Inhibitory action of methyl and phenyl thiosemicarbazone derivatives on the corrosion of mild steel in hydrochloric acid

The inhibition of corrosion of mild steel (98% Fe) in hydrochloric acid (HCl) by derivatives of thiosemicarbazones has been studied using weight loss and hydrogen evolution techniques. The thiosemicarbazone derivatives used as corrosion inhibitors were 2-acetylpyridine-(4-phenylthiosemicarbazone) (2AP4PTSC) and 2-acetylpyridine-(4-methylthiosemicarbazone) (2AP4MTSC). 2AP4PTSC exhibited a higher maximum inhibition efficiency (80.67%) than 2AP4MTSC (74.59%). Generally, inhibition was found to increase with increasing inhibitor concentration and decreasing temperature. A first-order type of mechanism has been deduced from the kinetic treatment of the results, and the process of inhibition was attributed to physisorption. The difference in the inhibition behaviour of the two compounds is explained in terms of the difference in their molecular structures. © 1995.