CB/T 3764-1996 Thickness series and quality requirements for metal coatings and chemical coatings
Some standard content:
Shipbuilding Industry Standard of the People's Republic of China
CB/T3764-1996
Metallic coating and chemical coating thickness
Series and quality requirements
Published on September 3, 1996
China State Shipbuilding Corporation
Implemented on April 1, 1997
Shipbuilding Industry Standard of the People's Republic of China
Metallic coating and chemical coating thickness
Series and quality requirements
1 Subject content and scope of application
CB/T3764-1996
Classification number: U06
Replaces CB744-83
CB'745-83
This standard specifies the selection principles, thickness series, quality requirements, inspection methods and inspection rules for metal and alloy coatings obtained by electrochemical method, chemical method and hot dip method, and non-metallic (inorganic) film layers formed by chemical method and anodic oxidation method. This standard applies to marine electronic and electrical equipment and instrumentation. 2 Reference standards
GB2423.28—82
GB/T434291
GB4955—85
GB4956—85
GB4957—85
GB527085
GB5927—86
GB5928—86||t t||GB5930—86
GB5935—86
GB6458—86
GB6459—86
GB6462—86
GB6463—86
GB8015.1-
GB8754-
Basic environmental testing procedures for electrical and electronic productsMethods for testing metal micro-Vickers hardness
Test T: Soldering test method
Measurement of thickness of metal coatingAnodic dissolution Coulomb methodMeasurement of thickness of non-magnetic coating on magnetic metal substrateMagnetic method
Measurement of thickness of non-conductive coating on non-magnetic metal substrateEddy current methodTest method for adhesion strength of metal coating (electrodeposited layer and chemically deposited layer) on metal substrateTimed liquid flow method
Test method for thickness of metal coating on light industrial productsMetal coating and aluminum oxide film on light industrial products Thickness test method Gravimetric method
Thickness test method for metal coating on light industrial products Spot method
Porosity test method for metal coating on light industrial products Metal coating
Metal coating
Neutral salt spray test (NSS test)
Acetic acid salt spray test (ASS test)
Metal and oxide coating
Cross-section thickness microscope measurement method
Review of thickness measurement methods
Metal and other inorganic coatings
GB9792-
GB12334-
Thickness of anodized film on aluminum and aluminum alloys Test methods for thickness Gravimetric method Anodizing of aluminum and aluminum alloys
Conversion film on metal materials
Testing insulation by breakdown potential determination Determination of film mass per unit area
Gravimetric method
Definition and general rules for thickness measurement Metal and other inorganic coatings
GB/T12611—90
GB/T13911—92
Technical requirements for quality control of metal parts before plating Methods of expression for metal plating and chemical treatment
3 Technical requirements for parts before plating
3.1 Before plating, the oil seal of the parts should be removed. After removing the oil seal, the surface of the parts should be free of oil stains, paint, metal chips, and coloring of machine processing lines.
3.2 The parts (components) to be plated shall be free of mechanical deformation and mechanical damage, and shall be free of defects such as scale, spots, pits, nodules, burrs, scratches, pores, cracks, etc. that affect the quality of the coating and the performance of the product. 3.3 For all parts (components) with matching requirements specified in the design, the process dimensions of the coating thickness must be reserved before plating. Approved by China State Shipbuilding Corporation on September 3, 1996 and implemented on April 1, 1997
CB/T3764-1996
The process and economic rationality of the coating; f. Metal contact with each other occasionally See Appendix D (reference). 4.2 See Appendix E (reference) for examples of the selection of coatings. 4.3 See Appendix A (supplement) for the selection of coating thickness for threaded fasteners. Conditions of use of coatings
The conditions of use of coatings are divided into five categories according to the working, storage, and transportation conditions of parts (components), see Table 2. If the product parts (components) are involved in several use conditions during operation, storage and transportation, they should be considered according to the specific situation, according to the category of the most serious corrosion or the category of the main use conditions. Table 2
Classification of use conditions
Extremely harsh
Representation method of coating
Classification of use conditions to be determined
Exposure to severe corrosive atmospheric environment, including seawater splash, direct contact with seawater, or frequent exposure to saturated sea fog and direct erosion by industrial wastewater at high temperature and humidity
Exposure to general atmospheric environment, direct damage by sunlight, rain, snow, dew, or direct influence by a small amount of industrial gas or medium vapor, with large changes in temperature and humidity In general atmospheric environment, it is not directly damaged by sunlight, rain, snow, dew, seawater, etc., but there is a small amount of industrial gas, medium vapor or sea fog, which may produce condensation Warm and dry atmospheric environment with strict control of temperature and humidity, without industrial gas, medium vapor and other corrosive media
Affected by special corrosive media, or subjected to Examples include parts that are subject to wear, high voltage, conduct electricity, insulation, and require improved process performance.
