatings Silver and silver alloy electroplated coatings for engineering purposes GB/T12307.1\u20141990 Metallic coatings Test methods for silver and silver alloy electroplated coatings GB/T12307.2\u20141990 Metallic coatings
Test methods for silver and silver alloy electroplated coatings
Published by the Ministry of Information Industry of the People's Republic of China on January 31, 2002 Part 6: Determination of residual salts
Part 1: Determination of coating thickness
Part 2: Bonding strength test
Implemented on May 1, 2002
GB/T 12307.3\u20141997
SJ20818\u20142002
Metallic coatingsTest methods for silver and silver alloy electroplated coatingsPart 3: Determination of residual saltsGB/T12333\u20141990Metallic coatingsCopper electroplated coatings for engineering purposesGB/T12599\u20141990
GB/T12600\u20141990
GB/T12607 \u20141990
GB/T12610\u2014-1990
GB/T12611-1990
GB/T12612\u20141990
GB/T13912\u20141992
GB/T13913\u20141992
GB/T17461-1998|| tt||GJB150.111986
GJB1720\u20141993
SJ20146\u20141992
QJ1824\u20141989
QJ2855\u20141996
Metallic coatingTin electroplating layer
Copper + nickel + chromium electroplating layer on plastic
Metallic coating
Design and naming method of thermal spray coating
Thermal cycle test of electroplating layer on plastic
Technical requirements for quality control of metal parts before platingGeneral technical conditions for multifunctional steel surface treatment liquidMetallic coatingTechnical requirements for hot-dip galvanizing layer of steel productsTechnical requirements and test methods for autocatalytic nickel-phosphorus platingMetallic coatingTin-lead alloy electroplating layer
Environmental test methods for military equipmentSalt spray testCorrosion and protection of dissimilar metals
General specification for silver electroplating layer
Zinc nickel Technical conditions for alloy coatings
Technical conditions for tin-zinc alloy coatingsWww.bzxZ.net
JB/T5070\u20141991
ISO2179\u201486
MIL-C\u20145541
MIL\u2014A-8625
Common terms for thermal spraying
Specifications and test methods for tin-nickel alloy electroplating Chemical conversion coatings for aluminum and aluminum alloys
Aluminum and aluminum alloys Anodized film
MIL\u2014A-10727B
MIL-C14550
MIL\u2014C\u201426074
MILG\u201445204
MIL\u2014P\u2014450209
MIL\u2014R\u201446085
MIL\u2014P\u201481728
MIL\u2014C\u201487115||tt| |QQ\u2014N\u2014290
QQ\u2014S\u2014365
Tin plating
Engineering copper electroplating
Specifications for electroless nickel plating
Gold electroplating
Palladium electroplating
Electroplating
Tin-lead alloy plating
Immersion zinc-chromium film military specification
Nickel electroplating
Federal specification: General requirements for electroplated silver coatings ASTM A380\u201496
ASTM B607\u201491
ASTM B733\u201490
ASTM B679\u201498
Standard practice for cleaning, derusting, and passivating stainless steel parts, assemblies, and systems Standard specification for autocatalytic nickel-boron coatings for engineering applications Standard specification for autocatalytic nickel-phosphorus coatings on metals Standard specification for electroplated palladium for engineering applications
ASTM B841\u201494| |tt||Standard specification for electroplated zinc-nickel alloy coatings
ASTMB86795
ASTMB904-00
Standard specification for electroplated palladium-nickel alloy for engineering useStandard specification for autocatalytic nickel plating on autocatalytic copper for electromagnetic interference shieldingStandard specification for electroplated coatings on threaded fasteners (metric)ASTMF1941M-00
AMS2413D
Silver-plated
YKAONIKAca-
AMS2422D Gold-plated
3 Definition
Metallic covering
Metallic coating
SJ20818-2002
refers to a metal layer used for protection, decoration or functionality that is plated on the surface of a metal or non-metallic workpiece by chemical, electrochemical or physical methods.
refers to the surface protection, decoration or functional film containing the metal compound formed on the metal surface by chemical or electrochemical methods, including chemical conversion film, chemical oxidation layer, aluminum anodizing film, phosphating film, passivation film, etc. 3.3 Significant surface The specified surface of the part before and after electroplating, on which the appearance and (or) performance are very important. Or the arithmetic average of the local thickness measurements of the uniformly distributed non-significant parts of the main surface by selecting a specified number of basic measurement surfaces for measurement. 3.5 Minimum coating thickness
The minimum value of the local thickness measured on the main surface of the workpiece
4 General requirements
4.1 Minimum plating thickness
The minimum value of the local thickness measured
on the surface of the metal coating
Main factors to be considered in the selection of metal plating and chemical treatment
Summary.
There are many factors to be considered in the selection of metal plating, and the relationship between them is relatively complex.
Plating characteristics
Material and
Properties
Design of plated parts
Processability
Purpose and requirements of plating
Usage environment and
Working conditions
Selection of metal plating and chemical
NFOL
Metal electrochemical couple and
Matching tolerance
Note: The two-way arrows in the figure indicate the relationship of mutual dependence and mutual restriction. Figure 1 Factors to be considered in the selection of metal coatings and chemical coverings 4.2 Properties of the base material Use Figure 1 to represent and post-plating treatment conditions Type, thickness and plating marking Quality requirements before parts plating The coating layer should be reasonably selected based on the nature of the selected material. For example, if aluminum and aluminum alloys are to be plated for decorative protective coating, the decorative chemical sand surface treatment and anodizing plating system of aluminum are much better than the electroplating decorative copper/nickel/chromium system in terms of protective performance and comprehensive economic indicators, which is determined by the plating characteristics of aluminum. 3
4.3 Operating environment and working conditions
4.3.1 Classification of protected surfaces
For the coating systems of ground, ship and airborne electronic equipment, the protected surfaces can be divided into the following two types according to the differences in exposure conditions:
Type I (exposed) surface--Type I surface refers to the surface exposed to the natural environment when the equipment is in operation or in motion, or the surface that is not exposed to the natural environment but can be directly affected by various climatic factors. Climatic factors include: extreme temperature, extreme humidity, rain, ice, snow, rain and snow, salty atmosphere, industrial atmosphere, direct sunlight, dust, wind and sand, etc. For example, the outer surface of the electronic equipment shelter belongs to Type I surface.
