化工管道连接法兰磷化工艺条件优化及磷化膜的耐蚀性

以化工管道连接使用的Q235钢法兰为研究对象,对其进行磷化处理以提高耐蚀性.采用正交试验法考察了磷酸二氢锌浓度、氟化钠浓度、硝酸镧浓度、磷化液温度和磷化时间对磷化膜耐CuSO4点蚀时间的影响,并通过极差分析得到最佳磷化工艺条件为:磷酸二氢锌浓度60 g/L、氟化钠浓度2.5 g/L、硝酸镧浓度40 mg/L、磷化液温度...

Optimization of Phosphating Process Conditions for Chemical Pipe Connection Flange and Corrosion Resistance of Phosphating Film

The Q235 steel flange for chemical pipe connection was treated by phosphating in order to improve its corrosion resistance,and the influence of zinc dihydrogen phosphate concentration,sodium fluoride concentration,lanthanum nitrate concentration,phosphating solution temperature and phosphating time on CuSO₄ pitting time of phosphating film was investigated by orthogonal experiment.The optimal phosphating process conditions obtained by range analysis were as follows:zinc dihydrogen phosphate 60 g/L,sodium fluoride 2.5 g/L,lanthanum nitrate 40 mg/L,phosphating solution temperature 70℃and phosphating time 15 min,and the optimal phosphating process conditions were applied to the phosphating treatment of flange.The results showed that the phosphating film on the surface of flange was dark gray,completely covered and has good compactness,the phase composition was Zn₃(PO₄)₂·4H₂O and Zn₂Fe(PO₄)₂·4H₂O.The corrosion potential of phosphating film was about 70 mV higher than that of Q235 steel matrix,and the corrosion current density was reduced by at least one order of magnitude.This phosphating film can effectively block the corrosive medium and delay the corrodoision,so that the corrosion resistance of the flange after phosphating treatment was significantly improved.