Mitigation of Fireside Corrosion of Stainless Steel in Power Plants: A Laboratory Study of the Influences of SO2 and KCl on Initial Stages of Corrosion

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• 作者：Sofia Karlsson ; Torbj枚rn Jonsson ; Josefin Hall ; Jan-Erik Svensson ; Jesper Liske
• 刊名：Energy & Fuels
• 出版年：2014
• 出版时间：May 15, 2014
• 年：2014
• 卷：28
• 期：5
• 页码：3102-3109
• 全文大小：464K
• 年卷期：v.28,no.5(May 15, 2014)
• ISSN：1520-5029

文摘

The effect of SO₂(g) on the initial oxidation of the stainless-steel 304L, sprayed with 0.1 mg/cm² KCl and exposed in 5% O₂ and 40% H₂O at 600 掳C, was investigated. In the absence of SO₂(g), KCl accelerates the corrosion attack by the formation of K₂CrO₄. The reaction with KCl depletes the oxide in chromium and converts it into an iron-rich, poorly protective oxide. When SO₂(g) was introduced to the gas flow, KCl rapidly transformed into K₂SO₄. In contrast to KCl, K₂SO₄ does not form K₂CrO₄. Hence, it does not accelerate the corrosion rate. Although the conversion of KCl to K₂SO₄ is fast, the corrosion rate of KCl samples exposed in the presence of SO₂(g) is higher than samples exposed in the presence of K₂SO₄. It is therefore suggested that small amounts of unreacted KCl react initially with the protective oxide, forming K₂CrO₄, which depletes the oxide in chromium. However, because of the presence of SO₂(g), K₂CrO₄ immediately reacts with SO₂(g) to form K₂SO₄. This study shows that the initial stages of the corrosion attack are of great importance. The initial complex interactions between the flue gas, deposit, and oxide scale affect the future corrosion resistance of the steel.