Type II (shielded) surface--Type II surface refers to the surface that is not exposed to the natural environment when the equipment is working, and will not be directly affected by rain, ice cap, snow, snow, direct sunlight and direct wind and sand. For example, the inner surface of the electronic equipment shelter and the surface of the electronic equipment in the electronic equipment shelter belong to Type I surface. Generally speaking, the exposure conditions of Type 1 surfaces are equivalent to outdoor environments; the exposure conditions of Type II surfaces are equivalent to indoor environments. Any coating and finishing of Type I surfaces can meet the protection requirements of Type II surfaces. 4.3.2 Working temperature
As the working temperature or intermediate processing temperature of the plated parts and electronic circuits increases, the metal diffusion between the intermediate layer of the base metal and the surface plating layer will be accelerated. For mutually soluble and easily diffusible metals such as copper-silver, silver-gold, copper-gold, copper-tin, etc., the heat has a greater accelerating effect on diffusion: the result of diffusion will change the nature of components and (or) circuits, causing corrosion. A diffusion barrier layer should be used when necessary. 4.3.3 Electromagnetic environment
Electric fields will accelerate the corrosion of metals. For example, in a plastic-encapsulated integrated circuit, the corrosion rate of two metal wires with a spacing of 12.7\u03bcm (0.5mil) will increase linearly with the increase of the potential difference between the two wires in the potential difference range of 5V to 100V. The plating system and coating thickness should be reasonably selected according to the requirements of the electromagnetic environment of the plated parts and circuits. 4.3.4 Mechanical performance requirements of the environment
The coating used for fasteners should have low torque tension. Otherwise, other auxiliary measures (such as lubricants) should be used to improve the torque tension relationship to meet the requirements of reliable mechanical assembly performance of fasteners. 4.3.5 Organic atmosphere corrosion in closed environments Organic materials such as plastics, rubbers, organic coatings, adhesives, etc. in certain sealed structures of electronic equipment may release organic atmospheres, such as formic acid, acetic acid, etc., which are harmful to most metals and coatings. This should be considered in advance in material selection and structural design. 4.4 Properties of metal plating and chemical coatings 4.4.1 Anodic coating and cathodic coating
If the coating is more active than the base metal, and its potential is more negative than the base metal, it is an anodic coating. The anodic coating plays an electrochemical protective role on the base metal, and its protective characteristics and durability mainly depend on the thickness of the coating. If the base metal is more active than the coating, that is, the coating potential is more positive than the base metal, then the coating is a cathodic coating. When the coating has pores or is partially damaged, the corrosion of the base metal will be accelerated through the action of the corrosion cell. The greater the potential difference between the two, the greater the corrosion damage. Only when the coating is intact and has no pores can it protect the base. Therefore, the protective characteristics of the cathodic coating depend on the porosity and thickness of the coating. It can be seen that the protective characteristics of the anodic coating are better than those of the cathodic coating. Therefore, under certain medium environmental conditions, the anodic protective layer should be selected as much as possible. In actual anti-corrosion design, how to judge whether it is an anodic coating or a cathodic coating, practice has proved that the corrosion of electroplated parts under most actual use conditions is related to the corrosion potential series of metals in seawater. Table 1 gives the types of metal coatings under seawater conditions for reference. The anodic and cathodic coatings can also be determined based on the quantitative data of the potential series of metals in seawater in Tables 5a and 5b. 4
YKAONiKAca=
Base metal
Aluminum and aluminum alloys
Copper and copper alloys
SJ20818-2002
Table 1 Types of metal coatings (under seawater conditions) Anodic coating
Cathode coating
Cu, Ni, Cr, Ag, Sn, Au, Pb, Pt, Pb-Sn, Zn, Cd, Zn-Ni, Zn-Ti, Zn-Fe, Sn-Zn (Zn 25%), ZnCr film
Zn, Cd
Zn, Cd, Zn-Ni (Ni10%), Sn-Zn (Zn25%) Note: 1) It is an anodic coating in organic acid medium. 4.4.2 Basic properties of commonly used metal plating
The basic properties of commonly used metal plating are shown in the table
Pb-In, brass
Sn, Cu, Ni, Cr, Ag
Au, Ag, Pd, Rh, Pt
2 Base water properties of commonly used metal plating buffer layers
Categories
Galvanized,
film is a commonly used nose
protective;
damaged
protective
saw vibration, galvanized lock
Basic properties of the coating
(Ni6%\uff5e15%wt) alloy, tin-zinc (Zn25%wt) alloy and chemically treated zinc-chromium effective protective coating. Among them, galvanizing has the lowest cost, has good anti-corrosion performance under industrial conditions, can withstand bending and mechanical deformation, and can be welded: but galvanizing has poor wear resistance, and the chromate passivation film galvanized layer is too tough, loose, and has no protective ability of white rust, which will have a good impact on the performance of electronic equipment; galvanizing is generally. The protective performance of cadmium plating in the environment of ash filling is better than that of zinc plating. Moreover, the coating is soft, has good re-weldability and low contact resistance; 3~5\u03bcm cadmium coating has good protective ability, can have low tensile stress, and is used for copper and aluminum coating.
The tight wind line with precise tolerance has different electro-tempering corrosion performance for magnesium
inch. Now
chemical treatment is used to treat
zinc-nickel alloy
and copper with small electrochemical corrosion tendency. The coating is used to reduce the cost of dissimilar metals (such as galvanized steel). The replacement coating is electroplated zinc (z20%30%wt) alloy nickel!
