Performance of nonionic surfactants derived from tannic acid in preventing the acidic dissolution of carbon steel

Abstract

Corrosion inhibition tendency of four modified nonionic tannic acid derivatives containing dodecyl, hexadecyl, octadecyl and oleyl chains on carbon steel was investigated using gravimetric measurements, polarization and electrochemical impedance spectroscopy (EIS). The effect of concentration and immersion time was studied. The results show that the synthesized inhibitors act as efficient inhibitor for the corrosion of carbon steel in 0.5 M H 2 SO 4. Inhibition efficiency ( %) increases with the inhibitor concentration, and the maximum  % values at 400 ppm by weight are 94.4%-96.4% at 25 C.The adsorption of the different inhibitors on carbon steel surface obeys Langmuir adsorption isotherm. The inhibitors act as mixed-type inhibitor in 0.5 M H 2 SO 4 and their inhibition on carbon steel is caused by physical adsorption (physisorption).EIS spectra exhibit one capacitive loop which indicates that the corrosion reaction is controlled by charge transfer process. The addition of the inhibitors to 0.5 M H 2 SO 4 solutions enhances R t values while reduces C dl values.