US3181976A

US3181976A - Phosphating process and composition

Info

Publication number: US3181976A
Application number: US150128A
Authority: US
Inventors: George A Yager
Original assignee: Purex Corp Ltd
Current assignee: Purex Corp Ltd
Priority date: 1961-11-06
Filing date: 1961-11-06
Publication date: 1965-05-04
Anticipated expiration: 1982-05-04

Description

United States Patent This invention relates to the phosphating, also known as phosphatizing, of metals such as steel, and is particularly concerned with means and procedure for controlling sludge formation in phosphating baths during the phosphating process.

Phosphating of metals such as iron or steel, aluminum, zinc, and magnesium, or alloys thereof, is carried out in order to prevent corrosion of the metal and to provide a bonding surface for paints and lacquers. Phosphating is accomplished by contacting a cleaned surface of the iron or other metal suitable for phosphating, with a dilute solution of phosphoric acid, or aqueous acid solution containing phosphate ions. The solution also preferably contains various metal compounds such as, for example, one or more zinc, iron, manganese, magnesium, nickel, and molybdenum compounds. These compounds may be present in the phosphating solution as phosphates. Various oxidizing materials such as nitrates, nitrites or chlorates are usually also added to these baths to accelerate the coating action. Application of the phosphating solution to the metal to be treated may be by spraying, dipping, or other suitable means.

The phosphating process, e.g. on steel, results in the formation on the metal being processed, of a coating comrising phosphate compounds, e.g. iron, manganese, nickel, magnesium or zinc phosphate, which are probably of a complex nature. These phosphate coatings are termed herein heavy-metal phosphates. Such coatings are usually resistant to being rubbed or cracked off the coated metal, exhibit good corrosion resisting properties, and form a good bond with paints.

The art of producing an inorganic heavy-metal phosphate coating on such metals as iron and zinc has progressed from the early stages of development, when extremely high temperature and long contact time were required to produce a substantial coating, to the modern status wherein coatings of superior quality are produced, for example, by zinc phosphate spray applications of about one minute, at temperatures only slightly in excess of 100 F.

When processing steel, it is generally recognized that a freshly prepared phosphating bath as described above will not produce coatings of optimum quality until some iron has been dissolved into the working bath. This may be done by first processing a few initial loads of work pieces and tolerating inferior work for a short time, or preferably by directly introducing into the bath ferrous phosphate, old sludge, steel wool, iron powder, or clean scrap iron objects. A limited amount of iron is thus dissolved and is held in the bath'as ferrous phosphate and, in very small amounts, as ferric phosphate. Ferrous phosphate is soluble in phosphating baths in limited proportion, but it is easily oxidized to the nearly insoluble ferric phosphate.

Most operating baths have a white, milky or cloudy appearance due to a colloidal condition probably representing some kind of ferrous-ferric phosphate complex. Such a condition, bordering on insolubility, usually coexists with the presence of a solid phase of sludge in or at the bottom of the bath. The sludge appears to consist mostly of a mixture of ferrous and ferric phosphates when the bath is being used to process steel parts. There is probably some kind of dynamic equilibrium between the various soluble, insoluble and colloidal ferrous and ferric phosphates present.

iijhlflib Patented May 4, i965 Such sludge formation often takes place in the early stages of operation. However, when employing certain types of phosphating solutions, such as those containing substantial amounts of acid phosphates, and which may also contain appreciable proportions of nitrate, sludge tends to form at a later stage of processing.

The presence of the insoluble phase of sludge causes considerable difficulties at times. The sludge sometimes accumulates to the point that it clogs spray nozzles, or interferes with the coating action of the bath, necessitating the removal of sludge from the tank at frequent intervals.

The accumulation of excessive sludge has inspired much investigation of ways to reduce or eliminate its formation and still maintain adequate but limited amounts of soluble iron phosphates in the bath, which are needed for good coating action. Various agents have been suggested as siudge suppressors, such as certain forms of tartaric acid and tartrates, amino compounds or derivatives, and the like. Some of the suggested agents have been beneficial, in limited degree, but most have been either insufficiently effective or definitely harmful to the phosphate coating.

