Localized corrosion of laser surface melted 2024-T351 aluminium alloy

Laser surface melting of 2024-T351 aluminium alloy with a CO2 laser operating at 2 kW with a spot size of 1.5 mm and a substrate traverse rate of 20 mm s(-1) produced a relatively thin surface-melted layer with a refined microstructure and a modified distribution of the alloying elements. The laser treatment changed both the anodic polarization behaviour and the form of localized corrosion in deaerated 3% NaCl solution. Immersion tests in the same solution under the condition of natural aeration showed that for the as-received alloy both intergranular and pitting corrosion occurred with pits distributed mainly along the rolling direction while for the laser surface melted material only pitting corrosion was present with pits distributed uniformly. This difference in corrosion behaviour as a result of laser surface melting is attributed to changes in the distribution and composition of the second-phase particles present in the alloy.