Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/73—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals characterised by the process

Definitions

• This invention relates to the art of producing phosphate coatings 1 alloys thereof and is particularly useful in connection with that type of phosphate coating process in which rapid production of a phosphate coating of maximum smoothness, adherence, and corrosion resistance is of primary importance, such, for example, as in the preparation of the metal for the reception of a final finish of paint, varnish, lacquer, japan, or the like.
• the principal object of the invention is to pro-v vide a process for producing phosphatecoatings of exceptionally smooth, adherent and .corrosion feet of this mechanical treatment will resistant character with a minimum consumption of time and labor and with maximum uniformity. in quality'regardless of certain variables which ordinarily, adversely affect coatings of the kind in question.
• the invention is also of especial significance in connection with the coating of articles of iron,
• the phosphate coating art generally recognizes that it is usually necessary to clean metal surfaces before subjecting them to the action since the presence of grease, dirt, oxide and other impurities. interferes with the uniformity and quality of the coating.
• difiiculties are encountered because the common methods of removing such impurities (including pickling, alkali cleaning, etc.) bring about the deleterious changes in the behavior of the surfaces tions which have already been referred to.
• Mechanical action, by the wiping effect above described almost invariably: improves the behavior of metal surfaces cleaned, but it should be .noted that under the influence of prolonged exposure to solutions of strong alkalies, iron or steel surfaces may be so badly impaired that even vigorous mechanical rubbing or wiping will not correct the condition.
• an acid-treated surface may be put a into condition to behave perfectlyin the phosphate coating solution if it is first wiped, but an alkali treated or cleaned surface may or may not the wiping effect,
• Aonther variable familiar to those skilled in this-art is introduced by the fact that no two samples of metal to be treated will behave in the same manner toward a phosphate coatingsoli tion, but substantial] uniformity in the application of a phosphate coating may be attained if the pieces are subjected to the wiping effect or mechanical action.
• the present invention is based upon the discovery that the wiping effect can in most instances be substantially duplicated-in fact, almost exactly equaled or paralleled-without any mechanical action whatsoever, simply by exposing the surface briefiy to an acid solution comprising oxalic acid. It is an object of the invention, therefore, to so duplicate the wiping effect by chemical means and without the necessity for time-consuming, expensive and laborious mechanical action.
• the treatment of the invention when suitably carried out as described below, seems in almost every instance to affect the surface to be coated in exactly the'same way as does the mechanical action above referred to.
• the invention consists in pretreating a surface, which is to be phosphate coated, with an acid solution comprising oxalic acid.
• Aqueous solutions of oxalic acid alone may be used over a wide range of concentrations.
• the pretreating solution may contain a variety of substances of an inorganic or organic nature, without great detriment to the effect of the pretreating solution.
• the inorganic substances which may be present in fairly large amounts along with oxalic acid, without doing.
• acids such as sulphuric acid, nitric acid, hydrochloric acid, acetic acid, phosphoric acid; salts such as sodium or potassium phosphate, sulphate, chloride, nitrate, acetate, etc.
• Organic substances which may be present, without detriment, along with the oxalic acid of my pretreating solution are alcohols, ethers, acetone, etc.; wetting agents such as isopropyl naphthalene sulphonic acid; organic corrosion inhibitors such as bases derived from coal tar, thioureas, sulphite pulp waste liquor, condensation products of aldehydes and amines, etc., may be present in small amounts without detriment to the solution.
• pretreating solution containing, in addition to oxalic acid, some other strong acid like hydrochloric acid or sulphuric acid.
• the copper may be added in any desired form, so long as sufficient copper remains dissolved in the solution.
• the copper may be added as the sulphate, chloride, carbonate, oxide, etc., to any acid pretreating solution, along with another substance if necessary, to bring a sufficient quantity of copper into solution.
• the amount of copper permissible in my pretreating solution is not critical. However, large quantities of copper in the solution tend to give heavy visible deposits of copper on the metal to be phosphate coated which are undesirable for reasons well understood in the art of phosphate coating. Therefore, I prefer to use an amount of copper insufficient to give a visible coating on the surface to be phosphate coated, although a very thin, barely visible copper film or deposit seems not to be especially harmful to the subsequently produced phosphate coating.
• silver also serves to accelerate the action of my pretreating solution and if employed should be used in amounts substantially equivalent to the amounts of copper which are utilized.
• phosphate coating solutions especially those for useon iron or steel surfaces
• the first type is employed to produce heavy, crystalline coatings which are generally left unpainted, although they are frequently'oiled or dyed.
• Coatings of this type are produced by boiling the surfaces for comparatively long periods of time generally ranging from 30 to 120 minutes, and the solutions generally consist of iron or manganese phosphate or of combinations of these.
• the resulting coatings are essentially coarsely crystalline, but they achieve relatively great thickness to which latter fact much of their corrosion resistantv value is due.
• thestructure and appearance of this type of coating commonly produced in boiling solutions for protracted periods may be modifled to some extent by various treatments of the surface.
• myimproved pretreating solution prior to such a coating process is often without significant effect, since a visibly crystalline structure is characteristic of, and generally considered desirablein this kind of coating.
