US3531384A - Process of treating surfaces of metallic articles - Google Patents
Process of treating surfaces of metallic articles Download PDFInfo
- Publication number
- US3531384A US3531384A US693131A US3531384DA US3531384A US 3531384 A US3531384 A US 3531384A US 693131 A US693131 A US 693131A US 3531384D A US3531384D A US 3531384DA US 3531384 A US3531384 A US 3531384A
- Authority
- US
- United States
- Prior art keywords
- acid
- electrolytic bath
- chromium
- treating
- aqueous electrolytic
- 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
- 238000000034 method Methods 0.000 title description 25
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 22
- 238000000576 coating method Methods 0.000 description 17
- 150000001447 alkali salts Chemical class 0.000 description 16
- KRVSOGSZCMJSLX-UHFFFAOYSA-L chromic acid Substances O[Cr](O)(=O)=O KRVSOGSZCMJSLX-UHFFFAOYSA-L 0.000 description 16
- 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 16
- 229910052751 metal Inorganic materials 0.000 description 16
- 239000002184 metal Substances 0.000 description 16
- 239000000654 additive Substances 0.000 description 13
- 239000011248 coating agent Substances 0.000 description 13
- 229910000831 Steel Inorganic materials 0.000 description 11
- 239000007864 aqueous solution Substances 0.000 description 11
- 238000005868 electrolysis reaction Methods 0.000 description 11
- 229910052742 iron Inorganic materials 0.000 description 11
- 239000010959 steel Substances 0.000 description 11
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 10
- 230000000996 additive effect Effects 0.000 description 10
- 229910052804 chromium Inorganic materials 0.000 description 10
- 239000011651 chromium Substances 0.000 description 10
- FXADMRZICBQPQY-UHFFFAOYSA-N orthotelluric acid Chemical class O[Te](O)(O)(O)(O)O FXADMRZICBQPQY-UHFFFAOYSA-N 0.000 description 8
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 description 6
- 229910001430 chromium ion Inorganic materials 0.000 description 6
- 229910000423 chromium oxide Inorganic materials 0.000 description 6
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 description 6
- GNTDGMZSJNCJKK-UHFFFAOYSA-N divanadium pentaoxide Chemical class O=[V](=O)O[V](=O)=O GNTDGMZSJNCJKK-UHFFFAOYSA-N 0.000 description 6
- QYHFIVBSNOWOCQ-UHFFFAOYSA-N selenic acid Chemical class O[Se](O)(=O)=O QYHFIVBSNOWOCQ-UHFFFAOYSA-N 0.000 description 6
- DJHGAFSJWGLOIV-UHFFFAOYSA-N Arsenic acid Chemical class O[As](O)(O)=O DJHGAFSJWGLOIV-UHFFFAOYSA-N 0.000 description 5
- 239000002253 acid Substances 0.000 description 5
- 229910052782 aluminium Inorganic materials 0.000 description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 5
- 150000001450 anions Chemical class 0.000 description 5
- 229940000488 arsenic acid Drugs 0.000 description 5
- 150000001875 compounds Chemical class 0.000 description 5
- 150000003839 salts Chemical class 0.000 description 5
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 4
- 150000002739 metals Chemical class 0.000 description 4
- VLAPMBHFAWRUQP-UHFFFAOYSA-L molybdic acid Chemical class O[Mo](O)(=O)=O VLAPMBHFAWRUQP-UHFFFAOYSA-L 0.000 description 4
- 239000003973 paint Substances 0.000 description 4
- 229910052718 tin Inorganic materials 0.000 description 4
- WQEVDHBJGNOKKO-UHFFFAOYSA-K vanadic acid Chemical compound O[V](O)(O)=O WQEVDHBJGNOKKO-UHFFFAOYSA-K 0.000 description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- 235000014113 dietary fatty acids Nutrition 0.000 description 3
- 229930195729 fatty acid Natural products 0.000 description 3
- 239000000194 fatty acid Substances 0.000 description 3
- 150000004665 fatty acids Chemical class 0.000 description 3
- -1 fluorine ions Chemical class 0.000 description 3
- SQTLECAKIMBJGK-UHFFFAOYSA-I potassium;titanium(4+);pentafluoride Chemical compound [F-].[F-].[F-].[F-].[F-].[K+].[Ti+4] SQTLECAKIMBJGK-UHFFFAOYSA-I 0.000 description 3
- 239000011253 protective coating Substances 0.000 description 3
- FERIUCNNQQJTOY-UHFFFAOYSA-N Butyric acid Chemical compound CCCC(O)=O FERIUCNNQQJTOY-UHFFFAOYSA-N 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 150000007513 acids Chemical class 0.000 description 2
