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首页> 外文期刊>Journal of Materials Engineering and Performance >Corrosion of Stainless Steels and Carbon Steel by Molten Mixtures of Commercial Nitrate Salts
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Corrosion of Stainless Steels and Carbon Steel by Molten Mixtures of Commercial Nitrate Salts

机译：商业硝酸盐的熔融混合物对不锈钢和碳钢的腐蚀。

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The isothermal corrosion behavior of two stainless steels and a carbon (C) steel in mixtures of NaNO_3 and KNO_3 was evaluated to determine if the impurities found in commodity grades of alkali nitrates aggravate corrosivity as applicable to an advanced solar thermal energy system. Corrosion tests were conducted for approximately 7000 hours with Types 304 and 316 stainless steels at 570 deg C and A36 C steel at 316 deg C in seven mixtures of NaNO_3 and KNO_3 containing variations in impurity concentrations. Corrosion tests were also conducted in a ternary mixture of NaNO_3, KNO_3, and Ca(NO_3)_2. Corrosion rates were determined by descaled weight losses while oxidation products were examined by scanning electron microscopy (SEM), electron microprobe analysis (EPMA), and x-ray diffraction (XRD). The nitrate mixtures were periodically analyzed for changes in impurity concentrations and for soluble corrosion products. Results of these tests indicated that the short-term corrosion rates of the stainless steel specimens in many of the mixtures could be described in terms of parabolic kinetics. However, no single rate law could be assigned to the corrosion kinetics resulting from exposure in all of the mixtures. For engineering applications, corrosion rates over the entire exposure period are best described as linear with respect to time. In the binary nitrate mixtures, the annualized rates of metal loss were found to be between 6 and 15 mum/year for the stainless steel specimens at 570 deg C depending on the particular mixture. Metal loss for the C steel specimens immersed in these same mixtures at 316 deg C extrapolated to approximately 1-4 mum/year. SEM and XRD revealed that the complex, multiphase surface oxides formed on the stainless steel coupons were composed primarily of iron-chromium spinel, iron oxides, and sodium ferrite. Magnetite was the principal corrosion product formed on the carbon steel specimens. Overall, for the typical range of impurities in commercially available nitrate salts, corrosion rates for solar thermal energy applications remained acceptable for all of the materials examined.
机译：评价了两种不锈钢和碳（C）钢在NaNO_3和KNO_3的混合物中的等温腐蚀行为，以确定适用于高级太阳能热能系统的商品等级的碱金属硝酸盐中发现的杂质是否会加剧腐蚀性。在含有杂质浓度变化的NaNO_3和KNO_3的七种混合物中，分别在570℃的304型和316型不锈钢和316℃的A36 C型钢上进行了大约7000小时的腐蚀测试。在NaNO_3，KNO_3和Ca（NO_3）_2的三元混合物中也进行了腐蚀测试。腐蚀速率通过除鳞失重确定，而氧化产物通过扫描电子显微镜（SEM），电子微探针分析（EPMA）和X射线衍射（XRD）检查。定期分析硝酸盐混合物的杂质浓度变化和可溶性腐蚀产物。这些测试的结果表明，许多混合物中不锈钢试样的短期腐蚀速率可以用抛物线动力学来描述。但是，不能对暴露于所有混合物中的腐蚀动力学指定单一速率定律。对于工程应用，最好将整个暴露时间内的腐蚀速率描述为与时间呈线性关系。在二元硝酸盐混合物中，发现不锈钢样品在570摄氏度下的年化金属损失率在6到15毫米/年之间，具体取决于特定的混合物。在316℃下浸入这些相同混合物中的C型钢样品的金属损失外推至大约1-4毫米/年。 SEM和XRD结果表明，在不锈钢试样上形成的复杂的多相表面氧化物主要由铁铬尖晶石，氧化铁和亚铁酸钠组成。磁铁矿是在碳钢试样上形成的主要腐蚀产物。总体而言，对于市售硝酸盐中杂质的典型范围，太阳能热应用的腐蚀速率对于所有检查的材料仍然可以接受。

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