• the second type of phosphate coacting solution and process in common use accounts for the greater bulk of metal surface area at present solutions employed generally contain zinc and/or manganese phosphate, although they may accumulate a certain amount of ferrous phosphate during use.
• Many expedients have been employed for expediting their coating action in order to meet mass production methods and requirements, and the solutions are usually used at temperatures considerably below the'boiling point.
• the accelerating means commonly employed may be physical, electrical and/or chemical.
• the coating speed may be due to the violent impingement of the solution onto the surfaces tobe coated, or the piece to be coated may be used as an electrode in the coating solution as an electrolyte with passage therethroughof an alternating current via the surface being coated.
• Chemical accelerators are also em-' ployed, and these include'oxidizing agents, metals less basic than iron, such as copper, and other metals, such as cobalt and nickel.
• the coated surfaces are generally intended to be covered with a final finish of paint, varnish,
• Rust and scale may be removed with an acid pickle followed by a wash with water, and oil and grease .may be removed either by vapor degreasing or by dipping into an oil solvent, but preferably by spraying the stamping with an alkaline cleaning agent, such as a solution of caustic soda and soap. After washing off theexcess of alkali cleaning solution by means of 'a spray of clean water, the stampingis immersed for 15 seconds,
• the stamping may then be immersed in a phosphate coating solution prepared in accordance with the following instructions:
• the zinc oxide should be the acid should be gradually added until the solution is clear.
• This solution may be used at any temperature from room temperature to the boiling point.
• the immersion of the surface to be pretreated should preferably not exceed 30 seconds.
• the concentrated solution resulting from the above mixture is dilutedwith water to a concentration of 3% by volume. It is used under the same conditions as the solution of Formula No. 2 above. It is to be noted that the above solution will product phosphate coatings which contain a very small amount of metallic copper. The time of coating will be somewhat shorter than with the solution of Formula No. 2.
• pretreating solutions formulated above these too are merely illustrative and are not intended to be limiting.
• the above material may be applied to iron or steel surfaces, allowed to act for a sufficient time, and may then be washed or wiped off.
• the iron or steel surfaces may then be subjected to a rust-' proofing solution such as the solution of Formula No. 2 or Formula No. 4. If the above solution is applied to a galvanized iron or zinc surface, the surface will be cleaned and etched. It may then be washed or wiped off and subjected to a solution such as the solution of Formula. No. 6. In both cases the surfaces will be found to acquire a very uniform, smooth phosphase coating.
• pretreating solution need not be washed off the pretreated surface before the surface is subjected to the action of the phosphate coating solution.
• the oxalic acid or other ingredient present in the pretreating solution may be harmful to the continued correct operation of the phosphate coating solution.
• the oxalic acid treating solution also includes dissolved metal from the group consisting of copper and silver.
• steps which includes cleaning the said surface and treating it with an acid solution comprising oxalic acid and dissolved metal from the group consisting of copper and silver,
• a process of preparing surfaces of iron, zinc and alloys of either for the reception of a phosphate coating comprises chemically cleaning the surface and treating it with an acid solution comprising oxalic acid.
• the oxalic acid treating solution also includes dissolved.- metal from the group consisting of copper and silver.
• a conditioning treatment for articles having surfaces of iron, zinc and alloys thereof which articles are to be coated with a phosphate coating solution comprising subjecting the article to the action of an acid solution comprising oxalic acid.
• the oxalic acid solution also includes dissolved metal from the group consisting of copper and silver.
• the method of coating surfaces of iron, zinc and alloys of either which comprises chemically cleaning the surface, treating it with an acid solution comprising oxalic acid, removing the residues of the treatment with said acid solution, and then subjecting it to the action of a phosphate coating solution before the surface has dried, said coating solution comprising metal f:om the group consisting of zinc and manganese as the principal metallic coating constituent.
• a pretreating solution for conditioning surfaces of iron, zinc'and alloys of either for the reception of a phosphate coating from phosphate coating solutions comprising oxalic acid and dissolved metal from the group consisting of copper and silver.
• a pretreating solution for conditioning surfaces of iron, zinc and alloys of either for the reception of a phosphate coating from phosphate coating solutions comprising substantially the following:
• An admixture for use in preparing surfaces of iron, zinc and alloys of either for the reception of a phosphate coating from phosphate coating solutions said admixture including oxalic acid and metal from the group consisting of copper and silver.

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• Chemical & Material Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Treatment Of Metals (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)

Priority Applications (5)

Applications Claiming Priority (1)

Publications (1)

Family

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Family Applications (1)

Country Status (5)

Cited By (17)

Families Citing this family (1)

Family Cites Families (4)

• 0
  • BE BE434557D patent/BE434557A/xx unknown
• 1938
  • 1938-05-27 US US210425A patent/US2164042A/en not_active Expired - Lifetime
  • 1938-09-07 DE DEA88017D patent/DE753730C/de not_active Expired
  • 1938-12-20 GB GB37069/38A patent/GB522954A/en not_active Expired
• 1939
  • 1939-05-26 FR FR908661D patent/FR908661A/fr not_active Expired

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