钛-钢螺栓搭接件涂层腐蚀失效分析及影响

涂层是飞机的主要防腐体系，涂层局部破损失效后往往对其他完好区域产生影响，但有些位置比较隐蔽难于发现，给飞行安全带来了隐患。模拟飞机服役环境，对钛-钢螺栓搭接件进行腐蚀试验，基于电偶腐蚀数学模型，选取相应的边界条件，用有限元法分析了搭接件表面涂层失效原因及影响。结果表明，涂层失效过程分三个阶段，电偶腐蚀效应使搭接件周围形成电场，在电势梯度作用下，Cl^-发生定向加速移动，导致电渗起泡。随着涂层失效面积的增加，阴、阳极面积比例不断变小，阳极腐蚀得到减轻；最大腐蚀电流密度的位置发生变化，数值变小，降低了发生点蚀的风险。通过对搭接结构周围溶液腐蚀电场的计算，可以预测涂层失效区域，为飞机涂层体系的维护保养提供技术支持。

Coating corrosion failure analysis and influence of titanium-steel bolted lap joints

Coating is the main anti-corrosion system of aircraft, and local damage of coating has an impact on other complete areas. The coat failure in concealed position is difficult to be found and affects the flight safety. Corrosion experiment is performed for titanium-steel bolted lap joints with airplane service environment simulation. After selecting appropriate boundary conditions, the causes and effects of lap surface coating failure are analyzed by finite element method which is based on the mathematical model of galvanic corrosion. The results indicate that the coating failure process could be divided into three stages; the effect of galvanic corrosion causes the electric field around the lap area; the directional accelerated motion of Cl^- under the potential gradient causes electroosmotic blistering of coating. With the increase of the coating failure area, the proportion of the cathode and anode area is smaller, the corrosion of the anode reduces, the position of the maximum corrosion current density changes, and the value of the corrosion current density decreases. The failure area of the coating could be predicted through calculation of electric field of the solution around the overlapping structure. It provides the technical support for the maintenance of the aircraft coating system.