유/무기 하이브리드 용액이 코팅된 냉간압연강판의 열처리 온도에 따른 내식특성

Abstract

In the past a very popular way to reduce the corrosion rate of zinc was the use of chemical conversion layers based on Cr+6. However, there is the important problem that the use of chromium salts is now restricted because of environmental protection legislation. So, earlier researcher investigated the optimum of galvanized steel about organic/inorganic solution with Si. The result showed that the optimum corrosion resistance was at 190℃ in 5 min. The demand of cold rolled steel(CR) for structural member is gradually increasing. If surface treatment(coating for corrosion resistance) of CR is not conducted, the use is very limited. Because, CR is vulnerable to corrosion. Therefore we need the development of coating solution of high corrosion resistance about CR. In this study, Urethane solution (only Urethane 20 wt.% ; S-700), organic/inorganic solution with Si (Si polysilicate 10 wt.% + Urethane 10 wt.% LR-0317) and organic/inorganic solution with Si and Ti(Si polysilicate 7 wt.% + Urethane 13 wt.% + Ti amorphous 0.5 wt.% ; LR-0727(1), Si polysilicate 7 wt.% + Urethane 7 wt.% + Ti amorphous 0.5 wt.% + epoxy 6 wt.% ; LR-0727(2)) are used for evaluation of corrsion resistance of cold rolled carbon steel under salt spray test. Based on the salt spray test of 7 h, LR-0727(1) and LR-0727(2) had a superior effect for the corrosion resistance on CR steel. The organic/inorganic coating solution with Si and Ti(Si polysilicate 7 wt.% + Urethane 13 wt.% + Ti amorphous 0.5 wt.%; LR-0727(1)) are used for evaluation of corrosion resistance of CR under salt spray test. The specimens with LR-0727(1) coating had heat treatment in the drying oven at 120 ~ 210℃ for 5 minute. Corrosion resistance was investigated with salt spray test of 7 hours. And adhesive test was conducted, too. The rust shows under heat treatment of 150 ℃ and found no vestiges over 160 ℃. The specimens with heat treatment of 160 ℃ or more hasn't happened delamination. From these results, it is considered that limited temperature of optimum heat treatment is 160 ℃ considering energy efficiency.