US3647568A - Colored phosphate coatings and method of application - Google Patents
Colored phosphate coatings and method of application Download PDFInfo
- Publication number
- US3647568A US3647568A US871952A US3647568DA US3647568A US 3647568 A US3647568 A US 3647568A US 871952 A US871952 A US 871952A US 3647568D A US3647568D A US 3647568DA US 3647568 A US3647568 A US 3647568A
- Authority
- US
- United States
- Prior art keywords
- phosphate
- zinc
- copper
- bath
- coating
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000000576 coating method Methods 0.000 title abstract description 41
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 title abstract description 31
- 229910019142 PO4 Inorganic materials 0.000 title abstract description 30
- 239000010452 phosphate Substances 0.000 title abstract description 30
- 238000000034 method Methods 0.000 title description 20
- 239000011248 coating agent Substances 0.000 abstract description 27
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical group [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 abstract description 24
- 229910052751 metal Inorganic materials 0.000 abstract description 23
- 239000002184 metal Substances 0.000 abstract description 23
- 238000005260 corrosion Methods 0.000 abstract description 10
- 230000007797 corrosion Effects 0.000 abstract description 10
- -1 FERROUS METALS Chemical class 0.000 abstract description 7
- 239000000203 mixture Substances 0.000 abstract description 4
- LRXTYHSAJDENHV-UHFFFAOYSA-H zinc phosphate Chemical compound [Zn+2].[Zn+2].[Zn+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O LRXTYHSAJDENHV-UHFFFAOYSA-H 0.000 description 26
- 229910000165 zinc phosphate Inorganic materials 0.000 description 26
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 21
- 229910052802 copper Inorganic materials 0.000 description 21
- 239000010949 copper Substances 0.000 description 21
- 239000000243 solution Substances 0.000 description 18
- 239000011701 zinc Substances 0.000 description 13
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 12
- 229910052725 zinc Inorganic materials 0.000 description 12
- 238000004519 manufacturing process Methods 0.000 description 9
- 229910000831 Steel Inorganic materials 0.000 description 8
- 239000010959 steel Substances 0.000 description 8
- 229910002651 NO3 Inorganic materials 0.000 description 7
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 7
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 7
- 239000002253 acid Substances 0.000 description 7
- 238000007654 immersion Methods 0.000 description 7
- 239000003921 oil Substances 0.000 description 7
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 6
- 150000001879 copper Chemical class 0.000 description 5
- ARUVKPQLZAKDPS-UHFFFAOYSA-L copper(II) sulfate Chemical compound [Cu+2].[O-][S+2]([O-])([O-])[O-] ARUVKPQLZAKDPS-UHFFFAOYSA-L 0.000 description 5
- 238000004043 dyeing Methods 0.000 description 5
- ONDPHDOFVYQSGI-UHFFFAOYSA-N zinc nitrate Chemical compound [Zn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ONDPHDOFVYQSGI-UHFFFAOYSA-N 0.000 description 5
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 4
- 229910000365 copper sulfate Inorganic materials 0.000 description 4
- 150000002739 metals Chemical class 0.000 description 4
- 239000011347 resin Substances 0.000 description 4
- 229920005989 resin Polymers 0.000 description 4
- OSKILZSXDKESQH-UHFFFAOYSA-K zinc;iron(2+);phosphate Chemical compound [Fe+2].[Zn+2].[O-]P([O-])([O-])=O OSKILZSXDKESQH-UHFFFAOYSA-K 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- VEQPNABPJHWNSG-UHFFFAOYSA-N Nickel(2+) Chemical compound [Ni+2] VEQPNABPJHWNSG-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- XTVVROIMIGLXTD-UHFFFAOYSA-N copper(II) nitrate Chemical compound [Cu+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O XTVVROIMIGLXTD-UHFFFAOYSA-N 0.000 description 3
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 3
- 229910052759 nickel Inorganic materials 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 241000054822 Lycaena cupreus Species 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 2
- 238000004532 chromating Methods 0.000 description 2
- KRVSOGSZCMJSLX-UHFFFAOYSA-L chromic acid Substances O[Cr](O)(=O)=O KRVSOGSZCMJSLX-UHFFFAOYSA-L 0.000 description 2
- 239000008199 coating composition Substances 0.000 description 2
- 238000004040 coloring Methods 0.000 description 2
- ORTQZVOHEJQUHG-UHFFFAOYSA-L copper(II) chloride Chemical compound Cl[Cu]Cl ORTQZVOHEJQUHG-UHFFFAOYSA-L 0.000 description 2
- 239000010408 film Substances 0.000 description 2
- AWJWCTOOIBYHON-UHFFFAOYSA-N furo[3,4-b]pyrazine-5,7-dione Chemical compound C1=CN=C2C(=O)OC(=O)C2=N1 AWJWCTOOIBYHON-UHFFFAOYSA-N 0.000 description 2
- 230000007935 neutral effect Effects 0.000 description 2
- 239000007800 oxidant agent Substances 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- JIAARYAFYJHUJI-UHFFFAOYSA-L zinc dichloride Chemical compound [Cl-].[Cl-].[Zn+2] JIAARYAFYJHUJI-UHFFFAOYSA-L 0.000 description 2
