| 摘要 |
Cold rolled mild steel sheet is coated on at least one surface by degreasing; pickling; and then electroplating with max. 0.8 g/m2, pref. 0.5 g/m2 of Sn ot obtain max. 0.12 mu m and pref. 0.07 mu m tin thickness. The coated sheet is next heated above the m.pt. of Sn so the latter melts, followed by cooling to convert all the Sn to FeSn2. The FeSn2 layer is pref. passivated in an electrolytic bath contg. 15-80 g/l chromic acid, 0.15-0.8 g/l H2SO4 and 0.15-0.8 g/l sodium fluorosilicate (SFS) using 0.1-0.5 seconds immersion and 20-80 A/dm2 to obtain a passive film based on Cr. The sheet may be coated on one side with FeSn2 whereas its other side with FeSn2 whereas its other side is coated with free tin. A new process for mfg. tin coated steel which is much less expensive in materials and energy than conventional tinplate, and has a microporosity acting as an anchor for the passive film or varnish. The new tinplate can replace existing plate coated with organic materials, or black tinplate used for drums, etc. |
