Influence of Manufacturing Conditions of Steel Substrate on Corrosion Resistance of Phosphated and Electropainted Steel Sheets

Abstract

Corrosion resistance of phosphated and electropainted steel sheets has been investigated. Low carbon Alkilled steels containing 0.09% Sb and 0.04% Mo were used.
The higher the cold reduction and the annealing temperature of the steel substrates, the greater the corrosion resistance after painting. The corrosion resistance depends on the density of pohosphate nuclei which is mainly affected by the texture and the oxide film thickness appearing in the specific manufacturing condition: that is, the higher the axis density of (111) parallel to the rolling surface, or the thinner the oxide film thickness, the higher the density of phosphate nuclei. It has been observed that the texture of steels also influences the anodic dissolution rate of the phosphate crystals during the electropainting. However, since the dissolution is less than 20% of the total amount of the phosphate film, it results in only minor effect on corrosion resistance.