Protection of Mg Alloys against Galvanic and Other Forms of Corrosion

Zheng, W.; Derushie, C.; Lo, Jason

doi:10.4028/www.scientific.net/msf.488-489.787

Cited by 2 publications

(2 citation statements)

References 7 publications

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“…; frequently followed by a final layer of sealant and/or paint . In single-and multi-layer coating concepts, the interface between the substrate alloy and the initial coating layer is critical to coating adherence and performance.Delamination or through attack in this region can allow the environment to access the underlying alloy and result in local corrosion and coating failure.Chemical conversion coatings are frequently used industrially as the first coating step after surface cleaning due to their relatively low cost and ease of implementation [17,19,29,30,33,38]. They are primarily used to provide a receptive surface for subsequent coating layer step adherence, but can also contribute to overall corrosion resistance of the multi-layer coating system [17,19,23,26].…”

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confidence: 99%

Advanced characterization study of commercial conversion and electrocoating structures on magnesium alloys AZ31B and ZE10A

Brady

Leonard

Meyer

et al. 2016

Surface and Coatings Technology

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The local metal-coating interface microstructure and chemistry formed on commercial magnesium alloys Mg-3Al-1Zn (AZ31B) and Mg-1Zn-0.25Zr-<0.5Nd (ZE10A, ZEK100 type) were analyzed as-chemical conversion coated with a commercial hexafluoro-titanate/zirconate type + organic polymer based treatment (Bonderite® 5200) and a commercial hexafluorozirconate type + trivalent chromium Cr 3+ type treatment (Surtec® 650), and after the same conversion coatings followed by electrocoating with an epoxy based coating, Cathoguard® 525.Characterization techniques included scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and cross-section scanning transmission electron microscopy (STEM). 2Corrosion behavior was assessed in room temperature saturated aqueous Mg(OH) 2 solution with 1 wt.% NaCl. The goal of the effort was to assess the degree to which substrate alloy additions become enriched in the conversion coating, and how the conversion coating was impacted by subsequent electrocoating. Key findings included the enrichment of Al from AZ31B and Zr from ZE10A, respectively, into the conversion coating, with moderate corrosion resistance benefits for AZ31B when Al was incorporated. Varying degrees of increased porosity and modification of the initial conversion coating chemistry at the metal-coating interface were observed after electrocoating.These changes were postulated to result in degraded electrocoating protectiveness. These observations highlight the challenges of coating Mg, and the need to tailor electrocoating in light of potential degradation of the initial as-conversion coated Mg alloy surface. IntroductionMagnesium and its alloys are of great interest for engineering applications ranging from functional uses such as biomedical implants to structural alloys to achieve automotive and aircraft vehicle light weighting [1][2][3]. In vehicle light weighting applications, the rapid corrosion of Mg, particularly when exposed to salt species under aqueous conditions, is a key issue [4][5][6][7][8][9][10][11][12][13][14][15][16].Alloying generally results in only moderate improvement in the aqueous corrosion resistance of Mg. Therefore, coatings are typically used to provide corrosion protection for Mg components [17][18][19][20][21].Coatings for Mg structural components generally utilize a multi-layer strategy, involving an initial cleaning step; a surface pre-treatment such as chemical or electrochemical conversion coatings, surface alloying, anodization, etc.; a second coating layer such as electrocoatings, platings, powder coatings, organic coatings, etc.; frequently followed by a final layer of sealant and/or paint . In single-and multi-layer coating concepts, the interface between the substrate alloy and the initial coating layer is critical to coating adherence and performance.Delamination or through attack in this region can allow the environment to access the underlying alloy and result in local corrosion and coating failure.Chemical conversion coatings are frequently used industrially as the ...

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Advanced characterization study of commercial conversion and electrocoating structures on magnesium alloys AZ31B and ZE10A

Brady

Leonard

Meyer

et al. 2016

Surface and Coatings Technology

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“…The anodic oxidation (AO) film in Mg-MgO-Cu coating could not improve the corrosion resistance of samples, but it could avoid the galvanic corrosion between Mg and Cu (Mg as the anode), and maintain the corrosion resistance of MAC and MACP. 31,32 So, the PHB films could improve the corrosion resistance of materials obviously.…”

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The effect of composite PHB coating on the biological properties of a magnesium based alloy

Liang

Liu

et al. 2021

J Biomater Appl

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Magnesium alloys have been widely investigated as biodegradable cardiovascular temporal implants due to their better mechanical properties and biocompatibility, but the rapid degradation limited its application. In this study, the anodic oxidation-Cu structure was used to improve the adhesive strength and stability between poly-β-hydroxybutyrate (PHB) and magnesium alloys, and the effects of anodic oxidation magnesium alloys with copper film and PHB film (MACP) on human umbilical vein endothelial cells (HUVECs), blood compatibility and antibacterial properties were investigated in this research. As the result, the MACP structure had a stable structure and better corrosion resistance, and significant antibacterial properties. The coating would not affect the original excellent biocompatibility of the magnesium alloy. It was indicated that MACP was a potential surface modification strategy for vascular stents candidate material.

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Protection of Mg Alloys against Galvanic and Other Forms of Corrosion

Cited by 2 publications

References 7 publications

Advanced characterization study of commercial conversion and electrocoating structures on magnesium alloys AZ31B and ZE10A

Advanced characterization study of commercial conversion and electrocoating structures on magnesium alloys AZ31B and ZE10A

The effect of composite PHB coating on the biological properties of a magnesium based alloy

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