GB385971A - Improvements relating to coating with metals by dipping - Google Patents

Abstract

385,971. Coating with metals. SENDZIMIR, T. K., 24, Yuen Ming Yuen Road, Shanghai, China, and BOSTROEM, T. J., 38, Avenue de la Gare, Meudon, Seine-et-Oise, France. April 27, 1931, No. 12361. [A Specification was laid open to inspection under Sect. 91 of the Acts, April 28, 1931.] [Class 82 (ii).] In a process for coating sheets, wire, pipes, or other articles with metal by dipping in which the article is preheated to annealing temperature and protected from oxidation during transfer from the preheating means to the coating bath, the article is subjected to a gradual cooling from annealing temperature to a temperature of about 50-100‹ C. above the melting-point of the coating metal before immersion in the coating bath. Preferably the preheating means, which may be a furnace or a molten bath, is heated at a point near to the entry end so that the article has cooled to the desired temperature before leaving the preheating means. In a method of coating wire according to the invention the preheating means consists of a bath C containing molten lead L heated by electrodes D immersed in the lead and situated nearer the entry end of the bath. A bath F for the coating metal, e.g. zinc, is separated from the bath C by a partition N and a continuous layer M of pulverized coal, charcoal, &c. covers the lead L, the partition N, and the zinc J. The wire B is drawn through the air-excluding layer M into the lead where it is heated to annealing temperature and gradually cooled. It passes over the partition N into the bath F without passing out of the airexcluding layer M, the excess heat of the wire maintaining the zinc in contact therewith in a molten state so that no external heating of the zinc bath is necessary. The zinc in contact with the walls of the vessel F is therefore cool and may solidify, so that the life of the vessel F is prolonged. Pickling or electrolytic cleaning of the articles prior to preheating is necessary only in special cases, e.g. if the articles are coated with lime or other calcium compound. Reference has been directed by the Comptroller to Specifications 19696/07, [Class 82, Metals and alloys], and 287,201, [Class 82 (ii), Washing granular &c.].