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) solution using 2-acetylphenothiazine (2APTZ) at 303 K and 313 K at concentrations 1 x 10 - 3 M, 1 x 10 - 4 M, 7.5 x 10 - 5 M, 5 x 10 - 5 M and 1 x 10 - 5 M was studied using the weight loss and hydrogen evolution techniques. The order of % inhibition efficiency of 2APTZ in MCA is 1 x 10 - 3 M (60.24%) > 1 x 10 - 4 M (44.58%) > 7.5 x 10 M (35.54%) > 5 x 10 - 5 M (32.14%) > 1 x 10 - 5 M (27.71%) at 303 K. Similar trend was observed at 313 K and lower values were observed for DCA and TCA. 86.16% inhibition efficiency was obtained at the highest concentration studied using the hydrogen evolution technique. The two techniques used however reveal that 2APTZ inhibits corrosion reaction. The mechanism of physical adsorption is proposed from the obtained average. E a values of 76.05 KJmol - 1 for MCA, 70. 75 KJmol - 1 for DCA and and 68.52 KJmol - 1 for TCA. 2APTZ was also found to obey the Freundlish adsorption isotherm equation at the concentration studied. The two techniques employed revealed a first order kinetics.