Inhibition effects of 2,5-dimercapto-1,3,4-thiadiazole on the corrosion of mild steel in sulphuric acid solution

The effect of 2,5-dimercapto-1,3,4-thiadiazole (DMTD) on the corrosion of mild steel (MS) in 1.0 M H2SO4 was investigated. DMTD acted as a mixed-type inhibitor without change of the mechanism of hydrogen evolution. The inhibition efficiency increased with the increase in concentration of DMTD but decreased with the increase of temperature. Adsorption of the inhibitor on the MS surface obeyed the Langmuir adsorption isotherm. The potential of zero charge suggests MS surface is positively charged in 1.0 M H2SO4. Thermodynamics and quantum chemical calculations reveal that the adsorption process of DMTD includes electrostatic interaction and electron donor–acceptor interactions.

► DMTD adsorbed acts as a mixed type inhibitor for MS in 1.0 M H2SO4.
► MS surface is positively charged in 1.0 M H2SO4 with and without DMTD.
► Corrosion inhibition discussed by adsorption mode and thermodynamic parameters.
► Adsorption includes electrostatic and electron donor–acceptor interactions.