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Evaluation of the corrosion protection of organic-coated zinc-alloy galvanised steels using novel, environmentally-friendly corrosion inhibitor pigments

Gwynfor Callaghan, Sonny Ngo, Geraint Williams

Progress in Organic Coatings, Volume: 210, Start page: 109646

Swansea University Authors: Gwynfor Callaghan, Geraint Williams

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DOI (Published version): 10.1016/j.porgcoat.2025.109646

Abstract

The corrosion behaviour of steel coated with either: a primarily zinc coating comprised of 0.15 wt% Al (HDG) or a zinc-aluminium-magnesium coating, 1.6 wt% Mg, 1.6 wt% Al, and 96.8 wt% Zn (ZAM) are investigated in the presence of industry standard and emerging, environmentally-friendly corrosion inh...

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Published in: Progress in Organic Coatings
ISSN: 0300-9440 1873-331X
Published: Elsevier BV 2026
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URI: https://cronfa.swan.ac.uk/Record/cronfa70311
Abstract: The corrosion behaviour of steel coated with either: a primarily zinc coating comprised of 0.15 wt% Al (HDG) or a zinc-aluminium-magnesium coating, 1.6 wt% Mg, 1.6 wt% Al, and 96.8 wt% Zn (ZAM) are investigated in the presence of industry standard and emerging, environmentally-friendly corrosion inhibitor technologies. With this paper evaluating the inhibitory performance of a functionalised oxy-amino-phosphate-salt of magnesium (OPMG), a hydrotalcite carbonate clay loaded with 4-aminobenzoic acid (HT-PABA), a calcium ion exchange pigment (Ca-Ex), and an inhibitor based on 2-(1,3-benzothiazol-2-ylithio) succinic acid (BTSA) dispersed in model poly-vinyl-butyral (PVB) coatings and 3.5 wt% NaCl (aq) solutions. With their inhibitory performance evaluated against two corrosion-driven coating failure mechanisms: cathodic disbondment (CD), and filiform corrosion (FFC) as a function of inhibitor loading. In the case of CD, an inhibitor ranking order of BTSA > HT-PABA > OPMG > Ca-Ex is observed, while OPMG and HT-PABA are the most effective at slowing rates of FFC. Potentiodynamic and scanning vibrating electrode (SVET) experiments were conducted to evaluate the efficiency of the most promising inhibitors at slowing rates of corrosion on the bare ZAM alloy surface and the exposed cut edges immersed in chloride solutions. With OPMG and BTSA both shown to act as net anodic inhibitors, resulting in an increase in the polarisation resistance by over an order of magnitude. Both inhibitors produced a derived 67 % reduction in total (zinc) metal loss at the exposed ZAM cut-edges over a 24 h immersion period against the control.
Keywords: Galvanised steel; Cathodic disbondment; Filiform corrosion; Corrosion inhibitive pigments; Scanning vibrational electrode technique; ZMA
College: Faculty of Science and Engineering
Funders: This work was sponsored by: Beckers Industrial Coatings, the EPSRC as part of the centre for Doctoral training in Functional Industrial Coatings (COATED) grant reference (EP/S02252X/1). The author would like to thank Beckers Industrial Coatings, the EPSRC, Swansea University, Tata steel and COATED M2A for the funding, materials and support during the EngD studentship.
Start Page: 109646

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