钛合金与NiAl封严涂层的电偶腐蚀行为研究

钛合金材料与不同材料相互连接,并处于富含氯离子的电解质溶液中,有可能使得材料发生电偶腐蚀而遭到破坏。采用极化曲线的方法分别研究了NiAl涂层、TA15的电化学行为。结果表明NiAl涂层的腐蚀电位较TA15的低,二者相差约30 mV,NiAl涂层腐蚀电流为1.718×10-4A,TA15腐蚀电流为1.170×10-5A。研究了NiAl封严涂层和TA15钛合金之间在5%NaCl水溶液中的电偶腐蚀行为。测试了NiAl-TA15电偶对的电偶电流-时间曲线,并通过计算出的平均电偶电流密度,评价了钛合金和NiAl封严涂层的电偶腐蚀敏感性。结果表明,TA15钛合金和NiAl封严涂层之间的电位差很小,电偶腐蚀倾向很小,电偶电流密度为0.0253μA.cm-2。电偶腐蚀过程中,腐蚀电位较低的NiAl涂层作为电偶对的阳极发生腐蚀,钛合金作为阴极得到保护。电偶腐蚀后电偶对的阳极、阴极的自腐蚀电位均升高,阳极电位从-347 mV正移到-242 mV,阴极电位从-323 mV正移到-210 mV;电偶电位为-300 mV。NiAl涂层含有较多孔洞,可以作为腐蚀介质的渗透通道,在含有Cl-并且有溶解氧存在的腐蚀性介质中,容易导致腐蚀的发生与发展。

Galvanic Corrosion Behavior of Titanium Alloy and NiAl Seal Coating

When the titanium alloys and different materials interconnected and existed in the electrolyte solution enriched chloridion,it could bring about galvanic corrosion to damage the materials.The electrochemical behaviors of NiAl seal coating and TA15 were investigated by polarization curve.It showed that the corrosion potential of NiAl coating was 30 mV lower than TA15,the corrosion current of NiAl coating was 1.718×10-4 A,the corrosion current of TA15 was 1.170×10-5 A.The galvanic corrosion behaviors of NiAl seal coating and TA15 titanium alloy in the 5% NaCl solution were studied.Variation of galvanic current with time of NiAl-TA15 couple was tested,and the average galvanic current density was calculated to evaluate the galvanic corrosion sensitivity of the titanium alloy and NiAl seal coating.Based on the results,the galvanic current density was about 0.0253 μA · cm-2 showed that the trend of galvanic corrosion for TA15 titanium alloy substrate and NiAl seal coating was slight.In the process of galvanic corrosion,NiAl seal coating with the lower corrosion potential served as an anode,the titanium alloy served as a cathode and the alloy was protected.The corrosion potential of the anode increased from-347 mV to-242 mV(SCE) after the galvanic corrosion,and corrosion potential of the cathode increased from-323 mV to-210 mV(SCE).The galvanic potential was about-300 mV(SCE).Lots of holes were in NiAl seal coating and it might serve as a channel for corrodent to permeate,in the corrodent with Cl-and dissolved oxygen,it was easy to cause the occurrence and development of the corrosion.