Thiosemicarbazide, phenyl isothiocyanate and their condensation product as corrosion inhibitors of copper in aqueous chloride solutions

The inhibition of copper corrosion in 1.5% NaCl solution has been studied at 25, 35 and 45 °C using three structurally different inhibitors thiosemicarbazide (Inh I), phenyl isothiocyanate (Inh II), and their condensation product 1-pheny1-2,5-dithiohydrazodicarbonamide (Inh III). The inhibition efficiencies of these compounds have been evaluated by weight loss and electrochemical polarisation techniques. The inhibition efficiencies of the inhibitors follow the sequence: Inh III>Inh I>Inh II. Thiosemicarbazide appears to inhibit corrosion process through formation of Cu(I) complex of thiosemicarbazide and its subsequent oxidation into Cu(II) complex, phenyl isothiocyanate inhibits only through adsorption while the condensation product inhibits the process through its adsorption as well as complex formation.