热镀锌钢表面硅烷膜的腐蚀电化学性能

Electrochemical Corrosion Behavior of Silane Coatings on Hot-dip Galvanized Steel

将热镀锌钢板在7%(体积比)、pH=4的乙烯基三甲氧基硅烷溶液中40℃下处理2 min,获得了硅烷膜试样。应用极化曲线和电化学交流阻抗谱(EIS)评价了硅烷膜在5%NaCl溶液中的耐蚀性能,采用俄歇电子能谱(AES)分析了膜层的成分和结构特性。结果表明,硅烷膜主要由C、O、Si等元素组成,硅烷分子并非是简单地以物理吸附的方式存在于热镀锌层上,而是通过Si–O–Zn键使得硅烷界面层与热镀锌层紧密结合在一起。硅烷膜能同时抑制Zn腐蚀过程中的阳极和阴极反应,其极化阻抗值Rp可达5.53 k?.cm2。硅烷膜的低频与高频容抗弧几乎合成一个弧,表明腐蚀过程中硅烷膜层已经很致密,界面电容很大,Cl﹣难以通过膜层间隙到达Zn基体表面。

In this paper, silane coatings are prepared by dipping hot-dip galvanized （HDG） steel sheets in 7 vol.% vinyltrimethoxysilane solutions with 4 of pH value at 40 ℃ for 2 min. The corrosion resistance of the silane coatings is compared to that of bare samples in 5 % NaCl solution by polarization curves and electrochemical impedance spectra （EIS）. The structure and composition of the silane coatings are investigated using Auger electron spectroscopy （AES）. The results reveal that the silane coatings are mainly composed of C, O, Si elements, especially the silane molecules in the silane coatings are not combined with hot-dip galvanized coating by simple physical absorption, but chemical action is generated between Si-OH from silane solution and Zn-OH on hot-dip galvanize coating surface and formed Si-O-Zn bonds. This action makes the interface of the silane coatings be combined with hot-dip galvanized coating tightly. While the silane coatings can markedly restrain the anodic and cathodic react in the zinc corrosion process, thereby its corrosion protective efficiency remarkably increased. The polarization resistance of the silane coatings is up to 5.53 kΩ.cm^2. The low frequency loop and high frequency capacitive loop of the silane coatings seem to be one loop, which demonstrate that the silane coatings during the corrosion process are so compacted that the chloride ion is difficult to reach zinc substrate surface through the hole of the coatings.