Two super duplex stainless steels (SDSS) with different W content, namely UNS S32750 (W-free) and UNS S39274 (2.1 wt.% W), were tested in simulated crevice corrosion environments to determine the influence of W on their corrosion resistance. Anodic potentiodynamic polarization experiments were performed in two different crevice-like-solutions: 1 M HCl (as reference for a pH = 0 environment), and 7 M LiCl, adjusted to the same pH value. Galvele’s critical acidification model was used to estimate the theoretical critical potential (E_crit) and comparatively evaluate the corrosion resistance of the two SDSS. The anodic potentiodynamic polarization results showed a statistically significant difference between the two materials in only one test condition, i.e., 7 M Cl⁻ at 60 °C. Additionally, the quantification of chemical dissolution of the metal cations after the tests suggested a surface enrichment in W only in the 7 M chloride solution. Scanning electron microscope (SEM) analysis indicated a uniform dissolution experienced by UNS S32750 in this environment, whereas UNS S39274 suffered selective corrosion of the ferrite-phase. These observations were reflected in a slight increase in the E_crit values of UNS S32974 estimated with Galvele’s model.

中文翻译：

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使用临界酸化模型估算W对25Cr超级双相不锈钢局部耐腐蚀性能的影响

在模拟的缝隙腐蚀环境中测试了两种具有不同W含量的超级双相不锈钢（SDSS），即UNS S32750（无W）和UNS S39274（2.1 wt。％W），以确定W对耐蚀性的影响。在两种不同的缝隙状溶液中进行阳极电势极化实验：1 M HCl（作为pH = 0环境的参考）和7 M LiCl（调节至相同的pH值）。Galvele的临界酸化模型用于估计理论临界电位（E _crit）并比较评估两个SDSS的耐腐蚀性。阳极电位极化结果显示仅在一个测试条件下，即，-7 M氯两种材料之间存在统计学差异显著^-在60°C下。另外，测试后对金属阳离子化学溶解的定量分析表明仅在7 M氯化物溶液中表面富集了W。扫描电子显微镜（SEM）分析表明，UNS S32750在这种环境中经历了均匀的溶解，而UNS S39274遭受了铁素体相的选择性腐蚀。这些观察结果反映在略有增加é_暴击与Galvele的模型估计UNS S32974的值。