Comparison of Methods for Removal of Corrosion Product from AA2024-T3

A variety of methods are currently used by researchers to remove corrosion products from aluminum alloys to facilitate analysis. This work compares three different cleaning methods with the goal of determining the most effective means of removing corrosion products from AA2024-T3 (UNS A92024). The methods tested were nitric acid (HNO3) cleaning, ASTM standard G1, and a method developed by the Civil Aviation Authority (CAA) of the United Kingdom. Mass and thickness loss data were compared for three sample types (aircraft doubler, laboratory-corroded sample, and uncorroded sample) for each cleaning method. All comparisons indicated that the least damage to the sample was achieved in exposure to concentrated HNO3 (15.8 N). This method removed the white corrosion product in less than 20 min and did not alter the underlying corrosion topography. The addition of ultrasound to this method aided in the removal of the dark, tightly adhered corrosion product within a reasonable time period (60 min). HNO3 cleaning also had the lowest metal loss rates of 0.19 mA/cm2 for the base alloy. This method is recommended for the removal of corrosion products when mass loss data or line-of-sight topography analyses are intended.