(1) Parts that are fully or partially immersed in seawater; (2) Exposed parts of offshore instruments (1) Exposed parts of offshore instruments; (2) Commonly used hand-held tools and handle parts (1) Internal parts of general non-sealed instruments; (2) Parts of hydraulic systems
(1) Parts in sealed housings; (2) Internal parts of sealed instruments in cabins; (3) Parts used in cabins with complete air conditioning equipment
(1) Parts such as pistons that are subject to wear; (2) Structural parts and fasteners that require improved welding and sealing performance
6.1 The name and thickness of the coating layer shall be marked in the product drawings and technical documents in accordance with the provisions of GB/T13911. 6.2 For the explanation of the coating marking of this standard, see Appendix F (reference). Characteristics, uses, thickness series and quality requirements of the coating 7
7.1 Electrochemical coating
7.1.1 Galvanizing
7.1.1.1 The characteristics, uses and thickness series of zinc coating are shown in Table 3. 3
Characteristics of coating
Main uses of coating
Usage conditions
Coating thickness
Base material
Plating mark
CB/T3764-1996
The zinc coating is silver-gray with a slightly light yellow hue. After passivation treatment, it has different colors. The zinc coating has good protective properties in industry and general atmosphere. Its corrosion resistance is significantly better than that of cadmium plating in industrial atmosphere; it can reliably prevent parts from corrosion in mineral oil; but in direct contact with seawater, its protective performance is lower than that of cadmium plating; its corrosion resistance is significantly reduced in water below -70C or above 70C. Zinc plating has medium hardness and can withstand bending and expansion, but is not wear-resistant. It becomes brittle above 250C and has low decorative value.
Under sealed or air-impeded conditions, volatiles of non-metallic materials (such as low-molecular carboxylic acids, phenols, aldehydes, ammonia, etc.) can corrode the zinc plating, causing it to quickly produce "white frost". The protective performance of the zinc plating is significantly improved by chromating (chromate treatment) or phosphating. Usually, zinc plating requires passivation treatment, but parts that require conductivity, magnetic conductivity, and welding should not be passivated. In order to further improve the protective ability of the zinc plating, the zinc plating can also be phosphated. Galvanizing has a tendency to cause "hydrogen embrittlement" in the steel matrix. Load-bearing structural parts, high-strength steel, and elastic parts need to be dehydrogenated after galvanizing (before passivation).
Zinc plating is the most widely used protective coating for steel. Zinc plating is mainly used for parts that require protection but not high requirements for appearance and wear resistance; zinc plating can reduce contact corrosion when copper and aluminum parts come into contact with each other1
Fe/Ep·Zn5·c1A
Fe/Ep·Zn5·c1B
Fe/Ep·Zn5·c2C
Fe/Ep·Zn5·c2D
Note: 1) Phosphating after galvanizing or painting after phosphating. 7.1.1.2
The quality requirements of zinc coating are shown in Table 4.
