Inhibition of Brass (80/20) by 5-Mercaptopentyl-3-Amino-1,2,4-Triazole in Neutral Solutions

The effect of the adsorption of 5-mercaptopentyl-3-amino-1,2,4-triazole (MPATA) on the corrosive behavior of brass (Cu80/Zn20) in neutral (pH 7.4) borate buffer solutions with and without 0.01 M NaCl was studied. Electrochemical methods show significant decrease of the anodic and cathodic currents on the polarization curves in the presence of MPATA. X-ray photoelectron spectroscopy (XPS) reveals MPATA adsorption on the brass surface from an inhibitor solution. After 17 h of exposure, a mixed complex [Cu(x)Zn(y)MPATA(z)] with a thickness of about 3-3.5 nm is formed on the surface. This nanolayer has sufficient protective ability to withstand corrosion tests in a salt fog chamber: after 5 days of testing, the samples remain glossy and less than 1% of the surface has been damaged. After corrosion tests in a salt fog chamber, the surface of unprotected samples is enriched with zinc, while at the surface of inhibitor-treated samples, the copper and zinc are present in practically equal contents.