It is accordingly an object of the invention to provide compositions and procedure for phosphating metals, e.g. steel, while suppressing sludge formation in the phosphating baths.

Another object is the incorporation in conventional phosphating compositions, such as phosphating compositions containing zinc compounds, eg zinc phosphate, of a material which functions to minimize or eliminate sludge formation in such baths during processing therein of metals such as steel, without adversely afiecting the quality of the phosphate coating produced.

Still another object is the provision of phosphating compositions and procedure, employing means for initially providing dissolved iron in the phosphating bath, while at the same time preventing formation of iron-containing sludge.

Yet another object is to provide a novel composition suitable for incorporation into conventional phosphating compositions or baths, especially compositions containing a zinc compound, eg zinc phosphate, such novel compositions including a material functioning as a source of dissolved iron in such baths, and a second compatible substance which functions to suppress tendency toward sludge formation in the resulting bath, due to the iron phosphates formed therein.

A particular object of the invention is the provision of a low sludge forming, zinc-containing phosphating composition for steel, suitable for producing a fine grained phosphate coating of good corrosion resistance and paint bonding qualities.

Other objects and advantages of the invention will be apparent hereinafter.

I have found that when a small quantity of an ascorbic acid is incorporated into phosphating compositions or baths comprising an aqueous acid solution containing phosphoric acid or phosphate ions, the formation of sludge therein is greatly retarded and minimized, and in some instances almost completely eliminated, without adversely affecting the quality of the phosphate coating produced. The mechanism by which ascorbic acid causes suppression of such sludge is presently not known to me.

Ascorbic acid exists in two forms, the l and d forms. Each of the l and d forms of ascorbic acid also exists in two tautomeric forms, namely, the keto and eno forms. I have found the commercially available type of ascorbic acid marketed as vitamin C to be particularly useful. However, any of the above noted forms of ascorbic acid, or mixtures thereof, can be employed in the invention, and the term an ascorbic acid as employed in the specification and in the claims herein is intended to denote any of the known forms of ascorbic acid including, but not limited to, any of those forms noted above.

According to the invention, an ascorbic acid can be incorporated into an aqueous acid phosphating solution containing phosphoric acid or phosphate ions. In addition to phosphoric acid, other sources of a phosphate radical or ion can also be employed, including, for example, borophosphoric acid, and acid phosphate salts such as alkali metal, e.g. potassium and sodium, or ammonium dihydrogen phosphates, and alkali metal or ammonium dihydrogen pyrophosphates. These compounds and phosphoric acid can be present separately or in combinations of two or more thereof. The term phosphate radical or phosphate ion employed in the specification and claims hereof is intended to denote the phosphorus-containing radical or anion derived from any of the aforementioned sources. A simple phosphating solution containing phosphoric acid or phosphate ion is operative to produce phosphate coatings on, for example, steel, and the ascorbic acid present in such solution will inhibit or prevent formation of sludge in the phosphating operation.

Although ascorbic acid alone is effective for sludge suppression, I have also found that the presence of calcium in the above phosphating solution further enhances the elfectiveness of the ascorbic acid in minimizing sludge formation. Such calcium ions can be produced by incorporating into the phosphating solution any soluble calcium compound which does not adversely affect the bath or the coatings to be formed. Thus, for example, the calcium may be incorporated as calcium nitrate, calcium carbonate, or calcium hydroxide. I prefer to employ calcium nitrate, since it is readily soluble and economical, and also introduces some nitrate ion which is beneficial as a phosphating accelerator, as noted below. While I am presently unaware of the mechanism by which calcium combines with the ascorbic acid to suppress sludge in the phosphating bath, it is probable that in the case of processing steel, the iron dissolved from the work surface enters into a soluble complex with the calcium, the phosphate ion, and the ascorbic acid. The calcium ion also aids in providing an improved fine grained phosphate coating.

