Electroplating of Al-Zr alloys in AlCl3-NaCl-KCl molten salts to improve corrosion resistance of Al

To improve the corrosion resistance of Al in chloride solutions, electrodeposition of Al-Zr alloys of various compositions was carried out at 448 K by constant potential control in AlCl3-NaCl-KCl molten salt containing ZrCl4. Cathodic reduction of the Zr ions starts at a potential of 0.4 V vs. Al/Al(III) in the molten salt. The electrodeposition of Al and Zr occurred at potentials more negative than -0.02 V. The concentration of Zr in the electrodeposit increased to 23 at.% at -0.02 V. In the XRD analysis, the electrodeposits formed at -0.05 to -0.15 V had good crystallinity, the electrodeposits containing higher concentrations of Zr formed at -0.02 or -0.04 V show an amorphous or fine crystal structure. The pitting potentials of Al-Zr alloys containing 5-23 at.% Zr in 0.1 M NaCl solution shifted from +0.1 to +0.3 V compared with those of pure Al.