Stress Corrosion and Cathodic Protection of X80 Pipeline Steel Weldment in Acidic Seawater

The stress corrosion cracking of TMCP X80 pipeline steel weldment and its inhibition by potentiostatic cathodic protection in acidic seawater were studied by microstructure observation, polarization curves, four-point bending test, potentiostatic cathodic polarization and weight loss method. The results show that the base metal and heat affected zone of X80 pipeline steel weldment have similar microstructure and electrochemical properties, the weldment is the weak area against stress corrosion cracking because of the defect of weld. Four-point bending conditions can promote the corrosion of weldment, but this kind of corrosion is not serious in such acidic seawater without the ions such as S2- etc which are easy to combine with iron; -900 mV (vs. SCE) is more suitable to inhibit the stress corrosion of X80 pipeline steel weldment in such a medium.