Effect of Applied Cathodic Potential on Susceptibility to Hydrogen Embrittlement in High Strength Low Alloy Steel

Abstract

In order to investigate the effects of applied cathodic potential and chemical hydrogen absorption promoter (thiourea) on the susceptibility to hydrogen embrittlement of the high strength low alloy (HSLA) steel, slow strain rate tensile (SSRT) tests were conducted in various buffer aqueous solutions of pH 10.0. During SSRT tests, the specimens were cathodically polarized under potentiostatic control. Polarization levels were varied from the corrosion potential (E corr ) to hydrogen gas evolution potential (E H 2 gas ), including the adsorbed hydrogen potential (E Hads ) determined by cyclic voltammetry (CV). Additionally, thermal desorption spectroscopic (TDS) analyses were applied to the specimens fractured by SSRT test and the dependence of hydrogen absorption characteristic on applied potential was also examined for understanding the SSRT test results. Experimental results revealed that the hydrogen embrittlement behavior was strongly dependent on the applied cathodic potential. In the E Hads region, the susceptibility to hydrogen embrittlement increased with increasing cathodic overpotential. On the other hand, in the E H 2 gas region, the susceptibility was independent of the applied potential. Moreover, by adding thiourea to the solution, the susceptibility to hydrogen embrittlement increased slightly in the E H 2 gas region compared with that in the solution without thiourea. There was a relatively good correlation between the amount of hydrogen absorption per unit time (C H /t f ) and the time to failure (t f ), namely, the susceptibility to hydrogen embrittlement has a tendency to increase monotonically with increasing C H /t f . As a consequence, the potential dependence of hydrogen embrittlement was closely associated with the variation in hydrogen absorption rate under applied potential.KEY WORDS: hydrogen embrittlement; high strength low alloy steel; slow strain rate tensile test; cyclic voltammetry; thermal desorption spectroscopic analysis; potential dependence; hydrogen gas evolution; adsorbed hydrogen; hydrogen absorption.

Effect of Plastic Deformation on Hydrogen Diffusion Behavior of Martensitic Steel in Hydrogen Absorption Environment

“…(6) dominates the hydrogen atom absorption, the applied cathodic polarization linearly enhances the generation of hydrogen atoms, causing the hydrogen atoms to penetrate the steel membranes. 21) In this solution, in the performance range, no current drop in the cathodic region was observed. During the generation of hydrogen absorption reaction, the absorbed hydrogen atom concentration will linearly increase in the cathodic polarization potential without a sudden drop in current flux.…”

“…18,19) However, most early experiments on hydrogen embrittlement were carried out at the cathodic polarized overpotential (E H 2 gas ) where the evolution of hydrogen gas occurs. 20,21) In this study, to check the hydrogen charging condition at potential (E H ads ) generating stable adsorbed hydrogen on surface, cyclic voltammetry (CV) was performed at the low range of potential from E corr . We expected to obtain necessary information for clarifying the entire process and mechanism of stable hydrogen absorption from the CV test results and to possibly distinguish the relationship between hydrogen adsorption and evolution characteristics.…”

“…We expected to obtain necessary information for clarifying the entire process and mechanism of stable hydrogen absorption from the CV test results and to possibly distinguish the relationship between hydrogen adsorption and evolution characteristics. 21) The CV measurements were performed on a three-electrode system by potentiostatic equipment using a working electrode, a saturated calomel electrode (SCE) as the reference electrode, and a coiled platinum wire as the counter electrode. All estimated potentials were converted to values relative to SCE.…”

“…However, in this hydrogen permeation test, it is important to distinguish the hydrogen absorption reaction from the hydrogen evolution in the range of the cathodic region under galvanostatic mode. 21) At overpotential applied on the hydrogen charging cell, there is too much hydrogen evolution reaction, interrupting hydrogen absorption on the membrane and challenging proper hydrogen permeation.…”

Hydrogen Entry in Crevice Region: Evaluation by Hydrogen Permeation Technique

“…Mechanical, material and electrochemical approaches have been used to identify/understand this deleterious effect of hydrogen. [1][2][3] The problem of hydrogen embrittlement of iron and its alloys has recently attracted considerable attention after development of new high strength steels. The high strength steels developed at our institute finds their use in various applications.…”