Wang is seeking the latest technology and
5%wt) alloy and chemical
metal film. Its sales volume is mainly used by tight merchants to reduce losses and conduct electricity, Grounding requirements for parts: high breaking load (HV250 ~ 400), mainly used for the protection of tree parts with high corrosion resistance requirements; zinc-chromium film-impregnated zinc flake/chromate dispersion bag film is mainly used for spring steel that is sensitive to hydrogen embrittlement, high strength, and has heat resistance requirements (such as working temperature exceeding 71\u00b0C and requiring a stable relationship between fastening load and torque with high corrosion resistance, but no requirements for conductivity and ductility). The fastening performance of zinc, pot, zinc-nickel, and tin-zinc alloys has been greatly improved by drilling acid at every degree (generally increased by 5 times). Galvanizing and plating are very susceptible to atmospheric corrosion of organic materials in a closed environment, so attention should be paid to this when designing structures. Protective decorative coatings generally refer to multi-layer decorative chrome plating. Traditional copper/nickel/chrome plating on steel and aluminum is a cathodic protective layer. On Type I surfaces, it can only provide good protection when the coating is very thick (\u226550um). Semi-bright nickel/bright nickel/decorative chrome is a coating system with electrochemical protective properties, which can reduce the total thickness of the coating and obtain better protective performance. The bottom semi-bright nickel accounts for The total thickness of the nickel layer is about 2/3, the coating has good toughness and leveling properties, does not contain sulfur or has a very low sulfur content (<0.005%), and has a relatively positive potential. The bright nickel layer on it accounts for about 1/3 of the total thickness of the nickel layer, the coating is bright, has a high sulfur content (>0.04% and <0.15%), has a relatively negative potential, and the potential difference of the double-layer nickel is 120~150mV. Bright nickel has an electrochemical protective effect on semi-bright nickel. Statistical data show that the protectiveness of a copper/nickel/chromium coating with a total thickness of 20\u03bcm is not as good as that of a double-layer nickel/chromium coating with a total thickness of 10\u03bcm .
If a thin layer of "nickel seal" is plated on the basis of double-layer nickel, that is, a bright nickel layer with non-conductive particles, the thickness of the coating is only 2-2.5\u03bcum, and then microporous chromium can be plated on it. In this way, the chromium coating area that serves as the anode in micro-battery corrosion is divided into countless small pieces, thereby greatly reducing the corrosion current and protecting the bright nickel coating below, thereby further improving the corrosion resistance of the entire coating system. 5
Category
SJ20818\u20142002| |tt||Table 2 (continued)
Basic properties of the coating
Functional coatings are coatings that have one or more functions while ensuring good protection in the specified environmental conditions. Commonly used functional coatings for electronic equipment include: (1) Conductive coatings: such as gold, silver, copper, tin-lead, nickel-phosphorus, nickel-boron alloys, palladium and palladium alloys. These coatings are mainly used in printed circuit boards, integrated circuit lead frames, etc. to form conductive paths for devices or circuits. (2) High-frequency characteristic coatings: such as gold, silver, and copper. These coatings are mainly used in high-frequency circuits and devices such as waveguides, resonator cavities, and filters.
(3) Electrical contact coatings: gold, palladium and palladium alloys, nickel, platinum, etc., are mainly used in contacts, switches, connectors, and electrical connectors to ensure stable contact resistance and reliable electrical connections. (4) Electromagnetic shielding coatings: Chemical copper plating, chemical nickel plating, etc. provide electromagnetic shielding for electronic circuits and electronic equipment. (5) Magnetic coating: nickel cobalt (Co80%) alloy (hard magnetic coating), nickel iron (Fe20%) alloy (soft magnetic coating), cobalt phosphorus, nickel cobalt phosphorus, nickel phosphorus, etc. These coatings are mainly used for disks, magnetic tapes, and thin film heads to provide the necessary magnetic properties. (6) Solderability coating: tin and tin alloys, silver, gold, copper, palladium, nickel, etc. are used for electronic components, semiconductor devices, and printed circuit boards to provide reliable solderability.
(7) Bondable coating: gold, silver, palladium, etc., are used for chip carrier printed circuit boards (COB) and semiconductor devices, and gold or aluminum wires are bonded between the chip and the conductive substrate coating to achieve electrical connection. (8) Diffusion barrier coating: In the process of use, mutual diffusion of metals is easy to occur between mutually soluble metal coatings such as copper-gold, copper-silver, silver-gold, copper-tin, or between the coating and the substrate. The diffusion results in changes in the electrical and mechanical properties of the coating, device, and circuit. For example, copper diffuses to the surface of the gold layer and oxidizes to copper oxide (CuO). Copper oxide is a semiconductor, which will cause high-frequency signal deformation and circuit noise, increase contact resistance, and reduce solderability. Cobalt phosphorus (P5%), nickel phosphorus, palladium and palladium alloys, and electroplated low-stress nickel coatings have a diffusion barrier effect. Plating between the above coatings and ensuring sufficient thickness can prevent the mutual diffusion of the above metals and improve the stability of the coating system.
(9) Special optical properties of the coating: For example, the low infrared emissivity (0.02-0.03) and high infrared reflectivity (0.9 or above) can be used as infrared detectors; polished silver, chemical nickel and aluminum plating have high reflective properties for visible light and can be used in different situations; the anti-reflective properties of satin nickel and aluminum forging can reduce visual fatigue. (10) Wear-resistant coating: can improve the surface hardness and wear resistance of parts, such as hard chrome layer, chemical nickel layer, nickel-tungsten alloy layer, aluminum hard oxide layer.
(11) Anti-friction coating: used to reduce the sliding friction of the surface of parts, such as silver plating, tin-lead alloy layer, tin-zinc (Zn25%) alloy layer and 0.05\u03bcm thin gold layer flash-plated on palladium and palladium alloy. (12) Process coating: the characteristics of the coating are used to meet the requirements of part processing technology, such as electroplating of etching-resistant tin-lead alloy layer on printed circuit board graphics, anti-carburization copper plating layer, anti-nitriding tin plating layer, and steel phosphating layer to prevent high-temperature metal bonding. 4.4.3 Applicable temperature range of metal coatings and chemical coatings All coatings can only be used within a certain temperature range. Exceeding the allowable operating temperature will not only affect their corrosion resistance, but some coatings may even cause cracking or brittle fracture of the base metal. The allowable temperature range of common coatings is shown in Table 3.6
HiikAoNiKAca
Coating categories
Chemical oxidation film of magnesium and magnesium alloys
Chemical oxidation film of aluminum and aluminum alloys
Anodic oxidation film of aluminum and aluminum alloys
Zinc coating
Zinc passivation layer
Piercing coating
Zinc-nickel alloy passivation layer
Zinc-chromium film
Chromic acid passivation layer of tin-zinc alloy
Silver coating
Palladium coating
Palladium Cobalt (Co20wt%) alloy
Gold layer
Palladium nickel (Ni20wt%)
Copper plating
Nickel plating
Phosphate layer
Gold plating
Plating layer on plastic parts
Tin plating
Tin-lead (Pb40%) alloy layer
SJ20818\u20142002
Table 3 Allowable temperature range for plating layer
Ambient temperature for use
<230\u2103
<60\u2103
<150\u2103. If it is greater than 150C, micro cracks will appear in the oxide film, affecting the appearance. However, it will not affect the corrosion resistance of the base metal after painting.
