US948663A - Method of coating metals by cementation. - Google Patents

Description

A. SANG" METHOD OF COATING METALS BY QEMENTATION. APPLICATION FILED JAN. 2, 1909.

Patented Feb. 8, 1919.

WITNESSES INVENTOR Wm A W MSW w Miff ALFRED sane, or BELLEVUE, PENNSYLVANIA.

METHOD OF COATING METALS BY CEMENTATION.

Specification of Letters Patent.

Application filed January 2, 1909.

Patented Feb. 8, 1910.

Serial No. 470,369.

To all whom it may concern:

'Be it known that I, ALFRED SANG, of Bellevue, Allegheny county, Pennsylvania, have invented a new and useful Method of Coatin Metals by Cementation, of which the fol owin is a full, clear, and exact description, re erence being had to the accompanying drawing, forming part of this specification, in which the figure is a longitudinal vertical section of one form of apparatus which may be used in carrying out my invent-ion. Z

My invention has relation to a method of coating metals with other metals, by cementation; and is designed to provide a novel, simple and effective method of this character which will largely overcome the difliculties heretofore experienced in this class of work; which will effect a large saving of time and heat, and which will reduce the danger of oxidation of the coating material. I Y

The great drawback heretofore in coating metals by cementation has consisted in the fact that the coating metals, which are either in the form of a salt of the metal, an oxid, or an oxidized powder, are non-conductors, of extremely poor conductors, of both heat and electricity. This has made it difficult to get theheat through the coating metal and to get an even distribution of heat at all portions of the surface or surfaces to be coated, except after a considerable period of tinie. The results, even where rotating drums and other meanshave been employed to facilitate the distribution of heat, have been very irregular. My improved method is designed to obviate these difliculties by overcoming the resistance of the coating material to the passage of heat and. by providing a simple and efiicient method whereby a proper heating action may be obtained.

In accordance with my invention, I immerse or bury the article or articles to be treated in the coating material, which is in the usual powdered form, and when an oxid, or oxidized dust is employed as the coating material a reducing agent, such as carbon, or better still, carbonic oxid gas is employed, If some other compound of\t he metal is used, suitable reagents are added excepting when the heat alone will reduce'tlie coating material to the proper condition. I then heat the article or articles by means of an electric current. This may be accomplished in the case of pipes, as shown in the accompanying drawing, in which the numeral 2 designates a retort of any suitable character, 3 the powdered coating metal or compound of the metals in which the article 4 to be coated (such as an iron or steel pipe) is immersed or buried. The pipes 4 are supported .at their ends by terminals 5, which may be of conical form, and which pass through non-conducting heads 6, or non-conducting portions of the heads, of the retort, and which are connected with any suitable source of electric energy (not shown). The article or articles may be quickly brought to the necessary temperature to bring about the decomposition of the c'oatin material and the deposition of the coatmg metal upon the article. This temperature will be substantially uniform throughout the extent of the article, thus insuring uniformity of result.

When a plurality of articles are to be simultaneously treated, they may be all buried or immersed in the coating material and connected in multiple in the heating circuit.

With articles which form good resistances,

and therefore heat up readily, they may be connected in various ways, as by copper conductors of sufficient capacity to prevent undue heating thereof.

My invention is applicable to the coating of various articles with various coating met als, a specific instance being the coating of iron or steel articles with zinc, in which case the zinc used is preferably in the form of owdered zinc oxid, or zinc dust, the articles being buried or immersed in the oxid or dust, with a reducin agent, and heated in the manner describe Where the coating material is a straight metal, the deposition takes place without a reducing agent, but carbon may be added to prevent oxidation. Where, however, the coating material 1s oxidized, as zinc dust, antimony dust,'precipitated copper dust, copper converter flue dust, and the like, and with the OXldS of these and other metals, a reducing agent should be employed. Various compounds of the metals may be used, with the addition of a suitable agent or agents for taking care of the non-metallic elements. I may also use a combination of difierentmetals which will either unite to form an alloy coating, or which will be separately deposited to form a compound coating. Thus, if copper dust and zinc dust are employed, a brass coating will be deposited. In some cases, however, I have noted a separation, or partial separation of the zinc and copper in the coating, showing or tending to show a precipitation of copper by the zinc before the zinc is deposited. It will also be obvious that various forms of apparatus may be used to carry out the invention.

What I claim is: p

1. The method of coating metal with another metal or metals by cementation, which consists in burying or immersing the article to be coated in a metallic coating material, and passing an electric current through the article to heat it to a sufficient temperature to cause the deposition of the coating material thereon; substantially as described.

2. The method of coating metal with another metal or metals by cementation, which consists in burying or immersing the article to be coated in the metallic coating material, and heating the article by an electric current, in the resence of a reducing agent, to thereby efl ect a reduction of the coating metal and its deposition upon the surfaces of the article to be coated; substantially as described.

3. The method of coating metals with another metal or metals by cementation, which consists in surrounding the article to be coated with the metallic coating material in finely divided form and with a reducing agent present, and then passing an electric current through the article as a resistance core to effect a reduction of the coating material and its deposition upon the surfaces of the article to be coated; substantially as described.

4. The method of coating metal with another metal or metals by cementation, which consists in bringing the metal surface of the article to be coated in contact with the metallic coating material, and then heating such article by passing an electric currenttherethrough; substantially as described.

In testimony whereof, I have hereunto set GEO. H. PARMELEE.

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