Crevice corrosion control in UV water treatment systems

加拿大商业紫外线（UV）辐射水消毒系统采用4-20 mA碳化硅（SiC）光电二极管传感器，该传感器专门调谐到用于处理住宅用水的杀菌UV-C（254 nm）光。传感器的316L型不锈钢外壳在特定的水条件下容易腐蚀。这造成了严重的问题，因为腐蚀会污染石英窗口，从而显著降低传感器“看到”紫外线的能力。虽然众所周知，紫外线辐射可以增强不锈钢的钝化性，但由于钝化性增强，其对缝隙腐蚀的有害影响尚未得到很好的理解，特别是当考虑与水温，pH值和总溶解固体（TDS）含量的相互作用时。本文提出的研究将（i）使用充分表征的工艺沃茨验证缝隙腐蚀失效模式，（ii）确定316 L型不锈钢缝隙腐蚀敏感性的温度TDS（或Cl-）阈值，（iii）分析升级到317 L型和/或2205双相不锈钢的适用性，并提出设计细节的变更。

A Canadian commercial ultra violet (UV) radiation-based water disinfection system employs a 4-20 mA silicon carbide (SiC) photo diode sensor that is specifically tuned to the germicidal UV-C (254 nm) light used to treat the residential water. The Type 316L stainless steel casing of the sensor is prone to corrosion under specific water conditions. This poses a serious problem as corrosion fouls the quartz window, which significantly reduces the sensor's ability to 'see' the UV light. While it is well known that UV radiation can enhance passivity of stainless steels, its detrimental effects on crevice corrosion as a consequence of the enhanced passivity is not well understood, especially when considering the interplay with water temperature, pH and total dissolved solids (TDS) content. The research proposed here will (i) validate the crevice corrosion failure mode using well characterized process waters, (ii) identify the temperature TDS (or Cl-) thresholds for crevice corrosion susceptibility of Type 316L stainless steel, (iii) analyze the suitability of upgrading to Type 317L and/or 2205 duplex stainless steel and proposed changes to the design details.