<250\u2103. If this temperature is exceeded, zinc cracks will appear in the base metal. <71\u2103. If the temperature is higher than this, the passivation film loses crystal water, cracks, and the corrosion resistance decreases. <230\u2103. If this temperature is exceeded, the base metal is prone to cracking. <71\u2103. If the temperature is too high, the passivation film loses crystal water, cracks, and the corrosion resistance decreases. NKANLARA
<649
\u2264450
3800
<148\u2103 (copper-based Ag plating without i bottom layer)
Ni bottom layer),
<150Above this temperature, the corrosion resistance decreases. 88
Purity 99.99%, 500%: purity 59.9%, <35b\u2103 purity 9.8
180\u2103~225\u2103.
232\u2103, should be used in an environment greater than -10\u2103, otherwise the tin temperature is easy to occur, and the maximum overflow should be less than 100\u2103. The use temperature of the temperature point 183 should not exceed 100\u2103.
The processability of the plated part design
The process limitations of metal plating and chemical treatment should be taken into consideration in the part design and plating selection. That is, on the same part, the electroplating layer, treatment layer, and diffusion layer are often uneven. The outer surface is thicker than the inner surface, and the edge is thicker than the middle. It is not easy to plate deep holes, especially small blind holes and gaps, inner walls, capillaries, etc. to reach the processability of the plated part design.
When designing and selecting the structure, try to consider the use of fillets at the edges of the parts as much as possible, with a radius of at least 0.8mm, and generally 1.6mm is appropriate. 4.5.1
4.5.2 The inner and outer corners of the flat bottom groove need to be rounded, and the depth limit should not exceed 50% of the width. It is better to have a U-shaped groove instead of a V-shaped groove.
4.5.3 Minimize blind holes. If it is unavoidable, its depth should be within 50% of its aperture, and the diameter should be as large as possible. 4.5.4 Where there is a cup wheel on the workpiece, a discharge hole for plating solution and gas should be reserved. 4.5.5 For assemblies with threaded connections, pressing, lap joints, riveting, spot welding, local brazing, single-sided welding, etc., during electroplating and chemical treatment, the solution enters the gap and is not easy to be completely removed. The residual acid, alkali and salt will accelerate the corrosion of parts during the storage or use period of the product. Therefore, such assemblies should generally be plated first, then assembled, or the gaps should be sealed with sealant before electroplating and chemical treatment. 4.5.6 For waveguide assemblies with complex shapes, materials with too different electrochemical properties (such as copper and aluminum) should not be used for combination. When designing a combined waveguide, the solution in the waveguide cavity should be easy to flow during electroplating and the internal current distribution should be uniform. 7
SJ20818-2002
4.5.7 In principle, electroplating and chemical treatment are not allowed for metal parts cast by sand or hard mold method, because the corrosion resistance of the coating layer of such parts is unreliable.
4.5.8 On the main working surface (such as the waveguide cavity), welds should be avoided or used less. When it is unavoidable, the welding quality should be guaranteed. 4.5.9 The coating thickness requirements of the main working surface should be marked on the drawing, which is the basis for processing and inspection. 4.5.10 For any dimensions with matching requirements, the dimensions and tolerance requirements before and after plating must be combined. The thickness of the plating layer must be reserved in advance. It should be noted that the median diameter of the external thread will increase after electroplating, and the increased size is 4 times the thickness of the plating layer in other parts. 4.5.11 Electroplating, chemical plating, anodizing, chemical oxidation, phosphating and other treatments should be carried out after all machining, welding, forming, drilling and other processes of the parts are completed.
4.5.12 For fasteners and parts with IT6 and IT7 matching tolerance requirements, in order to solve the contradiction between meeting the matching relationship and having sufficient protective performance under harsh environmental conditions, the following can be adopted: a) High corrosion-resistant plating should be used, such as Zn-Ni (Ni10%) or Sn-Zn (Zn25%) 47\u03bcm + color passivation; b) After assembly, paint can be used for additional protection. The process characteristics of electroplating and chemical treatment will cause some changes in the performance of parts, which are mainly manifested as follows: 1) Hydrogen is released during pickling, activation and electroplating, causing changes in the stress of the substrate and the coating, which can cause hydrogen embrittlement in some sensitive materials. 2) Except for bright and flat electroplating with a coating thickness within a certain range (about 30\u03bcm or less), the surface roughness of general electroplating increases with the increase of coating thickness. 3) In addition to the coating thickness affecting the size of parts, some oxide layers also have a greater impact on the size of parts. 4.5.13 Steel parts with a maximum tensile strength greater than 1050MPa (hardness 34HRC) may be subject to hydrogen embrittlement during pickling and electroplating. Therefore, when designing the plating, the heat treatment requirements for stress elimination before plating and hydrogen embrittlement elimination after plating should be proposed (see Table 4 and Table 7): When the maximum tensile strength of steel is greater than or equal to 166SMPa (49HRC), it is difficult to completely eliminate hydrogen embrittlement even with heat treatment measures. In this case, it is better to choose other protection methods, such as mechanical plating, vacuum plating, metal spraying and painting, and pickling is not allowed.
4.5.14 Parts that repeatedly bear complex loads, such as axles, springs, gears, etc., should be shot peened before plating to introduce beneficial compressive stress, improve fatigue strength, and improve resistance to stress corrosion cracking. 4.5.15 Design of surface roughness of plated parts before plating: a) For steel parts, non-ferrous metals and their alloy parts that require general protective coatings, the surface roughness Ra\u226412.5. For general decorative coatings, the surface needs to have a low roughness value. Full bright coating without precision requirements can be achieved by mechanical polishing, but the roughness of the parts before plating is Ra\u22641.6: the roughness of parts with precision requirements and bright coating before plating is Ra\u22640.8. Precision silver-plated, gold-plated, palladium-plated, plated parts and porcelain anodized parts have a surface roughness value of Ra\u22640.2. b) Generally, the surface roughness value after plating is about 1 to 2 times greater than the surface roughness value before plating, so plated parts with precision requirements should first be machined by machine tool finishing to make the base metal surface roughness value 1/2 of the required coating surface roughness value. c) For plated parts with threads and above level 3 precision, it is recommended to process the non-machined surface of the parts to a surface roughness of Ra\u22643.2 before plating.
