New, environmentally friendly, rare earth carboxylate corrosion inhibitors for mild steel

Four recently synthesized rare earth 3-(4-methylbenzoyl)propanoate (mbp) compounds (RE = La, Ce, Nd and Y) were evaluated as corrosion inhibitors for mild steel in 0.01 M NaCl. At a concentration of 0.25 mM all the compounds showed some level of inhibition after 30 min immersion, with the Y(mbp)3 complex giving the largest reduction in corrosion current density, from 1.92 μA/cm2 for the control sample to 0.25 μA/cm2 for the Y based inhibitor. All the RE(mbp)3 inhibitors acted predominantly as anodic inhibitors, showing little effect on the cathodic reaction after 30 min. Surface analysis after 6 h immersion using FTIR and EDS detected the presence of a thin film containing inhibitor components on all surfaces, thus accounting for the reduced corrosion rate, with the Y(mbp)3 compound having the most significant effect on corrosion and showing the most uniform surface coverage.