JB/T 6986-1993 Surface preparation methods for aluminum and aluminum alloys before electroplating
Some standard content:
H61 | | tt | | JB | tt||Ministry of Machinery Industry of the People's Republic of China
Implemented on 1994-07-01
Published
Machinery Industry Standard of the People's Republic of China
Surface preparation before electroplating of aluminum and aluminum alloys Method 1 subject content and scope of application
JB/T6986-93
This standard specifies the surface preparation methods that should generally be carried out before electroplating of aluminum and aluminum alloys, including cleaning, surface adjustment treatment, immersion plating, Pre-plating etc.
This standard is applicable to the surface preparation of aluminum-aluminum alloys (including commonly used cast aluminum and deformed aluminum alloys). This standard is not applicable to the surface preparation of aluminum and aluminum alloy mold cores for electroforming. 2 Reference Standards
GB1173＇Technical Conditions for Cast Aluminum Alloys
GB3190 Chemical composition of aluminum and aluminum alloy processing crystals Metal covering layer (electrodeposition layer and chemical deposition layer) on the metal matrix with relative strength Test method GB-5270 | | tt | 3.2 Surface conditioning conditioning
transforms the surface condition of the workpiece into a process suitable for successful treatment in subsequent processes. 4 Selection of electric chain preparation methods
4.1 Selection of common pre-plating preparation methods
The surface preparation process of aluminum parts before electroplating is generally cleaning → surface adjustment → no plating → pre-plating, heat-treated aluminum Before cleaning, machine grinding, polishing or acid or alkali etching is required to remove the heat treatment oxide film. When choosing a surface preparation method, attention should be paid to distinguishing between the following situations: the material grade of the aluminum part (compare GB1173 and GB3190): 8.
b.
The manufacturing method of the wrong part, such as casting or pressure Processing methods, manufacturing, etc.: c. Whether the aluminum parts have been heat treated?
4.2 Selection of other pre-plating preparation methods
According to different circumstances, cleaning → surface adjustment → anodizing, or Sand blowing-→cleaning→surface adjustment→+lighting and other pre-plating preparation processes.
In addition to zinc immersion and tin-free immersion, nickel, nickel-zinc alloy, iron and other heavy metals can also be immersed. When selecting these processes, the electroplated aluminum parts should be tested according to the methods specified in GB5270. The electroplated layer Must meet the requirements of good bonding strength. 5 Cleaning and surface adjustment treatment
5.1 Cleaning
The cleaning process consists of steam degreasing, organic solvent cleaning, soluble emulsifier cleaning, aluminum cleaning agent cleaning and corresponding water rinsing processes. Commonly used hot carbonate-phosphate aqueous solution cleaning fluid [see Appendix A (reference) Chapter A1]. Aluminum parts with serious oil stains can be cleaned using the method approved by the Ministry of Machinery Industry 1993-07-27
1994- 07-01 Implementation
1
Clean with weak alkaline or weak alkaline solution,
5.2 Surface adjustment treatment
5.2.1 Purpose of surface adjustment treatment|| tt||a. Remove the original oxide film on the surface of aluminum parts: b. To remove harmful trace components on the surface of aluminum parts, 5.2.2 Commonly used surface conditioning treatment melt wave
JB/T6986--93
The usual surface conditioning treatment is sodium hydroxide solution at medium temperature ( (see Chapter A2), rinse thoroughly with water, then immerse in nitric acid-ammonium binitride solution (see Chapter A3) to remove dust on the surface, and then rinse with water. In order to prevent nitrogen chlorides and oxides from polluting the environment, sulfuric acid-hydrogen peroxide solution (see Chapter A4) can also be used instead of nitric acid-ammonium hydrogen ammonia solution (see Chapter A3).