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- 229910001420 alkaline earth metal ion Inorganic materials 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 238000007743 anodising Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 229910052793 cadmium Inorganic materials 0.000 description 1
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 1
- 229910001424 calcium ion Inorganic materials 0.000 description 1
- KXZJHVJKXJLBKO-UHFFFAOYSA-N chembl1408157 Chemical compound N=1C2=CC=CC=C2C(C(=O)O)=CC=1C1=CC=C(O)C=C1 KXZJHVJKXJLBKO-UHFFFAOYSA-N 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- XTEGARKTQYYJKE-UHFFFAOYSA-M chlorate Inorganic materials [O-]Cl(=O)=O XTEGARKTQYYJKE-UHFFFAOYSA-M 0.000 description 1
- 238000007744 chromate conversion coating Methods 0.000 description 1
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000008139 complexing agent Substances 0.000 description 1
- 238000007739 conversion coating Methods 0.000 description 1
- 229910000366 copper(II) sulfate Inorganic materials 0.000 description 1
- 229960003280 cupric chloride Drugs 0.000 description 1
- 238000005238 degreasing Methods 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000000975 dye Substances 0.000 description 1
- 229940116007 ferrous phosphate Drugs 0.000 description 1
- 239000011790 ferrous sulphate Substances 0.000 description 1
- 235000003891 ferrous sulphate Nutrition 0.000 description 1
- 239000004519 grease Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- 229910000155 iron(II) phosphate Inorganic materials 0.000 description 1
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 1
- SDEKDNPYZOERBP-UHFFFAOYSA-H iron(ii) phosphate Chemical compound [Fe+2].[Fe+2].[Fe+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O SDEKDNPYZOERBP-UHFFFAOYSA-H 0.000 description 1
- 229910001437 manganese ion Inorganic materials 0.000 description 1
- 229910001453 nickel ion Inorganic materials 0.000 description 1
- 235000021110 pickles Nutrition 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 230000003449 preventive effect Effects 0.000 description 1
- 239000011253 protective coating Substances 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000005488 sandblasting Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 238000007655 standard test method Methods 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 239000011592 zinc chloride Substances 0.000 description 1
- 235000005074 zinc chloride Nutrition 0.000 description 1
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 aqueous phosphate coating compositions and to a method for producing phosphate coatings on metals. More particularly, it relates to zinc and zinc-iron phosphate compositions containing at least one copper salt and to a method for producing a reddishcolored zinc phosphate coating on the surface of a ferrous metal.
- the colored coating resulting when the aqueous solutions of this invention are employed to coat metals serves as an excellent means of identifying such articles and such coatings exhibit a high degree of corrosion resistance.
- Ferrous metal parts which most often require a distinguishing color or color coding are threaded fasteners.
- the usual practice has been to employ a pigmented resin over the conventional zinc phosphate coating.
- this system has proven itself to be a somewhat satisfactory means of color coding fasteners, because of the accumulated film in the threaded areas resulting from the additional coating applied it is necessary to take special handling precautions when processing metal pieces in this fashion.
- the accumulation or build up of the film in the threaded areas causes deviations in the fastener tension at given torque loads.
- One of the objects of thisvinvention is to produce a colored zinc phosphate coating on the surface of a ferrous metal directly from a coating bath itself without the employment of subsequent mordant and dyeing operations or the use of pigmented resin coatings.
- Another object of this invention is to form phosphate coatings on the surfaces of ferrous metals which are highly resistant to normal corrosion.
- ferrous metal surfaces are simultaneously provided with corrosion resistant and color coded phophate coatings by treating them first in a bath comprising an aqueous zinc phosphate solution or bath containing at least one soluble copper salt. Thereafter, the initially coated and colored metal surfaces are subjected to a second phosphating treatment by immersing them in a zinc phosphate solution of generally standard commercial composition, free of dissolved copper.
- the initial copper-containing zinc phosphate solutions of this invention soluble copper salts providing the equivalent of from about 0.15 to about 2.5 g./l. of copper.
- These initial solutions are prepared by adding at least one soluble copper salt to any of the various aqueous zinc phosphate solutions known in the art to be useful in forming protective coatings on ferrous metal surfaces.
- the zinc phosphate solutions of the art contain zinc, iron and phosphate ions.
