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.