What are the differences between sulfuric acid anodizing, hard anodizing, and conversion coating?
In the sulfuric acid anodizing process, the aluminum workpiece is placed in an acid-based electrolyte. An electric current is then passed through the part. During the oxidation process, the workpiece is coated with a hard, porous oxide layer. Organic coatings or dyes of various colors are later electrodeposited in the pores of the anodic coating. The primary difference between the sulfuric acid anodize and hard anodizing processes are the operating temperature and the current density at which the process occurs. Hard anodizing produces a heavier coating with better wear properties than a sulfuric acid anodize. The conversion coating, also known as chrome phosphate or chrome oxide (yellow chrome), is a process that treats the metal surface chemically when the metal is immersed in, or sprayed with, various solutions. As with anodizing, a thick oxide layer is formed although no electrical current is required in the conversion coating process. This finish provides protection and good adhes
