Extrinsic ion effect on corrosion behavior of anodized aluminum alloys in solution

The corrosion behavior of the anodized Al alloys in the electrolytes containing different metal ion has been investigated. The galvanic corrosion current of anodized AA6061 aluminum plate and C2800 brass plate couples was measured using a zero resistance ammeter for 8 hours in solution containing 3000ppm of copper sulfate. The corrosion current of AA6061-T6 specimen was 8.9 × 10
^-7
A/cm
²
and 3.1 × 10
^-5
A/cm
²
in the NaClO solutions and the NaClO+ Cu
²⁺
solutions, respectively. It means that the copper ions in the electrolyte increase the corrosion of the 6061 Al plate. When the anodic oxide film is not uniform, the local corrosion is occurred from thin coated area or defect. Redox potential of copper is higher than aluminum, when the aluminum metal was exposed in the solution including Cu ions; copper ions are reduced from the oxidation-reduction reaction by Al atoms. The aluminum atoms are oxidized into aluminum ion in the solution; therefore, this behavior accelerates the corrosion of anodized AA6061 aluminum.