ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY CHARACTERIZATION OF ZW3 MAGNESIUM ALLOY COATED BY DCPD USING LASV DEPOSITION TECHNIQUE

Abstract

The contribution deals with the preparation of the dicalcium phosphate-dihydrate (DCPD) coating on ZW3 magnesium alloy surface. The coating was prepared using large amplitude sinusoidal voltammetry (LASV) electrodeposition technique in water solution of 0.1M Ca(NO3)2.4H2O + 0.06M NH4HPO4 + 10 ml.dm-3of 50 vol.% H2O2. The influence of the DCPD coating on electrochemical characteristics was examined using potentiodynamic polarization (PD) tests and electrochemical impedance spectroscopy (EIS) at the temperature 22 ± 2 °C in 0.1M NaCl. The obtained PD curves were analysed using Tafel extrapolation method and the data obtained by EIS measurements in a form of Nyquist plots were analysed quantitatively by equivalent circuit method. The results showed the increase of corrosion resistance after application of DCPD coating on ZW3 Mg alloy in sodium chloride solution.