烷基苯磺酸钠储罐内防腐蚀涂层失效原因分析

Failure analysis on internal anti-corrosion coating for storage tank of sodium alkyl benzene sulfonate

针对大庆油田工程有限公司三元配注站烷基苯磺酸钠储罐内防腐蚀涂层脱落的问题,开展了现场调查、测试与室内分析试验。现场调查发现,储罐中下部和搅拌器叶轮相对位置的内防腐蚀涂层大面积连续脱落,并有明显的分界线,说明涂层脱落与搅拌时产生的剪切力有关;涂层失效部位附着力较低,说明涂层附着力受到介质的破坏作用;室内试验分析发现,失效涂层多有微孔、微裂纹等缺陷,同时,烷基苯磺酸钠溶液表面能较低,说明烷基苯磺酸钠溶液容易渗入涂层,并造成涂层和金属基体之间附着力降低。经综合分析后认为,烷基苯磺酸钠对涂层有较强的浸润作用,可渗入到涂层与金属基体之间后,降低它们之间的附着力,受到搅拌器产生的剪切力作用后造成涂层脱落。

In some stations of Daqing Oilfield, the internal anti - corrosion coating of storage tanks of sodium alkyl benzene sulfonate spalled. The field investigation, testing and laboratory analysis found that the internal anti - corrosion coating in the large area of middle and lower parts of the tank and the area where there was agitator operation spalled, and there was obvious boundary line. All these indicated that the coating spalling was related to the shear force from agitation. The field tests also found that the coating failure area had lower cohesion, which indicated that the cohesion of coating had been damaged by liquid media. The laboratory tests showed that the failed coating had defects of micro holes and micro cracks. In addition, the surface energy of liquid sodium alkyl benzene sulfonate was low. It was easy for liquid sodium alkyl benzene sulfonate to permeate into coating, reducing the cohesion between coating and base metal. The comprehensive analysis concluded that sodium alkyl benzene sulfonate had a strong infiltration on the coating and can permeate into between coating and base metal, reducing the cohesion between coating and base metal. The coating spalled under the effect of shear force of agitator.