- APUPEJJSWDHEBO-UHFFFAOYSA-P ammonium molybdate Chemical compound [NH4+].[NH4+].[O-][Mo]([O-])(=O)=O APUPEJJSWDHEBO-UHFFFAOYSA-P 0.000 description 2
- 239000011609 ammonium molybdate Substances 0.000 description 2
- 229940010552 ammonium molybdate Drugs 0.000 description 2
- 235000018660 ammonium molybdate Nutrition 0.000 description 2
- 229910052785 arsenic Inorganic materials 0.000 description 2
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000012267 brine Substances 0.000 description 2
- 238000000151 deposition Methods 0.000 description 2
- XBDQKXXYIPTUBI-UHFFFAOYSA-N dimethylselenoniopropionate Natural products CCC(O)=O XBDQKXXYIPTUBI-UHFFFAOYSA-N 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- CGFYHILWFSGVJS-UHFFFAOYSA-N silicic acid;trioxotungsten Chemical class O[Si](O)(O)O.O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1.O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1.O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1.O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1 CGFYHILWFSGVJS-UHFFFAOYSA-N 0.000 description 2
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 2
- XROWMBWRMNHXMF-UHFFFAOYSA-J titanium tetrafluoride Chemical class [F-].[F-].[F-].[F-].[Ti+4] XROWMBWRMNHXMF-UHFFFAOYSA-J 0.000 description 2
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 2
- CMPGARWFYBADJI-UHFFFAOYSA-L tungstic acid Chemical class O[W](O)(=O)=O CMPGARWFYBADJI-UHFFFAOYSA-L 0.000 description 2
- OMQSJNWFFJOIMO-UHFFFAOYSA-J zirconium tetrafluoride Chemical class F[Zr](F)(F)F OMQSJNWFFJOIMO-UHFFFAOYSA-J 0.000 description 2
- 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
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 description 1
- VMHLLURERBWHNL-UHFFFAOYSA-M Sodium acetate Chemical compound [Na+].CC([O-])=O VMHLLURERBWHNL-UHFFFAOYSA-M 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- SGGPVBOWEPPPEH-UHFFFAOYSA-N [K].[Zr] Chemical class [K].[Zr] SGGPVBOWEPPPEH-UHFFFAOYSA-N 0.000 description 1
- XHCLAFWTIXFWPH-UHFFFAOYSA-N [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] XHCLAFWTIXFWPH-UHFFFAOYSA-N 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 1
- 239000004327 boric acid Substances 0.000 description 1
- 239000013522 chelant Substances 0.000 description 1
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 238000005238 degreasing Methods 0.000 description 1
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 239000002932 luster Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 235000019260 propionic acid Nutrition 0.000 description 1
- IUVKMZGDUIUOCP-BTNSXGMBSA-N quinbolone Chemical compound O([C@H]1CC[C@H]2[C@H]3[C@@H]([C@]4(C=CC(=O)C=C4CC3)C)CC[C@@]21C)C1=CCCC1 IUVKMZGDUIUOCP-BTNSXGMBSA-N 0.000 description 1
- 229910052711 selenium Inorganic materials 0.000 description 1
- 239000011669 selenium Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 239000001632 sodium acetate Substances 0.000 description 1
- 235000017281 sodium acetate Nutrition 0.000 description 1
- CMZUMMUJMWNLFH-UHFFFAOYSA-N sodium metavanadate Chemical compound [Na+].[O-][V](=O)=O CMZUMMUJMWNLFH-UHFFFAOYSA-N 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 229910052714 tellurium Inorganic materials 0.000 description 1
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
- 229910000166 zirconium phosphate Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/38—Chromatising
Definitions
- This invention relates to a process of treating metal surfaces and more particularly to a process for the cathodic treatment of surfaces such as those of iron, steel and other base metals in an aqueous electrolytic bath of chromic acid including a proper additive.
- protective films in the form of a hydrated oxide of chromium may be produced on metallic articles having a surface of iron, or steel by treating the same as the cathode in an aqueous electrolytic bath of chromic acid and boric acid or its salts.
- protective coatings in the form of a mixture of phosphate and chromate may be formed on iron articles by treating the same as the cathode in an aqueous electrolytic bath including anions of phosphoric acid and hexavalent chromium ions.
