Corrosion and corrosion control of mild steel in concentrated H_2SO_4 solutions by a newly synthesized glycine derivative

摘要

A newly synthesized glycine derivative (GlyDl), 2-(4-(dimethylamino)benzylamino)acetic acid hydro-chloride, was used to control mild steel corrosion in 4.0 M H_2SO_4 solutions at different temperatures (278-338 K). Tafel extrapolation, linear polarization resistance (LPR) and impedance methods were used to test corrosion inhibitor efficiency. An independent method of chemical analysis, namely ICP-AES (inductively coupled plasma atomic emission spectrometry) was also used to test validity of corrosion rate measured by Tafel extrapolation method. Results obtained were compared with an available glycine derivative (GlyD2) and glycine (Gly). Tafel polarization measurements revealed that the three tested inhibitors function as mixed-type compounds. The inhibition efficiency increased with increase in inhibitor concentration and decreased with temperature, suggesting the occurrence of physical adsorption. The adsorptive behaviour of the three inhibitors followed Temkin-type isotherm and the standard free energy changes of adsorption (△G~0)_(ads) were evaluated for the three tested inhibitors as a function of temperature. The inhibition performance of GlyDl was much better than those of GlyD2 and Gly itself. Results obtained from the different corrosion evaluation techniques were in good agreement.