EVALUATION OF ANODISED COATINGS APPLIED TO MAGNESIUM ALLOY ZE41A-T5 FOR POTENTIAL USE IN RAN SEAHAWK HELICOPTERS

摘要

Corrosion of magnesium components (e.g. gearbox and generator housings) used in Seahawk helicopters flown by the Royal Australian Navy imposes a large maintenance burden on the operators and maintainers. Corrosion occurs at the attachment points and sharp corners, usually from damage during use or as a result of maintenance procedures. The magnesium components are costly to maintain and replace when the damage exceeds design limits. The current protection scheme used on the Seahawk helicopter consists of an anodised coating, sealer, primer and top coat. New anodised coatings have been developed which may provide greater protection than the currently used Dow 17. These new coatings have the added benefit of being environmentally friendly and do not make use of hexavalent chromium, a known carcinogen, in their formulations. This paper compares the performance of three commercially available alternative anodised coatings, as part of the corrosion protection scheme. The comparison is based on a series of laboratory tests that include: paint adhesion tests; electrochemical tests; and corrosion tests, and outdoor exposure trials.