5.2.3 Surface adjustment treatment of heat-treated aluminum parts. If the heat-treated aluminum parts require mechanical processing or polishing, the oxide film can be removed by polishing and polishing, and then appropriate surface adjustment treatment can be performed. Acid etching should be used to remove the oxide film on the surface of aluminum parts that is to be machined or polished. The commonly used acid etching solution is hot sulfuric acid-chromic acid solution (see Chapter A5). Some effective methods can also be used. patented etching solution. 5.2.4 Surface adjustment treatment of rolled aluminum parts
Aluminum parts prepared from industrial pure aluminum such as L5, L6, rust-proof aluminum such as LF21 and other rolled profiles, use carbonate-phosphate solution (see A1 Chapter) After cleaning, it can be dissolved in nitric acid at room temperature (see Chapter A6) to obtain satisfactory results. 5.2.5 Surface adjustment treatment of aluminum-magnesium alloy parts. The surface adjustment treatment of aluminum-magnesium alloy parts such as rust-proof aluminum LF2, forged aluminum LD2, LD31, etc. can be etched by hot sulfuric acid (see Chapter A7). This method is suitable for deformation of forged aluminum, etc. Aluminum-magnesium alloys and cast aluminum-magnesium alloys are both ideal. The no-corrosion time is related to the alloy type. Generally, the no-corrosion time of cast aluminum is shorter.
5.2.6 Surface adjustment of silicon-containing cast aluminum alloy parts Cast aluminum alloys with higher silicon content, such as ZL101, ZL101A, ZL102, ZL108, ZL109, etc., are treated with nitric acid-hydrofluoric acid (see Chapter A8) Surface conditioning treatment is carried out in the mixed solution. This solution can also be used to remove the heat-treated oxide film from heat-treated castings whose surfaces are not suitable for polishing or polishing.
6 Diffusion plating and pre-bonding
After cleaning and surface adjustment, the surface of the smart device should be dip-plated or dip-plated and pre-plated. It is often carried out by galvanizing, galvanizing and pre-plating steel, zinc-free and pre-nickel plating, silver-free and pre-plating steel. For certain brands or aluminum parts that have been heat treated in certain ways, in order to obtain the desired effect, the above process or bath solution often needs to be slightly modified.
6.1 Zinc-free
The ideal zinc-dip layer should be thin and uniform, with fine crystallization and a certain metallic luster, and a firm bond with the matrix. The quality of the zinc-dip layer is affected by the type of alloy and the surface. Adjust the influence of treatment process and zinc-free process. The deposition amount of the zinc layer is generally 15~50μg/cm, and the corresponding thickness value is 20~70nm. The ideal deposition amount should not exceed 30uμg/cm\. Excessive deposition amount can easily form a spongy zinc layer, which is difficult to combine with the matrix. The strength is also poor. Zinc deficiency is divided into primary zinc deficiency and secondary zinc administration.
For zinc-dip aluminum parts, a layer of copper is usually pre-plated on the zinc-dip layer using an appropriate process before electroplating other metals (see 6.2). Silver or yellow can also be electroplated directly on the zinc-dip layer. Copper, zinc or chromium. The electroplating process selected should be suitable for plating on zinc and the workpiece should be charged into the keyway.
6.1.1 Zinc dipping solution and process
The following table lists the zinc dipping solution and process parameters. 2
content (
drop
!L) and parameter values
liquid
composition and operating conditions
sodium hydroxide (NaOH )
Zinc oxide (ZnO)
Ferric trichloride (FeCl,·6H,O)
Potassium sodium tartrate (KNaC.H,O,·4H.O) sodium nitrate (NaNO,)
Temperature
Time
c
JB/T 6986-93
Zinc dipping solution and process parameters
1
520
100
15~20
3060
1
520
100
1.0
10
27
30~60
.
50
5.0
2.0
50
1. 0
2025
N
120
20
2.0
50
1.0
20~25
Note: Liquid dropped! ——When the process conditions are not strictly controlled, the zinc is deposited too fast, and a thick, phase-stable, crystalline, porous and poorly adhered crown layer is formed. Solution 1
is an improved version of Solution 1, which has the following advantages: (1) The deposited layer is uniform and consistent: (2) The working range is wide and suitable for secondary limited selection, (3) Except for a few brands of aluminum alloys , such as duralumin LY12 and super duralumin LC4, it can improve the corrosion resistance of most rolled and aluminum alloys. Solution I and N
are suitable for situations that are difficult to rinse or bring out a lot of liquid (for example: parts with complex shapes). Solution W has a higher zinc content and is more suitable for mass production. ||tt ||The zinc-free solution is generally relatively concentrated, and the solution brought out from the workpiece will change the composition of the dissolved wave. Therefore, the components should be replenished frequently according to the test results to ensure the quality of the zinc-free layer.
