New thio-compounds as corrosion inhibitor for steel in 1 M HCl

Some S-containing compounds newly synthesised have been tested as inhibitors for the corrosion of steel in 1 M HCl solution. Weight loss measurements, potentiodynamic polarisation and impedance spectroscopy (EIS) methods are used. The inhibiting action increases with the concentration of the compounds tested. The highest efficiency 95% is obtained at 10−4 M of [(11-hydroxyundecyl)thio]acetic acid (3 and 4). We note good agreement between gravimetric and electrochemical methods (potentiodynamic polarisation and EIS). Polarisation measurements show also that 3 and 4 act as mixed inhibitors. The cathodic curves indicate that the reduction of proton at the steel surface happens with an activating mechanism. 3 adsorbs on the steel surface according to Langmuir adsorption model. Effect of temperature is also studied between 308 K and 353 K.