INHIBITION OF ALKALINE CORROSION OF ALUMINUM AND ZINC BY CONDENSATIONPRODUCTS OF SOME CARBONYL-COMPOUNDS

The inhibitory effect of the condensation products of thiosermicarbazi de (TSC) with furfruldehyde (FrA), crotonaldehyde (CrA) or methyl viny l ketone (MVK) was investigated as corrosion inhibitors for aluminium and zinc in 0.5 M NaOH using gasometry and d.c. polarization technique . Correlation of the structural changes with the protection efficiency of CrTSCN, MVTSCN and FrTSCN with the parent TSC was reported. The ex perimental results indicate that the presence of adsorbed inhibitors o n aluminium sr zinc surfaces does not affect the mechanism of hydrogen evolution. Furthermore, polarization curves show that the compounds a ct as mixed-type inhibitors. Variation of the protection efficiency is evident for the different compounds, with increase of pi-electron den sity of the center of adsorption, by addition of double bonds or by he terocyclic ring, contributing to improvement in protection efficiency. All data were compared and fitted to kinetic-thermodynamic model. The number of active sites on the metal occupied by a molecule of the inh ibitor and the binding constant of the inhibitor to the active site we re calculated fur the investigated compounds. The results are compared with fits obtained from the application of other adsorption isotherms .