There are many types of zinc solutions, and different types of aluminum parts often use different zinc solutions. No matter which zinc immersion solution is chosen, the subsequent electroplating layer should meet the bonding strength test requirements specified in GB5270, 6.1.2 Secondary zinc coating
The first zinc coating layer is rough and porous and has poor adhesion. Secondary zinc coating can be used. After the second blasting, a fine, uniform and slightly metallic zinc layer can be obtained. The two zinc treatments can be carried out in the same tank, or they can be carried out in a more concentrated solution first and then in a dilute solution. In order to obtain the ideal zinc layer, sometimes it is even necessary to perform multiple zinc removals. The first layer of zinc is removed in a nitric acid solution (same as Chapter A6). The first zinc outage time is 45s; the second zinc outage time is 30s. 6.1.3 Precautions
Do not use steel or collar alloy for the hanger when zinc is diffused to prevent replacement of copper and aluminum or aluminum alloy contact. The steel wire, copper or copper alloy on the hanger should be nickel-plated. Then used for zinc dipping. Or use aluminum wire or non-metallic materials as zinc-free hanging fixtures. 6.2 zinc-free and pre-plated with copper | Zinc-finished aluminum parts can be pre-plated with copper in a cyanide copper plating solution, and then transferred to other electroplating solutions for electroplating after being fully washed with water. The copper plating electrolyte and process conditions are shown in Table B1 of Appendix B (Reference Parts). 6.3 Zinc-dip and pre-forged nickel
has been cleaned (see 5.1) and surface adjusted (see 5.2). Aluminum parts after secondary immersion can also be pre-plated with nickel in a nearly neutral nickel bath, and then further electroplated. Pre-plating ammonium electrolyte and process parameters are shown in Table B2, 6.4 without tin and pre-plated with bronze
In a humid corrosive environment, the front layer is prone to lateral corrosion and the electroplating layer peels off. In this case, it can Use pre-plated bronze after tin-diffusion,
6.4.1 Immersion in tin
After the aluminum parts are cleaned and surface adjusted according to the provisions of Articles 5.1 and 5.2, they are fully rinsed and then placed in a certain solution containing stannate. These patents do not plating in the tin 3
JB/T6986-93
solution or flash tin plating into the tank with electricity and then pre-bond the bronze. 6.4.2 Pre-plated bronze
After the tin is removed, the bronze can be pre-plated in a suitable oxidizing electrolyte without washing with water, and then fully washed with water before being transferred to other electroplating tanks. Safety
7
7.1 Certain corrosive and highly toxic drugs are used in this standard, and appropriate safety measures should be taken. 7.2 There must be sufficient water rinsing process between cyanide and acid treatment processes. Al
A2
Carbonate-nitrate cleaning solution
Sodium carbonate (NaCO·anhydrous)
Trisodium phosphate (Na, PO., anhydrous)
Temperature
Time
Container
Alkaline impregnation solution
Sodium hydroxide (NaOH)
Time
Temperature| |tt||Container
Acid dipping solution to remove hanging ash
A3
JB/T 6986—93
Appendix A
Aluminum parts cleaning and surface conditioning treatment solution
(reference part)
A3.1 solution
nitric acid (density 1.40g/mL, HNO,)
ammonium hydrogen oxide (NHHF, )
Time
Overflow
Container
A3.2 Precautions
The gas is poisonous and exhaust ventilation should be provided.
