Jian-Wei Chang

Relationship between heat treatment and corrosion behaviour of Mg-3.0%Nd-0.4%Zr magnesium alloy

Abstract The corrosion behaviour of Mg-3.0Nd-0.4Zr (NK30) magnesium alloy was investigated in as-cast (F), solution treated (T4) and peak-aged (T6) conditions in 5% NaCl solution by immersion tests and electrochemical measurements. The results of immersion test show that NK30 alloy exhibits better corrosion resistance in F condition than it does in the other two conditions due to the more compact corrosion film formed on alloy in F condition. The potentiodynamic polarization curves show that the overpotential of cathodic hydrogen evolution reaction on NK30-F is much higher than that on NK30-T4 and NK30-T6. The corrosion potentials of NK30 increase in the following order: F

Characterization of anodic coating formed on Mg-3Nd-0.2Zn-0.4Zr Mg alloy in alkaline electrolyte

Abstract Anodization of rare earth-containing Mg alloy of Mg-3Nd-0.2Zn-0.4Zr (mass fraction, %) (NZ30K) was performed in composite electrolyte containing NaOH, KOH, K2SiO3, Na2SiO3, NaF, KF etc. The anodic coating was characterized by using X-ray diffraction(XRD), field emission electron scanning microscope(FE-SEM) and electron probe microscopic analysis(EPMA). The corrosion resistance of the anodized alloy and the substrate was evaluated in 5% NaCl solution using electrochemical impedance spectroscopy(EIS). The results of XRD show that the anodic coating is mainly composed of MgO. EPMA indicates that magnesium and oxygen are almost uniformly distributed across the coating, and the fluorine content decreases gradually from the interface of coating-substrate to the surface, whereas the distribution of silicon is reverse to that of fluorine. The results of EIS analysis shows that the anodic coating exhibits the superior corrosion resistance for NZ30K alloy.