- these solutions may contain an accelerator or oxidizing agent, such as nitrate ions, nitrite ions, chlorate ions, peroxide ions, etc.
- Other modifying ions may also be present such as nickel ions, manganese ions, alkaline earth metal ions, such as calcium ions, etc.
- the aqueous initial copper-containing zinc phosphate solutions utilized in this invention have the following characteristics:
- Free acidity about 3.5 to about 25 points 1 Total acidity: about 14.5 to about points
- the points of total acid denote the number of mls. of 0.1 N sodium hydroxide required to neutralize a 10 ml. sample of the bath to a phenolphthaleln indicator end point.
- the ferrous iron is supplied as ferrous phosphate, or ferrous sulfate, zinc as zinc nitrate, zinc phosphate or zinc chloride, phosphate as phosphoric acid or zinc phosphate and nitrate as zinc nitrate.
- the selection of a particular copper salt for the phosphate bath of this invention is not critical and any copper salt which is soluble in the phosphate bath, such as cupric sulfate, cupric nitrate, cupric chloride, etc., may be employed provided the associated anion is functional (e.g., nitrate) or non-detrimental to the coating process.
- a workpiece for example a steel panel
- a workpiece is first cleaned by vapor degreasing, solvent cleaning, sand blasting or, preferably, by immersion in an alkaline cleaner, to remove grease, oil and dirt from the surface.
- the panel is rinsed in cold water, optionally pickled in an acid, such as sulfuric acid, phosphoric acid or hydrochloric acid of about 10 percent by volume, at about F., again rinsed in water and placed in the initial copper-containing aqueous phosphate coating bath described above for about 0.5 to about 60 minutesor more and preferably for about 10 to about 25 minutes.
- the temperature of the phosphating bath can be varied over a wide range and generally will be from 120 to about 210 F.
- the coated panel is then removed from the coating bath and rinsed with water. The result is a good quality, tight-grained, red-colored, zinc-iron phosphate coating. This color of the phosphating coating thus-formed is easily distinguished from the standard gray-colored zinc-iron phosphate coating of the prior art.
- This preliminarily coated and colored panel is then immersed in, or otherwise contacted with, a typical zinc phosphating solution for a period of about 10 to about 60 minutes or more at a temperature ranging from about 170 to about 210 F.
- Free acidity about 3.5 to about 25 points
- Total acidity about 14.5 to about 100 points
- Zinc (Zn++) about 1 to about 25 g./l.
- Nitrate Now about 1 to about 50 g./l.
- Phosphate (PO about 5 to about 55 g./l.
- the result is red-colored, zinc phosphate coating.
- the foregoing two-step process can be conveniently handled in existing process lines by incorporating a single station processing tank of small size to impart the red color to the steel pieces prior to immersion in the usual zinc phosphate coating bath.
- This two-stage processing technique yields red-colored zinc phosphate coated pieces which, after being sealed by dipping in a chromate solution and after being immersed in a water-soluble, rust preventive oil, pass all the necessary torque-tension requirements and the neutral salt spray requirements when tested according to the procedure of ASTM B117, a standard test method accepted by the industry.
- a suitable chromic acid solution for sealing the coated article contains about 1 oz. to 16 oz. of chromic acid per 100 gals. of water, and the solution is preferably maintained at a temperature of about 70 to 180 F.
- Application of the rust preventing oil can be accomplished in known manner by immersing the pieces in a water soluble or solvent cut-back corrosion resisting oil at a temperature of about 70 to 200 F. for a period of about /2 to 5 minutes or more.
- the pre-treated steel specimens were immersed for a period of about 20 minutes at 195 F. in a typical zinc phosphate solution having the following characteristics:
- Nitrate NO 11.2 g./l.
- Phosphate (POE) 26.3 g./l.
- Nickel (Ni++) 0.068 g./l.
- Example II In this example a typical production run was made in order to determine the commercial feasibility of the process of the invention. Threaded steel fasteners were loaded into a standard production type processing barrel and then dipped in an alkaline soak cleaner for 3 minutes to remove foreign soils and oils from their surface. After rinsing in water, the fasteners were pickled for three minutes in a hydrochloric acid solution, again rinsed in water and then immersed at a temperature of about F. for 3 minutes in a copper-containing, zinc phosphate coating bath having the following characteristics:
- the fasteners were removed from the phosphating bath, rinsed with water, and then immersed in a typical zinc phosphating coating bath for 20 minutes at a temperature of about F.
- the zinc phosphate bath utilized had the following characteristics:
- the fasteners were removed from the zinc phosphate bath, again water rinsed and finally immersed in a watersoluble, rust-preventive oil.
- the coated fasteners exhibited a red-colored zinc phosphate coating of excellent quality easily distinguishable from fasteners of the exact same size processed through a typical zinc phosphate coating bath which results in the production of gray colored fasteners.
