Studies on the inhibition of aluminium corrosion by 2‐acetylphenothiazine in chloroacetic acids

The inhibition of corrosion of aluminium in chloroacetic acids, namely monochloroacetic acid (MCA), dichloroacetic acid (DCA) and trichloroacetic acid (TCA) solutions, using 2‐acetylphenothiazine (2APTZ) at 30 and 40°C, at concentrations of 1×10 −3 M, 1×10 −4 M, 7.5×10 −5 M, 5×10 −5 M and 1×10 −5 M, was studied using the weight loss and hydrogen evolution techniques. At the highest concentration studied, using the hydrogen evolution technique, an inhibition efficiency of 86.16 per cent was obtained. The investigation revealed that 2APTZ inhibited the corrosion reaction. A physical adsorption mechanism is proposed on the basis of the obtained average E a values of 76.05 kJ/mol for MCA, 70.75 kJ/mol for DCA and 68.52 kJ/mol for TCA. 2APTZ was confirmed to obey the Freundlish adsorption isotherm equation at the concentration studied. The two techniques employed revealed a first‐order kinetics.