4.5.16 After anodizing, the size of aluminum and aluminum alloy parts will increase, and the size increment is half of the thickness of the oxide layer. For parts with matching requirements, especially those that require thick film hard anodizing, the size difference before and after treatment should be considered in the structural design, and the reasonable size before plating should be designed.
4.6 Quality requirements for plated parts before plating
In order to make the plated parts meet the qualified quality requirements, in addition to complying with the above-mentioned design principles, the processing quality of the plated parts before plating and the quality of the base material of the plated parts should also be controlled to meet the following requirements. 4.6.1 The oil seal of the parts should be removed before plating. After removing the oil seal, the surface of the parts should be free of oil stains, metal chips, and coloring of the machine processing lines and other excess materials.
SJ20818-2002
4.6.2 The parts to be plated shall be free from mechanical deformation and mechanical damage, and shall be free from defects such as scale, spots, pits, bumps, burrs, scratches, etc. that affect the quality of the coating layer and the performance of the product. 4.6.3 For decorative aluminum profiles, the surface to be decorated shall be marked on the drawings, and no defects such as cracks, corrosion spots, salt marks, etc. are allowed.
4.6.4 All workpiece dimensions with matching requirements shall be inspected according to the drawings before and after plating. 4.6.5 Metal-rubber/metal-plastic composite parts, assemblies connected by threaded connection or by pressing, overlapping, riveting, lap welding, spot welding, etc., ferrous metal and non-ferrous metal, finely machined parts and rough parts, powder metallurgy and other metals, etc., when special plating is required, it shall be discussed with the competent process department and the technical inspection specifications agreed by both parties before and after plating shall be formulated. 4.6.6 The welded parts shall be free of excess solder and welding materials, and shall be cleaned promptly by blasting or other methods. The welds shall be free of defects such as pores and unwelded years. The welding process shall not be rushed. 4.6.7 After heat treatment, the surface of the workpiece shall be cleaned. No unremoved scale and residue (such as salt, alkali, sand and sintered products caused by oil stains not removed from the surface of the workpiece before heat treatment, etc.) shall be allowed. Thick and black oxides shall be generated; slight oxidation color is allowed, but rust is not allowed. 4.6.8 The surfaces of castings, forgings and hot-rolled parts that have not been machined shall be shot peened. Hot-rolled parts with a strength of no more than 105MP can also be pickled to remove the scale. 4.6.9 The surface of the mounted parts after sandblasting shall be plated (including pretreatment) within 15 days. 4.6.10 Hardness value of quenched parts to eliminate residual heat treatment proof. Ultimate tensile strength of materials Nine high strength steel with a strength of more than 34HRC after sandblasting should be heat treated according to the conditions in Table 12 to precisely match the residual internal stress; the surface heat treatment is at least 30\u00b0C. Heat treatment to eliminate stress before electroplating of steel parts. Tensile strength of materials Lingka 1050~1450~1800>1800 Note: \u24601MPa=1N/mm2. Heat treatment temperature 190~210h. Before plating, the qualified data of this process should be provided
Heat treatment time
INSORN
\u2461Heat treatment should be carried out before all pre-plating preparations: parts with too much oil and dirt should be subjected to necessary degreasing treatment before heat treatment. 4.6.11 Parts (components) and springs that have been ground or inspected by flaw detection should be free of residual magnetism, magnetic powder and fluorescent powder. 4.6.12 Parts to be plated must be boxed or transferred between processes using special workpiece tools. Parts with surface roughness values \u200b\u200bRa\u22640.8um and precision parts should be packed in special packaging boxes to avoid damage and rust during transportation. 4.7 Selection of metal contact couples
4.7.1 Selection of metal contact couples
The protection of metal contact is a special finishing problem. When the coating and the base metal, or two different metals are coupled (mechanically connected or combined), in certain corrosive media, such as acid, alkali, salt, moisture, industrial gas, salt spray, etc., an electrolyte film will be formed on the metal surface to form a corrosion cell. If the metal electrochemical couple is not selected properly, the electromotive force of the corrosion cell formed by the coupled metal is very large, which will cause strong contact corrosion and accelerate the damage between metal parts or between the coating and the base. The relationship between different metal contact couples can be handled according to the following principles:
SJ20818-2002
a) The parts (components) of military electronic equipment should select the allowable contact couples between parts according to Table 5a and Table 5b. Table 5b is an additional explanation of Table 5a. In Table 5a and Table 5b, metals and alloys (or coatings) are listed in groups; the electromotive force (EMF) measured by the members of each group relative to the saturated calomel electrode in seawater at room temperature is very close, and the difference in electromotive force between each other is within 0.05V. Therefore, all metals in each group are considered to be compatible electrochemical couples regardless of whether their metallographic structures are similar. The maximum potential difference between compatible electrochemical couples in different groups in the table shall not exceed 0.25V; in an isolated environment, when the metal couples are not exposed to the atmosphere or salty atmosphere, but are only subject to temperature and humidity changes, the maximum potential difference between compatible electrochemical couples shall not exceed 0.5V. In Table 5a, the allowed electrochemical couple sequence is represented by the graph on the right. The members of each group connected by a straight line constitute an allowed electrochemical couple. "O" indicates the cathode metal with the largest EMF value in each series, "" indicates the anode