- anti-corrosive coatings consisting of chelate compounds of chromium were formed on articles of iron, steel or aluminum by treating the metal as the cathode in an aqueous electrolytic bath including essentially anhydrous chromic acid and a small amount of a proper organic compound.
- aqueous electrolytic bath including essentially anhydrous chromic acid and a small amount of a proper organic compound.
- the chief object of the invention is the provision of an improved process for forming a protective coating of chromium on a surface of metals such as iron, steel and the like.
- Another object of the invention is to form a protective oxide coating of chromium on a surface of metals such as iron, steel and the like.
- a further object of the invention is to provide additives to an aqueous electrolytic 'bath of chromic acid effective for forming a protective coating having excellent anti-corrosive and paint adhering properties on surfaces of metals such as iron, steel and the like during a short interval of time.
- the invention resides in a process of treating a surface of a metallic article by depositing chromium oxide thereon by electrolyzing between an anode surface and a cathode surface of said metal an aqueous solution of ionic components consisting essentially of hexavalent chromium ions and an additive selected from the group consisting of alkali salts of zirconium fluoride, alkali salts of titanium fluoride, alkali salts of tungstic acid, silico-tungstic acid, molybdic acid, alkali salts of molybdic acid, selenic acid, alkali salts of selenic acid, telluric acid, alkali salts of teluric acid, vanadic acid, alkali salts of vanadic acid, vanadium pentoxide, arsenic acid, and alkali salts of arsenic acid.
- the aqueous solution of ionic components may consist essentially of monobasic fatty acids or salts of monobasic fatty acids.
- the process is preferably caried out with metal surfaces of iron and steel; however other metallic surfaces such as those of aluminum and tin may also be treated in accordance with this invention. Normally the surface of the metallic article is subjected to a preliminary degreasing and acid immersion before carrying out the present process.
- the aqueous electrolytic bath comprises approximately 0.1 to 1 mol of chromic acid and approximately 0.1 to 5 g./l of the additive except for telluric acid the amount of which ranges from 10 to 200 g./l.
- the cathodic treatment may be advantageously performed at a temperature of from 20 to 60 C. within about 5 seconds and with a current density of from 10 to 50 amps./dm.
- the cathodic electrolysis of an aqueous solution including hexavalent chromium ions yields an oxide coating which consists essentially of trivalent chromium and approximates a monomolecular layer, formed on the cathode used.
- an oxide coating which consists essentially of trivalent chromium and approximates a monomolecular layer, formed on the cathode used.
- a density of electric current flowing through the electrolytic bath becomes higher, then the thickness of the oxide coating is progressively increased, resulting in the formation of a black chromium layer.
- the electrolytic deposit on the cathode changes from black chromium (or chromium oxide) to metallic chromium exhibiting metallic luster.
- the oxide coating deposited on the surface of the cathode is an ol-type compound of reticulate structure including trivalent chromium while the added anions sever the meshes in the ol-type compound resulting in a variation in the velocity at which the coating is electrochemically reduced.
- the term ol-type compound means a complex compound including metal atoms bonded to each other by bridging hydroyl groups.
- an aqueous electrolytic bath of chromic acid includes aded thereto, anions, capable of serving to sever meshes in a formed oxide coating, to thereby accelerate the velocity of electrochemical reduction, as well as to form a deposit in the form of chromium oxide, rather than in the form of metallic chromium, that then chromium oxide, having excellent anti-corrosive and paint adhering properties will be formed on the surface of the cathode Within a short interval of time, with the result that a process of forming chromium coating can be fundamentally improved.
- the invention is based upon the conclusion just described and characterized by the cathodic electrolysis of metallic articles in an aqueous electrolytic bath including from 0.1 to 1 mol of chromic acid and a proper amount of a special additive as will be subsequently described, at a temperature Within a range of from 20 to 60 C. and with a current density of from 10 to 50 amperes per square decimeter.
- chromium oxide is formed which exhibits different colors within a short interval of time, such as seconds.
- the concentration of the chromic acid dissolved in the aqueous electrolytic bath is preferably 0.1 mol or higher. It has been found that if the concentration of chromic acid is below the value specified above, it is difficult for a coating having good anti-corrosive properties to be formed.
- acids, salts and oxides of elements selected from the group consisting of zirconium, titanium, tungsten, molybdenum, selenium, tellurium, vanadium and arsenic may be used.
