TITLE:
Formation Process and Properties of Phytic Acid Conversion Coatings on Magnesium
AUTHORS:
Jian-Rui Liu, Yi-Na Guo, Wei-Dong Huang
KEYWORDS:
Magnesium; Chemical Conversion Coatings; Phytic Acid; Formation Mechanism
JOURNAL NAME:
Journal of Surface Engineered Materials and Advanced Technology,
Vol.1 No.1,
March
16,
2011
ABSTRACT: A chromium-free conversion coating treatment for magnesium by phytic acid solution was studied. The formation process of phytic acid conversion coating was studied through measuring the open circuit potential (OCP) and weight change of the pure magnesium in the different conversion treatment time. The morphologies and compositions of the coatings were determined by SEM and EDS respectively. The conversion coating has the multideck structure with netlike morphology which is similar to the chromate conversion coating, and is mainly composed of Mg, P, O and C. The contents of C and P and the size of the cracks in different layers decrease from the external layer to the inner layer. The hydroxyl groups and phosphate carboxyl groups in the coating which have the similar properties to organic paintcoat are beneficial to the combination of substrate and organic paintcoat. The formation mechanism and thickness variation of the conversion coatings are also discussed.