Characterisation of the galvanic protection of zinc flake coating by spectroelectrochemistry and industrial testing

Feldmann, Florian; Mears, Laura L. E.; Roth, Marcel; Valtiner, Markus

doi:10.1002/maco.202213719

Cited by 3 publications

(1 citation statement)

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“…Indeed, as the lines in Figure 14 were acquired at increasing X positions, the first lines obtained at the beginning of the exposure (eventually after each tip polishing step) provided measurable tip current, which next decays as a result of tip fouling. This excessive formation of corrosion products could be considered even detrimental to corrosion protection, as the surge of major heterogeneities and white rust at a faster rate may compromise the chemical and mechanical integrity of the material, alongside disadvantageous flexibility and adherence [57]. The local deposition of protective corrosion products must be associated primarily with the development of pH gradients and the presence of sufficient M n+ cations for the The local deposition of protective corrosion products must be associated primarily with the development of pH gradients and the presence of sufficient M n+ cations for the precipitation of metal hydroxides and/or carbonates [37].…”

Section: Electrochemical Behaviourmentioning

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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Section: Electrochemical Behaviourmentioning

confidence: 99%