- the acids of such elements include, for example, selenic acid, telluric acid, arsenic acid, etc.
- salts of zirconium-potassium fiuoride these elements include for example titanium-potassium fluoride, ammonium tungstate, ammonium molybdate, sodium vanadate, etc.
- Oxides of the above described elements also may be used satisfactorily, provided that the same form anions in the aqueous solution of chromic acid such as vanadium pentoxide.
- Monobasic fatty acids may also be used in the present process, such as acetic acid, propionic acid, butyric acid, etc., salts thereof such as sodium acetate.
- the amount of the additive used should be within a range of from 0.1 to 5 g./l. except for telluric acid the amount of which should range from 1.0 to 200 g./l.
- the density of current is within the range of from to 50 amperes per square decimeter and preferably within a range of from to amperes per square decimeter.
- the density of current above the value just specified does not lead to any decrease in the time of electrolysis.
- the optimum operating temperature has been found to be in the range of from 30 to 45 C. although it may range from 20 to 60 C. At any temperature exceeding 70 C. the coating formed has reduced anti-corrosive properties.
- the time of electrolysis is preferably about 5 seconds. If the time of electrolysis exceeds 5 seconds, then the anticorrosive properties of the deposited coating scarcely depend upon the time of electrolysis. Also the color exhibited by the coating can be adjusted by controlling the time of electrolysis.
- the test pieces were rinsed and dried.
- the coatings thus formed on the test pieces were excellent in anti-corrosive properties and gave excellent results in tests for corrosionresistance to brine spray and for paint adhesion. More specifically the results of brine spraying test determined according to the ASTM Standard Bl17-6l indicated no occurrence of rust after the lapse of 6 hours.
- the grid pattern test was conducted with a melaminealkyd resin coated upon the coating on the test pieces. Excellent results were obtained in that the number of grids bearing the resin coated on each of the test pieces was over eighty five.
- a process of depositing chromium oxide on a metal surface selected from the group consisting of steel, iron, aluminum and tin comprising electrolyzing between an anode surface and a cathode surface of said metal an aqueous solution of ionic components consisting essentially of hexavalent chromium ions and an additive selected from the group consisting of alkali salts of Zirconium fluoride, alkali salts of titanium fluoride, alkali salts of tungstic acid, silico-tungstic acid, molybdic acid, alkali salts of molybdic acid, selenic acid, alkali salts of selenic acid, telluric acid, alkali salts of telluric acid, vanadic acid, alkali salts of vanadic acid, vanadium pentoxide, arsenic acid, and alkali salts of arsenic acid, the concentration of said hexavalent chromium ions corresponding to the concentration which would be produced
- a process according to claim 8 in which the aqueous solution is electrolyzed at a temperature of from 20 to degrees centigrade.
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Chemical Treatment Of Metals (AREA)
Description
United States Patent Office 3,531,384 Patented Sept. 29, 1970 3,531,384 PROCESS OF TREATING SURFACES F METALLIC ARTICLES Katsuya Inouye, 38 Shimizu-cho, Suginami-ku, Tokyo,
Japan, and Hideya Okada, 64 Ida-sanmai-cho, Kawasaki, Japan No Drawing. Continuation-impart of application Ser. No. 260,886, Feb. 25, 1963. This application Dec. 26, 1967, Ser. No. 693,131
Claims priority, applic7atiorlisgapan, Feb. 24, 1962,
Int. Cl. A231) 11/00, 11/02 US. Cl. 204-56 12 Claims ABSTRACT OF THE DISCLOSURE This application is a continuation-in-part application of our copending application Ser. No. 260,886, filed Feb. 25, 1963 now abandoned.
BACKGROUND OF INVENTION This invention relates to a process of treating metal surfaces and more particularly to a process for the cathodic treatment of surfaces such as those of iron, steel and other base metals in an aqueous electrolytic bath of chromic acid including a proper additive.
In recent years various electrolytic processes have been proposed using an aqueous solution of chromic acid. For example, protective films in the form of a hydrated oxide of chromium may be produced on metallic articles having a surface of iron, or steel by treating the same as the cathode in an aqueous electrolytic bath of chromic acid and boric acid or its salts. Alternatively, protective coatings in the form of a mixture of phosphate and chromate may be formed on iron articles by treating the same as the cathode in an aqueous electrolytic bath including anions of phosphoric acid and hexavalent chromium ions. Further, anti-corrosive coatings consisting of chelate compounds of chromium were formed on articles of iron, steel or aluminum by treating the metal as the cathode in an aqueous electrolytic bath including essentially anhydrous chromic acid and a small amount of a proper organic compound. However, in view of the fact that prior art processes of the above type are based upon the formation of relatively thick oxide coatings produced by electrochemical reduction, it can hardly be said that basic improvements have been accomplished thereby, in a process of forming a coating on a metal surface.
