INHIBITION OF STEEL CORROSION IN HYDROCHLORIC-ACID BY PYRIDOXAL, 4-METHYLTHIOSEMICARBAZIDE, PYRIDOXAL-(4-METHYLTHIOSEMICARBAZONE) AND ITS ZN(II) COMPLEX

The effect of pyridoxal (PHC), 4-methylthiosemicarbazide (4MTS), pyrid oxal-(4)-methylthisemicarbazone) (P4TS) and Zn(II)-pyridoxal-(4-methyl thiosemicarbazone) (ZnP4TS) has been studied. Weight loss and hydrogen evolution measurements reveal that ZnP4TS exhibit a higher maximum in hibition efficiency than P4TS, PHC and 4MTS. Generally, inhibition was found to increase with increase in inhibitor concentration, half-life , activation energy and with decrease in the first-order rate constant s at 30 and 40 degrees C. Physical adsorption mechanism has been propo sed for the inhibitors and the difference in the inhibition behaviour of the compounds has been explained in terms of the difference in thei r molecular weights.