Inhibition Performance and Mechanism of Several Amino Acids in Acidic Media

The inhibition performance and mechanism of five amino acids as inhibitors for steel were studied in acidic media by weight loss method and electrochemical method. The results showed that the inhibition efficiency of these amino acids for A3 steel decreased with increasing the concentration of HCl at 30 ℃. The inhibition efficiency of cysteine for A3 steel in 2% HCl increased with the rise of the temperature while that of other amino acids decreased. To A3 steel, the inhibition efficiency of cysteine decreased with increasing the dosage of the amino acids while that of others increased. When the dosage of amino acids was 200 mg/L, the order of inhibition efficiency to A3 steel of these five kinds of amino acids was cysteine > histidine> tyrosine> arginine > leucine in 2% HCl. The optimal inhibiting condition of cysteine to A3 steel in HCl was confirmed through an orthogonal test. The results of the corrosion inhibition mechanism study show that all of these amino acids are cathodic inhibitors and the adsorption of leucine and histidine on A3 steel obeys the Frumkin equation while the adsorption of other amino acids do not obey it.