摘要
达克罗凭借优异的耐腐蚀性能,广泛应用于汽车、航海、风电等领域,但其所含铬酸盐存在严重的污染问题。采用硅烷偶联剂代替铬酸盐的无铬达克罗解决了污染问题,但相对于达克罗,其硬度低、附着力差、耐腐蚀性较差。通过加入硝酸铈铵和石墨烯对无铬达克罗涂料进行改性,并采用X射线衍射仪、扫描电镜、拉曼光谱仪、快速腐蚀试验、极化曲线试验研究了涂层的物相组成、组织形貌、耐腐蚀性能。结果表明:涂层表面主要是片状锌粉、片状铝粉,致密性好;涂层截面层状堆叠结构清晰。石墨烯添加量为200 mg/L时,改性无铬达克罗涂层的耐腐蚀性能最佳,耐腐蚀时间(5 h)最长,腐蚀电流密度(0.124μA/cm2)最小,腐蚀电压(-0.82 V)最正。硝酸铈铵通过对金属粉的钝化、粘结作用提高涂层的耐腐蚀性能;石墨烯通过物理屏蔽作用、促进牺牲阳极保护作用提高涂层的耐腐蚀性能。
Dacromet is an effective corrosion-resistant coating widely used in automobiles,ships and wind-power generators.However,it contains chromate which may cause severe environmental pollution.Chromium-free dacromet coating has been developed to address the pollution problem by replacing chromate with safe silane coupling agent.However,the hardness,adhesion strength and corrosion resistance of the chromium-free dacromet coating is worse than that of dacromet.Thus,diammonium cerium(IV) nitrate and graphene was used to modify the chromium-free dacromet coating.Various characterizations including X-ray diffraction,scanning electron microscopy,Raman spectroscopy,rapid corrosion test and electrochemical polarization show that the top layer of the coating is mainly composed by compact flake zinc powder and flake aluminum powder and the cross section of the coating shows a clear multi-layer structure.With a concentration of 200 mg/L graphene,the modified chromium-free dacromet coating has the best corrosion resistance,evidenced by the longest corrosion resistance time(5 h),the minimum corrosion current density(0.124 μA/cm^2),and the most positive corrosion voltage(-0.82 V).The improved corrosion resistance can be ascribed to the passivizing and powder-bonding effects of diammonium cerium(IV) nitrate as well as the physical shielding and increased sacrificial anode protection from graphene.
作者
任鹏禾
周宏明
许晓嫦
谭騛
朱晴晴
REN Penghe;ZHOU Hongming;XU Xiaochang;TAN Fei;ZHU Qingqing(School of Materials Science and Engineering,Central South University,Changsha 410083,China)
出处
《中国表面工程》
EI
CAS
CSCD
北大核心
2018年第6期73-80,共8页
China Surface Engineering
关键词
石墨烯
无铬达克罗
微观组织
耐腐蚀性能
极化曲线
graphene
chromium-free dacromet
microstructure
corrosion resistance
polarization curve.