In preferred practice, the phosphating solution of the invention also contains compounds of other metals, including, for example, ferrous iron, zinc, manganese, magnesium, nickel or molybdenum, or combinations thereof, in order to produce the above mentioned heavy-metal phosphate type coatings on the metal surface. Such compounds may be in the form of phosphates, nitrates, oxides, chlorides, sulfates, or molybdates, and may be of a soluble or relatively insoluble nature. In the latter case, acidic materials, such as nitric acid, can be incorporated into the phosphating solution to solubilize the compound in the phosphating bath. Under conditions of operation of the bath it is accordingly seen that a metal-containing ion, e.g. the zinc ion, is present in combination with the phosphate radical or ion derived, for example, from the phosphoric acid and/ or acid phosphates.

As previously noted, it is also often desirable to incorporate into the phosphating solution various oxidizing materials including nitrates, nitrites, chlorates and peroxides, e.g. hydrogen peroxide, to accelerate the coating action. Such oxidizers or accelerators can be supplied in the form of the free acid, such as nitric acid, to furnish the nitrate radical or ion, or the accelerator radical or anion can be derived from salts containing such radical, for example, sodium or zinc nitrate. In this connection it is preferred to employ as a source of nitrate at least some nitric acid since the use of this acid serves to solubilize any relatively insoluble metal compounds, for example, zinc oxide, which may be present in the bath.

If desired, compatible surface active agents or wetting agents can be included in the phosphating compositions of the invention. These may include, for example, nonionic or anionic wetting agents. The wetting agent functions to enhance the wetting power of the solution and improve its effectiveness. Examples of nonionics which can be employed are the alkyl aryl polyether alcohols, such as the material marketed as Triton X-114 and believed to be a water soluble octyl phenoxy polyethoxy ethanol. Exemplary of the anionic Wetting agents suitable for use in the phosphating solution hereof are the alkyl aryl sulfonates, such as Nacconol Z, believed to be an alkyl benzene sulfonate having an average of 12 carbon atoms in the alkyl chain. Alkyl aryl sulfonates having, for example, 9 to 15 carbon atoms in the alkyl chain, can be employed.

As previously noted, in order to obtain hard, uniform coatings from the commencement of operation of the bath, and with minimum break-in period, it is preferred to incorporate into the phosphating bath iron, either by working the bath initially on clean scrap iron, steel wool or iron powder or, for example, by incorporating an iron compound, such as ferrous phosphate into the bath. This expedient, however, causes the above noted formation of sludge which may be fiocculent and voluminous in the initial period of operation of the bath, and which precipitate is inhibited by the presence of an ascorbic acid according to the invention.

The range of proportions of ascorbic acid which can be employed in the working phosphating solution according to the invention is from about .0010 to about 1.0%, usually about .0015 to about 0.75%, by weight of the solution.

The use of quantities of an ascorbic acid below .0010% by weight results in decreased effectiveness While if quantities of ascorbic acid substantially greater than about 1.0% by weight are employed this tends to inhibit and adversely aiiect the coating action of the solution.

The proportion of phosphate radical or ion which is generally present in the phosphating baths ranges from about 0.05 to about 10% by Weight of the solution.

The amount of calcium in elemental or ionic form which may be present in the phosphating solution should be in the range of about 0.12 to about 0.3%, by weight of the solution. If the amount of calcium present in the bath is less than about 0.12%, it is essentially ineffective as a sludge suppression aid for the ascorbic acid. On the other hand, if the amount of calcium present exceeds about 0.3%, the formation of a satisfactory phosphate coating is inhibited.

The proportion of other metallic constituents in ionic or elemental form, such as zinc, iron, manganese, magnesium, nickel or molybdenum, which may be present, can vary from about 0.01 to about 5%, and preferably is in the range of about 0.1 to about 4%, by weight of the solution.

The proportion of nitrate radical, or ion, or other ac celerator type radical or material present, can range from about 0.05 to about 8%, preferably from about 1 to about 7%, by weight of the solution, and the amount of Wetting agent which can be employed, if desired, can range from about 0.001 to about 0.2%, by weight of the solution.

The working bath can be formed by adding the individual components separately to water or, in preferred practice, a concentrate is formed containing th desired components which, when added to Water in suitable proportions forms the phosphating bath. The ascorbic acid may be present in such concentrate or, if desired, the ascorbic cid can be added separately to the working bath after the concentrate has been properly diluted with water. Where the ascorbic acid is present in the concentrate, this material can be present in proportions of about 0.05 to about 3% by weight of the concentrate, preferably about 0.5 to about 3.0% by weight of the concentrate. The concentration of the other components described above and present in such concentrate are also increased proportionately.

