Die castings pose some of the most challenging problems in anodizing. This paper provides some explanations by tying together metallurgical science with anodizing practice. Die castings pose some of the most challenging problems in anodizing. The finish can be too thin, non-uniform and/or have an unfavorable appearance. These are common problems with a variety of practical solutions; they are easy to recognize, but in many instances, the source for the problem remains unknown. Critical to solving the problems of anodizing die castings is understanding the die cast substrate and the impact of surface condition, alloy composition, casting quality and microstructure on the anodizing process. Substrate quality issues are just as important, maybe more so, than anodizing conditions and technique. Certain optimum anodizing conditions may be used in some cases to help overcome less than advantageous metallurgical conditions. These include well known processing tools such as various pretreatment chemistries, higher anodizing bath concentration, and higher bath temperatures. These, and other recommended solutions are not successful in every case; sometimes trial and error testing on ...