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Publication numberUS2418608 A
Publication typeGrant
Publication dateApr 8, 1947
Filing dateJun 3, 1940
Priority dateMay 22, 1939
Publication numberUS 2418608 A, US 2418608A, US-A-2418608, US2418608 A, US2418608A
InventorsTanner Robert R, Thompson John S
Original AssigneeParker Rust Proof Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Corrosion-resistant metallic article and method of making the same
US 2418608 A
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Description  (OCR text may contain errors)

Patented Apr. 8, 1947 UNITED STATES- PATENT OFFICE CORROSION-RESISTANT METALLIC ARTI- CLE AND IVIETHOD OF MAKING THE SAME John S. Thompson and BobertR. Tamer, De-

troit, Mlch., assignors to Parker Rust Proof Company, Detroit, Mich. 1

No Drawing. Application June 3, 1940, Serial No. 338,582. In Canada May 22, 1939 2 Claims. 1

.paring metals for paint, to treat the metal with solutions of phosphates or oxalates by means of which phosphate or oxalate coatings are produced. These coatings result from an attack on the metal by the solution with the simultaneous formation of the coating as an integral part of the underlying metal. It is also common practice to employ solutions which result in the formation of oxides oi the metal treated. With these and similar processes, it is customary, after a coating of the desired nature is formed, to remove'the coated article from the solution, rinse, and dry it. Then, if desired, a paint finish can be applied at any convenient time.

The invention has as the object the treatment of metal surfaces for the prevention of corrosion and to provide a paint base for applying a film of corrosion-retarding chemicals and drying it on the metal surface. One specific object is to include a metal having a valence of two or more in a hexavalent chromium solution and thereby increase the corrosion-resistance of a coatin formed by drying a film of such a solution. Another specific object is to so select the chemicals employed that advantage may be taken of the corrosion-inhibiting quality of hexavalent chro mium compounds without excessive detrimental efiect from the usual hygroscopic nature of chromic acid. Another specific object is to increase the wetting ability of the solutions employed, thereby decreasing the necessity for a wetting agent.

These objects are accomplished by employing 40 a solution containing, in addition to a soluble phosphorous compound and a hexavalent chromiuin compound, a metal having a'valence of two or more. When the metal ls'introduced in the metallic form or is in a compound that will reduce some of the hexavalent chromium, the proportions must be such that hexavalent chromium will remain in the solution when it is used to coat the metal. It is usually more convenient to introduce the metal into the solution in the form of a soluble salt.

The solutions hereinafter described are effective on all industrial metals including iron, steel, zinc, cadmium, magnesium, tin, lead, nickel,

ment of ferrous surfaces, zinc, cadmium and nickel being especially important.

The effect of the presence in the solutions, of metals having a valence of two or more, is not entirely understood so far as the increase in corrosion-resistance is concerned. However, the fact that their presence provides a solution of 'a less hygroscopic nature than when, for example, only phosphoric and chromic acid is used, is more 10 easily explained. Chromic acid is well known for its tendency to absorb moisture. When metallic ions and ions of hexavalent chromium are introduced into a solution, an equilibrium is reached resulting usually in some dichromate of the metal.

15 Upon drying, the metal dichromate will not show the hygroscopic nature characteristic of chromic acid. When a metal having a valence of two or more is employed in the solution in the manner described, not only will the film on the surface of 20 the metal, resulting from application of the solution be less hygroscopic, but its corrosion-resistance is increased.

While the metals may be added in various other ways, it is preferable with most metals to intro- 25 duce themas phosphates or dichromates since this maintains the solution in its simplest form and no extra operations are necessary in the manufacture of the material.

A film of solution is applied to the metal surface and is dried thereon without the application of heat, or by baking. A small amount of free acid left in the coating does no harm from a practical viewpoint, if the surface is dried so that the treated article can be handled properly.

Solutions such as described below, containing chromic acid or dichromates, have some tendency to creep away from edges and perforations. These points are where corrosion usually starts and it is especially important that such areas retain the applied solution. In order to provide proper wetting, especially in cases where the cold solution is applied to cold metal, it is sometimes best to incorporate in the solution a suitable wetting agent. Amounts in the neighborhood of .5% have been found satisfactory under some conditions.

Where a heated solution is used, or the metal to be terated is heated, or both the solution and metal are employed at an elevated temperature, little or no wetting agent is required.

Following are examples of aqueous solutions which are especially adapted to the treatment of large structural members such as used in aluminum, copper, and alloys thereof, the treatbridges, freight cars, petroleum storage tanks and 3 so forth, where air drying of the applied film is especially. desirable.

Per cent 1. Zinc dihydrogen phosphate 2.8 75% phosphoric acid 2.5 Chromic acid 1.0

2. Chromic dihydrogen phosphate 2.5 75% phosphoric acid 2.5 Chromic acid 1.0

3. 75% phosphoric acid 3.0 Zinc dichromate 1.4

Usually it is most convenient to apply these solutions to structural members, etc., without heat, and .5% of a wetting agent may be added.

