Complementary corrosion protection of cast AlSi7Mg0.3 alloy using Zr-Cr conversion and polyacrylic/siloxane-silica multilayer coatings

IF 6.6 2区材料科学 Q1 MATERIALS SCIENCE, MULTIDISCIPLINARY

npj Materials Degradation Pub Date : 2024-05-28 DOI:10.1038/s41529-024-00467-5

Peter Rodič, Barbara Kapun, Ingrid Milošev

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Abstract

Aluminium cast alloy AlSi7Mg0.3 is a lightweight metal commonly used in automotive, aeronautical and mechanical applications. It has good corrosion resistance but, under harsh operative conditions, would benefit from additional protection. In this study, a corrosion-protective multilayer coating system for AlSi7Mg0.3 based on hexafluoro-zirconated trivalent chromium coating (Zr-CrCC) and polyacrylic/siloxane-silica (PEHA-SS) coating was developed. The Zr-CrCC was formed by immersion of the substrate in a commercial conversion bath (SurTec® 650). PEHA-SS synthesis was based on organic precursors (2-ethylhexyl acrylate and [3-(methacryloyloxy)propyl]trimethoxysilane) and an inorganic precursor, tetraethyl orthosilicate. After deposition on AlSi7Mg0.3, each coating was first characterised individually, followed by the analysis of the multilayer using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The adhesion of the coatings was evaluated with a cross-hatch cut test. The corrosion studies in sodium chloride solution using electrochemical impedance spectroscopy and salt spray testing showed that the multilayer system is superior to individual Zr-CrCC and PEHA-SS coatings. After 4 months in 0.1 M NaCl, the multilayer-coated samples exhibited the impedance at 10 mHz in the range of GΩ cm2, while scribed samples withstood the corrosion attack in a salt spray chamber for one week. Thus, albeit only about 100 nm thick, the Zr-CrCC deposited between the substrate and a 9-micrometre thick barrier sol-gel PEHA-SS coating acts as an active corrosion protection interlayer and contributes to the overall protectiveness of the multilayer system.

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使用 Zr-Cr 转换和聚丙烯酸/硅氧烷-二氧化硅多层涂层对铸造 AlSi7Mg0.3 合金进行互补性腐蚀保护

铝铸件合金 AlSi7Mg0.3 是一种轻质金属，常用于汽车、航空和机械应用领域。它具有良好的耐腐蚀性，但在恶劣的工作条件下，需要额外的保护。本研究开发了一种基于六氟锆三价铬涂层（Zr-CrCC）和聚丙烯酸/硅氧烷-二氧化硅涂层（PEHA-SS）的 AlSi7Mg0.3 多层腐蚀保护涂层系统。Zr-CrCC 是将基底浸入商用转化槽 (SurTec® 650) 中形成的。PEHA-SS 的合成基于有机前体（2-乙基己基丙烯酸酯和[3-(甲基丙烯酰氧基)丙基]三甲氧基硅烷）和无机前体（正硅酸四乙酯）。在 AlSi7Mg0.3 上沉积后，首先对每个涂层进行了单独表征，然后使用扫描电子显微镜和能量色散 X 射线光谱对多层涂层进行了分析。涂层的附着力通过十字划痕切割试验进行了评估。在氯化钠溶液中使用电化学阻抗谱和盐雾测试进行的腐蚀研究表明，多层系统优于单独的 Zr-CrCC 和 PEHA-SS 涂层。在 0.1 M NaCl 溶液中浸泡 4 个月后，多层涂层样品在 10 mHz 时的阻抗在 GΩ cm2 范围内，而划线样品在盐雾室中承受了一周的腐蚀。因此，沉积在基底和 9 微米厚的阻挡层溶胶凝胶 PEHA-SS 涂层之间的 Zr-CrCC 虽然只有约 100 纳米厚，但却起到了活性腐蚀保护夹层的作用，并提高了多层系统的整体保护能力。

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来源期刊

npj Materials Degradation MATERIALS SCIENCE, MULTIDISCIPLINARY-

CiteScore

7.80

自引率

7.80%

发文量

审稿时长

6 weeks

期刊介绍： npj Materials Degradation considers basic and applied research that explores all aspects of the degradation of metallic and non-metallic materials. The journal broadly defines ‘materials degradation’ as a reduction in the ability of a material to perform its task in-service as a result of environmental exposure. The journal covers a broad range of topics including but not limited to: -Degradation of metals, glasses, minerals, polymers, ceramics, cements and composites in natural and engineered environments, as a result of various stimuli -Computational and experimental studies of degradation mechanisms and kinetics -Characterization of degradation by traditional and emerging techniques -New approaches and technologies for enhancing resistance to degradation -Inspection and monitoring techniques for materials in-service, such as sensing technologies