ELECTRODEPOSITION OF ALUMINUM-CHROMIUM ALLOYS FROM ALCL3-BPC MELT ANDITS CORROSION AND HIGH-TEMPERATURE OXIDATION BEHAVIORS

The binary aluminum-chromium alloys were electrodeposited from 2:1 AlC l3-N-(n-butyl)pyridinium chloride room temperature molten salt. The ch romium 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. Depen ding upon the deposition parameters, the deposit microstructure consis ted of both Cr rich and Al rich solid solutions, and intermetallic com pounds. The rate determining step for deposition process of Cr(II) ion is suggested as the charge transfer step from monovalent ion to metal lic 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 oxid ation 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 L td.