Following are'examples of solutions which after application will usually require forced drying such as baking because of the higher concentrations of the chemicals used.

8. Ammonium dichromate 10.0 Zinc dihydrogen phosphate 5.5

In the preceding examples, a wetting agent commercially known as Duponol WA (registered trade-mark) paste may be used. Its active base is sodium lauryl sulphate. Other compatible wetting agents may be employed, one precaution being that they must not be excessively oxidized by the hexavalent chromium. Other materials which have been found satisfactory as wetting agents and are to a more or less degree compatible with the solution are the sulphonation products of the higher alcohols.

Where solutions such as described above are properly dried on ferrous surfaces, there is some reaction resulting in ferric iron in the dried coating. Magnesium, cadmium, nickel and other metals having a valence of two or more, can be substituted for the metals given in the examples, and two or more of these metals may be employed in the same solution if desired.

The solution may be applied in any desired .manner such as dipping, spraying, brushing, and

so forth, care being taken to produce on the metallic surface, a uniform film. In every case the success of the invention lies in drying the film on the surface of the metal since the beneficial effects of the invention are obtained from the film dried on the surface.

It should be understood that in place of orthophosphoric acid or its compounds, other compounds of phosphorous, such as meta, pyIO, and hypo, may be employed for making up the soution, but in'a solution of the kind described such compounds will result in orthophosphoric compounds.

While a number of metals have been mentioned which added to the solution will attain the objects of the invention, zinc is preferred.

It is to be understood that the aforementioned materials, conditions, temperatures and other factors may be varied without departing from the spirit of the invention, the scope of which is to be measured only by the following claims.

What we claimis:

l. A process which comprises applying to an industrial metallic surface a film of an acidulous aqueous solution the chief compounds in the solution as applied containing the P04 radical, hexavalent chromium and a metal having a valence of at least two and acting as a cation, said film containing sufflcient chemicals to form a corrosion-resistant paint-holding coat when dried, and drying the film on the metallic surface.

2. A process which comprises applying to an industrial metallic surface a solution containing as its chief ingredients when applied phosphoric acid, chromic acid and a salt of a metal having a valence of at least two and acting as a cation. said film containing sufficient chemicals to form a corrosion-resistant paint-holding coat when dried and drying the film on the metallic surface.

3. A process which comprises applying to an industrial metallic surface a film of an acidulous aqueous solution the chief compounds in the solution containing the P04 radical, hexavalent chromium and zinc, said film containing sufilcient chemicals to form a corrosion-resistant paintholding coat when dried, and drying the film on the metallic surface.

4. A process which comprises applying to a surface of iron or steel a film of an acidulous aqueous solution the chief compounds in the solution as applied containing the P04 radical, hexavalent chromium and. a metal having a valence of at least two and acting as a cation, said film containing sufficient chemicals to form 'a corrosion-resistant paint-holding coat when dried, and drying the film on the metallic surface.

5. A process which comprises applying to a surface of iron or steel a film of an aqueous solution containing as its chief ingredients phosphoric acid, chromic acid and a compound of zinc, said film containing sufficient chemicals to form a corrosion-resistant paint-holding coat when dried, and drying the film of the solution on the metallic surface.

6. A process which comprises applying to a surface of zinc a film of an aqueous solution containing as its chief ingredients phosphoric acid, chromic acid and a compound of zinc, said film containing sufficient chemicals to forma corrosion-resistant paint-holding coat when dried, and drying the film of the solution on the metallic surface.

7. A process which comprises applying-to a surface of cadmium a film of an aqueous solution containing as its chief ingredients phosphoric acid, chromic acid and a compound of zinc, said film containing sufficient chemicals to form a corrosion-resistant paint-holding coat when dried, and drying the film of the solution on the metallic surface. v

8. An article of manufacture having a surface of an industrial metal covered with a corrosionresistant paint-holding coat having the composition resulting from drying on said surface a film of an acidulous aqueous solution the chief compounds in which solution as applied contain the P04 radical, hexavalent chromium and a metal having a valence of at least two and acting as a 5i of iron or steel covered with a corrosion-resistant paint-holding coat having' the composition resulting from drying on said surface a, film of an acidulous aqueous solution the chief compounds in which solution as applied contain the P04 radical, hexavalent chromium and zinc.

11. An article of manufacture having a surface of zinc covered with a corrosion-resistant paintholding coat having the composition resulting from drying on said surface a, film of an acidulous aqueous solution the chief compounds in which solution asapplied contain the P04 radical, hexavalent chromium and a metal having a valence of at least two and acting as a cation.

12. An article of manufacture having a surface of cadmium covered with a corrosion-resistant paint-holding coat having the composition resulting from drying on said surface a film of an acidulous aqueous-solution the chief compound in which solution as applied contain the P04 radical, hexavalent chromium and a metal having a valence of at least two and acting as a cation.

' JOHN S. THOMPSON.