In producing the working solution from a concentrate, the concentrate is generally diluted with water in proportions such that the amount of concentrate present in the working solution may range from about 1 to about 20% by weight of the solution, usually about 2 to about %.by weight of the solution.

Under certain conditions, but usually not in preferred practice, a relatively concentrated solution of the components can be employed without dilution as a working solution. It is of course intended that the most dilute to the most concentrated solutions containing ascorbic acid and the other components of the bath, be within the purview of the invention. Hence, for example, the concentration of the components of the phosphating solutions or compositions of the invention can range broadly as follows: from about 0.05 to about 50% of phosphate radical, from about .0010 to about 3% of an ascorbic acid, from about 0.12 to about 5% of calcium, from about 0.01 to about of ferrous iron, zinc, manganese, magnesium, nickel or molybdenum, from about 0.05 to about 40% of an accelerator, such as nitrate radical, and from about 0.001 to about 5% of wetting agent, by weight of the solution. The above ranges cover concentrations of these components from dilute working solutions thereof to high concentrates. It will be understood, however, that the various individual components stated above as being present within the range of about 0.01 to about 20%, e.g. Zinc, manganese and nickel, can be employed conveniently in different respective amounts in the working solution and in the concentrate, to obtain the desired coating results. For example, in the concentrate, when employing manganese, usually it is preferred to use not more than about 10%, and when employing nickel or molybdenum, preferably an amount of the order of not more than about 4% is used, based on the weight of the concentrate.

It has been found particularly convenient to prepare a concentrate of all of the desired materials except the ascorbic and the ferrous iron, and after diluting such concentrate with water in the proportions described above, adding to the resulting solution a solid composition containing an ascorbic acid and a soluble ferrous salt, for example, ferrous phosphate, ferrous chloride, ferrous nitrate, ferrous sulfate, and the like, preferably, ferrous phosphate. Such composition furnishes the iron ion in the phosphating bath, which functions to produce uniform, hard, satisfactory phosphate coatings substantially from the initial operation of the bath and with very little, if any, break-in period, and also furnishes the ascorbic acid to minimize or prevent sludge as result of the ferrous phosphate-ferric phosphate colloidal complexes and sludge produced particularly in the early stages of the operation of the bath. The proportions of the ascorbic acid and ferrous salt, e.g. ferrous phosphate present in such solid mixtures, can range from about 10% of ferrous salt and about 90% of ascorbic acid, to about 90% of ferrous salt and about 10% of ascorbic acid, by weight of the composition. Such mixture can be added to the working phosphating bath in an amount ranging from about 1 to about 100 ounces per 100 gallons of the solution.

The phosphating bath, containing the ascorbic acid according to the invention, is generally operated at a pH of between about 2 and 4, preferably from about 2.5 to about 3.2. The amount of phosphoric acid and/or acid phosphates employed is generally sufficient to achieve such pH range, and particularly so where nitric acid is also present. It is often necessary to adjust the pH of the bath, particularly at the commencement of the operation, by the addition of an alkali, such as caustic soda, to bring the pH up to a desired operating value, say of about 2.8.

In order to obtain best coating results employing the phosphating solutions of the invention, it is preferred to operate at relatively high temperatures, ranging generally from about to about 210 F., preferably maintaining the phosphating bath at between about to 190 F. Time of treatment of the metal being coated, e.g. steel, can range from about 30 seconds to as high as 30 minutes, depending on the phosphating composition employed, the type of application of the solution, for example, whether by spray or dip application, amount of coating desired, and other factors. The normal contact time is usually from about 1 to about 5 minutes.

The following are examples of operation of the invention:

EXAMPLE 1 The following concentrate was prepared:

Composition A Percent by weight 75% phosphoric acid 15 42 B. nitric acid 24 Zinc oxide 11 Calcium nitrate 24 Water 26 Composition E Percent by weight Ferrous phosphate 50 Ascorbic acid (vitamin C) 50 A fourth Solution F was prepared by adding to still another separate portion of Solution B, ascorbic acid in a proportion of 3 ounces per 100 gallons of Solution B.