metal, and the arrow points to the anode direction. In addition to the electromotive force to the calomel electrode, the table also gives a derived "anode index". The anode index of group 1 (gold, etc.) is 0, and that of group 18 (magnesium, etc.) is 175. Subtract the anode index of one group from the anode index of the other group and multiply by 0.01 to get the potential difference (V) between the two groups. When considering whether the contact between two metal parts is compatible, the compatibility of their coatings should be considered, rather than whether the base metal is compatible; if there is a passivation film on the coating (such as zinc passivation film), only the compatibility of the coating should be considered without considering the passivation film. b) When designing the metal plating system of the parts, you can also refer to Table 5a and Table 5b to select the type of metal coating, and try to make the maximum potential difference of adjacent metal coatings not exceed 0.25V for cathodic coatings. c) In seawater, marine atmosphere and industrial atmosphere, the corrosion and protection issues of dissimilar metal contact not mentioned in a) and b) above can be further referred to Table 6 and GJB1720. 4.7.2 Control of bimetallic galvanic corrosion
For bimetallic corrosion to occur, three conditions must be met at the same time: first, there is a corrosive electrolyte; second, there is a metal with a more positive potential or a non-metal that can conduct electricity, such as graphite and carbon fiber composite materials; third, the contact of two metals will conduct the corrosion battery. As long as one of the conditions is isolated and weakened, bimetallic corrosion can be eliminated or reduced. Therefore, the specific measures to reduce bimetallic contact corrosion are: a) When two metals that are not allowed to contact must be connected conductively (see Tables 5a and 5b), in addition to the method of adding metal gaskets to adjust, transition, and reduce the potential difference, metal plating can also be used to achieve adjustment and transition. That is, one of the metals in the non-allowed galvanic couple is plated with an appropriate metal plating so that it forms an allowed galvanic couple with another metal. For example: when aluminum alloy conductive oxidized parts are in contact with steel and copper parts, the steel and copper parts can be plated with zinc-nickel alloy. It should be emphasized that no matter what environmental conditions the non-contact galvanic couple is used under, its coating thickness should be selected according to the requirements of Type 1 surface. b) Use a small cathode and a large anode structure: the corrosion rate of the galvanic couple increases with the increase of the cathode/anode area ratio. Reducing the cathode area can reduce the amount of anodic corrosion. For example: stainless steel and aluminum are not allowed galvanic couples. Stainless steel is the cathode. In actual use, stainless steel screws, bolts, and rivets can be used to fasten aluminum alloy parts, but never the other way around. Since stainless steel and aluminum alloy connections are susceptible to crevice corrosion, it is best to use sealant to fill the gaps when connecting. c) Key parts are made of cathodic materials: for example, the resonant cavity is made of copper alloy. When it comes into contact with anodic materials such as aluminum, the cavity itself is protected.
d) Protect the non-contact galvanic couples that have no conductivity requirements according to Table 6. e) Select the coating system for various parts. f) Implement feasible whole-machine protection after the parts are assembled to reduce various contact corrosion. 10
HTiKAoNiKAca=1 Before plating, the oil seals of parts should be removed. After removing the oil seals, the surface of the parts should be free of oil stains, metal chips, and coloring of machining lines.
SJ20818-2002
4.6.2 The parts to be plated should be free of mechanical deformation and mechanical damage, and should not have defects such as scale, spots, pits, bumps, burrs, scratches, etc. that affect the quality of the coating layer and the performance of the product. 4.6.3 For decorative aluminum profiles, it is indicated on the drawings that cracks, corrosion spots, salt marks, etc. are not allowed on the surface to be decorated.
4.6.4 All workpiece dimensions with matching requirements should be inspected according to the drawings before and after plating. 4.6.5 Metal-rubber/metal-plastic composite parts, assemblies connected by thread or by pressing, overlapping, riveting, lap welding, spot welding, etc., ferrous metal and non-ferrous metal, finished parts and rough parts, powder metallurgy and other metal assemblies, when special plating is required, it should be discussed with the competent process department, and the technical inspection specifications agreed by both parties before and after plating should be formulated. 4.6.6 Welded parts should be free of excess solder and welding inspection, and should be cleaned in time by blasting, spraying or other methods. The welds should be free of defects such as pores and unwelded years. The operation process should not be rushed. VDART4.6.7 After heat treatment, the surface of the workpiece should be cleaned. Untreated scale and residues (such as salt, alkali, sand and sintered products caused by oil stains not removed from the surface of the workpiece before heat treatment) are not allowed. Thick and black oxides should not be generated; slight oxidation color is allowed, but rust is not allowed. 4.6.8 The surfaces of castings, forgings and hot-rolled parts that have not been machined shall be shot peened. Hot-rolled parts with a strength of no more than 105 MPa can also be pickled to remove the oxide scale. 4.6.9 The surface of the parts after sandblasting shall be plated (including pretreatment) every 15 days. 4.6.10 The proof of hot processing shall be used to eliminate the residual oxide scale, rust, oil stains, and sand marks on the surface of the parts after sandblasting.
Ultimate tensile strength of materials
Steel with high strength of more than 34HRC after sandblasting should be heat treated according to the conditions in Table 12 to precisely match the residual internal stress; surface heat treatment at 30
Insulation is not less
Heat treatment strips for eliminating stress before electroplating of steel parts
Strength of materials
1050~
1450~1800
>1800
Note: \u24601MPa=1N/mm2.