- Fasteners, thus treated, were tested in a neutral salt spray testing cabinet according to the procedure of ASTM B-117 and showed no sign of corrosion after 72 hours exposure.
- the chemical make-up of the phosphate solutions employed in the treating baths changed somewhat due to chemical consumption while the fasteners were being processed.
- the copper content for example, was in the range of 0.163 to 0.282 gram of copper per liter (introduced as copper sulfate) during the production run.
- Example III A second production test was run employing copper in the pre-coating bath at a higher level for the purpose of imparting a more significant red color to the steel fasteners. Otherwise, the phosphate coating compositions were exactly the same as in Example II and the'same processing techniques were used as described in that example.
- Fasteners coated in the same manner as in Example II exhibited an intense, uniform, reddish-colored, zinciron phosphate coating.
- the copper containing phosphate coating bath employed during this test was held at 0.682 to 0.714 gram of copper per liter, introduced as copper sulfate. During this production run, frequent small additions of copper sulfate were made to maintain the copper at the desired level. In practice, the use of a low volume proportioning pump is recommended to maintain the copper at the required concentration.
- the processing barrels employed during this particular production run were constructed of stainless steel and a portion of the consumed copper galvanically deposited on the stainless steel. It was also noted that after the processing barrels were removed from the typical coating bath most of the galvanically deposited copper had dissolved and it is believed that it redeposited on the work intended to be coated.
- the copper retained on the barrels after processing can easily be removed in an alkaline soak cleaner by incorporating a small amount of oxidizing agent, such as sodium meta-nitrobenzene sulfonate and a complexing agent, sodium cyanide. This eliminates the possibility of contaminating the acid pickle with copper which would easily deposit on the work being pickled.
- oxidizing agent such as sodium meta-nitrobenzene sulfonate and a complexing agent, sodium cyanide.
- a process for treating the surface of a ferrous metal, to provide a uniform, reddish-colored, zinc phosphate coating thereon which comprises:
- Free acidity about 3.5 to about 25 points
- Total acidity about 14.5 to about 100 points Fe++z about 0.1 to about 12 g./l.
- Zn++ about 1 to about 25 g./l.
- N0 about 1 to about 50 g./l.
- Cu++ about 0.15 to about 2.5 g./l.
- Free acidity about 3.5 to about 25 points
- Total acidity about 14.5 to about points
- Fe++ about 0.1 to about 12 g./l.
- Zn++z about 1 to about 25 g./l.
- Free acid 7.9 points
- Total acid 51.2 points
- Fe++ 1.2 g./l.
- Zn++ 11.3 g./l.
- Ne -z 12.5 g./l.
- Cu++z 0.25 g./l.
- step (a) the temperature of the said bath is about 175 F. and the time of immersion is about 3 minutes and in the step (b) the temperature of the said bath is about F. and the time of immersion is about 20 minutes.
Abstract
PHOSPHATE COMPOSITIONS CONTAINING AT LEAST ONE COPPER SALT ARE UTLILIZED FOR COATING SURFACES OF FERROUS METALS. THE PHOSPHATE COATINGS ACHIEVED, WHICH POSSESS A REDDISH COLOR, SERVER AS AN EXCELLENT MEANS OF IDENTIFICATION OF THE ARTICLES THIS COATED AND, IN ADDITION, THE FINISH IS OF GOOD CORROSION RESISTANCE.
Description
United States Patent ABSTRACT OF THE DISCLOSURE Phosphate compositions containing at least one copper salt are utilized for coating surfaces of ferrous metals. The phosphate coatings achieved, which possess a reddish color, serve as an excellent means of identification of the articles thus coated and, in addition, the finish is of good corrosion resistance.
This invention relates to aqueous phosphate coating compositions and to a method for producing phosphate coatings on metals. More particularly, it relates to zinc and zinc-iron phosphate compositions containing at least one copper salt and to a method for producing a reddishcolored zinc phosphate coating on the surface of a ferrous metal. The colored coating resulting when the aqueous solutions of this invention are employed to coat metals serves as an excellent means of identifying such articles and such coatings exhibit a high degree of corrosion resistance.
The identification of certain articles by using color coding techniques has long been implemented in the metal finishing industry. After providing corrosion resistant coatings to metals, it is often necessary and desirable to impart a color to the coated article.
' The art is aware of many systems which can be utilized to produce colored final finishes on metal surfaces including: zinc and cadmium plating followed by chromating and dyeing, aluminum chromating and dyeing, aluminum anodizing and dyeing. The above systems serve two purposes: (1) they are corrosion resistant and (2) they are colored for identification and/or appearance as a final finish. The above-mentioned chromate conversion coatings and anodized aluminum finishes are such that they lend themselves to dyeing by the use of conventional dyes and thus color coding of these articles presents no problems.
