Influence of low tensile stress on the kinetics of hydrogen permeation and evolution behavior in alkaline environment

Abstract

The hydrogen behavior the surface of X70 pipeline steel in alkaline environment after applying low tensile stress was investigated by electrochemical tests. It is found by hydrogen permeation tests that the steady-state hydrogen permeation current density (i∞) and sub-surface hydrogen concentration (C0) greatly increased, whereas apparent diffusivity (D) was almost unchanged after applying low tensile stress. LSV and EIS measurements indicated that the activity of hydrogen evolution reaction (HER) was improved by elastic tensile stress. The mechanism of stress enhanced the hydrogen embrittlement sensitivity was conducted by Iyer-Pickering-Zamanzadeh (IPZ) and surface effect model. The results demonstrated that the Volmer reaction was facilitated, and the Tafel reaction was restricted by the application of tensile stress. The activation energy obtained by the Arrhenius equation indicated that when the specimen suffered from tensile stress, the adsorption activation energy decreased, and the desorption activation energy increased, leading to the remarkable increase of C0.