No abstract

Panels of AA2024-T3 were fastened using Cu and Cu-Ni fasteners, pretreated, and coated with around 25 µm of polyurethane film. The pretreatments were based on typical conversion coating processes. Samples included alkalinecleaned, deoxidized, and conversion-coated. The conversion coatings included chromate and cerium-based conversion coatings. Samples were tested by scribing around the fastener and on the AA2024-T3 (matrix), exposing them to HCl vapor for 15 min, and subjecting them to a filiform corrosion test by exposure to 82% relative humidity at 40 ± 1°C for up to 1000 hr. Inspection showed that the filiform corrosion that developed from a scribe around the fastener was an order of magnitude larger than from a scribe on the matrix (scribe on AA2024-T3). With respect to the surface treatments, the amount of filiform corrosion for scribes on the matrix was greatest on the alkaline-cleaned samples, followed by the deoxidized samples, with the conversion-coated samples performing the best. The amount of filiform corrosion for scribes around the fasteners was highest for the deoxidized sample.