The effect of temperature and H2S concentration on hydrogen diffusion and trapping in a 13% chromium martensitic stainless steel in acidified NaCl

Abstract

The hydrogen uptake and trapping characteristics of a 13% Cr martensitic stainless steel have been determined as a function of the temperature (23–77°C) and H2S content of acidified solutions of NaCl. The sub-surface hydrogen content, evaluated from the steady-state permeation flux, increases with increasing temperature for constant solution composition. Analysis of the permeation transients has been undertaken using a diffusion-trapping model which incorporates both reversible and irreversible trapping with varying degrees of occupancy. The density of reversible trap sites is independent of temperature and is approximately 2.3 × 1019 sites cm−3. The binding energy is −(40–46) kJ mol−1. The higher values in this range are associated with the elevated temperatures. The density of irreversible trap sites shows a decrease in value above 23°C. These temperature effects may reflect uncertainty in characterizing the lattice diffusion coefficient.