Surface and corrosion properties of AA6063-T5 aluminum alloy in molybdate-containing sodium chloride solutions. (15th July 2020)

• Record Type: Journal Article
• Authors: Kharitonov, Dmitry S.; Dobryden, Illia; Sefer, Birhan; Ryl, Jacek; Wrzesińska, Angelika; Makarova, Irina V.; Bobowska, Izabela; Kurilo, Irina I.; Claesson, Per M.
• Is Part Of: Corrosion science. Volume 171(2020)
• Publication Date: 2020-07-15
• Subjects: Aluminum -- Raman spectroscopy -- SEM -- XPS -- Scanning probe microscopy -- Molybdate inhibitor; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2020.108658
• Languages: English
• ISSNs: 0010-938X

Abstract

Highlights: Intermodulation electrostatic force microscopy revealed variations of Volta-potential over the AA6063-T5 alloy with high spatial resolution. Fe-rich intermetallic particles in the AA6063-T5 alloy are initiation cites for the molybdate inhibition process. XPS and confocal Raman measurements revealed the chemical state of molybdenum compounds. The inhibition effect is provided by a surface film consisting of mixed Mo(IV), and Mo(V), Mo(VI) species. The inhibition mechanism by aqueous molybdate species has been proposed. Abstract: Corrosion properties of aluminum alloy AA6063-T5 were investigated in molybdate-containing NaCl solutions. Electrochemical, microscopic, and spectroscopic experiments were utilized to examine the mechanism of corrosion inhibition by molybdates. SEM-EDX, magnetic force, and intermodulation electrostatic force microscopy data suggested that the inhibition initiation preferentially occurred over Fe-rich cathodic IMPs. Spectroscopic measurements demonstrated that the formed surface layer consists of mixed Mo(VI, V, IV) species. This layer provided inhibition with an efficiency of ∼90% after 4 h of exposure. High efficacy of ∼70% was achieved even after one week of exposure. A two-step oxidation-reduction mechanism of corrosion inhibition by aqueous molybdates was proposed.