Characterization of Alkaline Cleaned and Cerium Oxide Coated Al 2024-T3

Hexavalent chromium (Cr6+), a corrosion inhibitor in conversion coatings on aluminum alloys, has been identified as carcinogenic and non-toxic substitutes must be found. Cerium oxide conversion coatings have been seen as a possible replacement. Corrosion of cerium oxide conversion coatings is sensitive to the processing conditions, including the cleaning process, cerium oxide deposition method, and post deposition phosphate treatment. The temperature of the cleaning process was identified as an important factor in salt fog performance (ASTM B117). The cleaning solution evaluated was a commercial alkaline cleaner. Aluminum alloy panels were immersed at temperatures of 45ºC, 55ºC, or 65ºC for 5 minutes. Conversion coatings were deposited on the cleaned substrates by spraying a cerium-based solution on the panels. The effect of cleaning solution temperature on conversion coating thickness and morphology was characterized using scanning electron microscopy, and auger electron spectroscopy depth profiling