Electrochemical Behavior of Zinc Layers Passivated in Phosphate Solutions

Abstract

Phosphate conversion coatings are used on the galvanized steel. By forming a thin protective film on the surface of the steels this treatment enhances corrosion resistance. This paper presents studies on phosphate passivation solutions. The results of treatments for different treatment times and more compositions were analyzed in terms of layer thickness, structural aspects, adherence, and continuity of films. Corrosion resistance was assessed by the linear voltammetry test. Activepassive curves were analysed and compared with unpassivated galvanised samples. For each passivation solution experimented Tafel curves were drawn and corrosion rates were determined. The optimal passivation conditions were settled as function on obtained results.

Keywords

• galvanized steel
• phosphate conversion coatings
• corrosion behaviour