Corrosion of 316 SS in chloride molten salt for thermal energy storage: Inhibitory effects of Al powder

Tianjiao Li, Ming Zhu, Peng Deng, Anqi Chen, Haitong Yan, Han Yi
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Abstract

MgCl2-KCl-NaCl is regarded as one of the most prospective high-temperature thermal energy storage mediums and heat transfer fluids (HTF) for 3rd generation concentrated solar power (CSP) systems. However, high corrosion to alloys limits its application. In this paper, corrosion tests were conducted on 316 SS, in MgCl2-KCl-NaCl at 800°C with different content (0 wt.%,1 wt.%, and 10 wt.%) of Al powder addition as a corrosion inhibitor. The impact of Al powder was assessed through electrochemical methods, specifically impedance spectroscopy (EIS) and potentiodynamic polarization (PDP). Following corrosion tests, the morphologies and phase compositions of 316 SS were determined by using scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD). The addition of Al powder can significantly reduce the corrosion current density of 316 SS in MgCl2-KCl-NaCl at 800°C, which was 183.29 times higher than that with 10 wt.% without Al addition. Al and the degree increased with increasing content of Al. With the addition of 1 wt.% Al, the thickness of the diffusion layer is significantly reduced, which was 54.6 μm (100 h), 275.1 μm (200 h), 370.4 μm (300 h), and 500 μm (400 h), respectively. When the addition of Al reaches up to 10 wt.%, the inwards diffusion of Al caused the formation of Al enriched layer, which was identified as the FeAl phase, on the surface of 316 SS during the high-temperature corrosion processes. The thickness of the Al enriched layer was associated with the diffusion time of Al, and its depth was 40.4 μm (100 h), 45.3 μm (200 h), 103.5 μm (300 h), and 139.5 μm (400 h).
用于热能储存的 316 SS 在氯化物熔盐中的腐蚀:铝粉的抑制作用
氯化镁(MgCl2-KCl-NaCl)被认为是第三代聚光太阳能(CSP)系统最有前景的高温热能储存介质和传热液体(HTF)之一。然而,对合金的高腐蚀性限制了它的应用。本文在 MgCl2-KCl-NaCl 溶液(800°C)中对 316 SS 进行了腐蚀试验,并添加了不同含量(0 wt.%、1 wt.% 和 10 wt.%)的铝粉作为缓蚀剂。通过电化学方法,特别是阻抗光谱法(EIS)和电位极化法(PDP),对铝粉的影响进行了评估。腐蚀测试后,使用扫描电子显微镜与能量色散光谱仪(SEM/EDS)和 X 射线衍射仪(XRD)测定了 316 SS 的形态和相组成。结果表明,铝粉的加入能明显降低 316 SS 在 MgCl2-KCl-NaCl 溶液(800°C)中的腐蚀电流密度,是 10 wt.% 无铝粉加入时的 183.29 倍。随着 Al 含量的增加,腐蚀程度也随之增加。添加 1 wt.% Al 时,扩散层的厚度明显减小,分别为 54.6 μm (100 h)、275.1 μm (200 h)、370.4 μm (300 h) 和 500 μm (400 h)。当铝的添加量达到 10 wt.%时,在高温腐蚀过程中,铝的向内扩散导致 316 SS 表面形成富铝层,该层被确定为铁铝相。富铝层的厚度与铝的扩散时间有关,其深度分别为 40.4 μm(100 小时)、45.3 μm(200 小时)、103.5 μm(300 小时)和 139.5 μm(400 小时)。
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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