Laser densification of sol–gel silica coatings on aluminium matrix composites for corrosion and hardness improvement

Sol–gel coatings are usually densified using a thermal treatment stage in oven at temperatures above 500 °C that can cause in low melting temperature substrates a decrease in the substrate mechanical properties. The use of a high power diode laser to densify sol–gel silica coatings previously settled on aluminium matrix composite substrates resulted in consolidated coatings that provide effective corrosion protection and unmodified or even improved substrate properties. After 168 h of immersion in an aggressive electrolyte (3.5 wt.% NaCl aqueous solution), the laser treated sol–gel silica coatings showed better corrosion rates and polarization resistances than the in oven heat treated coatings. Moreover, the hardness of the substrates after laser treatment of the coatings was 45% higher than that of the heat treated ones.