阴极极化对LY12CZ铝合金腐蚀疲劳寿命的影响

INFLUENCE OF CATHODIC POLARIZATION ON CORROSION FATIGUE LIFE OF ALUMINIUM ALLOY LY12CZ

在LY12CZ铝合金腐蚀疲劳寿命曲线的基础上,研究了不同阴极电位下有无涂层试件在3.5%NaCl溶液中腐蚀疲劳寿命的变化规律.记录了一定阴极电位下阴极电流的变化情况.并通过对腐蚀疲劳断裂微观形貌的观察、分析,探讨了阴极极化对有无涂层保护的LY12CZ铝合金腐蚀疲劳寿命影响机理.对于无涂层试样,一定范围内的阴极电位会抑制阳极反应,明显提高腐蚀疲劳寿命,但当阴极电位达到一定值时(-1400 mV以上),发生铝合金的阴极腐蚀,使腐蚀疲劳寿命显著降低.对于有涂层试样,由于涂层的保护,一定电位值范围的阴极保护作用并不显著,阴极电位超过一定值,涂层阻碍抑制了阴极腐蚀作用,试样腐蚀疲劳寿命较无涂层试样有显著提高.

Based on S-N curve of corrosion fatigue (CF) for LY12CZ aluminum alloy, the tendency of CF lives of the uncoated and coated specimens in 3.5%NaCl solution was studied. The evolution of the cathodic current with cyclic number under cathodic polarization was measured. The morphology of fracture surface was observed and the mechanism of the effect of the cathodic polarization on the CF life of LY12CZ aluminum alloy with and without coating was analyzed. CF lives of the uncoated specimens were increased evidently as cathodic protection in certain range of potential restrained anodic corrosion. But the potential reached some value (exceeding -1400 mV), cathodic corrosion of aluminum alloy made CF lives obviously decrease. For coated specimens, in certain range of potential the cathodic protection did not appear due to coating. When the potential was over some value, CF lives of coated specimens were ligher than those of uncoated specimens because the coating prevent cathodic corrosion.