Effect of silicate pretreatment, post-sealing and additives on corrosion resistance of phosphated galvanized steel
Sodium silicate (water glass) pretreatment before phosphating,silicate post-sealing after phosphating and adding silicate to a traditional phosphating solution were respectively carried out to obtain the improved phosphate coatings with high corrosion resistance and coverage on hot-dip galvanized(HDG) steel.The corrosion resistance,morphology and chemical composition of the coatings were investigated using neutral salt spray(NSS) tests,scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS).The results show that pretreatment HDG steel with silicate solutions,phosphate coatings with finer crystals and higher coverage are formed and the corrosion resistance is enhanced.Adding silicate to a traditional phosphating solution,the surface morphology of the coatings is nearly unchanged.The corrosion resistance of the coatings is mainly dependent on phosphating time.Phosphating for a longer time (such as 5 min),the corrosion resistance,increasing with concentration of silicate,is improved significantly.Post-sealing the phosphated HDG steel with silicate solutions,the pores among the zinc phosphate crystals are sealed with the films containing Si,P,O and Zn and the continuous composite coatings are formed.The corrosion resistance of the composite coatings,related to the pH value,contents of hydrated gel of silica and .2 5 2O Si and post-sealing time,is increased markedly.The improved coatings with optimal corrosion resistance are obtained for phosphating 5 min and post-sealing with 5 g/L silicate solution for 10 min.
galvanized steel phosphate coatings silicate corrosion resistance
XU Yu-ye LIN Bi-lan
College of Civil Engineering,Huaqiao University,Quanzhou 362021,China College of Materials Science and Engineering,South China University of Technology,Guangzhou 510640,C
国际会议
2007年国际有色金属大会(International Conference of Nonfereous Materials 2007)(ICNFM)
长沙
英文
2007-11-28（万方平台首次上网日期，不代表论文的发表时间）