Anodizing is used to protect the aluminum parts by making the surface much harder than natural aluminum. It is difficult to achieve a good, consistent anodized film on castings. There are two main forms of the anodizing process, coil anodizing and batch anodizing. An anodizing finish on aluminum is chemically stable and non-toxic. The process is non- hazardous and involves no volatile compounds; it involves water-based chemistry which is easily treated. Most anodizing facilities adjust the pH of the wastewater and remove much of the aluminum solids left in solution.