Hydrogen Induced Cracking of Buried Steel under Over Cathodic Protection

Abstract

The mechanical properties of steel buried in marine clay at various cathodic potentials in the range from -0.85 to -3.0V vs. Cu/CuSO₄ were studied by means of slow strain rate test. The content of hydrogen in the steel entered from over protection environment was also measured by an electrochemical method (Ni-plating method). The reduction in area decreased drastically at -2.0V and downed to one-half of the value obtained in the air at less noble potential than -2.5V. The hydrogen content in the steel increased almost exponentially with cathodic potential. The fractured surface at -3.0V revealed typical quasi-cleavage mode. Then, the decrease in the reduction in area would be due to the influence of hydrogen which entered from steel surface under over protection.