Role of atmospheric corrosion of aluminum alloys in viability of intrinsic-surface methods for tagging military hardware

摘要

A primary requirement for authentication of tags for military equipment desigated as treaty-limited items (TLIs) is that the surface topograhy of the tag area be maintained after exposure to a variety of atmospheric conditions over many years. This report summarizes the chemical and physical properties of atmospheric as they relate to localized corrosion of aluminum and aluminum alloys. The role of impurity species that exacerbate corrison, and that hence may interfere with tag verification, is discussed. Because exposure times for the tag materials are much longer than those practical in laboratory experiments, it is important to understand the kinetics of processes occurring in these alloys and the viability of various protection schemes. General principles and limitations of testing in natural atmospheres and in the laboratory are discussed. Corrosion results indicate that the tag surface must be protected, and a tag protection scheme is proposed.