Corrosion inhibition of aluminium alloy AA6063-T5 by vanadates: Local surface chemical events elucidated by confocal Raman micro-spectroscopy

•In-situ and ex-situ confocal Raman measurements revealed chemical states of vanadium compounds.•The inhibition effect is mostly provided by a polymerized film with mixed V(V) and V(IV) species.•Intermetallic particles in the alloy have a strong influence on the vanadate inhibition process.•Deposition of polymerized vanadate compounds is mainly connected with micrometer-sized IMPs.•The inhibition mechanism involves first reduction and then re-oxidation of the vanadium species.