Corrosion inhibition of aluminium alloy AA6063-T5 by vanadates: Local surface chemical events elucidated by confocal Raman micro-spectroscopy. (March 2019)

• Record Type: Journal Article
• Authors: Kharitonov, Dmitry S.; Sommertune, Jens; Örnek, Cem; Ryl, Jacek; Kurilo, Irina I.; Claesson, Per M.; Pan, Jinshan
• Is Part Of: Corrosion science. Volume 148(2019)
• Page Start: 237
• Page End: 250
• Publication Date: 2019-03
• Subjects: A. Aluminium -- A. Alloy -- B. Raman spectroscopy -- B. SEM -- B. XPS -- C. Vanadate inhibitor; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2018.12.011
• Languages: English
• ISSNs: 0010-938X

Abstract

Highlights: 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. Abstract: Chemical interactions between aqueous vanadium species and aluminium alloy AA6063-T5 were investigated in vanadate-containing NaCl solutions. Confocal Raman and X-ray photoelectron spectroscopy experiments were utilised to gain insight into the mechanism of corrosion inhibition by vanadates. A greenish-grey coloured surface layer, consisting of V +4 and V +5 polymerized species, was seen to form on the alloy surface, especially on top of cathodic micrometre-sized IMPs, whereby suppressing oxygen reduction kinetics. The results suggest a two-step mechanism of corrosion inhibition in which V +5 species are first reduced to V +4 or V +3 species above cathodic IMPs, and then oxidized to mixed-valence V +5 /V +4 polymerized compounds.