Laser surface modification for corrosion protection

Laser surface modification of materials has been the subject of considerable interest as a means of enhancing the corrosion performance of metallic alloys. Microstructural modification with or without changing surface chemical composition, in terms of homogenization/refinement of microstructure, dissolution/redistribution of intermetallic particles and extended solid solubility, resulting from rapid rates of cooling, provides the basis for property enhancement. This paper reviews our work on laser surface melting and laser surface alloying for the purpose of improved corrosion performance. Microstructural evolution and corrosion performance in a range of metallic alloys, followed by different treatments with different types of lasers, are presented. For laser surface melting of aerospace light alloys (aluminium alloys and magnesium alloys), the corrosion mechanisms of the laser-melted alloys have been discussed in the consideration of electrochemical characteristics of intermetallic particles with respect to the aluminium matrix, and cooling rates leading to different degrees of refinement/removal of intermetallic particles. For laser surface alloying, an example of titanium foil alloyed with nickel or palladium has been given to demonstrate the achievement of micro-alloying using an excimer laser for improvement of corrosion protection in hot H₂SO₄ solution.