铬盐废水蒸发系统腐蚀突变与缓蚀工况研究

针对铬盐废水蒸发系统运行过程中的腐蚀问题,采用失重法、pH值检测、扫描电镜(SEM、EDS)和XRD等手段,模拟研究了温度、Cr^3+质量浓度对20#碳钢腐蚀速率、腐蚀产物的影响,并从废水pH值和形貌分析角度探索腐蚀速率发生突变的原因。研究表明:废水Cr^3+质量浓度在150~180 mg/L范围,碳钢腐蚀速率发生突增,废水酸性迅速增强(pH<4)以及腐蚀产物的致密度和结晶遭到破坏是腐蚀速率发生突变的重要原因;工业生产中可调节工况(温度约65℃和Cr^3+质量浓度低于150 mg/L)来实现安全、经济缓蚀,亦可通过废水pH值和腐蚀产物形貌初步判定蒸发系统腐蚀程度。

Study on Corrosion Mutation Behavior and Corrosion Inhibition of Chromium Salt Wastewater Evaporation System

Aiming at the corrosion problem in the evaporation system of chromium salt wastewater,the effects of temperature and Cr^3+on the corrosion rate and corrosion products of 20#carbon steel were simulated by means of weight loss method,pH value detection,SEM,EDS and XRD,and the reasons for the abrupt change in corrosion rate were explored from the perspective of pH value of wastewater and morphology analysis.The results showed that the corrosion rate of carbon steel was significantly increased when the concentration of Cr^3+in the wastewater ranged from 150~180 mg/L,the acidity of the wastewater was rapidly enhanced(pH<4),and the densification and crystallization destruction of the corrosion products were the important reasons for the abrupt change in the corrosion rate.In industrial production,the adjustable working conditions(the temperature is about 65℃and the concentration of Cr^3+is less than 150 mg/L)can be used to achieve safe and economical corrosion inhibition.The corrosion degree of evaporation system can also be determined by the pH value of wastewater and the morphology of corrosion products.