Lopez Kathryn G, Xiao Jinghua, Crockett Christopher, Lytle Christian, Grubbs Haley, Edwards Marc
Department of Civil & Environmental Engineering, Virginia Tech, Blacksburg, Virginia 24060, United States.
Aqua America, Bryn Mawr, Pennsylvania 19010, United States.
ACS ES T Water. 2024 Jul 30;4(8):3153-3162. doi: 10.1021/acsestwater.3c00786. eCollection 2024 Aug 9.
Nitrate-induced spallation of lead-bearing solder particles into drinking water is not sufficiently controlled by phosphate-based inhibitors, although adding zinc can improve their performance. Studies using copper coupons coated with new lead-tin solder in water with up to 12 mg/L nitrate demonstrated that zinc orthophosphate reduced lead release by more than 90% and outperformed orthophosphate alone. Lead release and spallation from harvested pipes with decades-old lead-tin solder in a high nitrate water were improved but not eliminated with zinc orthophosphate over a period of months. When applied at a water utility with high source water nitrate, monthly in-home field sampling showed that 90th percentile lead levels dropped below the action level after dosing zinc orthophosphate at full scale for 6 months. Scanning electron microscopy (SEM) analysis of pipe scales revealed that zinc and orthophosphate codeposit at the copper-solder interface and may act as a mixed inhibitor, with zinc inhibiting the cathodic reaction on the copper pipe, phosphate limiting the anodic reaction, and an added benefit of zinc orthophosphate preferentially precipitating at the galvanic interface between the anode and the cathode. Updates to corrosion control guidance for waters with higher nitrate due to seasonal runoff or source water changes are needed.
尽管添加锌可以改善基于磷酸盐的抑制剂的性能，但硝酸盐导致含铅焊料颗粒剥落进入饮用水的情况并未得到充分控制。在含有高达12毫克/升硝酸盐的水中使用涂有新型铅锡焊料的铜试片进行的研究表明，磷酸锌使铅释放量减少了90%以上，且性能优于单独的正磷酸盐。在几个月的时间里，对于在高硝酸盐水中使用了数十年的铅锡焊料的采集管道，磷酸锌改善了铅的释放和剥落情况，但并未消除。在一个原水硝酸盐含量高的自来水厂应用时，每月进行的家庭现场采样显示，在全规模投加磷酸锌6个月后，第90百分位数的铅含量降至行动水平以下。对管道水垢的扫描电子显微镜（SEM）分析表明，锌和正磷酸盐在铜 - 焊料界面共沉积，可能作为一种混合抑制剂起作用，其中锌抑制铜管上的阴极反应，磷酸盐限制阳极反应，并且磷酸锌优先在阳极和阴极之间的电偶界面沉淀还有额外益处。由于季节性径流或原水变化，对于硝酸盐含量较高的水，需要更新腐蚀控制指南。
