热浸镀层在青岛站的海水腐蚀行为对比(Ⅰ)——全浸区

Seawater corrosion behavior of hot dip coatings at Qingdao test station(Ⅰ)——Immersion zone

开展了热浸镀锌(GI)、锌-5%铝-稀土(GF)和锌-55%铝-1.6%硅(GL)镀层钢板在青岛站的全浸区海水腐蚀测试,并利用质量损失腐蚀测试、显微结构分析和电化学测试,研究了3种镀层钢板的海水腐蚀行为。结果表明:GI镀层的腐蚀电流密度最大,在流动海水中以很快的速度溶解而又难于形成稳定的保护性腐蚀产物膜,耐海水腐蚀性能最差;GF和GL镀层的腐蚀电流密度较小,腐蚀产物具有抑制保护性,表现出较为优异的耐海水腐蚀性能。对位于海水全浸区的钢材基体提供1年保护期所需的镀层最小厚度分别为:GI镀层45μm;GF镀层18μm;GL镀层25μm;3种镀层在海水全浸区的耐蚀性强弱顺序依次为:GL>GF>GI;如果考虑到局部腐蚀,那么GF镀层可能会比GL具有更强的综合优势。

The corrosion behavior of hot dipping Galvanized （GI）, Galfan （GF） and Galvalume （GL） coated steels exposed to immersion zone of Qingdao site was investigated with seawater corrosion test, microscopy morphology analyses and electrochemical measurements. The inferior performance of GI mainly results from its largest corrosion current density and not forming a stable and protective corrosion product layer in the flowing seawater. The suPerior performance of GF and GL is attributed to their optimal combination of lower corrosion current densities and more protective corrosion products. The minimum coating thicknesses requirement for one year protection afforded to steel structures exposed to immersion zone are then calculated as： GI, 45μm; GF, 18μm; GL, 25μm. The corrosion resistances of these coatings are therefore readily listed in descend order as： GL〉GF〉GI. However, the performance of GF immersed in seawater would probably be better than that of GL if pitting corrosion was taken into accounted.