Effects of Solution pH, Sodium Chloride and Amino Acids on the Corrosion of a Steel Plate in Lime Water
Yutaka TSURU, Yuji TAMAE, Youko NAGAI, Tomomi NAKAHATA and Katsu MATSUI
Abstract:The galvanic cell current between a steel plate and a platinum wire cathode immersed in oxygenated lime water containing sodium chloride and various amino acids as inhibitors was measured, permitting continuous monitoring and evaluation of corrosive effects of the solution pH and of the efficacy of the corrosion inhibitors. A relation of log[Cl-] = 0.41log[OH-] - 0.17 was found in a criterion concentration between Cl- and OH- for the onset of pitting corrosion on the steel surface. It was also found that the amino acids functioned as corrosion inhibitors. Especially, the composite additive consisting of DL-glycine and DL-aspartic acid, or of DL-serin and DL-aspartic acid effectively adsorbed on the steel surface and greatly suppressed the pitting corrosion of the steel. Key Words:Reinforced-concrete, Lime water, Pitting corrosion, Chloride ions, Solution pH, Amino acid, Inhibitors