Effect of benzamide on the corrosion inhibition of mild steel in sulphuric acid

Abstract

The effect of benzamide as a chemical inhibitor on mild steel corrosion in 0.5M H₂SO₄ was studied at ambient temperature. The experimental work was performed with gravimetric and potentiostatic polarization measurement methods. Potentiostatic polarization measurement was performed with a potentiostat (Autolab PGSTAT 30ECOCHIMIE) interfaced with a computer for data acquisition and analysis. The benzamide inhibitor achieved very effective corrosion inhibition of the steel specimens in the H₂SO₄ test medium. The inhibition performance increased with increasing concentration of the inhibitor. Benzamide’s best performance was achieved with the 4 g 200 mL^–1 H₂SO₄ concentration and closely followed by the 3 g 200 mL^–1 of the H₂SO₄. In 0.5 MH₂SO₄, the 4 g and 3 g 200 mL^–1 H₂SO₄ gave the optimal performance with weight loss of 2.99 g at 480 h of the experiment, respectively. The corrosion rate for 4 g’s was 6.4mmyr^–1. The experiment also achieved polarization resistance values of 3.98 and 2.37E+01Ω; corrosion rate,CR, of 7.48E+00 and 1.26E+01mmyr^–1 and current density (Icorr) values of 6.45E–04 and 1.08E – 03A cm^–2, respectively. The corrosion inhibition efficiency values are, respectively, 60 and 70 % for both 3 g and 4 g 200 mL^–1 H₂SO₄ concentrations at 48 h.Results of ba and bc indicated a mixed type inhibitor. Benzamide adsorption on the steel’s surface obeys the Freundlich adsorption isotherm.

Keywords: Electrochemical corrosion, benzamide, inhibitor, sulphuric acid, mild steel, polarization