Ni60/Cu定向结构涂层在不同浓度H_(2)SO_(4)中的耐蚀性能

Corrosion Resistance of Ni60/Cu Directional Structure Coatings in Different Concentrations of H_(2)SO_(4)Solution

为了研究Cu元素对Ni基合金定向结构涂层耐腐蚀性能的影响,向Ni60合金粉末中添加了5%Cu(质量分数,下同),制备了定向结构Ni60/Cu复合涂层。采用电化学试验和浸泡试验,评估了涂层在不同浓度H_(2)SO_(4)溶液中的电化学腐蚀特性和浸泡腐蚀性能,探讨了涂层在不同浓度H_(2)SO_(4)溶液中的腐蚀行为。结果表明,涂层在不同浓度H_(2)SO_(4)溶液中的腐蚀均表现为活化-钝化-过钝化的过程,电化学阻抗谱在整个时间常数内具有典型的容抗特征,H_(2)SO_(4)溶液浓度从5%增至80%时,电荷转移电阻先减小后增大,涂层的耐腐蚀性呈现先降低后升高的趋势。随着H_(2)SO_(4)溶液浓度的增加,涂层表面的腐蚀程度先加剧后逐渐减缓,且在H_(2)SO_(4)溶液浓度为40%时,腐蚀电位移至最负,腐蚀电流密度增至最大。但在H_(2)SO_(4)溶液浓度达到80%时,涂层表面伴有致密均匀的主要由NiO、Cr_(2)O_(3)以及Cu_(2)O等组成的腐蚀反应钝化膜生成,这些反应钝化膜在涂层表面有效地阻止了H_(2)SO_(4)溶液的进一步渗透,使得涂层在高浓度硫酸中表现出良好的耐蚀性能。

In order to study the influence of Cu element on the corrosion resistance of directional structure coating of Ni-based alloy,5%Cu element was added to Ni60 alloy powder,and the directional structure Ni60/Cu composite coating was prepared.The electrochemical corrosion properties and immersion corrosion properties of the coatings in different concentrations of H_(2)SO_(4)solutions were evaluated by electrochemical tests and immersion tests,and the corrosion behavior of the coatings in different concentrations of H_(2)SO_(4)solutions was discussed.The results show that the corrosion of the coatings in different concentrations of H_(2)SO_(4)solution shows the process of activation,passivation,over-passivation,and the electrochemical impedance spectroscopy has typical capacitive reactance characteristics in the whole time constant.The charge transfer resistance decreases first and then increases,and the corrosion resistance of the coating shows a trend of first decreasing and then increasing when the concentration increases from 5%to 80%.With the increase of H_(2)SO_(4)concentration,the corrosion degree of the coating surface first intensifies and then gradually slows down,and the corrosion potential shifts to the most negative and the corrosion current density increases to the maximum when the concentration of H_(2)SO_(4)solution is 40%.However,the surface of the coating is accompanied by the formation of a dense and uniform corrosion reaction passivation film mainly composed of NiO,Cr_(2)O_(3) and Cu_(2)O when the concentration of H_(2)SO_(4)solution reaches 80%.These reactive passivation films effectively prevent H_(2)SO_(4)solution on the coating surface,making the coating exhibit good corrosion resistance in high concentrations of acid.