Effect of 2-mercaptobenzothiazole on aciddissolution and hydrogen absorption of steel

The dissolution of mild steel in H2SO4 at 40°C with and without 2-mercaptobenzothiazole has been studied. The corrosion rate, corrosion potential, anodic and cathodic polarization, and H2 absorption and permeability have been determined. 2-mercaptobenzothiazole was found to be a very effective inhibitor, which inhibited mainly the cathodic reactions, especially at higher concentrations. The inhibitor progressively decreased the HZ absorption and permeability with increase in inhibitor concentration. The log i vs. H2 absorption curves can be represented by two straight lines intersecting at 12 mA/cm2.

The results have been discussed in the light of adsorption theory and rate-controlling step of hydrogen discharge at cathode.