When a zinc or zinc-iron phosphate is employed as a corrosion resistant coating on metals, such coatings cannot be dyed in the same manner as the above-described chromated and anodized coatings. Methods for coloring phosphate coatings described in the art involve the use of a subsequent conversion coating of the phosphate to a state in which it can be dyed. Other methods employed for coloring phosphate coatings involve the use of a thin film forming resin pigmented with the desired color.
Ferrous metal parts which most often require a distinguishing color or color coding are threaded fasteners. In the past, the usual practice has been to employ a pigmented resin over the conventional zinc phosphate coating. Although this system has proven itself to be a somewhat satisfactory means of color coding fasteners, because of the accumulated film in the threaded areas resulting from the additional coating applied it is necessary to take special handling precautions when processing metal pieces in this fashion. The accumulation or build up of the film in the threaded areas causes deviations in the fastener tension at given torque loads. Further, in processing fasteners utilizing the pigmented resin systems, it is also necessary, to completely dry the pieces prior to placing them in 3,647,568 Patented Mar. 19 72 'ice a water soluble rust preventing oil which is usually the final step in such a phosphate coating process. Thorough drying of bulk processed work is not easily accomplished where large loads are involved.
One of the objects of thisvinvention is to produce a colored zinc phosphate coating on the surface of a ferrous metal directly from a coating bath itself without the employment of subsequent mordant and dyeing operations or the use of pigmented resin coatings.
Another object of this invention is to form phosphate coatings on the surfaces of ferrous metals which are highly resistant to normal corrosion.
In the process of this invention ferrous metal surfaces are simultaneously provided with corrosion resistant and color coded phophate coatings by treating them first in a bath comprising an aqueous zinc phosphate solution or bath containing at least one soluble copper salt. Thereafter, the initially coated and colored metal surfaces are subjected to a second phosphating treatment by immersing them in a zinc phosphate solution of generally standard commercial composition, free of dissolved copper.
The initial copper-containing zinc phosphate solutions of this invention soluble copper salts providing the equivalent of from about 0.15 to about 2.5 g./l. of copper. These initial solutions are prepared by adding at least one soluble copper salt to any of the various aqueous zinc phosphate solutions known in the art to be useful in forming protective coatings on ferrous metal surfaces. Typically the zinc phosphate solutions of the art contain zinc, iron and phosphate ions. Additionally, these solutions may contain an accelerator or oxidizing agent, such as nitrate ions, nitrite ions, chlorate ions, peroxide ions, etc. Other modifying ions may also be present such as nickel ions, manganese ions, alkaline earth metal ions, such as calcium ions, etc.
Preferably, the aqueous initial copper-containing zinc phosphate solutions utilized in this invention have the following characteristics:
Free acidity: about 3.5 to about 25 points 1 Total acidity: about 14.5 to about points Ferrous iron (Fe++): about 0.1 to about 8 g./l. Zinc (Zn++): about 1 to about 25 g./l. Phosphate (PO about 5 to about 55 g./l. Nitrate (NO about 2 to about 50 g./l. Copper (Cu++): about 0.15 to about 2.5 g./l.
The points of total acid denote the number of mls. of 0.1 N sodium hydroxide required to neutralize a 10 ml. sample of the bath to a phenolphthaleln indicator end point.
In preparing the copper-containing phosphate solution of this invention generally the ferrous iron is supplied as ferrous phosphate, or ferrous sulfate, zinc as zinc nitrate, zinc phosphate or zinc chloride, phosphate as phosphoric acid or zinc phosphate and nitrate as zinc nitrate. The selection of a particular copper salt for the phosphate bath of this invention is not critical and any copper salt which is soluble in the phosphate bath, such as cupric sulfate, cupric nitrate, cupric chloride, etc., may be employed provided the associated anion is functional (e.g., nitrate) or non-detrimental to the coating process.
In the process of this invention, a workpiece, for example a steel panel, is first cleaned by vapor degreasing, solvent cleaning, sand blasting or, preferably, by immersion in an alkaline cleaner, to remove grease, oil and dirt from the surface. Then the panel is rinsed in cold water, optionally pickled in an acid, such as sulfuric acid, phosphoric acid or hydrochloric acid of about 10 percent by volume, at about F., again rinsed in water and placed in the initial copper-containing aqueous phosphate coating bath described above for about 0.5 to about 60 minutesor more and preferably for about 10 to about 25 minutes. The temperature of the phosphating bath can be varied over a wide range and generally will be from 120 to about 210 F. and, preferably, will be about 150 to about 200 F. depending upon the particular bath employed and the other reaction conditions. The coated panel is then removed from the coating bath and rinsed with water. The result is a good quality, tight-grained, red-colored, zinc-iron phosphate coating. This color of the phosphating coating thus-formed is easily distinguished from the standard gray-colored zinc-iron phosphate coating of the prior art.
