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Publication numberUS2800422 A
Publication typeGrant
Publication dateJul 23, 1957
Filing dateApr 20, 1953
Priority dateApr 20, 1953
Publication numberUS 2800422 A, US 2800422A, US-A-2800422, US2800422 A, US2800422A
InventorsAchille Piccinelli
Original AssigneeAchille Piccinelli
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Process for rust-proofing and passivating iron articles
US 2800422 A
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Description  (OCR text may contain errors)

United States Patent PROCESS FOR RUST-PROOFING AND PASSIVATING IRON ARTICLES Achille Piccinelli, Turin, Italy No Drawing. Application April 20, 1953, Serial No. 349,963

1 Claim. (Cl. 148-615) It is known to prepare the surfaces of iron articles for painting by previously providing thereon at protecting film of inorganic salts, such as iron, zinc and manganese phosphates or coating them with a metallic film, for example, by zinc-plating, chrome-plating, nickel-plating, or copper-plating. It is also known to treat protecting phosphate films with chromate or dichromate ions.

Such treatments suffer, however, from a serious drawback consisting in the formation, on the surface of the treated iron articles and underneath the paint film, of a layer of considerable thickness, easily susceptible to cracking and forming a brittle base for the coat of paint provided on the surface of the articles. 1

The object of the present invention is to provide an improved process for preparing the surfaces of iron articles for receiving paint coatings and making them rustproof, without providing them with a brittle coating.

The process according to this invention consists in:

(a) Forming on the surface of such articles a coating of a phosphate, or phosphates of iron, zinc and/or manganese,

(b) Dissolving the phosphate coating so formed, and

(c) Passivating the newly exposed surface by the use of a solution containing chromate or dichromate ions.

The treatment according to the above disclosed process will preferably be preceded by cleaning or degreasing of the articles to be treated when they are particularly soiled or smeared. This may, however, be eliminated if the articles are relatively clean by reason of the fact that the composition used in carrying out the process cleans the article surface to a sufficient extent.

An example of a manner of carrying out the process according to this invention as well as substances suitable for this purpose will now be described. The substances may be for instance as follows:

The term ethylene oxide condensate used below is intended to designate any of the well-known detergents which are sold commercially under trade names such as Igepal.

Substance No. 1: Any of the known detergent agents known for cleaning sheet metal, when this step is required:

Substance No. 2: Percent Zn (NO3)2 (zinc nitrate) 11 H3PO4 (phosphoric acid) 5.7 Zn(H2PO4)2 (acid zinc phosphate) 64 Ethylene oxide condensate 19.3

Substance No. 3:

Zn(NOa)2 (zinc nitrate) 18 HNOa (nitric acid) 38.5 H3PO4 (phosphoric acid) 35 Ethylene oxide condensate 8.5

2,800,422 Patented July 23, 1957 1 2 Substance No. 4: Percent CrzOa (chromic anhydride) 46 H3PO4 (phosphoric acid) 54 Substancev No. 5: Silicone containing foam inhibiter.

A manner of carrying out the process by using the above mentioned substances shall now be described.

1st liquid-preliminary pickling, if necessary.Any desired pickling and scouring agents, such as higher sulphonated fatty alcohols at a temperature of approximatively 6070 C. can be employed.

2nd liquidcleaning and phosphatising.This liquid is prepared of substance No. 2 in a proportion of 7 grams to the liter of solution ready for use, its free acidity should range between 0 and 0.2 and its total acidity should range between 5 and 12.

The treatment is carried out by spraying at room temperature for a period of one to three minutes according to the type and conditions of sheet metal or other ferrous articles treated.

3rd liquid-solution of the freshly formed phosphates.-This solution is prepared by substance No. 2 in a proportion of 7 grams to the liter of solution ready for use, which is further admixed with substance No. 3 in a proportion of 3 grams to the liter of solution ready for use. Treatment is effected by spraying for a period of about one minute at room temperature.

The solution should be made up by using exclusively substance No. 3 in order to maintain the following values constant: free acidity, 1-2.5; total acidity, 20-25. The articles treated by this liquid are rapidly rinsed in cold water.

