سال انتشار: ۱۳۸۵
محل انتشار: یازدهمین کنگره ملی مهندسی شیمی ایران
تعداد صفحات: ۶
Khoshvaght – Master of Science from Sharif University of Technology, Tehran, Iran
Hosseini – Assistant of professor of Tabriz University, Tabriz, Iran
Arshadi – professor of chemistry of Sharif University of Technology, Tehran, Iran
The changes in crystal structure, grain size and corrosion resistance that occur in zinc phosphate coatings on sheet steel substrates when calcium ions are incorporated in a zincphosphating formulation are reported. Stable samples of phosphating formulations with and without calcium salts were prepared and the structure and corrosion resistance of the phosphate coatings were determined using X-ray diffraction (XRD) technique, scanning electron microscopy and ASTM salt spray test. XRD shows that the incorporation of calcium changes the structure of phosphate coatings from essentially phosphophylite-hopeite to schlozite-paraschlozite with considerable reduction in grain size (from 150 to 3 mm) and a substantial improvement in compactness as evidenced by scanning electron micrographs (secondary emission). The corresponding increase in corrosion resistance has been demonstrated by sale spray tests on painted phosphated panels.