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How To Prevent White Spots

Aluminum alloy casting has porous structure and high porosity. It contains many types of metallic and non metallic impurities. It is difficult to ensure the quality of anodic oxide film. We can take the following measures to get normal quality of the film and avoid white spot on anodic oxide film after dyed.

1. Density impact method with high voltage and large current. In the initial stage of anodizing people usually use high voltage and large current impact to make them connected together. 

2. Grinding method on aluminum alloy casting surface. Grinding can make aluminum fill to the casting pore. It can play an important role on connecting. In fact this method will not be very ideal because that some filling positions will fall off in the process of alkaline etching and anodic oxidation. 

3. Peening on the aluminum alloy casting. Generally speaking wall thickness of casting can meet the requirements of pressure during shot peening. Big pressure can be in favor of improve the blasting quality. It can closed pores and cracks through extruded pellets. And also improve the strength and clean on the surface of aluminum alloy casting. As we all know, there is no white spots on the unprocessed casting surface. This is because the casting surface has a dense oxide film.