- Aug 30, 2018 -
Aluminum and aluminum alloy have a high affinity for oxygen, and an oxide film is easily formed, and once the oxide film is removed, a new oxide film is generated in a very short time, which seriously affects the adhesion of the plating layer. The electrode potential of aluminum is very negative. When immersed in the plating solution, it is easily replaced with metal ions having a positive potential, which affects the adhesion of the plating layer, and aluminum is an amphoteric metal, which is unstable in both acidic and alkaline plating solutions. Aluminum alloy die-casting parts have sand holes and pores, which will leave plating solution and hydrogen gas, which will easily bubble, which will reduce the bonding force between the plating layer and the base metal. For these reasons, aluminum and aluminum alloys require special pretreatment before the pretreatment, in addition to conventional degreasing, etching, and light extraction. A layer of transition metal or conductive porosity must be prepared before electroplating. The chemical film layer is used to ensure good adhesion of the subsequent plating layer. At present, there are two commonly used methods: first chemical zinc immersion, and then electroplating other metals; or anodizing first, electroplating other metals.