Journal of the Electrochemical Society, Vol.144, No.10, 3377-3384, 1997
Oxide Film Formation on a Microcrystalline Al-Alloy at Various Temperatures in Neutral Borate Solution
FVS0812 is a rapidly solidified Al alloy consisting of an intermetallic (dispersoid) phase, containing Al, Fe, V, and Si, surrounded by a predominately Al matrix. The electrochemical behavior and the oxide film structure of FVS0812 were compared to that of its two phases, as well as pure Al, in neutral berate solution at a range of temperatures. While in acidic solution, FVS0812 is unable to form an adherent, thick, porous oxide film, in 60 degrees C neutral solution, stable, although substantially thinner, porous oxides are formed on Al, FVS0812, and the matrix. In contrast to its dissolution in acidic medium, the dispersoid phase is retained within the porous film formed on the alloy in neutral solution. However, the dispersoid phase also causes the formation of a somewhat contorted porous oxide structure. Impedance measurements suggest that solution penetration into fine flaws in the barrier oxide at the barrier/porous oxide interface, a phenomenon exacerbated by increased temperature and time at applied potentials, is more prevalent for FVS0812 than for Al and the matrix.