• Somers, A. E.
• Macfarlane, Douglas
• Tan, M. Y. J.
• Junk, P. C.
• Hinton, B. R.
• Forsyth, M.

Abstract

In 2002, our group and collaborators began initial investigations on the use of rare-earth carboxylates as non-toxic and environment-friendly corrosion inhibitors for mild steel. This was followed by a more comprehensive study, reported in 2004 by Blin et al., in which a range of such carboxylate compounds were investigated. This study identified lanthanum 4-hydroxycinnamate, La(4-OHcin)3 as a promising compound. In the review presented here our more recent investigations on mild steel corrosion inhibitors with structures closely related to La(4-OHcin)3 are presented.<br/><br/>In another study, Lee investigated the effect on corrosion of subtle changes to the La(4-OHcin)3 structure. Seter et al. found that small structural changes could have a major effect on the inhibition performance.<br/><br/>Nam et al. investigated cerium, lanthanum and praseodymium 4-hydroxycinnamate as corrosion inhibitors for mild steel in carbon dioxide atmospheres in sodium chloride solution. In this particular situation, Pr(4-OHcin)3 led to the largest reduction in corrosion current.<br/><br/>A totally organic complex, imidazolinium 4-hydroxycinnamate (Imn 4-OHcin) has been investigated with the aim of developing a compound that can inhibit both corrosion and microbial growth. This compound was found to inhibit mild steel corrosion across a wide pH range and was particularly effective at a pH of 2.<br/><br/>We have also been investigating a rare-earth compound with an alternative carboxylate structure to the cinnamate; 3-(4-methylbenzoyl)propionate(mbp). This ligand differs from 4-hydroxycinnamate by having a carbonyl group present, which may give an extra anchor point to a metal surface when forming a barrier coating. A range of rare-earth mbp complexes was investigated, with Nd(mbp)3 resulting in the largest reduction in corrosion current density at a concentration of 0.125 mM.

Topics

• density
• surface
• compound
• Carbon
• corrosion
• steel
• Sodium
• Lanthanum
• forming
• current density
• Cerium
• Praseodymium