Fe/Ep·Zn12·c2CFe/Ep·Zn25·PhFe/Ep·Zn8·clA
Fe/Ep·Zn8·c1B
Fe/Ep·Zn12·c2DFe/Ep·Zn25·c2CFe/Ep·Zn8·c2C
Fe/Ep·Zn8·c2D
Fe/Ep·Zn25·c2D
Adhesion strength
No defects allowed
Defects allowed
CB/T3764-1996
(1) The zinc coating is silver-grey with a slightly yellowish hue and has uniform and fine crystals. (2) Zinc coatings treated with chromate passivation are divided into four types according to different processes. Their typical appearance is as follows: Bright: bright, clear, sometimes with a light blue hue; Bleached: clear, slightly iridescent;
Iridescent;
Dark: grass green, olive green, brown, black, etc. (1) Partially without coating;
(2) Iridescent, purple-red after passivation; (3) More water marks or chromate residues; (4) Peeling, blistering or more serious streaks; (5) Burning, roughness, pinholes, pitting or black spots; (6) Dendritic, spongy crystals;
(7) Excessive corrosion or mechanical abrasion;
(8) Erasable varnish or partial varnish-free (1) Due to different materials, processing methods and surface conditions of parts, the coating is slightly uneven (1) uniform color and gloss; (2) slight water marks and chromate residues; (3) slight local scratches and point-shaped mechanical scratches on the passivation film; (4) the color of the holes or knocking parts of fasteners such as screws and rivets is slightly worse; (5) the color of the parts after dehydrogenation is slightly darker;
(6) there is slight roughness on the sharp edges of the parts that does not affect assembly; (7) slight fixture marks;
(8) the coating at the weld of the welded parts is dark or has small black spots: (9) a blind hole with a diameter not exceeding 8mm is allowed to be uncoated at the depth exceeding one diameter, or a through hole with a diameter not exceeding 6mm is allowed to be uncoated at the depth exceeding two diameters (10) the thickness of the zinc coating on the partially electroplated parts is allowed to be enlarged without affecting assembly and performance. The thickness of the zinc coating shall meet the requirements of Table 3, and its inspection shall be carried out according to the appropriate method in Table 61. The thickness of the chromate conversion film shall meet the following requirements, and its inspection shall be carried out according to the weight method in Table 61. Type code
Color film quality per unit area
After the adhesion strength test in 8.2, the zinc coating should not be separated from the substrate in any form. There is no requirement for the adhesion strength of type A and type B chromate conversion coatings; the adhesion strength requirements and tests of type C and type D chromate conversion coatings are as follows: Hold a sand-free rubber or soft paper and rub the surface of the film back and forth 10 times with normal pressure. The film is qualified if it does not wear and fall off to expose the zinc layer. 3.4
CB/T3764-1996
When parts (components) with threaded connections, press-fitting, overlapping, riveting and welding must be plated due to special needs, corresponding acceptance requirements should be formulated.
5 For metal-rubber and metal-plastic composite parts that require special plating, the rubber or plastic part should be free of cracks and scratches; there should be no burrs, inclusions and unbonded parts at the junction of rubber or plastic 3.5
and the exposed metal part; there should be no rubber or plastic residue on the surface of the exposed metal part.
Before plating, welded parts with complex inner cavities should be left with process holes for liquid and gas discharge at locations that do not affect use. Welded parts should be free of excess solder and slag. Welds should be cleaned by sandblasting or other methods; welds should be free of defects such as pores and loose welds. The workpieces after heat treatment should be cleaned on the surface, and no unremoved oxide scale and residue are allowed. The surfaces of castings, forgings and hot-rolled parts that are not machined should be sprayed or shot peened. 3.10 There should be no residual oxide scale, rust, oil stains, sand, fingerprints, etc. on the surface after sandblasting or shot peening. All high-strength steel parts (components) that have been sandblasted or shot peened should be plated within 1 hour (including pretreatment). Parts (components) and springs that have been ground or inspected by flaw detection should be free of residual magnetism, magnetic powder, fluorescent powder, etc. 3.11
3.12 For steel parts (components) and surface hardened parts with a maximum tensile strength greater than 1050MPa, the corresponding heat treatment to eliminate residual stress should be carried out in accordance with GB/T12611. 3.13 Except for parts (components) whose surface roughness values before plating have been specified in the design, in order to ensure the quality of the coating, the surface roughness value R and the fillet value of the parts (components) before plating should comply with the provisions of Table 1. If it exceeds the provisions of Table 1 or 3.14, it shall be agreed upon by the supply and demand parties. Table 1
Types of coatings
Engineering chrome plating, porosity inspection required
Engineering chrome plating, loose-pore chrome plating without porosity inspection
Decorative chrome plating
Porcelain anodizing
Hard anodizing
Copper or tin plating for anti-carburizing, anti-nitriding, anti-cyaniding Surface roughness value R before plating
Determined by light brightness requirements
Rounded corner value
3.14 If the final surface roughness value of the parts (components) is specified on the drawing, the surface roughness value before plating should generally not be greater than half of the roughness value marked on the drawing.