SUMMARY OF INVENTION The chief object of the invention, therefore, is the provision of an improved process for forming a protective coating of chromium on a surface of metals such as iron, steel and the like.
Another object of the invention is to form a protective oxide coating of chromium on a surface of metals such as iron, steel and the like.
A further object of the invention is to provide additives to an aqueous electrolytic 'bath of chromic acid effective for forming a protective coating having excellent anti-corrosive and paint adhering properties on surfaces of metals such as iron, steel and the like during a short interval of time.
With these objects in view, the invention resides in a process of treating a surface of a metallic article by depositing chromium oxide thereon by electrolyzing between an anode surface and a cathode surface of said metal an aqueous solution of ionic components consisting essentially of hexavalent chromium ions and an additive selected from the group consisting of alkali salts of zirconium fluoride, alkali salts of titanium fluoride, alkali salts of tungstic acid, silico-tungstic acid, molybdic acid, alkali salts of molybdic acid, selenic acid, alkali salts of selenic acid, telluric acid, alkali salts of teluric acid, vanadic acid, alkali salts of vanadic acid, vanadium pentoxide, arsenic acid, and alkali salts of arsenic acid.
In accordance with one aspect of this invention, it has also been found that the aqueous solution of ionic components may consist essentially of monobasic fatty acids or salts of monobasic fatty acids.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The process is preferably caried out with metal surfaces of iron and steel; however other metallic surfaces such as those of aluminum and tin may also be treated in accordance with this invention. Normally the surface of the metallic article is subjected to a preliminary degreasing and acid immersion before carrying out the present process.
Preferably the aqueous electrolytic bath comprises approximately 0.1 to 1 mol of chromic acid and approximately 0.1 to 5 g./l of the additive except for telluric acid the amount of which ranges from 10 to 200 g./l.
The cathodic treatment may be advantageously performed at a temperature of from 20 to 60 C. within about 5 seconds and with a current density of from 10 to 50 amps./dm.
The cathodic electrolysis of an aqueous solution including hexavalent chromium ions yields an oxide coating which consists essentially of trivalent chromium and approximates a monomolecular layer, formed on the cathode used. In this case, if a density of electric current flowing through the electrolytic bath becomes higher, then the thickness of the oxide coating is progressively increased, resulting in the formation of a black chromium layer. Under these circumstances, if anions of an additive such as those of sulfuric acid, fluorine ions or the like are added in a very small amount to the bath of chromic acid, then the electrolytic deposit on the cathode changes from black chromium (or chromium oxide) to metallic chromium exhibiting metallic luster. This appears to result from the fact that the oxide coating deposited on the surface of the cathode is an ol-type compound of reticulate structure including trivalent chromium while the added anions sever the meshes in the ol-type compound resulting in a variation in the velocity at which the coating is electrochemically reduced. The term ol-type compound means a complex compound including metal atoms bonded to each other by bridging hydroyl groups.
Thus the inventors have arrived at the conclusion that, if an aqueous electrolytic bath of chromic acid includes aded thereto, anions, capable of serving to sever meshes in a formed oxide coating, to thereby accelerate the velocity of electrochemical reduction, as well as to form a deposit in the form of chromium oxide, rather than in the form of metallic chromium, that then chromium oxide, having excellent anti-corrosive and paint adhering properties will be formed on the surface of the cathode Within a short interval of time, with the result that a process of forming chromium coating can be fundamentally improved.
The invention is based upon the conclusion just described and characterized by the cathodic electrolysis of metallic articles in an aqueous electrolytic bath including from 0.1 to 1 mol of chromic acid and a proper amount of a special additive as will be subsequently described, at a temperature Within a range of from 20 to 60 C. and with a current density of from 10 to 50 amperes per square decimeter. On the surface of the metallic article serving as the cathode, chromium oxide is formed which exhibits different colors within a short interval of time, such as seconds.
