Hydrogen permeation through mild steel in temperature range 20-500 deg C measured by hydrogen collection method

摘要

Hydrogen permeation through steel plate maintained at various constant temperatures between 20 and 500 deg C was investigated using the hydrogen collection method. Fused salts were employed at elevated temperatures. Hydrogen entry was induced by step changes in cathodic charging current density. Emanating flux transients obtained at the hydrogen exit face corresponded closely to a model for permeation determined exclusively by bulk hydrogen diffusion through steel, induced by stepped changes in hydrogen concentration at the steel entry face subsurface, and zero hydrogen at the exit face subsurface. An Arrhenius plot of log(D) v. 1/T, using diffusion coefficients D derived from permeation transients was approximately linear in the range 20 - 310 deg C. The values derived for activation energy E_a of 17 kJ mol~(-1) and for the pre-exponential factor D_0 of 2.6 X 10~(-3) cm~2 S~(-1), according to D = D_0 exp (-E_a/RT) were similar to literature values. Between 310 and 500 deg C, stable permeation conditions were difficult to obtain, but flux measurements were repeatable and unaffected by moisture in air.