4th liquidpassivation.-The liquid is prepared by substance No. 4 in a proportion of 0.8-1 gram to the liter, according to the hardness of water. Free acidity of the bath should be 0.4 and its total acidity 2.

The liquid is kept during treatment at a temperature of 50-60 and the period of treatment is 30 to 60 seconds.

The liquid should be made exclusively by substance No. 4.

In order to avoid foaming of the first and second liquid, small percentages of foam inhibiter (substance No. 5) are added thereto.

In some cases the 1st liquid treatment (preliminary cleaning) may be omitted, when the article immediately undergoes the action of the liquid prepared by using substance No. 2 as disclosed above. The presence of ethylene oxide condensate ensures a sutficient cleaning if the article surface is not particularly soiled or smeared.

The process of the present invention may be carried out without treating the article surface, on which a coating of a phosphate or phosphates have been formed, with the liquid referred to above as the 3rd liquid. Thus, the coated surface may be subjected directly to the action of the liquid prepared by using substance No. 4 in the manner disclosed above, dissolving of the phosphate coating formed and passivating of the newly exposed surface being ensured by using a liquid of the specified acidity values.

It will be understood that in carrying out the present invention the preparation of the iron articles for painting need not necessarily be effected bythree separate liquids or in three separate baths. It is immaterial how the three stages in the process are caused to take place on the sheet metal.

Should it be impossible owing to the character of the plant or other reasons to carry out steps 1-2-3 or steps 'Re'ferencesCited in the file of this patent UNITED STATES PATENTS Jernstedt Feb. 9, Gibson June 20, Miles Feb. 8, Snyder Aug. 16, Douty et a1. July 25, Snyder et al May 15,

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2310239 *Oct 25, 1941Feb 9, 1943Westinghouse Electric & Mfg CoCorrosion resistant coating for metal surfaces
US2351605 *Mar 2, 1942Jun 20, 1944Parker Rust Proof CoMetal treatment
US2461228 *Jul 4, 1945Feb 8, 1949Magnesium Elektron LimitedDonald lee miles
US2479423 *Feb 7, 1946Aug 16, 1949American Chem Paint CoMethod of and materials for treating surfaces of iron, zinc, and alloys of each
US2516685 *Apr 19, 1944Jul 25, 1950American Chem Paint CoProcess of preparing iron and aluminum surfaces to receive organic coatings and solution therefor
US2552874 *May 1, 1950May 15, 1951American Chem Paint CoMethod of phosphatizing ferriferous surfaces
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2983634 *May 13, 1958May 9, 1961Gen Am TransportChemical nickel plating of magnesium and its alloys
US2987427 *Jan 27, 1958Jun 6, 1961Ici LtdMetal coating baths
US3005729 *Mar 13, 1958Oct 24, 1961Muirhead & Co LtdSurface blackening process for steels
US3101287 *Jan 3, 1961Aug 20, 1963Curtin Leo VConditioning treatment for metal surfaces
US3102830 *Mar 20, 1961Sep 3, 1963Bernard TiteuxEstablishment of ph value of a phosphoric acid solution by its reaction with iron prior to its use to treat ferrous surfaces
US3116177 *Oct 17, 1960Dec 31, 1963Montedison SpaProcess for degreasing and oxalating in a single spray stage
US3262903 *Jun 27, 1963Jul 26, 1966Du PontGreen chromium oxide pigment in epoxy resin and phosphatized epoxy resin coatings
US3397093 *May 19, 1964Aug 13, 1968Hooker Chemical CorpTreatment of metal surfaces
US3645797 *Dec 17, 1969Feb 29, 1972Hooker Chemical CorpMetal phosphatizing composition and process
US4231812 *Mar 13, 1979Nov 4, 1980Centre De Recherches Metallurgiques-Centrum Voor Research In De MetallurgieSurface treatment of metal strip
US4717431 *Feb 25, 1987Jan 5, 1988Amchem Products, Inc.Nickel-free metal phosphating composition and method for use
US6183570 *Apr 15, 1999Feb 6, 2001Nihon Parkerizing Co., Ltd.Surface treatment process of metallic material and metallic material obtained thereby
Classifications
U.S. Classification148/255
International ClassificationC23C22/83, C23C22/82
Cooperative ClassificationC23C22/83
European ClassificationC23C22/83