Electrochemical thermodynamics of stress corrosion of pipeline steel in active and passive environments studied by scanning Kelvin probe

Abstract

Electrochemical corrosion thermodynamics of an X52 pipeline steel under plastic stresses was studied by measurements of corrosion potential and Volta potential with a scanning Kelvin probe in an anaerobic near-neutral pH and an aerobic high pH corrosive environments, where the steel was under active dissolution and passivity, respectively. The stress-corrosion thermodynamics of the stressed steel in both environments was studied by Volta potential measurements. While the corrosion potential shifts negatively due to a stress-enhanced corrosion activity in both solutions, the shift of Volta potential is more indicative of the corrosion thermodynamics under identical stresses. Volta potential measurements provide a more promising method than corrosion potential to indicate the stress corrosion thermodynamics of the steel. The relationships between Volta potential and corrosion potential in both active and passive solutions deviate from linearity in the presence of stress. However, the difference between the two potentials increases linearly with stress .