Heat treatment temperature
190~210
h. Before plating, the qualified
heat treatment time
INSORN
\u2461Heat treatment should be carried out before all pre-plating preparations: parts with too much oil stains should be subjected to necessary degreasing treatment before heat treatment. 4.6.11 Parts (components) and springs that have been ground or inspected by flaw detection should be free of residual magnetism, magnetic powder, fluorescent powder, etc. 4.6.12 Parts to be plated must be boxed or transferred between processes using special workpiece tools. Parts with a surface roughness value of Ra\u22640.8um and precision parts should be packaged in special packaging boxes to avoid damage and rust during transportation. 4.7 Selection of metal contact couples
4.7.1 Selection of metal contact couples
The protection of metal contact is a special finishing issue. When the coating and the base metal, or two different metals are coupled (mechanically connected or combined), in certain corrosive media, such as acid, alkali, salt, moisture, industrial gas, salt spray, etc., an electrolyte film will be formed on the metal surface to form a corrosion cell. If the metal electrochemical couple is not selected properly, the electromotive force of the corrosion cell formed by the coupled metal is very large, which will cause strong contact corrosion and accelerate the damage between metal parts or between the coating and the base. The relationship between different metal contact pairs can be handled according to the following principles:
SJ20818-2002
a) The parts (components) of military electronic equipment should select the allowable contact pairs between parts according to Table 5a and Table 5b. Table 5b is an additional explanation of Table 5a. In Table 5a and Table 5b, metals and alloys (or coatings) are listed in groups; the electromotive force (EMF) measured by the members of each group relative to the saturated calomel electrode in seawater at room temperature is very close, and the difference in electromotive force between each other is within 0.05V. Therefore, all metals in each group are regarded as compatible electrochemical pairs regardless of whether their metallographic structures are similar. The maximum potential difference between compatible electrochemical pairs in different groups in the table shall not exceed 0.25V; in an isolated environment, when the metal pairs are not exposed to the atmosphere or salty atmosphere, but are only subject to temperature and humidity changes, the maximum potential difference of the compatible electrochemical pairs shall not exceed 0.5V. In Table 5a, the permissible galvanic series is represented by the graph on the right. The members of each group connected by a straight line constitute the permissible galvanic couple. "O" indicates the cathode metal with the largest EMF value in each series, "" indicates the anode metal, and the arrow points to the anode direction. In addition to the electromotive force to the calomel electrode, the table also gives a derived "anode index". The anode index of Group 1 (gold, etc.) is 0, and that of Group 18 (magnesium, etc.) is 175. The potential difference (V) between the two groups is obtained by subtracting the anode index of one group from the anode index of the other group and multiplying it by 0.01. When considering whether the contact between two metal parts is compatible, the compatibility of their coatings should be considered, rather than whether the base metal is compatible; if there is a passivation film on the coating (such as zinc passivation film), only the compatibility of the coating should be considered without considering the passivation film. b) When designing the metal plating system of the parts, the category of the metal plating can also be selected by referring to Table 5a and Table 5b. For the cathodic coating, the maximum potential difference between adjacent metal coatings should be kept within 0.25V. c) In seawater, marine atmosphere and industrial atmosphere, the corrosion and protection issues of dissimilar metal contact not mentioned in a) and b) above can be further referred to Table 6 and GJB1720. 4.7.2 Control of bimetallic galvanic corrosion
For bimetallic corrosion to occur, three conditions must be met at the same time: first, there is a corrosive electrolyte; second, there is a metal with a more positive potential or a non-metal that can conduct electricity, such as graphite and carbon fiber composite materials; third, the contact of two metals will conduct the corrosion battery. As long as one of the conditions is isolated and weakened, bimetallic corrosion can be eliminated or reduced. Therefore, the specific measures to reduce bimetallic contact corrosion are: a) When two metals that are not allowed to contact must be connected conductively (see Tables 5a and 5b), in addition to the method of adding metal gaskets to adjust, transition, and reduce the potential difference, metal plating can also be used to achieve adjustment and transition. That is, one of the metals in the non-allowed galvanic couple is plated with an appropriate metal plating so that it forms an allowed galvanic couple with another metal. For example: when aluminum alloy conductive oxidized parts are in contact with steel and copper parts, the steel and copper parts can be plated with zinc-nickel alloy. It should be emphasized that no matter what environmental conditions the non-contact galvanic couple is used under, its coating thickness should be selected according to the requirements of Type 1 surface. b) Use a small cathode and a large anode structure: the corrosion rate of the galvanic couple increases with the increase of the cathode/anode area ratio. Reducing the cathode area can reduce the amount of anodic corrosion. For example: stainless steel and aluminum are not allowed galvanic couples. Stainless steel is the cathode. In actual use, stainless steel screws, bolts, and rivets can be used to fasten aluminum alloy parts, but never the other way around. Since stainless steel and aluminum alloy connections are susceptible to crevice corrosion, it is best to use sealant to fill the gaps when connecting. c) Key parts are made of cathodic materials: for example, the resonant cavity is made of copper alloy. When it comes into contact with anodic materials such as aluminum, the cavity itself is protected.
d) Protect the non-contact galvanic couples that have no conductivity requirements according to Table 6. e) Select the coating system for various parts. f) Implement feasible whole-machine protection after the parts are assembled to reduce various contact corrosion. 10
HTiKAoNiKAca=1 Before plating, the oil seals of parts should be removed. After removing the oil seals, the surface of the parts should be free of oil stains, metal chips, and coloring of machining lines.
SJ20818-2002
4.6.2 The parts to be plated should be free of mechanical deformation and mechanical damage, and should not have defects such as scale, spots, pits, bumps, burrs, scratches, etc. that affect the quality of the coating layer and the performance of the product. 4.6.3 For decorative aluminum profiles, it is indicated on the drawings that cracks, corrosion spots, salt marks, etc. are not allowed on the surface to be decorated.
4.6.4 All workpiece dimensions with matching requirements should be inspected according to the drawings before and after plating. 4.6.5 Metal-rubber/metal-plastic composite parts, assemblies connected by thread or by pressing, overlapping, riveting, lap welding, spot welding, etc., ferrous metal and non-ferrous metal, finished parts and rough parts, powder metallurgy and other metal assemblies, when special plating is required, it should be discussed with the competent process department, and the technical inspection specifications agreed by both parties before and after plating should be formulated. 4.6.6 Welded parts should be free of excess solder and welding inspection, and should be cleaned in time by blasting, spraying or other methods. The welds should be free of defects such as pores and unwelded years. The operation process should not be rushed. VDART4.6.7 After heat treatment, the surface of the workpiece should be cleaned. Untreated scale and residues (such as salt, alkali, sand and sintered products caused by oil stains not removed from the surface of the workpiece before heat treatment) are not allowed. Thick and black oxides should not be generated; slight oxidation color is allowed, but rust is not allowed. 4.6.8 The surfaces of castings, forgings and hot-rolled parts that have not been machined shall be shot peened. Hot-rolled parts with a strength of no more than 105 MPa can also be pickled to remove the oxide scale. 4.6.9 The surface of the parts after sandblasting shall be plated (including pretreatment) every 15 days. 4.6.10 The proof of hot processing shall be used to eliminate the residual oxide scale, rust, oil stains, and sand marks on the surface of the parts after sandblasting.
Ultimate tensile strength of materials
Steel with high strength of more than 34HRC after sandblasting should be heat treated according to the conditions in Table 12 to precisely match the residual internal stress; surface heat treatment at 30
Insulation is not less
Heat treatment strips for eliminating stress before electroplating of steel parts
Strength of materials
1050~
1450~1800
>1800
Note: \u24601MPa=1N/mm2.
