Synthesis And Investigation On Inhibition Performance Of Amino Acid Derivatives

Metal corrosion is a hazard to economy and environment. The corrosion could be restrained with addition of corrosion inhibitors. Nowadays, on the principle of sustainable development, corrosion inhibitor has developed to be low toxic, high efficient and friendly to environment. In the paper, a series of amino acid derivatives were designed and synthesized. By means of synergy among different corrosion inhibiting units with multi-absorption in the molecules, corrosion of carbon steel in hydrocholric acid could be restrained.Two series of amino acid derivatives including Schiff base and benzimidazole compounds were synthesised with cheap and environmental amino acid, salicylaldehyde and o-phenylenediamine. The inhibiting performance of these compounds was evaluated by weight loss and potentiodynamic polarization studies. The corrosion inhibiting mechanism of these compounds and mode of action between the corrosion inhibitors and metal surface were analysed and discussed. The results were as follows.The four salicylaldehyde amino acid Schiff base compounds show excellent inhibition properties for inhibiting corrosion of Q235 carbon steel in 1.0 mol/L hydrochloric acid solution. They can inhibit reaction of cathode and anode, but the inhibition of anode is primary. The adsorption model of salicylaldehyde amino acid Schiff base at carbon steel obeys the revised Langmuir adsorption isotherm, and the adsorption inhibition process is proved to be spontaneous. The apparent activation energy which is calculated by the Arrhenius equation indicated that the energy barrier is increased with the addition of corrosion inhibitors. Complex of Schiff base compounds and KI was investigated. Owing to the synergetic effect, the complex of Schiff base compounds and KI has improved inhibition efficiency.The five benzimidazole compounds with amino acid groups show excellent inhibition effeciency of Q235 carbon steel in 1.0 mol/L hydrochloric acid solution. They can inhibit reaction of cathode and anode, and thus be regarded as a mixed corrosion inhibitor. The adsorption model of benzimidazole compounds at carbon steel obeys the Langmuir adsorption isotherm and is regarded to be a spontaneous processing. And the activation energy which is calculated by the Arrhenius equation is bigger than blank. The energy barrier is increased with the addition of corrosion inhibitors. Sodium N,N-bis(2-benzimidazolylmethylene)-dithiocarbamate, which is proved to be a better corrosion inhibitor, was synthesized by modifying the structure of bis(2-benzimidazolylmethyl)amine. Owing to the synergetic effect the complex of benzimidazole compounds with KI has better inhibition efficiency.