New eco-friendly corrosion inhibitors based on azo rhodanine derivatives for protection copper corrosion

The inhibitive action of some new azo rhodanine derivatives,namely 5-(4'-methoxyphenylazo)-2-thioxo-4-thiazolidinone (i),5-(phenylazo)-2-thioxo-4-thiazolidinone (ii) and 5-(4'-nitrophenylazo) -2-thioxo-4-thiazolidinone (iii) against the corrosion of copper in 2 m hno3 solution has been investigated using weight loss,tafel polarisation,electrochemical impedance spectroscopy (eis) and electrochemical frequency modulation (efm) techniques. the inhibition efficiency increased with increasing inhibitor concentrations and decreased with increasing temperature. potentiodynamic polarisation studies clearly showed that these compounds acted as mixed inhibitors. the ability of the molecule to adsorb on the copper surface obeyed freundlich adsorption isotherm and was dependent on the active centres and molecular size of the molecules. the thermodynamic activation parameters of the copper corrosion in 2 m hno3 were determined and discussed. molecular modelling was used to gain some insight,about structural and electronic effects in relation to the inhibiting efficiencies. inhibition efficiency values obtained from various methods employed were in reasonable agreement.