Effect of Localized Coating Damage on Stress Corrosion Cracking Resistance of API 5L Grade B Steel

Abstract

In this research slow strain rate testing (SSRT), scanning electron microscopy (SEM), hardness measurement, metallography and optical microscopy were used to investigate the effect of localized coating damage on stress corrosion cracking (SCC) resistance of API 5L Grade B steel. According to the results, by increasing the damaged coating surface area, resistance to SCC increased. This phenomenon had 2 reasons. Firstly, by reduction of damaged surface area of coating, the ratio of anode surface to cathode surface reduced and consequently the corrosion reduced. Other reason was reduction in toughness by reducing the area of damaged surface of coating which resulted in failure at lower stresses.