THE INFLUENCE OF THE CHROMIUM CONTENT ON THE INHIBITIVE EFFICIENCY OF SOME ORGANIC-COMPOUNDS

The inhibitive action of some series of organic compounds against the corrosion of four steels. with increasing Cr content, has been studied. The examined steels were: a low carbon steel, AISI 430, ELI 82 and ELI 84 superferritic steels. The composition of the two last steels was very similar to that of the ferritic phase of duplex steels. The organic compounds, tested in 4 N HCl solutions at 60-degrees-C, were: N-containing compounds-2,2'-biquinoline, n-dodecylpyridinium chloride, n-dodecylquinolinium bromide, n-dodecyltrimethylammonium bromide; HS-containing compounds-2 mercaptopyrimidine, 2 mercaptobenzimidazole. n-dibutylthiourea, phenylthiourea; compounds with multiple bonds-1-octyn-3-ol, 1-iodo-1-butyn-3-methyl-3-ol, propargyl alcohol, propargylamine, trans-cinnamaidehyde. Anodic and cathodic polarization curves have been recorded with a scanning rate of 1 mV s-1. The electrochemical results have been confirmed by some series of weight loss determinations. The results showed that the N-containing compounds exerted the same inhibitive effect on all the steels. The inhibitors containing multiple bonds reduced satisfactorily the corrosion of carbon steel and AISI 430, but they were either not efficient or stimulated the corrosion of superferritic steels. The HS-containing compounds usually showed a good inhibition on the superferritic steels; their inhibitive efficiency decreased on carbon steel and approached zero on AISI 430.