Laser Surface Modification and Galvanic Protection of 5XXX

Exfoliation corrosion of 5XXX series aluminum alloy is an issue related to sensitization of the aluminum substrate wherein internal stresses drive delamination of highly elongated outer layers due to preferential corrosion paths and volumetric expansion. The Navy is interested in preventing this corrosion to decrease lifetime costs on Littoral Combat Ships, Ship-to-Shore Connector vessels, and Ticonderoga class ships. In Phase I, Luna investigated and demonstrated feasibility of using a laser surface modification (LSM) treatment on the surface of the aluminum in order to reduce exfoliation corrosion LSM processed coupons exhibited reduced exfoliation corrosion susceptibility as demonstrated via potentiodynamic electrochemical testing, ASTM G66 ASSET exfoliation testing, ASTM G67 Nitric Acid Mass Loss Testing (NAMLT), and via in-situ stress-corrosion cracking (SCC) testing. In Phase II, Luna will scale up the treatment technology further using higher power laser components. Luna will assess 5XXX coupons using several techniques, including traditional accelerated corrosion testing (ASTM B117, ASTM G85-A5, GMW 14872), ASTM G47, ASTM G66, SEM/EDS analysis, and corrosion modeling. Luna will develop an integrated solution using available laser modules coupled with robotics to ensure consistent and repeatable processing.