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3,4-Dimethoxybenzaldehydethiosemicarbazone as corrosion inhibitor for anneaed 18Ni 250 grade maraging steel in 0.5m sulphuric acid

T.Poornima, Jagannatha Nayak, A.Nityananda Shetty*

The corrosion inhibition of the annealed 18 Ni 250 grade maraging steel in 0.5 M sulphuric acid by 3,4 dimethoxybenzaldehydethiosemicarbazone (DMBTSC) has been investigated by Tafel polarization and electrochemical impedance spectroscopy(EIS) techniques. The effect of concentration of inhibitor and solution temperature on inhibition efficiency of the inhibitor was studied. DMBTSC inhibits corrosion even at very low concentration. Polarisation curves indicate mixed type inhibition behavior affecting both cathodic and anodic corrosion currents. The mechanism of inhibition is discussed on the basis of an adsorption isotherm, and calculated thermodynamic parameters. Adsorption of DMBTSC on the annealed maraging steel surface is in agreement with the Langmuir adsorption isotherm model, and the calculated GibbÂ’s free energy values confirm the chemical nature of the adsorption.