Development of Amino Acid Inhibitors for Carbon Steel in H₂SO₄ Solution

The inhibition properties of compound amino acid corrosion inhibitors for carbon steel in 0.5 mol/L sulfuric acid medium were tested by using weight-loss and scanning electron microscopy methods.The results indicated that the inhibition efficiency increased with increasing of amino acid concentration.But when cysteine or methionine was used independently with concentration of 800 mg/L,the inhibition efficiency was 74.81% and 63.36% respectively.The corrosion inhibition efficiency of cysteine or methionine used independently with concentration of 800 mg/L mixed with KI with concentration of 800 mg/L and 500 mg/L respectively,the inhibition efficiency was only about 90%,and the cost of inhibitors was high.The inhibition efficiency reached 98.21% for the composite inhibitors with 20 mg/L methionine,10 mg/L HTAB and 20 mg/L KI,the cost of the inhibitor was low also,so it is an ideal composite corrosion inhibitor.Mechanism of corrosion was discussed by themodynamic and dynamic principles.The corrosion of the metal surface in sulfuric acid with inhibitors was slight,the surface of metal was smooth,and no pitting corrosion occurred.