Pre-plating treatment includes the main processes of degreasing, sand blowing and activation

1) Degreasing. The oil stains on the surface of the plated parts cause the chromium layer to be unable to deposit or the plating layer in the oil stains during electroplating, and the oil removal treatment is required.

2) Blow sand. If the passivation film on the surface of the plated part is not completely removed, it will cause the chromium layer to deposit difficult or relatively loose and easy to fall off. Sandblasting can effectively remove the passivation layer on the metal surface, and can make the surface rough, strengthen the mechanical bite force, thereby helping to improve the mechanical bonding between the coating and the substrate. But sandblasting will increase the stress of the workpiece, and it is not suitable for some parts that require high surface roughness or matching accuracy.

3) Activation. The activation process is the key to titanium alloy electroplating. It makes the oxide film on the surface of the titanium alloy removed, and at the same time generates a thin conversion film or metal bottom layer, so that the titanium substrate is not re-oxidized before electroplating, and at the same time, it can make the metal bottom layer get good The deposited coating. This work is to place the plated parts in a mixed solution of concentrated HC and H2SO4 for hydrogenation treatment, so that the surface of titanium is combined with hydrogen to form a gray to black continuous film layer, which can protect the substrate from being oxidized before electroplating. It can ensure good coating adhesion.

Electroplating process

1) Chrome plating solution. Common chromium plating solution components are sulfuric acid and chromic anhydride, of which chromic anhydride (CrO3) is the main component, and its mass concentration has a greater impact on the performance of the plating solution and coating performance. According to theoretical data and experimental conditions, too high or too low bath mass concentration is not conducive to obtaining the best current efficiency and coating quality; controlling p (chromic anhydride) and p (sulfuric acid) at 90~100:1 is beneficial to improve The bonding force between the plating layer and the substrate.

2) Electroplating parameters. The bath temperature and current density during chromium plating have a great influence on the coating performance, current efficiency, and dispersion ability, and they restrict each other. The optimized process parameters help to ensure a good combination of the coating and the substrate.