Post-treatment by Sodium Silicate after Zinc Phosphating on Cold-Rolled Steel

作者：Dech oup Supunsa; Thaiwatthana Sirinee; Chairaungsri Torranin^*

来源：Chiang Mai Journal of Science, 2012, 39(1): 30-40.

• Post-treatment
• sodium silicate
• zinc phosphating
• cold-rolled steel
• scanning electron microscopy

Post-treatment by sodium silicate after zinc phosphating on cold-rolled steel was studied. The steel substrates were firstly phosphated in a zinc-phosphating bath containing ZnO, NaF, H3PO4 and Ni(NO3)(2)center dot 6H(2)O under controlled conditions. Post-treatment by sodium silicate was consequently performed by varying the sodium silicate concentration and immersing time in the range of 33.3-100 wt% and 1-10 minutes, respectively. The coating layers before and after post-treatment were characterised by X-ray diffractometry and scanning electron microscopy-energy dispersive X-ray microanalysis. The phosphated layer was formed to be mainly hopeite and a minority of phosphophyllite, whereas the coating after post-treatment is mainly amorphous sodium silicate. The optimum post-treatment condition was using the 33.3 wt% sodium silicate solution at 5 minutes immersing time, by which an increase in corrosion resistance can be adequately obtained after post-treatment.

• 出版日期2012-1