Impact of alkaline and acid treatment on the surface chemistry of a hot-dip galvanized Zn–Al–Mg coating

Çetinkaya, Burak William; Junge, Fabian; Müller, Gregor; Haakmann, Florian; Schierbaum, K.D.; Giza, M.

doi:10.1016/j.jmrt.2020.11.070

Cited by 22 publications

(6 citation statements)

References 46 publications

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“…After MgZn 2 dissolves, it provides Mg 2+ cations and reacts with OH − to form Mg(OH) 2 precipitates, while Zn 2+ and Zn(OH) 2 eventually form ZnO. The precipitation of Mg(OH) 2 lowers the pH value, thereby creating the thermodynamic conditions for the formation of the water-insoluble simonkolleite (Zn 5 Cl 2 (OH) 8 •H 2 O) [13][14][15]. However, partial studies show that due to the relatively poor stress-strain behavior of MgZn 2 , it is easy to produce cracks during deformation processing, which leads to a decrease in the material performance.…”

Section: Introductionmentioning

confidence: 99%

Effect of Al/Mg Ratio on the Microstructure and Phase Distribution of Zn-Al-Mg Coatings

Zhang,

Zhao

et al. 2023

Metals

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In contrast with studies such as those on the effect of a single elemental variable on Zn-Al-Mg coatings, Mg/Al is considered a variable parameter for evaluating the microstructure of Zn-Al-Mg coatings in this work, and the combined effect of the two elements is also taken into account. The Mg/Al ratios in the continuous hot-dip plating of low-alumina Zn-Al-Mg coatings were 0.63, 0.75, 1.00, 1.25, and 1.63. respectively, and the microstructures of the different coatings were observed using scanning electron microscopy (SEM). The surface elemental distributions of the coatings were analyzed with energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) analysis to understand the phase distributions of the coatings, which mainly consisted of a zinc monomeric phase, a binary eutectic phase (Zn/MgZn2), and a ternary eutectic phase (Zn/Al/MgZn2). Statistical calculations of the phase distributions in colored SEM images were performed using ImageJ-win64 software, comparative analysis of the solidification simulation results was carried out with thermodynamic simulation software (PANDAT-2023), and evaluation of the corrosion resistance of the platings was performed using macroscopic cyclic immersion corrosion experiments. The results show that with the increase in the Mg/Al ratio, the binary eutectic phase in the coatings gradually increased, the variation trend of the ternary eutectic phase was not obvious, and the corrosion resistance of the coatings gradually improved.

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Section: Introductionmentioning

confidence: 99%

Effect of Al/Mg Ratio on the Microstructure and Phase Distribution of Zn-Al-Mg Coatings

Zhang,

Zhao

et al. 2023

Metals

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“…Li et al [ 7 ] remarkably improved the adhesion of Zn coating after the cold galvanizing by the use of γ-chloropropyl triethoxysilane. Cetinkaya et al [ 8 ] reported the impact of chemical treatment on Zn-Al-Mg coating produced by a hot-dip process in order to increase Zn fraction at the coating surface. The influence of galvanizing temperature on corrosion resistance was also investigated [ 9 ], as well as the contribution of Mn to the morphology and corrosion resistance of Zn coating [ 10 ].…”

Section: Introductionmentioning

confidence: 99%

Magnetic Measurement of Zn Layer Heterogeneity on the Flange of the Steel Road Barrier

et al. 2022

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This study deals with monitoring of Zn layer heterogeneity on the flange of steel road barriers using magnetic measurements. The Barkhausen noise technique is employed for such purpose, and parameters extracted from Barkhausen noise signals are correlated with the true thickness of the Zn layer. The true values of the Zn layer were obtained from the metallographic images, as well as the thickness gauge CM-8825FN (Guangzhou Landtek Instruments Co. Ltd., Guangzhou, China) device. It was observed that the diffusion region lies below the Zn protective layer, which makes the thickness of the Zn layer obtained from the CM-8825FN device thicker than that measured on the metallographic images. For this reason, the chemical gradient of Zn below the Zn layer can be reported, and it affects Barkhausen noise emission. Barkhausen noise decreases along with increasing thickness of the Zn layer, and Barkhausen noise envelopes are shifted to stronger magnetic fields. The number of strong MBN pulses drops down with the increasing thickness of Zn coating at the expense of the increasing number of the weak MBN pulses. The thickness of Zn coating can be polluted by the solidification of Zn melt after galvanizing. The presence of the diffusion layer dims the contrast between ferromagnetic and paramagnetic phases.

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“…[17][18][19][20] The same surfacescience oriented approach has been used by other groups of authors for stainless and hot-dip galvanized steel to study the effects of alkaline cleaning. 21,22 In a recent work Çetinkaya et al 23 studied the effects of treating Zn-Al-Mg coatings with strongly alkaline and acidic solutions and concluded that the coatings can be more consistently activated by acidic cleaners due to effective increase of Zn at the surface. This, according to the authors Çetinkaya et al, should enhance the applicability of adhesives as well as conversion chemistries designed for zinc-rich substrates to yield improved bonding properties on such Zn-Al-Mg coatings activated by acidic solutions.…”

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confidence: 99%

Alkaline Cleaning of Zn–Al–Mg Hot-Dip Galvanized Steels: Mechanisms and Surface Oxide Chemistry

Пономарева

Nadlinger

Schimo-Aichhorn

et al. 2023

J. Electrochem. Soc.

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Alkaline cleaning of Zn–Al–Mg coated hot-dip galvanized steel is a central process in the industrial galvanized steel production. This process removes carbonaceous contaminants from the surface and modifies the surface chemistry profoundly. We implement a combined analytical and surface science approach to characterize the dissolution mechanism and surface chemistry of Zn-Al-Mg coatings after treatment with industrial cleaners with pH 9.3 and 12.7, respectively. Our data indicate that weak alkaline cleaning can significantly increase the surface concentration of Zn-oxide, while strong alkaline cleaning dissolves the native oxide and generates a transient Zn/Mg-hydroxide on the surface. The observed dissolution mechanisms are largely consistent with the expectations from the Pourbaix diagrams, i.e. at pH 12.7 aluminium dissolution is expected while Mg is stable and forms a transient passive film. In contrast, mild alkaline cleaning at pH 9.3 is dominated by Mg and Zn dissolution, while the native Al passive film remains stable. Hence the cleaning provides an effective direct modification of the surface chemistry for subsequent process steps during the coating. Mild alkaline cleaning offers an increase of Zn at the surface, which has important implications for subsequent conversion and adhesive applications, that have been traditionally optimized for pure Zn coatings.

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Impact of alkaline and acid treatment on the surface chemistry of a hot-dip galvanized Zn–Al–Mg coating

Cited by 22 publications

References 46 publications

Effect of Al/Mg Ratio on the Microstructure and Phase Distribution of Zn-Al-Mg Coatings

Effect of Al/Mg Ratio on the Microstructure and Phase Distribution of Zn-Al-Mg Coatings

Magnetic Measurement of Zn Layer Heterogeneity on the Flange of the Steel Road Barrier

Alkaline Cleaning of Zn–Al–Mg Hot-Dip Galvanized Steels: Mechanisms and Surface Oxide Chemistry

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