The effect of composition and thickness on the mechanism and kinetics of filiform corrosion occurring on zinc-aluminium-magnesium coated steel. (February 2021)

• Record Type: Journal Article
• Authors: Wint, N.; Eaves, D.; Williams, G.; McMurray, H.N.
• Is Part Of: Corrosion science. Volume 179(2021)
• Publication Date: 2021-02
• Subjects: A Steel -- A Magnesium -- A Metal coatings -- C atmospheric corrosion -- C polymer coatings; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2020.109168
• Languages: English
• ISSNs: 0010-938X

Abstract

Highlights: Immersion of Zn-Al-Mg coatings of varying composition and thickness in acetic acid. Substrate iron exposure time increases with Zn-Al-Mg thickness and Al content. Filiform corroded area rate increases with coating thickness and Al (≤6 wt. %). Filiform propagation rate determined by time to iron exposure. Modification in coating composition can reduce rate of filiform corrosion. Abstract: The effect of coating thickness and composition on the kinetics of acetic acid-induced filiform corrosion (FFC) on Zinc-Aluminium-Magnesium (ZAM) coated steel is investigated. Scribe defects are created in organic coatings applied to ∼10 μm coatings of varying composition (1−6 wt.%. Al, 1−3 wt. % Mg), and fixed composition (Zn-1.5 wt. % Al- 1.5 wt.% Mg) but varying thickness (5−27 μm). FCC decreases with increasing Al (at fixed wt. % Mg) and thickness. A linear trend exists between thickness and iron exposure time. Findings are consistent with FFC advancing via a penetrative coating mechanism whereby exposed iron couples to the coating.