US1072091A - Process for protecting iron surfaces from corrosion. - Google Patents

Description

SHERARD OSIBOBN COWPER-COLES, OF WESTMINSTER, LONDON, ENGLAND.

PROCESS FOR PROTECTING IRON SURFACES FROM CORROSION.

1,072,091. No Drawing.

Specification of Letters Patent.

A Application filed November 23, 1912. Serial No. 733,097.

To all whom it may concern Be it known that I, SHERARD Osnonnv follows that is to say, I first remove all scale, grease and oxid from the articles to be treated, in any of the well known manners, such as by pickling or sand blasting, and I then electro-deposit upon them a coating of iron as pure as possible. The iron may be deposited from any suitable electrolyte, for example, ferrous sulfate. The articles after having been coated with pure or practically pure iron, are washed and then placed in a second vat, in which a coating of zinc or zinc-iron alloy is deposited upon the pure iron.

I would here remark that a thin coating or film of chemically pure iron has been suggested by other workers as a basis for the deposition of metals such as tin, nickel and copper, but whereas they deposited a film of iron, with the object of increasing the adhesion of the metal subsequently to be deposited upon the iron, I cause a comparatlvely thick coating of pure iron to be deposited upon the iron or steel, which deposit, being slightly electro-positive to the underlying metal, acts in itself as a protective coating. In fact, in many cases, the amount of iron deposited exceeds the amount of zinc or zinc-iron alloy subsequently deposited thereon.

In a modification of the invention, I may advantageously effect the deposition of both iron and zinc or zinc-iron alloy from the same electrolytic bath, which is made up of a mixture of zinc and iron salts. When this procedure is adopted, a low current density is employed in the first instance, so

as to deposit iron, and toward the end of the depositing process, the current density is increased, in order to deposit a zinc-iron alloy. The electrolyte is made up with iron and zinc sulfates, about 20 ounces of the crystallized salts of each metal to each gallon of water. Insoluble anodes are employed in conjunction with small iron anodes, and the electrolyte circulated over scrap zinc, in order to keep the zinc content in the electrolyte the same. The relative proportions of zinc and iron in solution are varied according to the current density it is desired to employ, which varies with the class of work to be coated, whether flat work or work having deep hollows. The current density usuallyemployed ranges from 5 amperes to 20 amperes or more per square foot of cathode surface.

In some cases the articles may finally be subjected to a heating or baking process, to effect a closer union of the deposits with the surface of the articles.

Claims:

1. A process for protecting iron and steel surfaces from corrosion, which consists in first depositing a thick protective coating of substantially pure iron upon the prepared surface and then depositing upon the protective coating, a further protective metallic coating. containing zinc.

2. A process for protecting iron and steel surfaces from corrosion, which consists in first depositing a thick protective coating of substantially pure iron upon the prepared surface, then depositing upon the iron a coating of zinc alloy and then subjecting the same to a final heating or baking treatment.'

3. A process for the protection of iron and steel surfaces from corrosion, which consists in subjecting the same to an electrolytic bath composed of zinc and iron salts, employing a low current density to effect the deposition thereon of iron, and then increasing the current density to effect a deposit of zinc iron alloy.

SHERARD OSBORN GOWPER-GOLES.

Witnesses WM. BRADDOCK, G. L. BUTLER.

Patented Sept. 2, 1913.