The concentration of the chromic acid dissolved in the aqueous electrolytic bath is preferably 0.1 mol or higher. It has been found that if the concentration of chromic acid is below the value specified above, it is difficult for a coating having good anti-corrosive properties to be formed.
The additive used is selected on the basis of the previously described conclusion. Thus acids, salts and oxides of elements selected from the group consisting of zirconium, titanium, tungsten, molybdenum, selenium, tellurium, vanadium and arsenic may be used. The acids of such elements include, for example, selenic acid, telluric acid, arsenic acid, etc., salts of zirconium-potassium fiuoride these elements include for example titanium-potassium fluoride, ammonium tungstate, ammonium molybdate, sodium vanadate, etc. Oxides of the above described elements also may be used satisfactorily, provided that the same form anions in the aqueous solution of chromic acid such as vanadium pentoxide.
Monobasic fatty acids may also be used in the present process, such as acetic acid, propionic acid, butyric acid, etc., salts thereof such as sodium acetate.
The amount of the additive used should be within a range of from 0.1 to 5 g./l. except for telluric acid the amount of which should range from 1.0 to 200 g./l.
The density of current is within the range of from to 50 amperes per square decimeter and preferably within a range of from to amperes per square decimeter. The density of current above the value just specified does not lead to any decrease in the time of electrolysis.
The optimum operating temperature has been found to be in the range of from 30 to 45 C. although it may range from 20 to 60 C. At any temperature exceeding 70 C. the coating formed has reduced anti-corrosive properties.
The time of electrolysis is preferably about 5 seconds. If the time of electrolysis exceeds 5 seconds, then the anticorrosive properties of the deposited coating scarcely depend upon the time of electrolysis. Also the color exhibited by the coating can be adjusted by controlling the time of electrolysis.
The following examples illustrate the practice of the invention, but must not be construed as limiting the invention in any manner whatsoever.
EXAMPLE 1 Aqueous electrolytic bath:
Anhydrous chromic acid50 g./l. Glacial acetic acidl cc./l. Temperature45 C. Density of current30 amps./dm. Treating time-5 seconds EXAMPLE 2 Aqueous electrolytic bath:
Anhydrous chromic acid50 g./l. Titanium-potassium fluoride.5 g./l. Temperature-45 C. Density of current-30 amps./dm.'- Treating time--5 seconds EXAMPLE 3 Aqueous electrolytic bath:
Anhydrous chromic acidSO g./l. Sodium metavanadate1 g./l.
4 Temperature- C. Density of current30 amps./dm. Treating time-5 seconds EXAMPLE 4 Aqueous electrolytic bath:
Anhydrous chromic acidSO g./l. Zirconium-potassium fluoride-.5 g./l. Temperature-45 C. Density of current30 amps./dm. Treating time5 seconds EXAMPLE 5 Aqueous electrolytic bath:
Anhydrous chromic acid g./l. Silicotungstic acid2 g./l. Temperature45 C. Density of current30 amps./dm. Treating time5 seconds EXAMPLE 6 Aqueous electrolytic bath:
Anhydrous chromic acid-1O g./l. Ammonium molybdate.5 g./l. Temperature-45 C. Density of current30 amps/dm. Treating time-5 seconds EXAMPLE 7 Aqueous electrolytic bath:
Anhydrous chromic acid50 g./l. Selenic acid2 g./l. Temperature30' C. Density of current30 amps./dm. Treating time-5 seconds EXAMPLE 8 Aqueous electrolytic bath:
Anhydrous chromic acid-10 g./l. Telluric acid20 g./l. Temperature-30 C. Density of current-20- an1ps./dm. Treating time5 seconds EXAMPLE 9 Aqueous electrolytic bath:
Anhydrous chromic acidlO g./l. Arsenic acid2 g./l. Temperature-30 C. Density of current20 amps/dm. Treating time-6 seconds EXAMPLE l0 Aqueous electrolytic bath:
Anhydrous chromic acidlO g./l. Vanadium pentoxide-.2 g./l. Temperature-30 C. Density of current20 amps/dm. Treating time-5 seconds Test pieces cut from a steel sheet were first degreased, acid immersed in the conventional manner and then subjected to the cathodic electrolysis in aqueous electrolytic baths as above described in Examples 1 through 10 under the conditions as also described in the same examples respectively.