Heat treatment temperature
190~210
h. Before plating, the qualified
heat treatment time
INSORN
\u2461Heat treatment should be carried out before all pre-plating preparations: parts with too much oil stains should be subjected to necessary degreasing treatment before heat treatment. 4.6.11 Parts (components) and springs that have been ground or inspected by flaw detection should be free of residual magnetism, magnetic powder, fluorescent powder, etc. 4.6.12 Parts to be plated must be boxed or transferred between processes using special workpiece tools. Parts with a surface roughness value of Ra\u22640.8um and precision parts should be packaged in special packaging boxes to avoid damage and rust during transportation. 4.7 Selection of metal contact couples
4.7.1 Selection of metal contact couples
The protection of metal contact is a special finishing issue. When the coating and the base metal, or two different metals are coupled (mechanically connected or combined), in certain corrosive media, such as acid, alkali, salt, moisture, industrial gas, salt spray, etc., an electrolyte film will be formed on the metal surface to form a corrosion cell. If the metal electrochemical couple is not selected properly, the electromotive force of the corrosion cell formed by the coupled metal is very large, which will cause strong contact corrosion and accelerate the damage between metal parts or between the coating and the base. The relationship between different metal contact pairs can be handled according to the following principles:
SJ20818-2002
a) The parts (components) of military electronic equipment should select the allowable contact pairs between parts according to Table 5a and Table 5b. Table 5b is an additional explanation of Table 5a. In Table 5a and Table 5b, metals and alloys (or coatings) are listed in groups; the electromotive force (EMF) measured by the members of each group relative to the saturated calomel electrode in seawater at room temperature is very close, and the difference in electromotive force between each other is within 0.05V. Therefore, all metals in each group are regarded as compatible electrochemical pairs regardless of whether their metallographic structures are similar. The maximum potential difference between compatible electrochemical pairs in different groups in the table shall not exceed 0.25V; in an isolated environment, when the metal pairs are not exposed to the atmosphere or salty atmosphere, but are only subject to temperature and humidity changes, the maximum potential difference of the compatible electrochemical pairs shall not exceed 0.5V. In Table 5a, the permissible galvanic series is represented by the graph on the right. The members of each group connected by a straight line constitute the permissible galvanic couple. "O" indicates the cathode metal with the largest EMF value in each series, "" indicates the anode metal, and the arrow points to the anode direction. In addition to the electromotive force to the calomel electrode, the table also gives a derived "anode index". The anode index of Group 1 (gold, etc.) is 0, and that of Group 18 (magnesium, etc.) is 175. The potential difference (V) between the two groups is obtained by subtracting the anode index of one group from the anode index of the other group and multiplying it by 0.01. When considering whether the contact between two metal parts is compatible, the compatibility of their coatings should be considered, rather than whether the base metal is compatible; if there is a passivation film on the coating (such as zinc passivation film), only the compatibility of the coating should be considered without considering the passivation film. b) When designing the metal plating system of the parts, the category of the metal plating can also be selected by referring to Table 5a and Table 5b. For the cathodic coating, the maximum potential difference between adjacent metal coatings should be kept within 0.25V. c) In seawater, marine atmosphere and industrial atmosphere, the corrosion and protection issues of dissimilar metal contact not mentioned in a) and b) above can be further referred to Table 6 and GJB1720. 4.7.2 Control of bimetallic galvanic corrosion
For bimetallic corrosion to occur, three conditions must be met at the same time: first, there is a corrosive electrolyte; second, there is a metal with a more positive potential or a non-metal that can conduct electricity, such as graphite and carbon fiber composite materials; third, the contact of two metals will conduct the corrosion battery. As long as one of the conditions is isolated and weakened, bimetallic corrosion can be eliminated or reduced. Therefore, the specific measures to reduce bimetallic contact corrosion are: a) When two metals that are not allowed to contact must be connected conductively (see Tables 5a and 5b), in addition to the method of adding metal gaskets to adjust, transition, and reduce the potential difference, metal plating can also be used to achieve adjustment and transition. That is, one of the metals in the non-allowed galvanic couple is plated with an appropriate metal plating so that it forms an allowed galvanic couple with another metal. For example: when aluminum alloy conductive oxidized parts are in contact with steel and copper parts, the steel and copper parts can be plated with zinc-nickel alloy. It should be emphasized that no matter what environmental conditions the non-contact galvanic couple is used under, its coating thickness should be selected according to the requirements of Type 1 surface. b) Use a small cathode and a large anode structure: the corrosion rate of the galvanic couple increases with the increase of the cathode/anode area ratio. Reducing the cathode area can reduce the amount of anodic corrosion. For example: stainless steel and aluminum are not allowed galvanic couples. Stainless steel is the cathode. In actual use, stainless steel screws, bolts, and rivets can be used to fasten aluminum alloy parts, but never the other way around. Since stainless steel and aluminum alloy connections are susceptible to crevice corrosion, it is best to use sealant to fill the gaps when connecting. c) Key parts are made of cathodic materials: for example, the resonant cavity is made of copper alloy. When it comes into contact with anodic materials such as aluminum, the cavity itself is protected.
d) Protect the non-contact galvanic couples that have no conductivity requirements according to Table 6. e) Select the coating system for various parts. f) Implement feasible whole-machine protection after the parts are assembled to reduce various contact corrosion. 10
HTiKAoNiKAca=6 The welded parts shall be free of excess solder and welding materials, and shall be cleaned promptly by blasting or other methods. The welds shall be free of defects such as pores and unwelded years, and the welding process shall not be rushed. 4.6.7 After heat treatment, the surface of the workpiece shall be cleaned, and no unremoved scale and residue (such as salt, alkali, sand and sintered products caused by oil stains not removed from the surface of the workpiece before heat treatment, etc.) shall be allowed; thick and black oxides shall be generated; slight oxidation color is allowed, but rust is not allowed. 4.6.8 The surfaces of castings, forgings and hot-rolled parts that have not been machined shall be shot peened. Hot-rolled parts with a strength of no more than 105MP can also be pickled to remove the scale. 4.6.9 The surface of the mounted parts after sandblasting shall be plated (including pretreatment) within 15 days. 4.6.10 Hardness value of quenched parts to eliminate residual heat treatment proof. Ultimate tensile strength of materials Nine high strength steel with a strength of more than 34HRC after sandblasting should be heat treated according to the conditions in Table 12 to precisely match the residual internal stress; the surface heat treatment is at least 30\u00b0C. Heat treatment to eliminate stress before electroplating of steel parts. Tensile strength of materials Lingka 1050~1450~1800>1800 Note: \u24601MPa=1N/mm2. Heat treatment temperature 190~210h. Before plating, the qualified data of this process should be provided
Heat treatmen
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