Aluminum alloy die castings are chemically active and easy to oxidize and corrode under natural conditions. In order to improve the corrosion resistance and oxidation resistance of aluminum alloy die castings, we often coat a layer of metal on the surface of aluminum alloy die castings. The adhesion between aluminum alloy die castings and electroplated metal determines the electroplating effect. Therefore, improving the adhesion between aluminum alloy die castings and electroplated metal has become an important factor to improve the electroplating effect. Today we will discuss how to improve the coating adhesion of aluminum alloy die castings.
Because of its good plasticity, aluminum alloy can die cast an ideal structure according to customer needs, which reduces the subsequent processing links, that is, high production efficiency. Therefore, aluminum alloy die castings have been widely used in parts manufacturing. In order to improve its corrosion resistance and other decorative properties in the atmosphere and meet its requirements in use, it is often necessary to carry out surface treatment such as electroplating.
It can be seen from the periodic table that the elements of aluminum alloy are active. Therefore, the chemical stability of aluminum alloy in acid and alkali medium is poor, so the electroplating on aluminum alloy die castings is much more difficult than that on other metals, such as steel, copper and copper alloy. It is easy to produce the disadvantages of poor adhesion such as blistering and falling off of the coating due to excessive corrosion of the base metal. This is also the main reason for waste and modification in aluminum alloy electroplating. Therefore, it is an important way to improve the electroplating qualification rate of zinc alloy die castings and ensure the product quality to pull out the factors affecting the electroplating adhesion of zinc alloy from the point electroplating process, and then take corresponding preventive and solving measures.
There are many reasons for determining the coating adhesion of aluminum alloy die castings. There are two main effects, namely, pretreatment and pre plating process. The electroplating of aluminum alloy die castings usually adopts the following process flow:
Chemical cleaning and degreasing – hot water washing – cold water washing – plating bottom layer – cold water washing – activation treatment – pre-plating – cold water washing according to the process requirements to coat the intermediate layer or surface layer.
To sum up, in the whole electroplating process of aluminum alloy die castings, each process has varying degrees of impact on the electroplating quality. The pretreatment and pre plating process are the primary and key factors to determine whether a good coating adhesion can be obtained.