Pd–P electroless deposition on carbon steel: An electrochemical impedance spectroscopy study

By the combination of two techniques, namely, polarization curves and electrochemical impedance spectroscopy (EIS) it is possible to obtain information about solution/metal surface interactions occurring during Pd–P electroless deposition at the equilibrium potential, on carbon steel. The polarization curves indicate that the deposition reaction does not obey the mixed potential theory. The values of the charge transfer resistance, when compared with those obtained by the equivalent circuit proposed to model the EIS data, indicate that there are changes in the rate-determining step of the reaction over the course of the deposition. The values obtained for the elements of the equivalent circuit that correspond to the film, permit the characterization of the film as a semiconductor. This conduction feature seems to be due to the presence of incorporated phosphorus (≈7wt.%) in the deposit at the end of the deposition process.