Corrosion effects of runway de-icing chemicals on aircraft alloys and coatings
By Huttunen-Saarivirta, E.; Kuokkala, V.-T.; Kokkonen, J. & Paajanen, H.
Published in Materials Chemistry and Physics
2011
Abstract
Corrosion effects of five runway de-icing chemicals on aluminium alloy 2024, magnesium alloy RZ5 and cadmium-plated and subsequently chromate-treated steel 4340 were investigated by cyclic polarisation measurements, open circuit potential monitoring and cyclic chemical exposure tests. The runway de-icing chemicals included in the study contained urea, which has a long history as a runway de-icing chemical, and four new commercial de-icing chemicals, which were based on betaine and potassium formate. Corrosion effects of urea on aluminium alloy 2024 were more pronounced than those of the new de-icing chemicals. In urea, the breakdown potential, indicating the onset of pitting, was clearly distinguishable in the cyclic polarisation curve and pitting corrosion was detected on the specimen surface after all three types of tests. Weight losses during the chemical exposure tests were also higher for urea than for the other four chemicals, where pitting corrosion was only occasionally detected. The opposite was true in the case of magnesium alloy RZ5: although the alloy experienced general corrosion in each de-icing chemical included in the study, the rate of corrosion was often higher in the new de-icing chemicals than in urea. Corrosion effects of the five de-icing chemicals on cadmium-plated and chromate-treated high-strength steel 4340 were slightly different in all three tests, indicating that differences in coating quality, particularly in the thickness of the coating layers, might have influenced the results. Overall, however, partial loss of the coating layers occurred in all studied de-icing chemicals.