The Effect of Spray Testing Condition on the Corrosion Performance of Hydrothermally Sealed Anodic Oxide on a 5005 Aluminum Alloy: Comparison between Neutral Salt Spray, Acetic Salt Spray and Prohesion Testing Methods

Abstract

In this work, the output of different accelerated tests on anodic aluminum oxide (AAO) coatings developed on AA5005 aluminum alloy (sulfuric acid bath and hydrothermal sealing) has been investigated. In particular, three corrosion testing methods, namely neutral salt spray test (NSS), acetic acid salt spray (AASS) and prohesion test, have been performed on the sealed AAO-coated panels in order to investigate the reliability of the obtained results to the electrochemical impedance ones. NSS and prohesion testing results are found to align with findings from electrochemical impedance spectroscopy (EIS). The acetic salt spray test appears to be highly corrosive, causing rapid depletion of the oxide layer’s protective capabilities, as indicated the EIS analysis. The findings suggest that the deterioration of the oxide layer’s barrier properties appears to be more pronounced than what optical image analysis suggests.