镀锌钢在红沿河大气环境中的腐蚀行为

目的研究镀锌钢在红沿河地区SO2和Cl-含量较高的大气环境中的腐蚀行为与机理。方法根据GB/T 6464—1997将制备好的试样在红沿河核电厂进行现场暴晒试验,分别暴晒4、12、18、24个月后取回试样。利用失重分析、X射线衍射(XRD)和扫描电镜(SEM)等技术,观察与分析试样暴晒后的腐蚀产物。结果镀锌钢腐蚀失重随暴晒时间的延长而线性增加;随着暴晒时间的延长,锌镀层表面形成的腐蚀产物成分变化不大,以Zn12(SO4)3Cl3(OH)15·5H2O和6Zn(OH)2·Zn SO4·4H2O为主;腐蚀产物随暴晒时间的延长逐渐增加,产物形貌略有变化,以球状和针状为主。暴晒18个月后,腐蚀产物分为双两层,内层致密,外层疏松;暴晒24个月后,腐蚀产物厚度稍有增加,疏松层向致密层转变。结论 SO2与Cl-是镀锌钢在红沿河地区的大气腐蚀过程的主要影响因子。镀锌钢表面形成的腐蚀产物对锌镀层的保护作用较差。

Atmospheric Corrosion of Galvanized Steel at Hongyanhe Nuclear Power Station

ABSTRACT:Objective To study the atmospheric corrosion behavior and mechanism of galvanized steel at Hongyanhe nuclear power station with high SO2 and Cl-concentrations. Methods The galvanized steel was exposed in the Hongyanhe atmospheric envi-ronment for 4, 12,18 and 24 months, according to GB/T 6464—1997. The corrosion products of galvanized steel after explosion were observed and analyzed by corrosion mass loss test, scanning electron microscopy ( SEM ) and X-ray diffraction ( XRD ) . Results The results of corrosion kinetics analysis showed that the galvanized steel corrosion weight loss increased linearly with the increase of the exposure time. XRD analysis results showed that with the extension of exposure time, there was no big change in the composition of corrosion products formed on the surface of the zinc coating, which were mainly Zn12(SO4)3Cl3(OH)15·5H2O and 6Zn(OH)2·ZnSO4·4H2O. SEM results showed that the corrosion products increased gradually with the extension of exposure time, and the product morphology changed slightly, with balls and needles as the main shapes. From the point of cross section analysis, after 18 months, the corrosion products were divided into two layers, while after 24 months, the thickness of the corrosion products increased slightly, and the loose layer was transformed into dense layer. Conclusion For galvanized steel corrosion in the atmosphere of Hongyanhe region, SO2 and Cl- were the main influencing factors of the corrosion process. The corrosion products formed on the surface of galvanized steel had relatively poor protective effect.