Electrochemical behaviour of some copper alloys in sodium chloride solutions containing different inorganic additives

摘要

The corrosion behavior of Cu-Fe and Cu-Fe-Al was studied in NaCl solutions without and with different concentrations of some inorganic additives, Na2MoO4, K2Cr2O7, and KIO3. The measuring techniques used were, open-circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The potentiodynamic polarization measurements indicated that the corrosion current, Icorr, o;f Cu–Fe is less than that of Cu–Fe–Al. The investigated additives in 3.5% NaCl shift corrosion potential Ecorr to more positive values (except in K2Cr2O7reverses the action for Cu-Fe alloy) and increase Icorr. Impedance measurements indicated that Nyquist plots for Cu–Fe and Cu–Fe–Al may be regarded as part of semicircle (arc), the values of Rpfor Cu–Fe are higher than those for Cu–Fe–Al except in K2Cr2O7. On the other hand, the values of Cdlfor Cu–Fe are lower than those obtained for Cu–Fe–Al. The presence of these additives in NaCl solutions increases the values of polarization resistance (Rp) and decreases the values of (Cdl).