3.15 The cleaning quality of the pre-plating treatment can be checked by checking the continuity of the water film, and the water film is qualified if it lasts for 30 seconds without breaking. 3.16 Unless otherwise specified, plating shall be carried out after all machining is completed. 4
Selection of coating
The selection of coating shall generally take into account the following factors: 4.1
Purpose and requirements of plating;
Protective characteristics and application scope of coating: materials, structures, shapes, processing methods, dimensional accuracy, roughness and matching tolerances of manufactured parts (components); environmental conditions of parts (components) during use, transportation and storage; Item
Protective ability
CB/T3764-1996
Continued Table 4
After the neutral salt spray test (NSS) of 8.5.1, the corrosion resistance of chromate conversion film shall meet the following requirements: Type code
Shortest time for the appearance of white corrosion products
7.1.2 Cadmium plating
The characteristics, uses and thickness series of cadmium plating are shown in Table 5. Table 5
The coating is grayish white to silvery white, and has different colors after passivation. Cadmium coating is a cathode coating for steel under normal atmospheric and industrial atmospheric conditions, and its protective performance is worse than that of zinc coating. In humid atmosphere or marine atmosphere without industrial impurities, its protective performance is slightly better than that of zinc coating. Under the condition of direct contact with seawater, it is significantly better than zinc coating. The use temperature of cadmium coating should not exceed 230C, otherwise it will cause cadmium to form on the base metal. Under sealed or airtight conditions, volatiles of non-metallic materials (such as low molecular carboxylic acids, phenols, aldehydes, ammonia, etc.) can corrode the radium coating, causing it to quickly produce "white frost". Coating characteristics
Main uses of coating
Usage conditions
Coating thickness
Base material
Coating mark
The protective performance of cadmium coating is significantly improved after phosphating. Cadmium coating can also be phosphated to improve its protective performance and serve as a paint base.
Cadmium plating has good toughness. But it is not wear-resistant. Www.bzxZ.net
Cadmium plating is not suitable for parts working in nitric acid-based oxidants and steam. Steel parts with a tensile strength of more than 1240MPa, parts in contact with titanium alloys, and parts in contact with hydraulic oil and fuel are not allowed to be cadmium-plated
For steel parts under extremely harsh conditions of use (direct contact with seawater), cadmium plating is one of the protective coatings available
Fe/Ep·Cd15·Ph
Note: 1) Cadmium plating is phosphated before painting.
2) Thin-walled, elastic, and high-strength steel parts need to be dehydrogenated before passivation. 7.1.2.2 The quality requirements of cadmium coating are shown in Table 6.6
Fe/Ep·Cd25·c2C2
Fe/Ep·Cd25·c2D
Adhesion strength
Protective ability
7.1.3 Copper plating
No defects allowed
Defects allowed
CB/T3764-1996
(1) The coating is grayish white to silvery white, with uniform and fine crystals. (2) Cadmium coatings treated with chromate passivation are divided into four types according to different processes, and their typical appearance is as follows:
Bright: bright, clear, sometimes with a light blue hue; Bleached: clear, slightly iridescent;
Rainbow: rainbow;
Dark: grass green, olive green, brown, black, etc. (1) Partially without coating;
(2) Iridescent, the color is purple-red after passivation. (3) More water marks or chromate residues; (4) Peeling, blistering or severe streaks; (5) Dendritic or spongy crystals;
(6) Roughness, burning, pitting, pinholes or black spots; (7) Excessive corrosion or mechanical scratches;
(8) Erasable passivation film or local non-passivation film (1) Due to different materials and surface conditions of parts, the same part has uneven color and gloss; (2) Slight water decay and chromate residues; (3) Slight local scratches and point-like mechanical scratches on the passivation film; (4) The color of the parts after dehydrogenation is slightly darker;
(5) The color of the holes or knocked parts of fasteners such as screws and rivets is slightly worse; (6) There is slight roughness on the sharp edges of the parts that does not affect assembly; (7) Slight fixture marks;
(8) The plating at the weld of the welded parts is dark or has small black spots; (9) The blind holes with a diameter of not more than 8mm are allowed to be unplated at the depth exceeding one diameter, or the through holes with a diameter of not more than 6mm are allowed to be unplated at the depth exceeding two diameters; (10) Under the premise of not affecting assembly and performance, the thickness of the cadmium plating on the plating surface of the local electroplated parts shall be allowed to be expanded. The thickness shall meet the requirements of Table 5, and the inspection shall be carried out according to the appropriate method in Table 61. The thickness requirements and inspection of chromate conversion coatings are the same as those in the "Thickness" column in Table 4. The requirements and tests for adhesion strength of radiant plating and its chromate conversion film are the same as those in the column "Adhesion Strength" in Table 4. The requirements and tests for protective ability of cadmium plating and its chromate conversion film are the same as those in the column "Protection Ability" in Table 4. The characteristics, uses and thickness series of copper plating are shown in Table 7. 7.1.3.1
Coating properties
Main uses of plating
Service conditions
Coating friction
Base material
Plating mark
Plating thickness
Plating mark
Plating thickness
Plating mark
CB/T3764—1996
Copper plating is light red or rose red.
