Inhibition of La-Fe-Co-Si compound corrosion in distilled water by sodium molybdate and disodium hydrogen phosphate

A comparative study of Na2MoO4·2H2O and Na2HPO4·12H2O as inhibitors for magnetic refrigeration material La-Fe-Co-Si compound corrosion in distilled water at room temperature was carried out. Moreover, the inhibiting behavior of the mixture of Na2MoO4·2H2O and Na2HPO4·12H2O was investigated. Potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) measurements were applied to study the corrosion behavior of the compound in the absence or presence of different concentrations of these inhibitors under the same experimental conditions. The study revealed that the mixture of 3.0×10−3 kg/L Na2MoO4·2H2O and 5.0×10−3 kg/L Na2HPO4·12H2O was the best inhibitor reaching the value of inhibition efficiency (ɛ%) up to 93.9%. Polarization curves showed that the studied compounds acted as anodic inhibitors. The potential of zero charge (PZC) of La-Fe-Co-Si compound was determined in distilled water in the absence of the studied inhibitors. Corrosion inhibition mechanisms for inhibitors were proposed in this work.