The chemical properties of aluminum alloys are relatively active, so aluminum alloy die casting components are prone to oxidation and corrosion under natural conditions. In order to improve the corrosion resistance and oxidation resistance of aluminum alloy die casting components, a layer of metal is often plated on the surface of aluminum alloy die casting components and the bonding force between the die-cast aluminum alloy and the plated metal determines the electroplating effect. Therefore, improving the bonding force between the aluminum alloy die-casting components and the plated metal becomes an important factor to improve the electroplating effect.
(1) Because of their good plasticity, aluminum alloys can die-cast complex structures according to customer needs, reduce the subsequent processing links, and have the characteristics of high production efficiency, so aluminum alloy die casting components have been widely used in parts manufacturing. In order to improve its corrosion resistance and other decorative functions in the atmosphere and meet its requirements in use, surface treatments such as electroplating are often required.
(2) It can be seen from the periodic table of elements that aluminum alloy elements are active in nature. Therefore, the chemical stability of aluminum alloys in acid and alkali media is poor, so electroplating on aluminum alloy die casting components is much more difficult than electroplating on other metals such as steel, copper and copper alloys. And it is likely that there will be disadvantages such as the over-corrosion of the matrix metal leading to the poor bonding force such as blistering and falling off of the coating. This is also the main reason for waste and unqualified products in aluminum alloy electroplating. Therefore, it is an important way to improve the electroplating qualification rate of zinc alloy die casting components and ensure product quality by putting forward the factors affecting the bonding force of zinc alloy electroplating from the electroplating process method, and then take corresponding preventive and solution measures.
(1) There are many reasons for determining the bonding force of the coating of die-cast aluminum alloy parts. According to the experience of electroplating technicians for die-cast aluminum alloy, it is found that there are two main influences on the bonding force of the electroplated die-cast aluminum alloy, namely pre-plating treatment and pre-plating technology.
(2) The electroplating of aluminum alloy die casting components generally adopts the following processes:
Chemical cleaning and degreasing → hot water washing → cold water washing → bottom plating → cold water washing → activation treatment (some do not carry out) → pre-plating → cold water washing (coating the middle layer or outer layer according to the process requirements). In the whole process of electroplating of die-cast aluminum alloy, although each process has different degrees of influence on the quality of electroplating, the pre-plating treatment and pre-plating technology are the main and key factors that determine whether a good bonding force of coating can be obtained.