A method for the protection of flat steel surfaces against the deposition of carbon originating from the steel inner as graphite, as well as against a nitriding of the steel in the case of the recrystallization

摘要

1419534 Electro-deposition KAWASAKI SEITETSU KK 9 Oct 1972 [11 Oct 1971 23 Oct 1971 (2) 5 Nov 1971] 46502/72 Headings C7B and C7N Prior to annealing, cold-rolled low carbon steel sheet is coated with one at least of S, Al, Sb, Pb, Bi, As, Sn, Se or Te in elemental or compound form by deposition from a liquid phase containing a total coating concentration of up to 0.1 mol/ litre. The steel may be unkilled steel containing less than 0.002% N, killed steel containing 0.001- 0.5% of at least one of Al, Ti, Nb, V, Zr or B, or a killed steel containing 0.05-3.25% Si, while the coating may be applied at the rate of at least 2g./sq. m. of a solution containing a total concentration of 0.0001 to 0.1 mol/l of compounds of the coating elements, or of a dispersion containing a similar concentration of compounds. Alternatively the steel sheet may be coated electrolytically in an aqueous bath using a density of 1-20 coulombs/dmSP2/SP. Typical electrolytes are Al 2 (SO 4 )3, 18H 2 O and Na 2 S 2 O 3 . 5 H 2 O at concentrations of 0.00001, 0.00005, 0.0001, 0.001, and 0.01 mol/l, used at current densities of 0.15 A/dmSP2/SP and 1.5 A/dmSP2/SP and 80‹C, while use of S 2 Cl 2 , SbCl 3 , SeOCl 2 , Na 2 SeO 3 , TeCl 4 , Na 2 TeO 3 , NaAlO 2 , SnCl 2 . 2H 2 O, KH 2 AsO 4 , PbCl 2 , and BiCl 3 is exemplified. The compounds may be added to a sodium orthosilicate electrolytic degreasing bath.