Effect of SiO2-reinforcement and alkali treatment on the corrosion resistance of plasma electrolytic oxide coating on AZ31 magnesium alloy

IF 7.5 Q1 CHEMISTRY, PHYSICAL

Applied Surface Science Advances Pub Date : 2024-08-26 DOI:10.1016/j.apsadv.2024.100631

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Abstract

Plasma electrolytic oxidation (PEO) produces an oxide coating containing pores and cracks lowering corrosion protection. The defects can be sealed by in-situ or post-treatment methods. This work compares the sealing effect of SiO₂ particles and post-alkali treatment on the corrosion resistance of PEO coatings formed on AZ31 magnesium (Mg) alloy. PEO was conducted in a phosphate-based electrolyte containing 2 g/l nanoparticle SiO₂ at a constant current density of 300 A/m² for 10 min. The post-alkali treatment was performed in 0.5 M NaOH solution at 80 °C for 30 min. The corrosion resistance was evaluated using polarization, electrochemical impedance spectroscopy, and weight loss tests. The SiO₂ particles were successfully embedded uniformly in the Mg₃(PO₄)₂ coating, enhancing the coating compactness and stability. The reinforced coating exhibited ten times higher impedance modulus and lower corrosion current density. The post-alkali treatment improved corrosion resistance but not as high as the SiO₂ reinforcement. The impedance modulus of the alkali-treated specimen increased five times, and the corrosion current density decreased three times of the base coating. The weight loss test consistently showed that the SiO₂-reinforced coating generated lower mass loss during 14 days of immersion in simulated body fluid.

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二氧化硅强化和碱处理对 AZ31 镁合金等离子电解氧化物涂层耐腐蚀性的影响

等离子电解氧化（PEO）产生的氧化物涂层含有气孔和裂缝，可降低腐蚀防护能力。这些缺陷可通过原位或后处理方法进行密封。本研究比较了二氧化硅颗粒和后碱处理对 AZ31 镁（Mg）合金上形成的 PEO 涂层耐腐蚀性的密封效果。PEO 在含有 2 g/l 纳米颗粒 SiO2 的磷酸盐电解液中以 300 A/m2 的恒定电流密度进行 10 分钟。后碱处理在 0.5 M NaOH 溶液中进行，温度为 80 °C，时间为 30 分钟。使用极化、电化学阻抗光谱和失重测试对耐腐蚀性能进行了评估。二氧化硅颗粒成功地均匀嵌入了 Mg3(PO4)2 涂层，增强了涂层的致密性和稳定性。增强涂层的阻抗模量提高了十倍，腐蚀电流密度降低了。后碱处理提高了耐腐蚀性，但不如 SiO2 增强层高。碱处理试样的阻抗模量提高了五倍，腐蚀电流密度降低了三倍。失重试验一致表明，SiO2 增强涂层在模拟体液中浸泡 14 天后产生的质量损失较小。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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