Ⅰ The advantages of aluminum and aluminum alloy materials
With good electrical conductivity, fast heat transfer, light weight, easy to form and other advantages, but aluminum and aluminum alloys have low hardness, not wear-resistant, prone to intergranular corrosion, not easy to weld, and other shortcomings, affecting the scope of use. Therefore, in order to avoid the shortcomings, modern industry, the use of electroplating to solve this problem.
Ⅱ The advantages of aluminum plating
1 ） Improvement of decorative properties
2 ） Improve surface hardness and wear resistance
3 ） Reduce the coefficient of friction and improve lubrication.
4 ） Improve surface conductivity.
5 ） Improve corrosion resistance (including combinations with other metals)
6 ） Easy to weld
7 ） Improve the bonding force when hot pressing with rubber.
8 ） Improve reflectivity
9 ） Fixes dimensional tolerances
As aluminum is a more active metal, the plated material are more active than aluminum, therefore, before plating, must do the corresponding chemical transformation, such as dip zinc, zinc-iron alloy, zinc-nickel alloy, and make zinc and zinc alloy substrate has a good combination of intermediate layer of cyanide copper plating layer. Die-casting aluminum due to the loose structure of the body, sanding, can not be sanded off the surface of the body part, otherwise pinholes, spit acid, peeling and other phenomena.
Ⅲ The process flow of aluminum plating
Degreasing -> Alkaline Etching -> Activation -> Zinc Replacement -> Activation -> Plating (such as nickel, zinc, copper, etc.) -> Chromium Plating or Passivation -> Drying.
1 ） The common aluminum plating plating types
Nickel plating (pearl nickel, sand nickel, black nickel), silver plating (face silver, thick silver), gold plating, zinc plating (color zinc, black zinc, blue zinc), copper plating (bronze drum copper, white tin copper, alkali copper, burnt copper, acid copper), chromium plating (white chrome, hard chrome, black chrome) and so on.
2 ） Use of common plating
(1) Black plating, such as black zinc, black nickel, etc. are used in optical electronics and medical equipment.
(2) Gold plating, silver is the best conductor of electronic products, but also to improve the product's higher decorative, but the price is more expensive, generally used in electronic products conductive aspects, such as high-precision wire terminals and other plating.
(3) Copper, nickel, chromium is the most popular mixed plating in the field of modern science, no matter in the decorative, corrosion resistance, are currently the world's most popular plating. The price is low, can be used in sports equipment, lighting, most of the electronic industry.
(4) Copper plating, white tin copper is developed in the 70's and 80's for environmentally friendly plating, bright white, is the first choice of the jewelry industry. Bronze (lead tin copper can be made to imitate gold, so it is a better decorative plating), but the anti-color change of copper is relatively poor, so the development is relatively slow.
(5) Zinc plating: zinc plating layer is greenish-white, easily soluble in acids and alkalis. Since the standard potential of zinc is more negative than that of iron, it provides reliable electrochemical protection for steel. Zinc can be chosen as a protective layer for steel products used in industrial and marine atmospheres.
(6) Hard chromium, deposited under certain conditions of chromium plating layer has a high hardness and wear resistance, hardness of HV900-1200kg/mm, chromium is commonly used in the plating of the highest hardness of the plating layer, can improve the wear resistance of the parts, to extend the service life. Such as work, mold, measurement, clamps, and so on. Therefore, this plating is an indispensable treatment for cylinders, hydraulic and transmission systems.
3 ） Common abnormalities and improvement measures
(1) Stripping:
a, Zinc replacement is not good, the time is too long or too short, improvement measures, re-determine the replacement time, bath temperature, bath concentration and other operating parameters.
b, Activation is not enough, improvement measures, change the activation method.
c, Pre-treatment is not complete, the surface of the workpiece has oil, improvement measures, strengthen the pre-treatment.
(2) Surface roughness:
a, Plating solution light agent, softener, pinhole dose is not suitable, re-adjust the number of additives.
b, Body surface itself is rough, re-polished and then plated.
c, Surface yellowing is a low-potential trend is not correct, change the mounting method. Add the appropriate amount of alignment agent.
d, Surface hairy teeth: plating solution is too dirty, strengthen the filtration, for the appropriate tank treatment.
Ⅳ Quality requirements
1 ） Appearance without yellowing, pinholes, burrs, blisters, bruises, scratches and other undesirable phenomena.
2 ） Film thickness of 15um or more, salt spray test 48 hours, up to the U.S. military standard 9 or more, potential difference of 130-150mv area.
3 ） The bonding force can pass the 60 degree bending test.
4 ） The products in special environment can be changed accordingly.
Ⅴ Auminum and aluminum alloy plating operation notes
1 ） Aluminum parts plating should use aluminum alloy as hanging tool;
2 ） The processes of aluminum and aluminum alloy after etching must be carried out quickly, and the intervals between processes are as short as possible to avoid re-oxidation;
3 ） The second time of zinc dipping should not be too long, so as not to cause excessive corrosion;
4 ） The water washing must be clean;
5 ） The electroplating process should be prevented from power failure in the middle of the process.
