Formation of Self-Organized Nanoporous Anodic Films on Carbon Steel

Abstract

The growth behavior of nanoporous anodic films on carbon steel containing 0.213 mass% carbon has been examined during anodizing in ethylene glycol containing 0.1 mol dm-3 NH4F and 0.5 mol dm-3 H2O. The nanopores in the anodic films are generated preferentially along with steps and at “kink-like” sites of the steel surface generated by rf-GD sputtering. The steel contains carbide precipitates with a size of 50-800 nm. The anodic oxide formed on the carbide phase is more chemically soluble during anodizing, producing pits in the anodic films.