Improved Atmospheric Corrosion Testing for Aluminum Alloys, Part I: Deconstructing ASTM G85-A2

In this work, the testing environment generated during ASTM G85-A2 exposure was deconstructed for two different commercial salt spray chambers. It was found that relative humidity (RH) control was critical to obtaining consistent results among different salt spray chamber designs, and seemingly small differences in chamber operation could have a significant impact on RH and associated corrosion damage. When RH was too high during the dwell period of the wet-dry cycle, rinsing of the sample prevented the accumulation of corrosion products along grain boundaries, which was necessary for exfoliation formation. When RH during the dwell period was too low, local anodes stifled during the dry air purge and corrosion rate was very low for most of the repeating 6 hour cycle. This work was the first in a two part study.