Hydrogen Charging Methods to Low Alloy Steel Simulating Atmospheric and High Pressure Gaseous Hydrogen Environments

Abstract

Appropriate hydrogen charging methods were investigated to simulate hydrogen absorption from actual environments where high strength steels are used. Both absorbed hydrogen concentrations and hydrogen desorption profiles were compared between various hydrogen charging tests - immersion tests, cathodic charging tests, cyclic corrosion tests (CCT) and exposure tests in high pressure gaseous hydrogen. Absorbed hydrogen was analyzed using thermal desorption analysis (TDA) after the hydrogen charging tests. It was confirmed that acid immersion tests or cathodic charging tests in NaCl solution were appropriate to simulate hydrogen absorption from CCT. Fédération Internationale de la Précontrainte (FIP) tests or cathodic charging tests in NaCl - NH₄SCN solution could be used to simulate hydrogen absorption in high pressure hydrogen gas environments. Comparisons in TDA profiles showed that the ratio of strongly-trapped hydrogen and weakly-trapped hydrogen changed depending upon the total amount of absorbed hydrogen. This result means the state of hydrogen in steels, which affects hydrogen embrittlement, can change according to the amount of absorbed hydrogen. The above-mentioned hydrogen charging tests and hydrogen analysis were conducted in 15 laboratories to check the scatter of measured hydrogen concentration.