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 aci d (HCl) by derivatives of thiosemicarbazones has been studied using we ight loss and hydrogen evolution techniques. The thiosemicarbazone der ivatives used as corrosion inhibitors were 2-acetylpyridine-(4-phenylt hiosemicarbazone) (2AP4PTSC) and 2-acetylpyridine-(4-methylthiosemicar bazone) (2AP4MTSC). 2AP4PTSC exhibited a higher maximum inhibition eff iciency (80.67%) than 2AP4MTSC (74.59%). Generally, inhibition was fou nd 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 a ttributed to physisorption. The difference in the inhibition behaviour of the two compounds is explained in terms of the difference in their molecular structures.