New corrosion inhibitors, namely 3-vanilidene amino 1,2,4-triazole phosphonate (VATP) and 3-anisalidene amino 1,2,4-triazole phosphonate (AATP) were synthesised and their action along with biocide on corrosion control of copper in neutral aqueous environment has been studied. Potentiodynamic polarisation measurement and electrochemical impedance spectroscopy (EIS) has been employed to analyse of their inhibition behaviour. VATP showed better protection over the other inhibitors used. The dissolution of copper in presence of VATP and AATP with biocide mixture is negligible compared to blank. A combination of electrochemical methods and surface examination techniques are used to investigate the protective film and explain the mechanistic aspects of corrosion inhibition. (C) 2004 Elsevier B.V. All rights reserved.