600 MW机组汽轮机低压缸腐蚀原因分析与预防措施

Corrosion Cause Analysis and Preventive Measures of Steam Turbine Low Pressure Cylinder of 600 MW Unit

某600 MW机组在大修检查时发现汽轮机低压缸普遍锈蚀。低压缸转子经喷砂清除锈蚀产物后,底部暴露出明显坑蚀。通过扫描电镜(SEM)、能谱仪(EDS)、电感耦合等离子质谱(ICP)和离子色谱(IC)等对低压缸和其他部位(高压缸、中压缸)进行检查分析,查明腐蚀原因。经过检测分析认为,低压缸转子叶片的锈蚀主要是在停机期间形成的原位停机氧腐蚀,积盐中氯离子参与形成的含氧电化学腐蚀。停机中防锈蚀措施不当,自然冷却,真空破坏后空气侵入,湿度饱和,形成停机腐蚀条件。

It was found that the low pressure cylinder of the turbine was generally rusted during the overhaul inspection of 600 MW unit. After the rust products of the low pressure cylinder rotor was completely removed by sand blasting,the bottom showed the obvious pit corrosion. The low pressure cylinders and other parts were inspected and analyzed by electron microscopy( SEM),energy spectrum( EDS),inductively coupled plasma-mass spectrometry( ICP) and ion chromatography( IC) to find out the cause of corrosion,and the suggestions about the preventive measures were proposed. Results showed that the corrosion of the low pressure cylinder rotor blades was mainly in-situ oxygen corrosion formed during the shutdown. The electrochemical corrosion of oxygen involved in the formation of chloride salt was the most serious and dangerous. In the shutdown,the anti-corrosion measures were improper. The other conditions such as natural cooling,air intrusion after vacuum destruction and humidity saturation led to corrosion in the shutdown.