Abstract

Corrosion has severely hindered the development and application of high-temperature hydrothermal oxidation technologies for disposing of chloride-containing organic wastewater. This study explored the early corrosion behaviors of 316 stainless steel (316 SS) (UNS S31600), passivated by sodium phosphate (Na₃PO₄) in supercritical water in advance, in subcritical water (at 100, 160, 230, and 300 °C and 25 MPa) having high contents of oxygen (O₂) and sodium chloride (NaCl) for 50 h. The results show that the corrosion rate of the phosphate-passivated 316 SS was approximately half of that of the passivated 316 SS (pretreated in supercritical water without Na₃PO₄) under the same conditions. The surface oxides of the phosphate-passivated 316 SS consisted of Cr₂O₃, Fe₂O₃, CrPO₄, FePO₄, and Ni₃(PO₄)₂. The passivation pretreatment of 316 SS in supercritical water with Na₃PO₄ could form a stable and protective oxide film containing phosphates. These phosphates significantly improved the corrosion resistance of 316 SS in subcritical water (containing oxygen and chloride) by preventing corrosive substances from contacting the alloy substrate.

中文翻译：

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含氧和氯化钠的亚临界水中316不锈钢（在超临界水中用Na 3 PO 4钝化）的早期腐蚀特征

摘要

腐蚀严重阻碍了用于处理含氯有机废水的高温水热氧化技术的开发和应用。这项研究探索了预先在超临界水中，亚临界水中（在100、160、230和300°C下）用磷酸钠（Na ₃ PO ₄）钝化的316不锈钢（316 SS）（UNS S31600）的早期腐蚀行为。C和25 MPa）的氧气（O ₂）和氯化钠（NaCl）含量高，持续50 h。结果表明，磷酸盐钝化316 SS的腐蚀速率约为钝化316 SS的腐蚀速率的一半（在没有Na ₃ PO _4的超临界水中预处理））。磷酸盐钝化的316 SS的表面氧化物由Cr ₂ O ₃，Fe ₂ O ₃，CrPO ₄，FePO ₄和Ni ₃（PO ₄）_2组成。Na ₃ PO ₄在超临界水中对316 SS进行钝化预处理可形成稳定且具有保护性的磷酸盐膜。这些磷酸盐通过防止腐蚀性物质与合金基材接触，显着提高了亚临界水中（含氧和氯化物）中316 SS的耐腐蚀性。