钢铁表面氟铁酸盐转化膜的形貌、耐蚀性及其对应性

Morphology and Corrosion Resistance of Fluroferrite Conversion Coatings on Iron and Steel Substrate

为了弄清晶体颗粒氟铁酸钾转化膜的形貌、结构与其耐蚀性之间的关系,以不同工艺在Q195冷轧板表面制备了氟铁酸钾转化膜。采用扫描电镜观察其形貌、结构;采用能谱仪测试其成分;通过中性盐雾试验及电化学方法测试其耐蚀性,采用百格法测试其附着力;讨论了各工艺条件对氟铁酸盐转化膜的形貌及耐蚀性的影响及其对应性,优化了工艺条件。结果表明:晶体结构氟铁酸钾转化膜的形貌、结构与其耐蚀性存在对应关系;氟铁酸钾转化膜的最佳制备工艺为125 g/L KF,20 g/L(NH4)2S2O8,100 mL/L H2O2,85 mL/L HNO3,50℃,90 min;该工艺下,钢铁表面生成了晶体颗粒状氟铁酸钾转化膜,膜层由F,K,Fe,O等元素组成,膜层颗粒粗大、均匀、致密,与基体结合牢固,耐蚀性较好,耐中性盐雾时间达85 h以上。

Fluroferrite conversion coatings were prepared on Q195 iron and steel surface by different processes.The morphology of as-prepared fluroferrite conversion coatings was analyzed by scanning electron microscopy,and their composition,adhesion to substrate and corrosion resistance were determined and evaluated by energy dispersive spectrometry,cross-hatch test as well as neutral salt-spray test and electrochemical test,respectively.The effects of processing conditions on the morphology and corrosion resistance of fluroferrite conversion coatings were investigated,and the processing conditions were optimized.Results indicated that correlation among the morphology-microstructure and corrosion resistance of fluroferrite conversion coatings existed.The conversion solution with the optimal composition was composed of 125 g/L KF,20 g/L(NH_4)_2S_2O_8,100 mL/L H_2O_2 and 85 mL/L HNO_3.The optimized conversion temperature and time were determined to be 50 ? and 90 min.Resultant fluroferrite conversion coating obtained under the optimized conversion condition consisted of F,K,Fe and O? and contained uniform and compact crystal grains,possessing good adhesion to iron and steel substrate and corrosion resistance.