This preliminarily coated and colored panel is then immersed in, or otherwise contacted with, a typical zinc phosphating solution for a period of about 10 to about 60 minutes or more at a temperature ranging from about 170 to about 210 F.
Typical zinc phosphate solutions referred to above for use in this second step have the following characteristics:
Free acidity: about 3.5 to about 25 points Total acidity: about 14.5 to about 100 points Ferrous iron (Feabout 0.1 to about 8 g./l. Zinc (Zn++): about 1 to about 25 g./l.
Nitrate Now; about 1 to about 50 g./l. Phosphate (PO about 5 to about 55 g./l.
The result is red-colored, zinc phosphate coating.
The foregoing two-step process can be conveniently handled in existing process lines by incorporating a single station processing tank of small size to impart the red color to the steel pieces prior to immersion in the usual zinc phosphate coating bath. This two-stage processing technique yields red-colored zinc phosphate coated pieces which, after being sealed by dipping in a chromate solution and after being immersed in a water-soluble, rust preventive oil, pass all the necessary torque-tension requirements and the neutral salt spray requirements when tested according to the procedure of ASTM B117, a standard test method accepted by the industry.
A suitable chromic acid solution for sealing the coated article contains about 1 oz. to 16 oz. of chromic acid per 100 gals. of water, and the solution is preferably maintained at a temperature of about 70 to 180 F. Application of the rust preventing oil can be accomplished in known manner by immersing the pieces in a water soluble or solvent cut-back corrosion resisting oil at a temperature of about 70 to 200 F. for a period of about /2 to 5 minutes or more.
The following examples illustrate various embodiments of this invention and are to be considered not limitative:
EXAMPLE I A copper-containing phosphating solution having the following characteristics was prepared:
Free acid: 7.9 points Total acid: 51.2 points Fe: 1.2 g./l.
Zn++z 11.3 g./l. PO 26.4 g./l. NOy-z 12.5 g./l. Cu++: 0.25 g./l.
Steel panels were soak cleaned in an alkaline cleaner, rinsed in cold water, pickled in hydrochloric acid, again rinsed in water and placed in the coating bath described above for 20 minutes at 190 F.
Followng this pre-coating step, the pre-treated steel specimens were immersed for a period of about 20 minutes at 195 F. in a typical zinc phosphate solution having the following characteristics:
Free acidity: 9.7 points Total acidity: 49.9 points Ferrous iron (Fe++): 3.2 g./l. Zinc (Zn 9.54 g./l.
4 Nitrate (NO 11.2 g./l. Phosphate (POE): 26.3 g./l. Nickel (Ni++): 0.068 g./l.
quality,
Example II In this example a typical production run was made in order to determine the commercial feasibility of the process of the invention. Threaded steel fasteners were loaded into a standard production type processing barrel and then dipped in an alkaline soak cleaner for 3 minutes to remove foreign soils and oils from their surface. After rinsing in water, the fasteners were pickled for three minutes in a hydrochloric acid solution, again rinsed in water and then immersed at a temperature of about F. for 3 minutes in a copper-containing, zinc phosphate coating bath having the following characteristics:
Free acidity: 10.0 points Total acidity: 50.8 points Ferrous iron (Fe++): 1.0 g./l. Zinc (Zn++): 10.0 g./1. Nitrate (NO 9.2 g./l. Phosphate (PO 27.0 g./l. Nickel (Ni 0.075 g./l. Copper (Cu++): 0.282 g./l.
The fasteners were removed from the phosphating bath, rinsed with water, and then immersed in a typical zinc phosphating coating bath for 20 minutes at a temperature of about F. The zinc phosphate bath utilized had the following characteristics:
Free acidity: 9.7 points Total acidity: 49.9 points Ferrous iron (Fe++): 3.2 g./l. Zinc (Zn++): 9.54 g./l. Nitrate (NO 11.2 g./l. Phosphate (PO 26.3 g./l. Nickel (Ni++): 0.068 g./l.
The fasteners were removed from the zinc phosphate bath, again water rinsed and finally immersed in a watersoluble, rust-preventive oil. The coated fasteners exhibited a red-colored zinc phosphate coating of excellent quality easily distinguishable from fasteners of the exact same size processed through a typical zinc phosphate coating bath which results in the production of gray colored fasteners. Fasteners, thus treated, were tested in a neutral salt spray testing cabinet according to the procedure of ASTM B-117 and showed no sign of corrosion after 72 hours exposure.
