摘要
目的研究等离子喷涂的Al_(2)O_(3)-13%TiO_(2)涂层和封孔处理后的Al_(2)O_(3)-13%TiO_(2)复合涂层对TC4-H70异种金属电偶对的腐蚀防护效果。方法采用X射线衍射仪、扫描电镜、能谱仪对涂层的物相组成、组织形貌、元素分布进行表征分析,使用电化学工作站和电偶腐蚀测量仪对涂层及对比试样的耐蚀性能进行分析研究。结果等离子喷涂的Al_(2)O_(3)-13%TiO_(2)涂层由α-Al_(2)O_(3)和γ-Al_(2)O_(3)两相组成,以γ-Al_(2)O_(3)相为主。Al_(2)O_(3)-13%TiO_(2)涂层中存在微孔与微裂纹等缺陷,腐蚀介质易渗入,因此Al_(2)O_(3)-13%TiO_(2)涂层的耐蚀性较差。经过封孔处理后的Al_(2)O_(3)-13%TiO_(2)涂层,表层缺陷被充分填充,同时在陶瓷表层形成厚度为20~40μm的致密阻挡层,有效阻隔了NaCl腐蚀介质的渗入,涂层腐蚀电流密度相比于H70基体和Al_(2)O_(3)-13%TiO_(2)涂层试样减小了4个数量级,基底与涂层间的界面电荷转移电阻值相较于H70基体和Al_(2)O_(3)-13%TiO_(2)涂层提高了5个数量级,涂层耐蚀性和绝缘性显著提升。TC4-H70电偶对经15 d电偶腐蚀试验后,H70表面发生腐蚀,封孔处理后的Al_(2)O_(3)-13%TiO_(2)涂层可有效降低TC4-H70电偶对间的电偶腐蚀作用,经15 d电偶腐蚀试验后,试样未腐蚀,且涂层完整。结论封孔处理后的Al_(2)O_(3)-13%TiO_(2)涂层优异的电偶腐蚀防护效果主要得益于其高电阻和表层的高致密性,几乎阻隔了异种金属间的电子传输,使得异种金属间的电偶电池作用极其微弱,可有效延长异种金属海水管路的使用寿命,在电偶腐蚀防护领域具有巨大的应用前景。
The work aims to study the galvanic corrosion protection effects of plasma sprayed Al_(2)O_(3)-13%TiO_(2)coatings and sealed Al_(2)O_(3)-13%TiO_(2)composite coatings on TC4-H70 dissimilar metal galvanic couples.The phase composition,microstructure and element distribution of the coating were characterized and analyzed by X-ray diffractometer,scanning electron microscope and energy dispersive spectrometer.The corrosion resistance of the coating and the comparative samples were analyzed and studied by electrochemical workstation and galvanic corrosion testing instrument.XRD results showed that the plasma sprayed Al_(2)O_(3)-13%TiO_(2)coating was composed ofα-Al_(2)O_(3)andγ-Al_(2)O_(3)phases,withγ-Al_(2)O_(3)as the main phase.SEM and dynamic potential polarization polarization curve indicated that there were defects such as micro-pores and micro-cracks in the Al_(2)O_(3)-13%TiO_(2)coating,the corrosive medium was easy to penetrate,and the corrosion current density was(7.0±0.20)×10^(-5)A·cm^(-2),which was greater than the corrosion current density of H70 substrate[(4.6±0.63)×10^(-5)A·cm^(-2)],so the corrosion resistance of Al_(2)O_(3)-13%TiO_(2)coatings was inferior and cannot provide corrosion protection to the H70 substrate.After sealing treatment,the defects in the surface layer of the Al_(2)O_(3)-13%TiO_(2)coating were fully filled,and a dense barrier layer with a thickness of about 20-40μm was formed on the ceramic surface,which effectively blocked the infiltration of Na Cl corrosion medium,and the corrosion current density of the coating was only 1.0×10^(-9)A·cm^(-2),which was 4 orders of magnitude smaller than that of the H70 substrate and Al_(2)O_(3)-13%TiO_(2)coating sample,so the corrosion resistance of the coating was dramatically improved.The electrochemical impedance results demonstrated that the arc radius of capacitive resistance was in the order of sealing Al_(2)O_(3)-13%TiO_(2)coating>H70 substrate>Al_(2)O_(3)-13%TiO_(2)coating.It can be seen that the sealed Al_(2)O_(3)-13%TiO_(2)coating possessed the highest charge transfer resistance and the best corrosion resistance.The equivalent circuit analysis results manifested that the interfacial charge transfer resistance between the substrate and the coating of the sealed Al_(2)O_(3)-13%TiO_(2)coating was 1.9×10^(8)Ω·cm^(2),which was comparable to that of the H70(5.1×10^(3)Ω·cm^(2))substrate and the Al_(2)O_(3)-13%TiO_(2)coating(2.2×10^(3)Ω·cm^(2))increased by 5 orders of magnitude,indicating that the sealed Al_(2)O_(3)-13%TiO_(2)coating not only had the best corrosion resistance,but also presented the largest resistance to electron transport.This was beneficial to reduce galvanic corrosion between dissimilar metals.After 15 d galvanic corrosion test of TC4-H70 galvanic couple,the surface of H70 was corroded,and the Al_(2)O_(3)-13%TiO_(2)coating after sealing treatment could effectively reduce the galvanic corrosion between TC4-H70 galvanic couple.After 15 d galvanic corrosion test,none of the samples corroded and the coating was intact.The excellent galvanic corrosion protection effect of the sealed Al_(2)O_(3)-13%TiO_(2)coating is mainly due to its high resistance and high surface layer density,which almost block the electron transmission between dissimilar metals to make the effect of galvanic battery between dissimilar metals extremely weak.It can be seen that the coating could effectively prolong the service life of dissimilar metal seawater pipelines,and displace a great application prospect in galvanic corrosion protection.
作者
吴护林
张智峰
彭冬
杨钊
宋凯强
丛大龙
李毅
谢杨
陈爽
黄安畏
李忠盛
WU Hu-lin;ZHANG Zhi-feng;PENG Dong;YANG Zhao;SONG Kai-qiang;CONG Da-long;LI Yi;XIE Yang;CHEN Shuang;HUANG An-wei;LI Zhong-sheng(Southwest Institute of Technology and Engineering,Chongqing 400039,China;Nuclear Power Institute of China,Chengdu 610094,China)
出处
《表面技术》
EI
CAS
CSCD
北大核心
2023年第3期266-275,286,共11页
Surface Technology
