Effect of inhibitors on the permeability and diffusion co-efficient of hydrogen in steel

Investigation on the permeability and diffusivity of hydrogen in mild steel by stationary and non-stationary method is described. The variation of permeability in the presence of varying amounts of thiourea and its derivatives, and 2-mercaptobenzothiazole has been determined in 1N sulphuric acid at 40°C. The effect of cold working and annealing of mild steel on permeability and diffusivity in presence of the inhibitors has been studied. The inhibitors progressively decreased the permeability of hydrogen in both cold worked and annealed steel permeability and diffusivity were increased. No appreciable change in diffusivity was observed in presence of the inhibitors. The results have been discussed in the light of rate controlling step of hydrogen discharge at cathode. (Dr. Inder Singh, Senior Research Fellow, National Metallurgical Laboratory, Jamshedpur)