GB1101973A - Method of coating ferrous metal with molten aluminium or aluminium alloy - Google Patents

Abstract

<PICT:1101973/C6-C7/1> A process for coating a ferrous metal article with Al or Al alloy comprises annealing and reducing the surface by heating in a reducing gas, cooling, treating with at least one of the vapours of Bi, Sb, Se, P, As, Pb, Mg, Ca, Sr, Ba, Cd, KF, NaF, LiF, K2TiF6, Na2TiF6, MoO3 and halides of P, Si, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Pb, As, Sb, Bi, Se, and dipping into molten Al or Al alloy, air being excluded from the surface of the article between the reducing and annealing process and dipping. Steel strip is cleaned by heating and passes through a reducing annealing furnace 3 where it is heated to 800-950 DEG C. in a H2-N2 atmosphere to cooling zones 4, 5. Vapour is introduced over the strip from nozzles 13 above and below the strip before it enters an Al coating bath 7. The vapour is formed in a vapour generating system 11a inside or outside the furnace 3 and is carried to the nozzles by a reducing or inactive gas e.g. N2 or H2-N2 via a heated pipe 12a, the gas flow and temperature of the generating system being regulated to control the vapour flow. When several vapours are used they may be generated separately.