Abstract
The inhibitor effect of 1,7− bis (2- hydroxy benzamido)-4-azaheptane H4L3 on the corrosion of mild steel in 1M hydrochloric acid (HCl) has been investigated at 308 K using weight loss measurements and electrochemical techniques (impedance spectroscopy and polarisation curves). Inhibition efficiency is dependent upon the 1,7− bis (2- hydroxy benzamido)-4-azaheptane H4L3 concentration and its inhibition efficiency increases with the increase of concentration of inhibitor to attain 96 % since 10-3M. Polarisation curves indicate that 1,7− bis (2- hydroxy benzamido)-4-azaheptane H4L3act essentially as mixed inhibitors. EIS measurements show an increase of the transfer resistance with the inhibitor concentration. The temperature effect on the corrosion behaviour of steel in 1M HCl without and with the inhibitor at 10-3M was studied in the temperature range from 308 to 333 K, the associated activation energy have been determined. Adsorption of 1,7− bis (2- hydroxy benzamido)-4-azaheptane H4L3 on the mild steel surface in 1M HCl follows the Langmuir isotherm model. Significant correlations are obtained between inhibition efficiency with the calculated chemical indexes, indicating that variation of inhibition with structure of the inhibitor may be explained in terms of electronic properties.