Performance evaluation of phosphite NaCo(H2PO3)3•H2O as a corrosion inhibitor for aluminum in engine coolant solutions

The inhibiting action of a novel inorganic compound (NaCo(H2PO3)(3)center dot H2O) (NaCoPh) synthesized in our laboratory on the corrosion of aluminum in engine coolant solutions has been studied. In this study, potentiodynamic polarization measurements with SEM/EDX investigations were employed. Polarization curves reveal that NaCoPh is a mixed type (cathodic/anodic) inhibitor for aluminum corrosion in the engine coolant solution. The inhibition efficiency increases with increasing concentration of NaCoPh but decreases with increasing temperature and flow rate. SEM/EDX investigations reveal the adsorption of NaCoPh on the aluminum surface. A mixed adsorption (physisorption and chemisorption) for NaCoPh was proposed.