The chemical make-up of the phosphate solutions employed in the treating baths changed somewhat due to chemical consumption while the fasteners were being processed. The copper content, for example, was in the range of 0.163 to 0.282 gram of copper per liter (introduced as copper sulfate) during the production run.
Example III A second production test was run employing copper in the pre-coating bath at a higher level for the purpose of imparting a more significant red color to the steel fasteners. Otherwise, the phosphate coating compositions were exactly the same as in Example II and the'same processing techniques were used as described in that example.
Fasteners coated in the same manner as in Example II exhibited an intense, uniform, reddish-colored, zinciron phosphate coating.
The copper containing phosphate coating bath employed during this test was held at 0.682 to 0.714 gram of copper per liter, introduced as copper sulfate. During this production run, frequent small additions of copper sulfate were made to maintain the copper at the desired level. In practice, the use of a low volume proportioning pump is recommended to maintain the copper at the required concentration. The processing barrels employed during this particular production run were constructed of stainless steel and a portion of the consumed copper galvanically deposited on the stainless steel. It was also noted that after the processing barrels were removed from the typical coating bath most of the galvanically deposited copper had dissolved and it is believed that it redeposited on the work intended to be coated. The copper retained on the barrels after processing can easily be removed in an alkaline soak cleaner by incorporating a small amount of oxidizing agent, such as sodium meta-nitrobenzene sulfonate and a complexing agent, sodium cyanide. This eliminates the possibility of contaminating the acid pickle with copper which would easily deposit on the work being pickled.
What is claimed is:
1. A process for treating the surface of a ferrous metal, to provide a uniform, reddish-colored, zinc phosphate coating thereon, which comprises:
(a) immersing said metal surface in a first aqueous zinc phosphate bath containing copper in ionic condition to form a phosphate precoat on the said metal surface, the temperature of said first bath being about 120 to about 210 F. and the time of immersion being about 1 minute to about 10 minutes, wherein said first aqueous zinc phosphate bath has the following characteristics:
Free acidity: about 3.5 to about 25 points Total acidity: about 14.5 to about 100 points Fe++z about 0.1 to about 12 g./l.
Zn++: about 1 to about 25 g./l.
P about 5 to about 55 g./l.
N0 about 1 to about 50 g./l.
Cu++: about 0.15 to about 2.5 g./l.
(b) immersing the said precoated metal surface in a second aqueous zinc phosphate bath, the temperature of the said second bath being about 170 to about 210 F. and the time of immersion being about 10 to about minutes, wherein the said second aqueous zinc phosphate bath has the following characteristics:
Free acidity: about 3.5 to about 25 points Total acidity: about 14.5 to about points Fe++: about 0.1 to about 12 g./l.
Zn++z about 1 to about 25 g./l.
P0 about 5 to about 55 g./l.
NO about 1 to about 50 g./l.
2. The process of claim 1 wherein the said ferrous metal is steel.
3. The process of claim 1 wherein the temperature of the bath is about F., the time of immersion is about 20 minutes, and said first phosphate bath has the following characteristics:
Free acid: 7.9 points Total acid: 51.2 points Fe++: 1.2 g./l. Zn++: 11.3 g./l. P0 26.4 g./l. Ne -z 12.5 g./l. Cu++z 0.25 g./l.
4. In the process of claim l wherein in the first said phosphate bath the copper is derived from copper sulfate.
5. The process of claim 1 wherein the said metal is steel.
6. The process of claim 1 wherein in step (a) the temperature of the said bath is about 175 F. and the time of immersion is about 3 minutes and in the step (b) the temperature of the said bath is about F. and the time of immersion is about 20 minutes.