Copper plating is a cathode plating for steel and aluminum, and is easily affected by sulfide, ammonium carbonate and hand sweat. It is very easy to change color in the atmosphere, so it cannot be used alone as a coating for ferrous metals and aluminum alloys. Protective layer. The copper plating is uniform and fine, easy to polish, and has good bonding with other alloys. Therefore, it is often used as the bottom layer of other plating layers and multi-layer plating.
The copper plating has medium hardness, can withstand bending, extension and hole expansion, and has a lubricating effect. The copper plating can prevent carburizing, nitriding, decarburization and cyaniding.
The copper plating has good electrical and thermal conductivity. The copper plating can prevent the parasitism of marine organisms in seawater and serve as the bottom layer of multi-layer protective decorative chrome plating, nickel plating, etc.; as a protective layer for the non-carburized parts of partially carburized parts; can improve the conductivity and weldability of graphite electrodes; can also be used for dimensional repair of copper and copper alloy parts and other purposes.
Fe/Ep·Cu5\
Note: 1) The bottom layer of the tin covering layer prevents the base metal from diffusing into the tin layer. 2) Copper plating of electronic and electrical parts; copper plating is required for the tightness of threaded parts. 12~17
F e/Ep·Cu12\
Fe/Ep·Cu20\)
NM/Ep·Cu15
PL/Ep·Cu205)
3) Barrier layer for carburizing and decarburization; copper plating for through-holes in printed circuit boards; copper plating for engineering drawn wires. 4) Heat treatment barrier layer.
5) Prevent the parasitism of marine organisms in seawater.
The quality requirements of copper plating are shown in Table 8. || tt||Fe/Ep·Cu25
Adhesion strength
Porosity
Brass plating
No defects allowed
No defects allowed
CB/T3764-1996
The copper plating is light red or rose red, with uniform and fine crystals. (1) No plating in some parts;
(2) Dendritic, spongy or striped plating; (3》Black spots, burnt , roughness, blistering, peeling or cracking; (4) excessive corrosion or mechanical abrasion;
(5) traces of salts that have not been washed off
(1) slightly uneven color and slight water marks and slight fixture marks: (2) slight roughness on the sharp edges of parts that does not affect assembly; (3) a blind hole with a diameter not exceeding 8 mm is allowed to have no coating when its depth exceeds ~ diameters, or a through hole with a diameter not exceeding 6 mm is allowed to have no coating when its depth exceeds two diameters; (4) a copper coating used to prevent carburization has a slight oxide film or roughness; (5) a part in the storage process, the copper layer darkens. The thickness of the copper coating shall comply with the requirements of Table 7, and its inspection shall be carried out according to the appropriate method in Table 61. After the copper coating is subjected to the adhesion strength test in 8.2, there shall be no separation between the coating and the substrate. The porosity of the copper coating shall comply with the requirements of the drawing or technical documents, and its inspection shall be carried out according to 8.4. The characteristics, uses and thickness series of brass coatings are shown in Table 9. Table 9
Brass (Cu-Zn alloy) coating is light yellow to golden yellow. Brass coating is cathodic coating to steel and is easy to change color in the atmosphere. Therefore, except for special purposes, it is generally not used for protection or decoration. If it is selected, it needs varnish protection. Coating characteristics
Main uses of coating
Usage conditions
Coating thickness
Base material
Copper and copper alloy
Plating mark
Brass coating can withstand bending and extension. The coating is easy to polish and has good adhesion to the base metal, so it is often used as the bottom layer of other coatings.
