Determination of coating performance for coated metallic materials and metal corrosion

ABSTRACT MSc THESIS DETERMINATION OF COATING PERFORMANCE FOR COATED METALLIC MATERIALS AND METAL CORROSION MUZAFFER ÖZCAN DEPARTMENT OF CHEMISTRY INSTITUTE OF NATURAL AND APPLIED SCIENCES UNIVERSTY OF ÇUKUROVA Supervisor : Doç.Dr.îlyas DEHRİ Year: 2000, Page: 79 Jury : Prof.Dr. Mehmet ERBİL : Doç.Dr.Melih BAYRAMO?LU In this study, the effect of SO2 gas on the atmospheric corrosion of polyester coated galvanized steel substrates in different relative humidities was investigated. For this purpose the substrates were subjected to SO2 gas for 16 days in test cells with adjusted relative humidities %60, %70, %80, %90 and %100. Before the impedance measurements surface photographs of the substrates were taken. After that impedance measurements were done and Nyquist plots were obtained. Then current-potential graphs were drawn. Nyquist diagrams were interpreted by using semi ellipse model. It was seen that organic coatings were partially lost their protective properties at relative humidities %60, %70, %80, %90 and lost their protective properties at relative humidity %100. Two different electrical equivalent circuits were proposed for the corrosion of substrates at relative humidities %60-%90 and %100. Key Words: galvanized steel.organic coatings, SO2, EIS II