摘要
通过改变三价铬钝化工艺中的辊带比,在热浸镀锌板表面制备了3种厚度不同的钝化膜。分别采用X射线荧光光谱仪、辉光放电光谱仪和扫描电镜表征了钝化膜的厚度、元素深度分布和表面形貌。通过中性盐雾试验(NSS)以及塔菲尔曲线、电化学阻抗谱、莫特–肖特基曲线等的测量,研究了钝化膜的耐蚀性。结果表明,增大辊带比可以增大钝化膜的厚度。随膜厚增大,钝化膜表面裂纹减少,致密度提高,耐蚀性增强。其原因有二:一是钝化膜对腐蚀液的屏蔽作用增强,使锌层电化学反应过程中的电荷传输电阻增大;二是当厚度增大时,钝化膜的半导体结构由n型转变为n–p型,n–p型半导体结构能够同时阻碍阴、阳离子的迁移,且施主载流子浓度的减小减弱了钝化膜的导通能力。
Trivalent chromium passivation films of different thicknesses were respectively prepared on three hot-dip galvanized steel sheets by changing the ratio of coating roller speed to strip running speed. The thickness, element distribution along depth direction and surface morphology of passivation films were characterized using X-ray fluorescence spectrometer, glow discharge spectrometer and scanning electron microscope, respectively. The corrosion resistance ofpassivation film was studied by neutral salt spray （NSS） test, measurement of Tafel and Mott-Schottky curves, and electrochemical impedance spectroscopy. The results showed that the thickness of passivation films is increased by increasing the ratio of coating roller speed to strip running speed. The increase of thickness of passivation film results in the reduction of cracks on film surface and the improvement of its compactness and corrosion resistance. There are two reasons： firstly, the enhancement of shielding effect of passivation film on corrosive medium leads to the increase of charge transfer resistance of electrochemical reaction on zinc coating; and secondly, the semiconductive structure of trivalent chromium passivation film is changed from n type to n-p type, inhibiting the movement of cathodic and anodic ions simultaneously, and the concentration of donor carriers is reduced, weakening the conduction capacity ofpassivation film.
出处
《电镀与涂饰》
CAS
CSCD
北大核心
2016年第16期839-844,共6页
Electroplating & Finishing
关键词
热浸镀锌板
三价铬
钝化膜
耐蚀性
半导体结构
电化学
hot-dip galvanized steel sheet
trivatent chromium
passivation film
corrosion resistance
semiconductive structure
electrochemistry
