T91耐热钢在KCl·NaCl熔盐体系中的腐蚀电化学行为

Electrochemical Corrosion Behavior of T91 Heat- Resisting Steel in KCl·NaCl Molten Salt System

为了提高生物质电厂锅炉过热器的耐熔盐腐蚀性能,采用电化学方法研究了T91耐热钢在不同温度KCl·Na Cl熔盐中的腐蚀行为。采用扫描电镜及X射线衍射仪分析腐蚀形貌及腐蚀产物物相组成,研究了温度对T91耐热钢熔盐热腐蚀性能的影响。结果表明:腐蚀初期,T91耐热钢腐蚀较快,其腐蚀电化学阻抗谱呈典型的受氧化剂粒子扩散控制的特征;随着腐蚀的进行,T91耐热钢表面逐渐形成了Fe Cr2O4晶尖石型氧化膜,腐蚀速率显著降低;腐蚀后期电化学反应速度主要受金属腐蚀荷电粒子在氧化膜中的迁移速率控制;随着腐蚀温度的升高,T91耐热钢的自腐蚀电流密度逐渐增加,其耐腐蚀性能减弱;根据Arrhenius公式计算得出T91在KCl·Na Cl熔盐体中的腐蚀反应活化能为33.235 k J/mol。

Electrochemical methods were employed to study the corrosion behavior of T91 heat-resisting steel in KCl·NaCl molten salt system.The scanning electron microscope and X-ray diffractometer were used to analyze the corrosion morphology and phase compositions of corrosion products,and further investigate the influence of temperature on the molten salt corrosion resistance of T91 heat-resisting steel.Results showed that at the initial corrosion stage,T91 heat-resisting steel was corroded more quickly,and the corrosion electrochemical impedance spectroscopy exhibited typical characteristic controlled by oxidizer particle diffusion.Afterwards,with the corrosion process extending,a FeCr_2O_4 spinel-type oxide film was formed on the surface of T91 heat-resisting steel,and the corrosion rate decreased dramatically.At the later corrosion stage,the electrochemical reaction speed was mainly controlled by the migration rate of metal corrosion charged particles in oxidation film,and the corrosion resistance reduced.Besides,by calculation with Arrhenius formulas,the corrosion activation energy of T91 heat-resisting steel in KCl·NaCl molten salt system was 33.235 kJ/mol.