The amount of ascorbic acid present in each of Solutions D and F was therefore only about 023% by weight of the solution.

Similar steel parts were introduced into each of Solutions B, C, D and F above, and the baths were each operated in the range of about to about F. for production of a phosphate coating on the parts. The baths were each first adjusted to a pH of about 2.8 by addition of caustic soda to each of the baths.

It required an initial break-in period involving the treatment of a number of steel parts in Solution B, which did not contain any ferrous phosphate or ascorbic acid, in order to dissolve sufficient iron so as to obtain a uniform, hard, complete coating over the entire exposed surface of the parts placed in such solution, and such break-in pe riod was attended by formation of a sludge in the solution.

In the operation of Solution C, containing ferrous phosphate but no ascorbic acid, this initial break-in period was substantially eliminated due to the presence of ferrous ion in the solution, so that uniform and hard coatings were observed on the parts almost from commencement of the coating operation. However, in the initial period of operation of Solution C, sludge was formed in the bath, as in the case of operation using Solution B above.

When operating with Solution D, containing Composition E, including both ferrous phosphate and ascorbic acid, uniform and hard coatings were formed on the parts contained in Solution D substantially from commencement of the operation, and no sludge was formed in the bath.

In the operation of Solution F, containing ascorbic acid, but no ferrous phosphate, an initial period of operation on a number of steel parts was required in order to dissolve sufiicient iron to obtain uniform, hard coatings on the parts in such solution. However, no sludge was formed during such initial period or during the coating operation.

The parts were maintained in each of the above Solutions B, C, D and F for a total period of about minutes after which the parts were removed from the bath and rinsed. Superior fine grained, thick, hard phosphate coatings were obtained particularly on parts processed in Solutions D and F.

EXAMPLE 2 The following concentrate was prepared:

Composition G Percent by weight 75% phosphoric acid 48.5 Zinc oxide 11.4 42 B. nitric acid 11.4 Nickel carbonate 1.1

Water 24.5

Concentrate G is added to water in an amount to form an aqueous solution containing about 3% by weight of Concentrate G.

To such aqueous solution is added Composition H below in an amount such that the resulting solution contains about 0.5% by weight of Composition H.

Composition H Percent by weight Ferrous phosphate 40 Ascorbic acid (vitamin C) 60 The final Solution J is effective as a phosphating solution for steel, to form uniform, hard coatings from the initiation of operation, and without formation of sludge.

EXAMPLE 3 The following concentrate is prepared:

Composition K Percent by weight 75% phosphoric acid 39.4 Manganese carbonate 18.0 4-2 B. nitric acid 2.9 Water 39.7

Concentrate K is added to water in an amount to form an aqueous soltuion containing about by weight of Concentrate K.

To this aqueous solution is added Composition L below in an amount such that the resulting solution contains about 0.2% by weight of Composition L.

Composition L Percent by weight Ferrous nitrate 3O Ascorbic acid (vitamin C) 70 The final Solution M when used for treatment of steel parts produces uniform, hard coatings substantially from the commencement of treatment, and without formation of sludge in the bath.

3 EXAMPLE 4 The following concentrate is prepared:

Composition N Percent by weight Monosodium dihydrogen phosphate 59.0 Sodium dihydrogen pyrophosphate 15.0 Borophosphoric acid (BPO -H O) 7.0 Sodium molybdate 0.5 Triton X-114 3.5

Sodium nitrate -3. 15.0

Composition N is added to water in an amount to form an aqueous solution (Solution 0) containing about 3% by weight of Concentrate N. To such solution is added an ascorbic acid in an amount such that the resulting solution contains about 0.3% of ascorbic acid by weight of the solution. The final Solution 0 when used for treatment of steel parts produces uniform thin amorphous coatings substantially from the commencement of treatment, and without the formation of sludge.

From the foregoing, it is seen that the invention provides a novel means for preventing sludge in phosphating baths, namely, by incorporation of an ascorbic acid in the bath, thus facilitating the coating operation and avoiding the nuisance and disadvantages inherent in sludge formation in such baths, while at the same time achieving hard, uniform phosphate coatings.

