盐沉积条件下CO_2对LY12铝合金大气腐蚀的影响

Effects of CO_2 on Salt Deposition-induced Atmospheric Corrosion of Aluminum Alloy LY12

目的研究在有/无CO_2存在的恒温恒湿条件下,表面有沉积盐的LY12铝合金的大气腐蚀行为与腐蚀机理,搞清CO_2对其大气腐蚀的影响。方法将LY12铝合金表面分别沉积不同浓度的NaCl和MgCl_2,分别进行通/不通CO_2的恒温恒湿实验,借助扫描电镜(SEM/EDS)、X射线衍射(XRD)和X光电子能谱(XPS)等表面技术以及腐蚀失重分析方法,研究盐沉积条件下CO_2对LY12铝合金大气腐蚀的影响。结果在试验条件下,MgCl_2造成的LY12铝合金腐蚀都以点蚀为主,失重高于NaCl造成的。以MgCl_2为介质时,主要腐蚀产物都为(Mg1–xAlx(OH)_2)x+(Cl~–,CO^(2–))x×mH_2O(简写为LDH);以NaCl为介质时,主要腐蚀产物都为Al_2O_3或Al(OH)_3。两种介质的腐蚀产物都出现了Cu元素的富集。结论无论是否存在CO_2,Mg元素都参与了腐蚀产物的形成。合金元素Cu的存在及其富集,是造成CO_2对纯铝和LY12铝合金腐蚀行为不同影响的主要因素。

The work aims to study effects of CO2 on atmospheric corrosion as well as atmospheric corrosion behavior and corrosion mechanism of LY12 aluminum alloy with salt deposits on the surface in constant temperature and humidity with/without CO2. Different concentrations of Na Cl and Mg Cl2 were deposited on aluminum alloy LY12 and constant temperature and humidity test with/without CO2. Effects of CO2 on salt deposition-induced atmospheric corrosion of aluminum alloy LY12 were studied by means of SEM/EDS, XRD and XPS. In the test conditions, pitting was dominant in Mg Cl2-induced atmospheric corrosion of aluminum alloy LY12, and Mg Cl2-induced weight loss was higher than that induced by Na Cl.（Mg1–xAlx（OH）2）x＋（Cl^–, CO^2–）x×m H2O（LDH） was major corrosion product in the Mg Cl2-induced corrosion process. However, Al2O3 or Al（OH）3 was major corrosion product under the influence of Na Cl. Cu enriched in corrosion products of both mediums. Whether CO2 is present or not, Mg in MgCl2 takes part in forming corrosion products. Different effects of CO2 on corrosion behavior of pure Al and LY12 are mainly attributed to the presence or enrichment of Cu.