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Corrosion inhibition of mild steel in Nacl and Hcl solutions by amino acids extracted from soybean residue

The influence of some factors to extraction yield of amino acids from soybean residue (SR) was investigated. The composition of amino acids extracted from SR was determined by HPLC/MS-MS. The inhibitive effect of amino acids on mild steel in NaCl solution and HCl solution were investigated by potentiondyamic polarization. | Vietnam Journal of Science and Technology 55 (5B) (2017) 9-17 CORROSION INHIBITION OF MILD STEEL IN NaCl AND HCl SOLUTIONS BY AMINO ACIDS EXTRACTED FROM SOYBEAN RESIDUE Le Tu Hai*, Nguyen Thi Lan Anh Department of Chemistry, Da Nang University of Education, The University of Da Nang, 459 Ton Duc Thang, Lien chieu District, Da Nang City * Email: letuhai@yahoo.com Received: 1 August 2017; Accepted for publication: 4 Octorber 2017 ABSTRACT The influence of some factors to extraction yield of amino acids from soybean residue (SR) was investigated. The composition of amino acids extracted from SR was determined by HPLC/MS-MS. The inhibitive effect of amino acids on mild steel in NaCl solution and HCl solution were investigated by potentiondyamic polarization. As a result, we found that the optimal condition to extract amino acids from SR with the yield of amino acids extraction was 47.10 % of the weight (based on the oven dried powder of SR), amino acids extracted from SR consist of 17 amino acids, and the mild steel inhibition efficiency of amino acids was 74.71 % in 3.5 % NaCl and 80.20 % in 0.5 M HCl. Keywords: amino acids, soya-bean residue, corrosion, inhibition, green inhibitor. 1. INTRODUCTION Corrosion control of metals is an important activity of technical, economical, environmental and aesthetical importance. The use of inhibitors is one of the best options of protecting metal and alloys against corrosion. The toxicity of organic corrosion inhibitors to the environment has prompted the search for green corrosion inhibitors which are biodegradable and free of either heavy metals or other toxic compounds. Investigations of corrosion inhibiting abilities of tannins [1 - 3], amino acids [4 - 5] and organic dyes of plant origin are of interest, as in addition to being environmentally friendly and ecologically acceptable, plant products are inexpensive, readily available and renewable sources of materials. Amino acids are nontoxic, relatively cheap and easy to .