The Corrosion Behavior of Pb Free Cation Electrodeposited Steel Sheets Exposed to Indoor Environment for Long Period

Abstract

Since there were not so many reports concerning to the corrosion of painted steel in the indoor environment, we conducted long-term exposure test for Pb free cation electrodeposited painted steel sheet, which was widely used for steel industrialized housing, in the indoor environment. Further, observation and evaluation of blister width, red rust width, ratio of red rust area and the maximum corrosion depth were carried out. From results of evaluation and analysis after exposure test, better correlation between the corrosion on and under the paint film became clear, and the possibility of estimation for corrosion expansion and depth under the paint film by observing appearance of corrosion on the paint film was indicated. On the other hand, among the environmental factors, annual average relative humidity and amount of deposited sea salt are considered to influence in the corrosion behavior under the paint film.