Electrodeposition of aluminum-chromium alloys from AlCl3-BPC melt and its corrosion and high temperature oxidation behaviors

The binary aluminum-chromium alloys were electrodeposited from 2:1 AlCl3-N-(n-butyl)pyridinium chloride room temperature molten salt. The chromium content of the electrodeposit varies from 0 to 94 at. % Cr) and is dependent upon the deposition parameters, applied current density, applied potential, and concentration of Cr(II) ion in the bath. Depending upon the deposition parameters, the deposit microstructure consisted of both Cr rich and Al rich solid solutions, and intermetallic compounds. The rate determining step for deposition process of Cr(II) ion is suggested as the charge transfer step from monovalent ion to metallic state. The electrochemical response of the deposited Al-Cr alloys containing various concentration of Cr (4 to 40 at. % Cr) showed a low passive current and suppressed transpassive dissolution current in a neutral buffer solution at pH 6 and 9. Excellent high temperature oxidation resistance of a series of Al-Cr alloys containing 20 to 50 at. % Cr was revealed between 600 and 800 degrees C. (C) Elsevier Science Ltd.