A4 replaces A3 solution
A4.1 solution
Sulfuric acid (density 1.84g/mL.H,SO,)
Hydrogen peroxide (mass percentage 32% , H, O,) water
time
temperature
container
A4.2 Precautions
25g/L
25g/ L
70~80℃
1~3min
Steel
50g/L
30~60s
50~60℃
Steel
750mL
120g/L
30 s
20~25℃
Lining type
100mL
50mL
Dilute to 1L
15~60s
Room temperature
Stainless steel or plastic lined
When preparing the solution, please note: || tt||Vegetable acid should be slowly added to water accounting for about 80% of the volume of the container. After cooling to room temperature, hydrogen peroxide should be added and diluted to a predetermined volume.
Deoxidation film etching solution
As
A5.1 solution
Sulfuric acid (density 1.84g/mL, H, SO,)
100 mL
5
Chromic anhydride (CrO,)
Water
Time
Temperature
Container
A5.2 Notes
When preparing the solution, please note:
JB/T 6986-93
35 g
Dilute to 1L
2~5min||tt ||70~80℃
Lead
8. Dissolve chromic anhydride into water accounting for about 80% of the volume of the container, then slowly add sulfuric acid and stir quickly, cool to room temperature and dilute to predetermined The volume;
b, the gas is toxic + exhaust should be equipped.
A6 nitric acid impregnation solution
A6.1 solution
nitric acid (density 1.40g/mL, mass percentage 67%, HNO,) water
temperature||tt| |Container
A6.2 Precautions
The gas is toxic and should be equipped with exhaust,
A7
Sulfuric acid impregnation solution
Sulfuric acid (density 1.84g/mL .H,SO.)
Water
Temperature
Time
Container
Mixed acid dipping solution
A8
A8.1 solution
nitric acid (density 1.40g/mL. mass percentage 67%.HNO,) hydrofluoric acid (density 1.16g/mL. mass percentage 48%.HF) time
temperature| |tt||Container
A8.2 Precautions
The gas is toxic and exhaust ventilation should be provided.
6
500mL
Dilute to 1L
Room temperature
Lined with plastic
150mLbZxz.net
Dilute to 1L||tt ||80c
2~5min
village lead
750mL
250mL
3~5s
room temperature
lining Plastic
B1
B2
Pre-plating copper electrolyte and process parameters are shown in Table B1. Table B1
Skin and operating conditions
Copper cyanide (CuCN)
Chloride chain (NaCN) (total amount)
Free NaCN (max. Value)
Sodium carbonate (Na;CO,)
Potassium sodium tartrate (KNaC.HO4H,O)
Temperature
Time
c|| tt||min
Current density
pH
A/dmt
Note: ①The workpiece is charged into the groove,
JB/T 6986-93| | tt | After 2 minutes, replenish plating at 1.3A/dm. for 3~5 minutes. The pre-plating nickel electrolyte and process parameters are shown in Table B2 and Table B2
Composition and operation records
Sulfuric acid inlaid (NiSO.·7H,O)
Ammonium sulfate [(NH) ,SO.]
Chloride (NiCl,·6H,O)
Sodium Citrate (Na,C,H,O,·2H,O)
Sodium Gluconate (C,HnNaO,)
Temperature
Time
c
tmin
Current density
pH (at 60C)||tt ||Anode
Stirring method
A/dm
Note: The workpiece is charged into the tank,
Additional instructions:
Pre-plating nickel electrolyte and Process parameters
Content (g/L) and parameter values ??
40.0
50.0~55.0
5.7
30. 0
60.0
4045
2
2.5
10.2~10.5
Content (g/L) and value
140
35
30
140
30
50 ~60
3~5
2~3
6.8~7.2
comprehensive
anode moving or circulating filtration
This standard is composed of Proposed and managed by the Wuhan Material Protection Research Institute of the Ministry of Machinery Industry. This standard was drafted by the Wuhan Material Protection Research Institute of the Ministry of Machinery Industry. The main drafters of this standard are Tao Weizheng, Mao Guoguo, and He Jie. This standard refers to ASTMB253-1983 "Standard Method for Preparation of Aluminum Alloy Power Supply".
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