After the completion of the cathodic electrolysis the test pieces were rinsed and dried. The coatings thus formed on the test pieces were excellent in anti-corrosive properties and gave excellent results in tests for corrosionresistance to brine spray and for paint adhesion. More specifically the results of brine spraying test determined according to the ASTM Standard Bl17-6l indicated no occurrence of rust after the lapse of 6 hours. As to the paint adhering properties, the grid pattern test was conducted with a melaminealkyd resin coated upon the coating on the test pieces. Excellent results were obtained in that the number of grids bearing the resin coated on each of the test pieces was over eighty five.
The additives other than those described in the above examples also yielded excellent coatings.
While the invention has been particularly described in terms of steel articles it is to be understood that the invention is not limited to such articles and that it is equally applicable to articles of other metals such as iron, aluminum, and tin without departing from the spirit and scope of the invention.
What we claim and desire to secure by Letters Patent are:
1. A process of depositing chromium oxide on a metal surface selected from the group consisting of steel, iron, aluminum and tin, comprising electrolyzing between an anode surface and a cathode surface of said metal an aqueous solution of ionic components consisting essentially of hexavalent chromium ions and an additive selected from the group consisting of alkali salts of Zirconium fluoride, alkali salts of titanium fluoride, alkali salts of tungstic acid, silico-tungstic acid, molybdic acid, alkali salts of molybdic acid, selenic acid, alkali salts of selenic acid, telluric acid, alkali salts of telluric acid, vanadic acid, alkali salts of vanadic acid, vanadium pentoxide, arsenic acid, and alkali salts of arsenic acid, the concentration of said hexavalent chromium ions corresponding to the concentration which would be produced by chromic acid in said aqueous solution in a concentration of approximately 0.1 to 1 mol per liter and the concentration of said additive being approximately from to 220 grams per liter in the case of telluric acid and approximately from 0.1 to 5 grams per liter in the case of the other additives.
2. A process according to claim 1, in which said metal surface is steel.
3. A process according to claim 1, in which said metal surface is iron.
4. A process according to claim 1, in which said metal surface is aluminum.
5. A process according to claim 1, in which said metal surface is tin.
6. A process according to claim 1, in which the additive is selected from the group consisting of zirconium-potassium fluoride, titanium-potassium fluoride, selenic acid and telluric acid.
7. A process according to claim 1, in which chromic acid is in said solution whereby said hexavalent chromium ions derive from said chromic acid.
8. A process according to claim 1, in which the aqueous solution is electrolyzed with a current density of from 10 to amperes per square decimeter.
9. A process according to claim 8, in which the aqueous solution is electrolyzed at a temperature of from 20 to degrees centigrade.
10. A process according to claim 9, in which the aqueous solution is electrolyzed for a period of up to about 5 seconds.
11. A process according to claim 9, in which the duration of the electrolysis is about 5 seconds and the current density with which the electrolysis is performed is 20 to 30 amperes per square decimeter.
12. A process according to claim 11, in which the aqueous solution is electrolyzed at a temperature of from 30 to 45 degrees centigrade.
References Cited UNITED STATES PATENTS 2,746,915 5/1956 Giesker 204-56 FOREIGN PATENTS 1,024,926 4/1966 Great Britain.
HOWARD S. WILLIAMS, Primary Examiner R. L. ANDREWS, Assistant Examiner U.S. Cl. X.R.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP715562 | 1962-02-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3531384A true US3531384A (en) | 1970-09-29 |
Family
ID=11658164
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US693131A Expired - Lifetime US3531384A (en) | 1962-02-24 | 1967-12-26 | Process of treating surfaces of metallic articles |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US3531384A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3625844A (en) * | 1969-06-05 | 1971-12-07 | Circult Foll Corp | Stainproofing process and products resulting therefrom |
| US3926761A (en) * | 1973-04-09 | 1975-12-16 | Kansai Paint Co Ltd | Aqueous electrophoretic coating compositions comprised of polycarboxylic acid binder resin and sparingly soluble alkaline earth metal molybdate |