ROBERT E. TANNER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,923,502 Prier n Aug. 22, 1933 2,030,601 McDonald Feb. 1.1, 1936 1,826,866 Cole Oct. 13, 1931 1,791,715 Darsey Feb. 10, 1931 1,719,464 Cole Nov. 19, 1929

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1719464 *Mar 11, 1929Jul 2, 1929Howard Cole WilliamProofing of iron and steel against rust
US1791715 *May 13, 1929Feb 10, 1931Parker Rust Proof CoCoating metal
US1826866 *Feb 24, 1930Oct 13, 1931Howard Cole WilliamProofing of metal against corrosion and particularly of iron and steel against rust
US1923502 *Apr 6, 1931Aug 22, 1933Pierre PrierProcess and product for protecting aluminium, magnesium, zing and their alloys against corrosion
US2030601 *Feb 2, 1935Feb 11, 1936Victor Chemical WorksRustproofing composition and method of coating iron and steel
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2494909 *Feb 28, 1947Jan 17, 1950American Chem Paint CoMethod of coating copper, brass, terneplate, magnesium, zinciferous and ferriferous metals
US2497905 *Mar 3, 1945Feb 21, 1950Rheem Mfg CoCoating zinc or cadmium to impart corrosion and abrasion resistance
US2514941 *Jul 26, 1947Jul 11, 1950Walterisation Company LtdProcess for increasing the corrosion-resistance of metals
US2564864 *Jul 2, 1948Aug 21, 1951Parker Rust Proof CoMethod of and solution for increasing resistance to corrosion
US2657156 *Jul 21, 1949Oct 27, 1953Parker Rust Proof CoPhosphate coating composition and process
US2706171 *Mar 9, 1953Apr 12, 1955EnthoneStripping chromium plating from zinc electrolytically
US2737498 *Aug 28, 1951Mar 6, 1956Produits Chim Terres Rares SocProduct for and process of treating metallic articles before coating
US2753282 *Jul 27, 1953Jul 3, 1956Allegheny Ludlum SteelMethod of forming insulating coat on steel and composition therefor
US2769774 *Aug 5, 1952Nov 6, 1956Republic Steel CorpElectrodeposition method
US2868679 *Dec 5, 1955Jan 13, 1959Turco Products IncProcess and compositions for producing aluminum surface conversion coatings
US3144361 *Sep 21, 1959Aug 11, 1964Stefan KlinghofferPretreating iron or steel
US3151087 *Dec 9, 1957Sep 29, 1964Nalco Chemical CoCorrosion inhibiting compositions and method
US3154438 *Mar 8, 1962Oct 27, 1964Hooker Chemical CorpProcess for treating metal surfaces
US3192075 *Sep 10, 1962Jun 29, 1965Marsh Steel & Aluminum CoPhosphate treatment composition for iron and steel products
US3214302 *Feb 16, 1962Oct 26, 1965Hooker Chemical CorpMethod for forming insulating coatings on metal surfaces
US3404045 *Oct 17, 1963Oct 1, 1968Lubrizol CorpConversion coating containing partially reduced chromic acid, a metal dichromate and phosphoric acid
US3935036 *Feb 19, 1974Jan 27, 1976Zenith Radio CorporationMethod of forming a dark, very adherent coating on a CRT mask assembly
US4647315 *Jul 1, 1985Mar 3, 1987Olin CorporationChromic acid, phosphoric acid
US4952285 *Dec 22, 1989Aug 28, 1990Olin CorporationUsing mixture of chromic and sulfuric acid
US4961828 *Apr 5, 1989Oct 9, 1990Olin CorporationPretreating with chromic acid solution before forming copper or copper oxide dendrites or nodules on surface
US5022968 *Sep 20, 1990Jun 11, 1991Olin CorporationOxidation resistance; removable with dilute hydrochloric or sulfuric acid
US5071520 *Oct 30, 1989Dec 10, 1991Olin CorporationMethod of treating metal foil to improve peel strength
US5098796 *Mar 25, 1991Mar 24, 1992Olin CorporationChromium-zinc anti-tarnish coating on copper foil
US5164235 *Mar 6, 1990Nov 17, 1992Olin CorporationTreating copper with chromium and zinc ions
US5230932 *Mar 20, 1992Jul 27, 1993Olin CorporationChromium-zinc anti-tarnish coating for copper foil
US5338619 *Aug 4, 1992Aug 16, 1994Fukuda Metal Foil And Powder Co., Ltd.Copper foil for printed circuits and method of producing same
US5356527 *Aug 9, 1991Oct 18, 1994Olin CorporationRinsing in aqueous buffer solution of alkali metal or alkaline earth metal phosphates or borates maintained at specified pH
US7168110Dec 16, 2004Jan 30, 2007Benoit GirardParamedical transfer stretcher, harness and method
WO1990012129A1 *Apr 5, 1990Oct 18, 1990Olin CorpTreatment of metal foil
Classifications
U.S. Classification428/472.1, 106/14.12, 148/258
International ClassificationC23C22/05, C23C22/33
Cooperative ClassificationC23C22/33
European ClassificationC23C22/33