While I have described particular embodiments of my invention for the purpose of illustration, it should be understood that various modifications and adaptations thereof may be made within the spirit of the invention as set forth in the appended claims.

I claim:

1. An aqueous acid solution for phosphating metals, consisting essentially of a material containing an effective amount of a phosphate radical and about .0010 to about 3% by weight of an ascorbic acid.

2. An aqueous acid solution for phosphating metals, consisting essentially of a material containing an effective amount of a phosphate radical, about .0010 to about 3% by weight of an ascorbic acid, and about 0.12 to about 5% by weight of calcium.

3. A composition for phosphating metals, consisting essentially of a material containing the phosphate radical in an amount equivalent to about 0.05 to about 50% by weight of said phosphate radical, and about .0010 to about 3% by weight of an ascorbic acid.

4. A composition for phosphating metals, consisting essentially of a material containing the phosphate radical in an amount equivalent to about 0.05 to about 50% by weight of said phosphate radical, about .0010 to about 3% by weight of an ascorbic acid, and about 0.12 to about 5% by weight of calcium.

5. An aqueous phosphating composition consisting essentially of a material containing an effective amount of the phosphate radical, an effective amount of a component of the group consisting of ferrous iron, zinc, manganese, magnesium, nickel and molybdenum, and about .0010 to about 3% by weight of an ascorbic acid.

6. An aqueous phosphating composition consisting essentially of a material containing a phosphate radical in an amount equivalent to about 0.05 to about 50% by weight of such phosphate radical, about 0.01 to about 20% by weight of a component of the group consisting of ferrous iron, zinc, manganese, magnesium, nickel and molybdenum, and about .0010 to about 3% by weight of an ascorbic acid.

7. An aqueous phosphating composition consisting essentially of a material containing a phosphate radical in an amount equivalent to about 0.05 to about 50% by weight of such phosphate radical, about 0.01 to about 20% by weight of a component of the group consisting of ferrous iron, zinc, manganese, magnesium, nickel and molybdenum, a material containing the nitrate radical in an amount equivalent to about 0.05 to about 40% by Weight of said nitrate radical, and about .0010 to about 3% by weight of an ascorbic acid.

8. An aqueous acid phosphating solution consisting es sentially of about 0.05 to about 10% by weight of phosphate ion, about 0.01 to about by weight of a metalcontaining ion of the group consisting of ferrous iron, zinc, manganese, magnesium, nickel and molybdenumcontaining ions, and about .0010 to about 1% by weight of an ascorbic acid, said solution having a pH of from about 2 to about 4.

9. An aqueous acid phosphating solution consisting essentially of about 0.05 to about by weight of phosphate ion, about 0.01 to about 5% by Weight of a metalcontaining ion of the group consisting of ferrous iron, zinc, manganese, magnesium, nickel and molybdenumcontaining ions, about 0.12 to about 0.3% by weight of calcium ion, about 0.05 to about 8% by weight of nitrate ion, and about .0010 to about 1% by weight of an ascorbic acid, said solution having a pH of from about 2 to about 4.

10. An aqueous phosphating composition consisting essentially of phosphoric acid in an amount providing about 0.05 to about 50% by Weight of phosphate radical, about 0.01 to about by weight of zinc, and about .0010 to about 3% by weight of an ascorbic acid.

11. An aqueous phosphating solution consisting essentially of phosphoric acid, including from about 0.05 to about 10% by weight of phosphate ion, about 0.01 to about 5% by weight of ferrous ion, about 0.01 to about 5% by weight of zinc ion, and about .0010 to about 1% by weight of an ascorbic acid, said solution having a pH of from about 2 to about 4.

12. An aqueous phosphating solution consisting essentially of phosphoric acid, nitric acid, zinc oxide, calcium nitrate, ferrous phosphate and an ascorbic acid, and containing about 0.05 to about 10% of phosphate ion, about 0.01 to about 5% of zinc ion, about 0.01 to about 5% of ferrous ion, about 0.12 to about 0.3% of calcium ion, about 0.05 to about 8% of nitrate ion, and about .0010 to about 1% of an ascorbic acid, by Weight of solution, said solution having a pH of from about 2 to about 4.