| US4427499A (en) | 1981-06-04 | 1984-01-24 | Nippon Kinzoku Co., Ltd. | Process for surface treatment of stainless steel sheet |
| US4968392A (en) * | 1987-04-28 | 1990-11-06 | Bnf Metals Technology Centre | Treatment of condenser tubes |
| WO2003048416A1 (en) | 2001-12-04 | 2003-06-12 | Nippon Steel Corporation | Metal material coated with metal oxide and/or metal hydroxide coating film and method for production thereof |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2746915A (en) * | 1951-10-15 | 1956-05-22 | Autoyre Co Inc | Electrolytic metal treatment and article |
| GB1024926A (en) * | 1963-07-11 | 1966-04-06 | Pyrene Co Ltd | Improvements relating to the chromating of aluminium |
-
1967
- 1967-12-26 US US693131A patent/US3531384A/en not_active Expired - Lifetime
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2746915A (en) * | 1951-10-15 | 1956-05-22 | Autoyre Co Inc | Electrolytic metal treatment and article |
| GB1024926A (en) * | 1963-07-11 | 1966-04-06 | Pyrene Co Ltd | Improvements relating to the chromating of aluminium |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3625844A (en) * | 1969-06-05 | 1971-12-07 | Circult Foll Corp | Stainproofing process and products resulting therefrom |
| US3926761A (en) * | 1973-04-09 | 1975-12-16 | Kansai Paint Co Ltd | Aqueous electrophoretic coating compositions comprised of polycarboxylic acid binder resin and sparingly soluble alkaline earth metal molybdate |
| US4427499A (en) | 1981-06-04 | 1984-01-24 | Nippon Kinzoku Co., Ltd. | Process for surface treatment of stainless steel sheet |
| US4968392A (en) * | 1987-04-28 | 1990-11-06 | Bnf Metals Technology Centre | Treatment of condenser tubes |
| WO2003048416A1 (en) | 2001-12-04 | 2003-06-12 | Nippon Steel Corporation | Metal material coated with metal oxide and/or metal hydroxide coating film and method for production thereof |
| EP1455001A1 (en) * | 2001-12-04 | 2004-09-08 | Nippon Steel Corporation | Metal material coated with metal oxide and/or metal hydroxide coating film and method for production thereof |
| US20050067056A1 (en) * | 2001-12-04 | 2005-03-31 | Hiromasa Shoji | Metal material coated with metal oxide and/or metal hydroxide coating film and method for production thereof |
| EP1455001A4 (en) * | 2001-12-04 | 2005-05-18 | Nippon Steel Corp | Metal material coated with metal oxide and/or metal hydroxide coating film and method for production thereof |
| US7883616B2 (en) | 2001-12-04 | 2011-02-08 | Nippon Steel Corporation | Metal oxide and/or metal hydroxide coated metal materials and method for their production |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN100537845C (en) | Metal finishing treatment solution and surface treatment method | |
| US4273592A (en) | Coating solution for metal surfaces | |
| US5275713A (en) | Method of coating aluminum with alkali metal molybdenate-alkali metal silicate or alkali metal tungstenate-alkali metal silicate and electroyltic solutions therefor | |
| US3969152A (en) | Rare earth metal rinse for metal coatings | |
| JPS58181889A (en) | Preparation of single surface zinc electroplated steel plate | |
| KR20190125457A (en) | Manufacturing method of Sn plated steel sheet and Sn plated steel sheet | |
| JP2604387B2 (en) | Method of forming phosphate film on metal surface | |
| US2322208A (en) | Method of providing a protective coating on magnesium and its alloys | |
| US3531384A (en) | Process of treating surfaces of metallic articles | |
| US3479260A (en) | Treatment for ferrous surfaces | |
| US3454483A (en) | Electrodeposition process with pretreatment in zinc phosphate solution containing fluoride | |
| US3081238A (en) | Electrolytic treatment of metal surfaces | |
| JPS6148597A (en) | Chemical conversion treatment giving zinc phosphate | |
| US3335074A (en) | Anodic treatment of zinc and zinc-base alloys | |
| US3515650A (en) | Method of electroplating nickel on an aluminum article | |
| US2095519A (en) | Method for producing galvanic coatings on aluminum or aluminum alloys | |
| US3467589A (en) | Method of forming a copper containing protective coating prior to electrodeposition of paint | |
| US3278343A (en) | Conversion coating of magnesium alloy surfaces | |
| USRE27896E (en) | Method of forming a copper containing protective coating prior to electro- deposition of paint | |
| US3330744A (en) | Anodic treatment of zinc and zinc-base alloys and product thereof | |
| US3348979A (en) | Process for treating aluminum weld wire | |
| US4547269A (en) | Method of electrodepositing zinc on steel prior to phosphating | |
| US1910593A (en) | Process of forming oxalate coatings on iron and steel articles | |
| JPS5837192A (en) | Post-treatment for non-plated surface of steel plate electroplated with zinc on one side | |
| US1953999A (en) | Anodic coating of zinc base metals |