Protection of 5XXX Aluminum from Stress Corrosion Cracking

Ship superstructures are increasingly being constructed from marine-grade aluminum alloys (5XXX-series) because they are lightweight and strong. However, sensitized 5XXX series alloys are vulnerable to inter-granular corrosion which manifests itself as stress corrosion cracking (SCC) and exfoliation corrosion, and it is virtually inevitable that the aluminum will become sensitized under normal operating conditions.. Stress corrosion cracking is particularly threatening because crack initiation and growth can be driven by stresses that are far lower tha those for normal gross failure. The primary objective of this SBIR project is to develop an innovative anticorrosion protective coating additive that affords significantly better resistance to stress corrosion cracking and exfoliation corrosion than current technologies. In the Phase II we will optimize, test, and transition a new coating additive that prevents corrosion in Series 5XXX aluminum alloys in a marine environment. In the Phase I we identified several organic molecules which were able to stop stress corrosion cracking on sensitized 5000 series aluminum. These organic molecules can be incorporated into TDA"s proprietary carrier material and added to existing coatings to provide lasting active corrosion protection in a coating via its unique delivery system. In the Phase II project we will optimize the composition of the corrosion inhibitor additive composition and its use in marine shipbuilding coatings.