Multifunctional inhibitors for steel

The synergistic inhibition of steel with multifunctional compounds based on cerium(III) and substituted carboxylates was reported by Forsyth et al. in 2002. The work was aimed at developing an environmentally benign inhibitor that provided a high degree of protection to steel in corrosive environments. 

The study looked at the inhibitive properties of cerium glycollate, cerium salicylate and cerium anthranilate, and found cerium salycilate to be the most 

The focrrs of this research shifted to the use of rare earth cirmamate compounds as corrosion inhibitors for steel in2004. Given the reported corrosion protection afforded to steel by both tare earth salts and cirmamates and nitrociimamates independently, Blin and co-workers investigated rare earth cimiamate compovmds for potential synergies between the constituent components. Chemical modification of the organic component saw rare earth cations (Ce, La Y, Gd and Nd) combined with cirmamates, hydroxycinnamates, methoxycinnamates and nitrocinnamates. 

Standard corrosion testing such as weight loss. Unear polarization resistance (LPR) and cyclic potentiodynamic polarization (CPP) were used to assess each compound s inhibition efficiency for steel in 0.01 M NaCl solution. Cerium and lanthanum combined with cinnamate and substituted cinnamates produced the most effective corrosion inhibition for steel. As an example, lanthanum 4-nitrocirmamate achieved 92% inhibition for mild steel itmnersed for 7 days in sodium chloride solution. Cerium 4-methoxycinnamate was also effective as a corrosion inhibitor. Electrochemical measurements showed the rare earth cinnamate compounds to be mixed inhibitors, with an initial suppression of anodic processes, followed by a decrease in cathodic processes after longer exposure times. 

A subsequent pubUcation characterized the surface film that developed on the steel after exposure to solutions containing these inhibitor compoimds. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used to identify the species present on the steel surface. The cotmnon steel corrosion product lepidocrocite (y-FeOOH) was not present on the surface, an indication that effective corrosion protection had occrrrred. At short exposure 

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