Synthesis And Performance Evaluation Of Amino Acid Amide Containing Corrosion Inhibitors

Carbon steel is widely used in petroleum and chemical industry and which corrosion and protection is the significant challenge in the development of petroleum and chemical industry. Application of corrosion inhibitors is the effective way of dealing with carbon steel corrosion, therefore the development of low toxicity and environmental corrosion inhibitor is one of the significant research aspects in this field in the future. Amino acid corrosion inhibitors are widely used in the present stage of organic corrosion inhibitors due to its eco-friendly and low cost. Therefore, this paper selects glycine, methionine and histidine to synthesis amino acid derivatives by adding the adsorption sites and long hydrophobic chain on their molecular structure. At last the paper compared the corrosion inhibition of the amino acid and its derivatives on the carbon steel. The main research contents of this paper are:Using IR and NMR test three kinds of eco-friendly amino acid derivatives structure proved that three kinds of amino acid derivatives were synthesized. Their inhibition efficiencies under the condition of 3 wt% NaCl solution to protect N80 carbon steel tested by weight-loss method, electrochemical method and scanning electron microscopy. The results indicated that corrosion efficiencies of amino acid and its derivatives are increased with increasing the amount of the inhibitors, and the derivatives corrosion efficiencies were better than the natural amino acids. Polarization curve test results show that the three kinds of natural amino acid and its derivatives are mixed corrosion inhibitor, the corrosion current decreased gradually with the increase of corrosion inhibitor added amount. By scanning electron microscopy SEM, energy dispersive spectroscopy EDS, X-ray photoelectron spectroscopy XPS analysis show that three kinds of amino acid derivatives are absorbed on the steel surface to form a layer of dense and solid organic protective film, while the three kinds of amino acid adsorption capacity are weak. The adsorption behavior of amino acid and its derivatives on the surface of N80 steel accord with Langmiur adsorption isotherm and adsorption mode are mainly chemical adsorption of mixed adsorption. Amino acid and its derivatives was studied by quantum chemistry theory that corrosion inhibitor molecules adsorbed on the metal surface mainly depend on the adsorption sites of amide bond, double benzene molecule and heterocyclic molecule. From quantum chemistry theory we know that the efficiency of the corrosion inhibitor related to the molecule reaction activity and adsorption site, and the reactivity of amino acid derivatives were higher than the natural amino acids which means the laboratory evaluation results are coincident with the quantum chemistry calculation. By means of corrosion inhibitor atomic charge and Fukui analysis the specific adsorption process of the corrosion inhibitor molecules on the metal surface.