13. A process for phosphating metals selected from the group consisting of iron steel, aluminum, zinc and magnesium, which comprises contacting said metal with an aqueous solution consisting essentially of an effective amount of phosphate ion, an effective amount of a metalcontaining ion of the group consisting of ferrous iron, zinc, manganese, magnesium, nickel and molybdenumcontaining ions, and about .0010 to about 1% by weight of an ascorbic acid, said solution having a pH in the range of about 2.0 to about 4.0.

14. A process for phosphating metals selected from the group consisting of iron, steel, aluminum, zinc and magnesium, which comprises contacting said metal with an aqueous solution as defined in claim 8.

15. A process for phosphating metals selected from the 10 group consisting of iron, steel, aluminum, zinc and magnesium, which comprises contacting said metal with an aqueous solution as defined in claim 9.

16. A process for phosphating metals selected from the group consisting of iron, steel, aluminum, zinc and magnesium, which comprises contacting said metal with an aqueous solution as defined in claim 11.

17. in the process of phosphating steel with an aqueous solution of phosphate ion and zinc ion present in an amount of about 0.01 to about 5% by weight, the step of incorporating into said aqueous solution prior to contact thereof with said metal, a composition consisting essentially of ferrous phosphate and an ascorbic acid, in proportions ranging from about 10% of ferrous phosphate and about of an ascorbic acid, to about 90% of ferrous phosphate and 10% of an ascorbic acid, said composition being employed in an amount to form in the resulting solution about 0.05 to about 10% by weight of phosphate ion, and about .0010 to about 1% by weight of said ascorbic acid, the resulting solution having a pH of about 2 to about 4-.

18. A solid composition for use in phosphating solutions consisting essentially of ferrous phosphate and an ascorbic acid, in proportions ranging from about 10% of ferrous phosphate and about 90% of an ascorbic acid, to about 90% of ferrous phosphate and 10% of an ascorbic acid.

19. A process for phosphating metals which comprises contacting said metal with an aqueous solution containing as essential components phosphate ion and about .0010 to about 3% by weight of an ascorbic acid, said solution having a pH in the range of about 2.0 to about 4.0.

20. A process for phosphating metals which comprises contacting said metal with an aqueous solution containing as essential components phosphate ion and about .0010 to about 1% by weight of an ascorbic acid, said solution having a pH in the range about 2.0 to about 4.0.

21. A process for phosphating metals selected from the group consisting of iron, steel, aluminum, zinc and mag nesium, which comprises contacting said metal with an aqueous acid solution as defined in claim 2.

References Cited by the Examiner UNITED STATES PATENTS 2,499,261 2/50 Rosenbloom 148-6.15 XR 2,822,317 2/58 Gulesich et a1.

2,826,517 3/58 Miller 1486.15

OTHER REFERENCES Anelli: Chemical Abstracts 53: 12915:, July 25, 1959.

Martell and Calvin, Chemistry of the Metal Chelate Compounds, Prentice-Hall, Inc., Englewood Cliffs, N.J., 1952, pp. 389-892 relied on.

RICHARD D. NEVlUS, Primary Examiner.

RAY K. WINDHAM, Examiner.

Claims

13. A PROCESS FOR PHOSPHATING METALS SELECTED FROM THE GROUP CONSITING OF IRON STEEL, ALUMINUM, ZINC AND MAGNESIUM, WHICH COMPRISES CONTACTING SAID METAL WITH AN AQUEOUS SOLUTION CONSISTING ESSENTIALLY OF AN EFFECTIVE AMOUNT OF PHOSPHATE ION, AN EFFECTIVE AMOUNT OF A METALCONTAINING ION OF THE GROUP CONSISTING OF FERROUS IRON, ZINC, MANGANESE, MAGNESIUM, NICKEL AND MOLYBDENUMCONTAINING IONS, AND ABOUT .0010 TO ABOUT 1% BY WEIGHT OF AN ASXORBIC ACID, SAID SOLUTION HAVING A PH IN THE RANGE OF ABOUT 2.0 TO ABOUT 4.0.