US2038550A - Method of electroplating cadmium on cadmium-zinc alloys - Google Patents

Description

April 28, 1936. E Q DOMM 2,038,550

METHOD oF ELEGTROPLATING CADMIUM oN CADMIUM-ZINC ALLoYs Filed oct. 31, 1934 ferrous Ue/'re @@WM@ @www Patented Apr. 28, 1936 UNITED vSTATES METHOD OF ELECTROPLATING CADMIUM ON `CADMUltI-ZINC ALLOYS Elgin CarletonDomm, Niles, Mich., assignor to National-Standard Company,v Niles, Mich., a corporation of Michigan Application October 31, 1934, Serial No. -750,874

8 Claims.

'I'his invention relates to improvements in a method of coatingmetal.

This application is a continuation-impart of my co-pending application Serial No. 653,549, filed January 25, 1933.

In the Crapo patent No. 1,984,335 issued Dec. 11, 1934, is described a method of coating a ferrous article by hot-galvanizing it with zinc, and over that depositing by some other method an additional coating of cadmium. Y

It has now been discovered that in those methods the thickness of the undercoating may be decreased without injuring corrosion-resistance to the type of corrosion of which salt-spray is typical, if instead of the zinc under-coating an alloy of cadmium and zinc is used for such under-coating. At the same time, such an alloy may be applied at a lower temperature, and thus may be used .in certain instances where the application of zinc alone by the hot-dip method might interfere with the character of the base.

The invention is particularly applicable to coating strands of wire to be used in reinforcing the bead of a tire. 'I'he wire when so used commonly acts as a tension-member, and is imbedded in a rubber or rubber compound. When i so used, the wire is exposed tocorrosive and rusting agents, particularly to moisture which may seep into the tire.

The drawing shows in diagrammatic form an embodiiifnt of my invention.

In ac ordance with the invention, aemetal, for example wire suitable for' use in tire beads, is first hot-dipped to provide a coating of a cadmium-zinc alloy. This may be done, for example, by dipping the wire in a hot molten alloy of zinc and cadmium. Such an alloy always has a melting point 'lower than-that of zinc. and certain of the alloys have' a melting point below that of either zinc or cadmium.-

A coating of cadmium is then putover the rst coat by electrolysis or electroplatlng. Not only does a double coating applied by the above mentioned method give very good 'corrosion-resistance, but it has r tro-coat tends to ll in the depressions in the lower zinc-cadmium alloy coat and thus produce a uniform and smoothcoating. A coating of the order of thickness of the lower coat is preferred.

, may be applied If desired, copper or. other suitable material over the corrosive-resistant double coating in order to increase the adhesiveness of the 'wire tovrubber. It is frequently desirable to apply such a coating when wire is used as a reinforcement fora tire bead. 4

, The new process herein described is especially usefulln procuring a coating of a desired and uniform thickness. In practice, the wire is given a hot coat ilrst, and preferably! wipe this thin. In the next stage. the coating is put on by elecbeen discovered that the elec- (C1. sii-) troplating;` the operation can be continued to give exactly a desired thickness. time, the coating acquires a smooth, uniform character which is freefrom holes, defects, and the like.

As an example of the invention, it is preferred to use an alloy of approximately zinc and 20% cadmium as the undercoating, because of its marked corrosion-resistance to the type of corrosion of which the salt spray is typical.

In general it is preferred that the alloy contain at least 10% cadmium and at least 30% of zinc.

The foregoing description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, but the appended claims should be construed as broadly as permissible'in view of the prior art.

What I regard as new and desire to Letters Patent is:

l. 'Ihe process of coating a ferrous article which comprises applying;to it by the hot-dip secure by At the same zinc, and electro-depositing thereon an outer coating of cadmium.

2. The method of coating a metal to increase its corrosion-resistance comprising rst applying to it a molten zinc-cadmium alloy, and then applying a second coating of cadmiuml over the first coating.

3. 'Ihe method of producing-a ferrous tirebead reinforcement wire which comprises ilrst coating a ferrous wire with a zinc-cadmium alloy by the hot-dip process, and then electroplating cadmium over the hot-dipped wire to produce a uniform coating" of desired thickness.

4. 'I'he method as set forth in claim 1, in which 'the zinc-cadmium alloy contains approximately 80 parts of zinc to 20 parts of cadmium.

5. A coated ferrous article, comprising a ferrous base 'having a hot-dipped coating of a zinccadmium alloy thereon, and over that an electrodeposited coating substantially wholly of cadmium. 6- A coated ferrous wire comprising a ferrous base wire having a hot-dipped coating of a cadmium-zinc alloy thcreomand over that an electrodeposited coating substantially wholly of cad- 7. A' coated ltire bead wirecomprising a ferrous base wire having a hot-dipped coating of a zinc-cadmium alloy thereon, and electrodeposited coating substantially wholly of cadmium thereon, and having a coating of rubber vulcanized thereto. l

8. An article as set forth in claim 5, in which the zinc-cadmium alloy contains approximately 80partszinpto20partscadmium.

ELGIN CARIEI'ON DOIN.

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