PROCESS FOR COATING BY HOT DIPPING

• Main Author: MARC DEWITTE
• Format: Patent
• Language: English
• Published: 26.04.1974
• Subjects: CHEMICAL SURFACE TREATMENT; CHEMISTRY; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY IONIMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING MATERIAL WITH METALLIC MATERIAL; COATING METALLIC MATERIAL; DIFFUSION TREATMENT OF METALLIC MATERIAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL; METALLURGY; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THESURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION

1403245 Galvanizing wire or strip N V BEKAERTSA 23 Oct 1972 [21 Oct 1971] 48758/72 Heading C7F In a process for hot dipping continuous lengths of metal, e.g. steel wire or strip, with Zn, the formation of an oxide film forming on the coated substrate emerging from the bath is prevented by (1) covering the surface of the Zn bath where the coated substrate emerges with a layer of small, rounded refractory granules, inert to Zn, e.g. glass beads of 2.5 to 6 mm dia, (2) injecting a substantially non-oxidizing atmosphere into the granules e.g. CH 4 , C 3 H 8 , natural gas, Ar,N 2 ,C 4 H 10 , and (3) introducing a substance to the granules or the bath which reduces any Z n O formed, e.g. a small amount of Al in the bath, or the addition of a compound of the general formula R-(S) n -R1 to the granules, where R and R1 are aliphatic or aromatic groups, and R1 may also be H. Examples of these compounds are mercaptaus, e.g. methyl mercaptan CH 3 SH, disulphides e.g. dimethyl disulphide, monosulphides, and polysulphides. Other suitable substances include (NH 4 ) 2 S, NH 4 Cl and' compounds of the general formula R1 Cl. Prior to hotdipping, the material may be passed through a Pb bath, pickled in HCl, washed, passed through a flux of ZnCl 2 -NH 4 Cl and dried.