Characterization of the corrosion of a P-130x graphite fiber reinforced 6063 aluminum metal matrix composite.

Abstract

The corrosion behavior of a P-130x graphite fiber reinforced 6063 aluminum 0-90 cross plied metal matrix composite was studied. Electrochemical tests were performed on the composite and the monolithic matrix metal in aqueous 3.5% NaCl solutions. Immersion tests were performed on the composite in aqueous 3.5% NaCl solutions. The effects of pH, the presence of sulfite ions, and various heat treatments were investigated. The electrochemical tests included studies of galvanic corrosion, corrosion potential, galvanostaircase cyclic polarization and polarization resistance. Immersion tests showed accelerated corrosion at the exposed interfaces, with preferential attack at transverse fiber layers. Galvanic corrosion was large at low pH values, large graphite area fractions and when the matrix was in the over-aged state. The corrosion potential of the composite was found to be electronegative to the monolith when the Gr-Al interfaces were exposed to the electrolyte. Low pH values and over-aging increased pitting susceptibility. Solutionizing and quenching lowered pitting susceptibility at pH 8 but increased it at pH 4. Low pH values, the presence of sulfite ions and over- aging increased general corrosion rates.