Commercial hot‐dip galvanized zinc (Zn‐0.2% Al), galfan (Zn‐5% Al), and galvalume (Zn‐55% Al) coatings were exposed to wet scCO2, followed by an assessment of microstructural changes in the coating structure. Zinc and galfan coatings showed similar surface activity with abundant zinc dissolution and uniform corrosion product deposition. The Al‐rich phases of the galfan coating were intact in the studied atmosphere and eventually became embedded within the deposits. The zinc dissolution ended for zinc and galfan coatings when the free metal surface was blocked from the surrounding medium by a uniform corrosion product layer. Galvalume showed scarce reactivity: dissolution of zinc in the Zn‐rich interdendritic areas proceeded slowly compared to zinc and galfan, and the Al‐rich dendrites (with nm‐scale Zn inclusions) remained intact. The ion beam milling technique combined with modern nm‐resolution energy‐dispersive spectroscopy analysis enabled previously unseen visualization of the discussed corrosion processes.

中文翻译：

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铝合金热浸锌涂层在湿式超临界二氧化碳中的腐蚀机理

商用热浸镀锌 (Zn-0.2% Al)、galfan (Zn-5% Al) 和镀铝锌 (Zn-55% Al) 涂层暴露于湿 scCO 中2，然后评估涂层结构的微观结构变化。锌和加尔凡涂层表现出相似的表面活性，具有丰富的锌溶解和均匀的腐蚀产物沉积。加尔凡涂层的富铝相在研究的大气中完好无损，并最终嵌入沉积物中。当自由金属表面被均匀的腐蚀产物层与周围介质阻挡时，锌和高尔凡涂层的锌溶解结束。镀铝锌表现出稀缺的反应性：与锌和高尔凡相比，富锌枝晶间区域中锌的溶解进展缓慢，而富铝枝晶（具有纳米级锌夹杂物）保持完整。离子束铣削技术与现代纳米分辨率能量色散光谱分析相结合，实现了所讨论的腐蚀过程的前所未见的可视化。