ABSTRACT Hot-dipped galvanised (HDG) steel and Zn5Al-coated steel were exposed for 6 years at different atmospheric weathering sites worldwide. The mass loss of the coatings has been measured after 1, 2, 4 and 6 years of exposure. In addition, corrosion products have been determined using scanning electron microscopy, X-ray diffraction and FTIR spectroscopy. It is shown that Zn5Al is better than HDG-steel independently on the exposure duration and location. The mass loss of Zn5Al is also less dependent of the environmental parameters (such as chloride deposition, relative humidity and temperature) than HDG-steel. The ratio of performance after 6 years of exposure varied from 1.3 to 5.1 with the mean value of 3.1. The analyses of the corrosion products indicate the formation of protective Zn/Al - layered double hydroxide (LDH) and sulphate-containing corrosion products of Zn and Al after 6 years of exposure. A mechanism explaining the superior properties of Zn5Al is proposed.

中文翻译：

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Zn–5% Al 涂层钢和 HDG 在全球户外暴露期间的长期大气腐蚀

摘要 热浸镀锌 (HDG) 钢和 Zn5Al 涂层钢在全球不同的大气风化场所暴露了 6 年。在暴露 1、2、4 和 6 年后测量了涂层的质量损失。此外，腐蚀产物已使用扫描电子显微镜、X 射线衍射和 FTIR 光谱确定。结果表明，独立于暴露时间和位置，Zn5Al 优于热镀锌钢。与 HDG 钢相比，Zn5Al 的质量损失对环境参数（例如氯化物沉积、相对湿度和温度）的依赖性较小。暴露 6 年后的性能比从 1.3 到 5.1 不等，平均值为 3.1。腐蚀产物的分析表明，在暴露 6 年后形成了保护性 Zn/Al 层状双氢氧化物 (LDH) 和含硫酸盐的 Zn 和 Al 腐蚀产物。提出了解释 Zn5Al 优异性能的机制。