赵方超 1刘伟 1钱建才 1许斌 2钟勇 2蒲亚博 1方敏 2郭赞洪2
作者信息
- 1. 中国兵器装备集团西南技术工程研究所,重庆 400039||装备环境效应与防护重庆市重点实验室,重庆 400039
- 2. 中国兵器装备集团西南技术工程研究所,重庆 400039
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摘要
Abstract
The work aims to assess the corrosion protection effectiveness of thin(less than 15 μm)Al coatings on Ti/Al dissimilar metal connection components and explore their synergistic protection mechanisms,so as to support the design and preparation of high-performance thin Al coatings,and promote their applications in harsh environments such as galvanic corrosion and crevice corrosion.A thin Al coating with uniform film thickness and long-term corrosion resistance was prepared by optimizing the design of pigments and fillers and improving the spraying process.The results showed that after a 928 h of 5%neutral salt spray test,bubbles covered a small area of the surface of the(4-6 μm)Al coating,and no obvious bubbling,rusting,discoloration were found on the surface of the(12-15 μm)Al coating.To study the effects of different protective coatings on the contact corrosion behavior of TC4 Ti alloy and LC52 Al alloy,different TC4/LC52 connection test pieces were assembled by applying the different protective coatings on TC4 and LC52 test plates with M8 bolts.Two kinds of TC4 samples were prepared,one with no surface treatment and the other with Al coating(12-15 μm).Two types of LC52 samples were also prepared,one with hard anodizing(30-35 μm)+boiling water sealing,and the other with hard anodizing(12-15 μm)+Al coating(12-15 μm).The corrosion situations of different combinations of connection samples were assessed and compared by the neutral salt spray test.The microstructure changes of the samples before and after the test were analyzed with SEM,and the corrosion resistance of the coatings was characterized with electrochemical impedance spectroscopy(EIS).The results showed that for the untreated TC4/LC52 hard anodized connection components,the contact surface of Al alloy suffered the most severe corrosion,with a large amount of white corrosion products and coating peeling off.After the TC4 alloy was coated with Al,the galvanic current of the component decreased by an order of magnitude compared to that of the uncoated component,effectively suppressing the galvanic corrosion induced by the positive potential of the TC4 alloy,whereas small-scale coating peeling off could still be observed.By applying the Al coating on the hard anodized surface of LC52,peeling of the anodized coating from the contact surface was effectively suppressed,with the white corrosion products decreased from 50%to 5%.By applying Al coating to both contact surfaces of the connecting components(TC4+Al coating/LC52 hard anodized+Al coating),no corrosion product was observed,and only discoloration occurred on the Al coating.The SEM analysis showed that only pitting corrosion occurred on the surface of the Al coating,and oxides and Al salts were formed.The EIS analysis indicated that the low-frequency impedance modulus of anodized and Al-coated LC52 was 3 orders of magnitude higher than that of the uncoated component,demonstrating its good dielectric shielding performance.Lastly,Ti alloy did not exhibit corrosion in all connection structures,and the hard anodizing treatment of the Al alloy had little effect on the corrosion protection of the Ti plate and the Al alloy,probably because the hard anodizing film of Al alloy was not dense enough to effectively prevent galvanic corrosion of the Ti/Al connection structure.The Al coating can effectively improve Ti/Al contact corrosion resistance while meeting the assembly accuracy,based on the synergistic effects of Al powder electrochemical activity,the maze effect of sheet-like structure,and the enhanced dense barrier after oxidation.关键词
接触腐蚀/钛合金/铝合金/硬质阳极氧化/铝涂层Key words
contact corrosion/titanium alloy/aluminum alloy/hard anodizing/aluminum coating分类
金属材料
