Electrochemical hydrogen permeation tests under galvanostatic hydrogen charging conditions conventionally used for hydrogen embrittlement study

Abstract

AbstractElectrochemical hydrogen permeation tests using pure Fe sheet specimens were performed under various galvanostatic hydrogen charging conditions commonly applied to tensile test specimens used for evaluation of hydrogen embrittlement property to obtain a guideline for efficient hydrogen charging method for a wide range of hydrogen content. Aqueous NaCl solutions containing varied concentrations of ammonium thiocyanate and a 0.1-m NaOH solution were used as electrolytes for relatively high and low hydrogen content, respectively. Addition of ammonium thiocyanate changes the mechanism of hydrogen evolution reaction and enhances hydrogen entry. By changing the concentration of ammonium thiocyanate and by changing cathodic current density, a wide range of hydrogen content can be covered. The hydrogen content in an AISI 4135 steel estimated from hydrogen permeation current density obtained for a pure Fe specimen was in good agreement with the hydrogen content experimentally measured by hydrogen thermal desorption analysis for the AISI 4135 steel. The hydrogen permeation current density data in various hydrogen charging conditions can be used as a reference for hydrogen charging of specimens.