Brass coating (containing 68% to 78% copper) has a high adhesion to rubber. The use temperature of brass coating should not exceed 500C. It is used for rubber parts and also for parts requiring special decoration and protection. However, a coating layer should be added for protection.
Fe/Ep · Cu(70)-Zn3
Cu/Ep ·Cu(70)-Zn3
The quality requirements of brass plating are shown in Table 10.
Adhesion strength
Chemical composition
Defects are not allowed
Defects are allowed
CB/T3764-1996
The plating is light yellow to golden yellow, with uniform and fine crystals. (1) Partially without coating;
(2) White, red or gray-brown coating; Striped or spongy coating; (3) Rough, peeling or brittle;
(4) With spots or black spots;
(5) Unwashed salt traces
(1) Slight water marks or tool marks;
(2) Slightly uneven color;
(3) Pink coating in the concave part
The thickness of brass coating shall meet the requirements of Table 9. The inspection shall be carried out according to the appropriate method in Table 61. After the adhesion strength test of 8.2, the coating and the substrate shall not be separated in any form. Cu65~75 and Zn25~35 are guaranteed by the process and are allowed not to be inspected. Nickel plating
The characteristics, uses and thickness series of nickel plating are shown in Table 11. 7.1.5.1
The coating is silvery white with a slight yellow tint.
Nickel plating is a cathodic coating for ferrous metals and can only provide mechanical protection when the coating is free of pores. Steel parts can only be plated alone when the coating thickness increases. Nickel plating is an anodic coating for copper and copper alloys (except brass).
When nickel plating is used as a protective layer for parts, it is best to use a double-layer, multi-layer nickel plating or nickel-sealed plating method. The hardness of nickel plating is lower than that of chromium plating, and it can only withstand mild friction, but it is easy to polish. Polished nickel plating coating characteristics
Main uses of coating
It has a bright and beautiful appearance, but the nickel layer gradually darkens with time. Oil spots will appear on the surface of nickel plating after contact with acetic acid and oil.
Nickel plating is resistant to oxidation and can prevent steel parts from oxidation under medium temperature conditions (300-600C). Nickel is magnetic at room temperature and loses its magnetism when heated to 360°C. The new nickel plating can be brazed.
Nickel plating can prevent nitriding
Nickel plating is used as an intermediate layer or bottom layer in nickel-chromium or copper-nickel-chromium protective decorative multi-layer plating, and can also be used as a separate plating layer with magnetic requirements1
The coating is silvery white with a slight yellow tint.
Nickel coating is a cathode coating for ferrous metals, and can only play a mechanical protective role when the coating is non-porous. Steel parts can only be plated alone when the coating thickness increases. Nickel coating is an anodic coating for copper and copper alloys (except brass).
When nickel coating is used as a protective layer for parts, it is best to use a double-layer, multi-layer nickel plating or nickel-sealed plating method. The hardness of nickel coating is lower than that of chromium coating, and it can only withstand mild friction, but it is easy to polish. Polished nickel coating coating characteristics
Main uses of coating
It has a bright and beautiful appearance, but the nickel layer gradually darkens over time. Oil spots will appear on the surface of nickel coating after contact with acetic acid and oil.
Nickel coating has oxidation resistance and can prevent steel parts from oxidation under medium temperature conditions (300-600C). Nickel is magnetic at room temperature and loses its magnetism when heated to 360°C. New nickel-plated layers can be brazed.
Nickel plating can prevent nitriding
Nickel plating can be used as an intermediate layer or bottom layer in nickel-chromium or copper-nickel-chromium protective decorative multi-layer plating, and can also be used as a separate plating layer with magnetic requirements
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