AN ELECTROCHEMICAL INVESTIGATION OF THE DEVELOPMENT OF PHOSPHATE CONVERSION COATINGS

Potential and corrosion rate monitoring have been used to follow the g rowth of phosphate conversion coatings on mild steel, with impedance s pectroscopy being utilized to examine the complete coatings. Significa nt residual metal corrosion rates arc observed after coating completio n. Impedance spectroscopy indicates similar surface processes after co ating completion in both normal and accelerated baths. Analysis of the data indicates that only one electrode process is contributing to the low frequency response of the system, rather than the more general ca se of two, anodic and cathodic, parallel processes.