Initial dissolution of Mg-containing phase and corrosion product formation in cut-edge corrosion of Zn-11%Al-3%Mg-0.2%Si coated steel

Tokuda, Shimpei; Nishida, Yoshikatsu; Nishimoto, Masashi; Muto, Izumi; Shoji, Hiromasa

doi:10.1016/j.corsci.2023.111605

Cited by 4 publications

(1 citation statement)

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“…Frequently associated with the formation of stable layered double hydroxide (LDH) [23,24], the improved corrosion protection of ZnMgAl coatings, compared to pure zinc or binary zinc coatings, still presents unclear features. While salt spray and conventional electrochemistry of these alloys are frequently performed for their characterization [11,25,26], a comprehensive understanding of chemical interaction mechanisms requires the synthesis of micrometer-and nanometer-scale data from the activated sites [27], which is remarkable considering the microstructural heterogeneity of ternary-alloyed coatings [28].…”

Section: Introductionmentioning

confidence: 99%

Contributions to a More Realistic Characterization of Corrosion Processes on Cut Edges of Coated Metals Using Scanning Microelectrochemical Techniques, Illustrated by the Case of ZnAlMg-Galvanized Steel with Different Coating Densities

Bolsanello,

Abreu García,

da Cruz Lima

et al. 2024

Materials

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Corrosion processes at cut edges of galvanized steels proceed as highly localized electrochemical reactions between the exposed bulk steel matrix and the protective thin metallic coating of a more electrochemically active material. Scanning microelectrochemical techniques can thus provide the spatially resolved information needed to assess the corrosion initiation and propagation phenomena, yet most methods scan cut edge sections as embedded in insulating resin to achieve a flat surface for scanning purposes. In this work, the galvanized coatings on both sides of the material were concomitantly exposed to simulated acid rain while characterizing the cut edge response using SECM and SVET techniques, thereby maintaining the coupled effects through the exposure of the whole system as rather realistic operation conditions. The cut edges were shown to strongly promote oxygen consumption and subsequent alkalization to pH 10–11 over the iron, while diffusion phenomena eventually yielded the complete depletion of oxygen and pH neutralization of the nearby electrolyte. In addition, the cathodic activation of the exposed iron was intensified with a thinner coating despite the lower presence of sacrificial anode, and preferential sites of the attack in the corners revealed highly localized acidification below pH 4, which sustained hydrogen evolution at spots of the steel-coating interface.

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