Glass-like CexOy sol–gel coatings for corrosion protection of aluminium and magnesium alloys

Abstract

This work reports the preparation of glass-like, environmentally-friendly, cerium-based coatings for active corrosion protection of aluminiumandmagnesiumalloys. It describes the production of ceriumsol–gel sols from ceriumnitrate and their deposition by immersion and automatic spray onto aluminiumandmagnesiumalloys to produce uniform coatings with amorphous (glass-like) structures (CexOy). The coatings have been characterised by profilometry, scanning electron microscopy (SEM), spectral ellipsometry and UV–visible, in order to analyse the structure and density of the glass-like ceriumcoatings aswell as their redox ratio Ce4+/Ce3+ as a function of pH and sintering temperature. Finally, electrochemical measurements (EIS) and standard corrosion tests (neutral salt spray, filiform corrosion, immersion–emersion test and adhesion on embossing and T-bend test) have been performed to study the corrosion behaviour of the cerium glass-like coatings on aluminium and magnesium alloys. EIS measurements confirm the healing or blocking of the defects by the corrosion inhibiting species. Excellent corrosion protection is provided by cerium glass-like coatings, satisfying the most demanding industrial requirements.