Aluminum and aluminum alloy electroplating pretreatment process improvement

Aluminum and aluminum alloy metal plating surface , the surface can significantly improve their physical or chemical properties , made ​​of aluminum and aluminum alloy conductor, silver plating on its surface to increase the surface conductivity or electrical contact parts ; as the aluminum easy welding, plating on the surface of copper, nickel or tin ; order to improve its wear resistance , plating thickness on the surface of Ge . In the decorative aspect , in fact, mostly plating Ge .

Aluminum and Aluminum Alloys surface plating , a long time ago and have been trying for the actual production . However, the coating of aluminum and aluminum alloys and between the oxide , aluminum and aluminum and the metal plating layer different thermal expansion coefficients , and the residual coating with pinholes and other factors plating solution , resulting in poor coating adhesion , prolonged use may peel off even in the plating immediately after peeling , in the field of surface treatment of aluminum and aluminum alloy plating process is still in the exploratory stage, has long been no substantive breakthrough , has not formed a complete and mature technology . Coating adhesion is not strong aluminum and aluminum alloy plating quality and product qualification rate is still the industry bottlenecks.

Two traditional aluminum and aluminum plating

Aluminum and aluminum electrolysis in the electrolyte can form a coating, but the coating adhesion is not strong , easy to peel . Therefore, the first aluminum oxide compound in an aqueous solution containing zinc plating then electroplating deposition , this method both for zinc substitution method or a deposition method . But also the first in the surface treatment of aluminum and aluminum alloy obtained by anodic oxidation power thin layer of porous oxide film during plating.

2.1 Conventional aluminum and aluminum alloy electroplating process

Aluminum and aluminum alloy electroplating process have pre-plating treatment, plating , after plating processing three parts. Pre-treatment is related to the merits of the product quality plating of the most critical processes , its main purpose is to remove the aluminum and aluminum alloy surface oils , naturally formed oxide film and other contaminants .

Conventional general process: degreasing - washing - Less eclipse - washing - pickling - washing - Activation - washing - a dip zinc - washing - retired Zinc - washing - Secondary dip zinc - washing - Neutral Nickel - washing - subsequent plating.

There is also replaced the wave anodic oxide film during the subsequent post- dip zinc plating process .

2.2 conventional pre-treatment process deficiencies

1 long process , process more .

2 complex process, a narrow operating range , the process parameters must be strictly controlled .

3 . Process scope is not wide , different grades of aluminum pre-treatment process can not be identical, adjustments must be based on grade aluminum pre-treatment process .

4 In the strict control of pre-treatment process under the premise of electroplating products pass rate is very low, ordinary decorative plating passing rates of 85% to 90% , functional electroplating pass rate of 60% to 70%.

5 The pot life of each process solution is short, the processing cycle is short.

Since conventional pre-treatment of aluminum and aluminum agree more widespread lack , therefore, must be improved .

Three . Improved Universal aluminum and aluminum plating pre-treatment process

Degreasing alkaline etching combo - washing - pickling - washing - go gray - washing - alkali activation - dip zinc - washing - Neutral Nickel - washing - up plating.

Four . Practice summary

New processes for the current actual defects aluminum plating , combined with aluminum to teach their special physical and chemical properties, in the original process improvement on the basis of the specific advantages:

1 short process, through selective dissolution of the surface layer of aluminum and other metals to improve the purity of aluminum alloy surface , coating adhesion is improved .

(2) was first activated with alkaline acidic activation process to completely replace the clearance rate of alloy plating pre-treatment process of surface residual silicon and silicone, effectively improve coating adhesion .

3 alkaline activated zinc dipping directly without washing , to avoid acidic activation after washing and then the second dip zinc exposure in air to form an oxide layer .

4 Just a simple dip zinc can, significantly better than the secondary coating adhesion complex, multi -dip zinc and zinc cyanide leaching process .

5 . Process wide versatility , almost all grades of aluminum used in the plating pre-treatment.

6 products plating time pass rate was significantly higher than the traditional process . If a simple coating adhesion quality assessment, the product qualification rate of close to 100%.

7 actual production process is simple and convenient.

8 automatic production line for a long time scale gantry actual production proved , the improved new aluminum plating pre-treatment is very stable .

9 easy in the traditional aluminum plating process on the basis of process improvement .

10 Using power -ho into aluminum oxide can be achieved quickly improve the film speed, shorten the film on time, save resources, to achieve the effect of cost savings .