7. A ferrous metal article having the surface produced with the procedure of claim 1.
References Cited UNITED STATES PATENTS 2,272,216 2/ 1942 Lodeesen 1486.l5 Z
2,845,376 7/1958 Hyams 148--6.15 Z
3,467,589 9/1969 Rausch et a1. 1486.15 ZX FOREIGN PATENTS 1,060,693 7/ 1959 Germany 1486.15 Z
RALPH S. KENDALL, Primary Examiner U.S. Cl. X.R. 148-315
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US87195269A | 1969-10-28 | 1969-10-28 |
Publications (1)
Publication Number | Publication Date |
---|---|
US3647568A true US3647568A (en) | 1972-03-07 |
Family
ID=25358527
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US871952A Expired - Lifetime US3647568A (en) | 1969-10-28 | 1969-10-28 | Colored phosphate coatings and method of application |
Country Status (1)
Country | Link |
---|---|
US (1) | US3647568A (en) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2519028A1 (en) * | 1981-12-30 | 1983-07-01 | Asturienne Mines Comp Royale | PROCESS FOR THE PREPARATION OF A BLACK COATING ON THE SURFACE OF PARTS OF WHICH AT LEAST ONE FACE IS IN ZINC |
US4950339A (en) * | 1988-02-03 | 1990-08-21 | Metallgesellschaft Aktiengesellschaft | Process of forming phosphate coatings on metals |
US5089349A (en) * | 1989-06-05 | 1992-02-18 | Calgon Corporation | Compositions and method for applying coatings to metallic surfaces |
WO1995021278A1 (en) * | 1994-02-03 | 1995-08-10 | Henkel Kommanditgesellschaft Auf Aktien | Chromating process or phosphate-chromating process and materials suitable for identifying the treatment process |
WO2000052227A1 (en) * | 1999-03-02 | 2000-09-08 | Henkel Corporation | Nonsludging zinc phosphating composition and process |
WO2000073536A1 (en) * | 1999-05-28 | 2000-12-07 | Henkel Kommanditgesellschaft Auf Aktien | Post-passivation of a phosphatized metal surface |
-
1969
- 1969-10-28 US US871952A patent/US3647568A/en not_active Expired - Lifetime
Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2519028A1 (en) * | 1981-12-30 | 1983-07-01 | Asturienne Mines Comp Royale | PROCESS FOR THE PREPARATION OF A BLACK COATING ON THE SURFACE OF PARTS OF WHICH AT LEAST ONE FACE IS IN ZINC |
EP0083263A2 (en) * | 1981-12-30 | 1983-07-06 | Asturienne France | Process for applying a block coating to objects having at least one zinc surface |
EP0083263A3 (en) * | 1981-12-30 | 1984-05-09 | Asturienne Mines Comp Royale | Process for applying a block coating to objects having at least one zinc surface |
US4950339A (en) * | 1988-02-03 | 1990-08-21 | Metallgesellschaft Aktiengesellschaft | Process of forming phosphate coatings on metals |
US5089349A (en) * | 1989-06-05 | 1992-02-18 | Calgon Corporation | Compositions and method for applying coatings to metallic surfaces |
WO1995021278A1 (en) * | 1994-02-03 | 1995-08-10 | Henkel Kommanditgesellschaft Auf Aktien | Chromating process or phosphate-chromating process and materials suitable for identifying the treatment process |
WO2000052227A1 (en) * | 1999-03-02 | 2000-09-08 | Henkel Corporation | Nonsludging zinc phosphating composition and process |
US7422629B1 (en) | 1999-03-02 | 2008-09-09 | Henkel Kommanditgesellschaft Auf Aktien | Nonsludging zinc phosphating composition and process |
WO2000073536A1 (en) * | 1999-05-28 | 2000-12-07 | Henkel Kommanditgesellschaft Auf Aktien | Post-passivation of a phosphatized metal surface |
US6645316B1 (en) | 1999-05-28 | 2003-11-11 | Henkel Kommanditgesellschaft Auf Aktien | Post-passivation of a phosphatized metal surface |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US2312855A (en) | Method of coating aluminum | |
US4419199A (en) | Process for phosphatizing metals | |
US5294266A (en) | Process for a passivating postrinsing of conversion layers | |
US4278477A (en) | Metal treatment | |
CA1333147C (en) | Process of phosphating steel and/or galvanized steel before painting | |
JPS6136588B2 (en) | ||
US7029541B2 (en) | Trivalent chromate conversion coating | |
US3977839A (en) | Coated metal article and method of coating | |
US4849031A (en) | Process of producing phosphate coatings on metal surfaces | |
US2665231A (en) | Coating process with alkali metal phosphate and added fluoride salt | |
US3468724A (en) | Metal coating process | |
US4451304A (en) | Method of improving the corrosion resistance of chemical conversion coated aluminum | |
US4497668A (en) | Phosphating process for zinc-plated metals | |
US3647568A (en) | Colored phosphate coatings and method of application | |
US3755018A (en) | Composition and process for inhibiting corrosion of non-ferrous metal surfaced articles and providing receptive surface for synthetic resin coating compositions | |
US2327002A (en) | Coated article and method of making the same | |
US2244526A (en) | Process of treating metal surfaces | |
US3843430A (en) | Chromate-free bright dip for zinc and cadmium surfaces | |
US3895969A (en) | Composition and process for inhibiting corrosion of non-ferrous metal surfaced articles and providing surface for synthetic resin coating compositions | |
US3720547A (en) | Permanganate final rinse for metal coatings | |
JPH04507436A (en) | Method of forming a manganese-containing zinc phosphate layer on galvanized steel | |
US2272216A (en) | Method of coating copper and its alloys | |
US4416705A (en) | Composition and process for production of phosphate coatings on metal surfaces | |
US3573111A (en) | High lubricity corrosion resistant threaded fastener and method | |
JPS62174385A (en) | Pretreatment for painting by cationic electrodeposition |