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
  • C23C22/74—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 for obtaining burned-in conversion coatings
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24802—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]
  • Y10T428/24851—Intermediate layer is discontinuous or differential
  • Y10T428/24868—Translucent outer layer
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24802—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]
  • Y10T428/24917—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.] including metal layer
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24942—Structurally defined web or sheet [e.g., overall dimension, etc.] including components having same physical characteristic in differing degree
  • Y10T428/2495—Thickness [relative or absolute]
  • Y10T428/24967—Absolute thicknesses specified
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/26—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
  • Y10T428/263—Coating layer not in excess of 5 mils thick or equivalent
  • Y10T428/264—Up to 3 mils
  • Y10T428/265—1 mil or less
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31678—Of metal
  • Y10T428/31681—Next to polyester, polyamide or polyimide [e.g., alkyd, glue, or nylon, etc.]

Definitions

• ABSTRACT A method of providing a decorative exposed metallic surface with protection from marring, marking and staining. comprising the steps of coating the surface with an aqueous solution which contains ions of magnesium, ammonium, chromate and phosphate and curing said coating.
• a composite article comprising a layer of metal having a decorative exposed surface and at least one layer of a substantially water insoluble, transparent, cured coating which offers protection from marring, marking and staining.
• the cured 1 coating being comprised of magnesium cations and anionic polymeric chains of chromium, oxygen and phosphorus atoms.
• the present invention relates-to a method for protecting a decorative metallic surface from marring, marking and staining and to a composite article comprising'a layer of metal and acoating which protects'the metal from marring, marking and staining.
• Numerous articles of manufacture such as waterfountains and building panels have decorative metallic surfaces;.e.g.,.
• stainless'steel These surfaces are in needof protection as they are subjected to severe abuse. They are scratched, smeared by natural skin oils and other contaminants found on hands, weathered by various atmospheric conditions and stained-by different solvents and chemicals.
• the method of this invention comprises the steps of coating the metal to be protected with an aqueous solution which contains ions of magnesium, ammonium, chromate and'phosphate and curing the coating so as to render it substantially water insoluble.
• phosphate ion includes all ions related to phosphoric acid in an aqueous solution.
• the species H PO.,,-H PO,, HPO, andPO and any polymeric phosphorous oxyacidanions are collectively referred to asphosphate' ion.
• CF05 in solution may exist'as CrO Cr O-,,-etc., as well as in variousprotonated forms, all oflwhich are included in the term chromate ion.
• the ions i.e., magnesium, ammonium, chromate and phosphate
• Magnesium ion may be supplied as the'oxide, hydroxide, carbonate, bicarbonate, phosphate-or chromate.
• Ammonium ion maybe supplied as uncombined ammonia,.aqueous ammonium hydroxide, or as' the phosphate, chromate, carbonate or bicarbonate salts.
• Phosphate ion is most conveniently supplied'as orthophosphoric acid. it can also besupplied as magnesium phosphate, ammonium phosphate or magnesium ammonium phosphate.
• Chromate ion may be supplied as chromium trioxide or asthe'chromateor dichromat'e salts of magnesium'or ammonium.
• the composition ratios of the solution are limited to the composition ratios of the particular salts used. Variations of these composition ratios can, however, be produced by adding extra magnesium or ammonium as one of the other acceptable compounds.
• the most convenient-method for producing the coating solution is to use magnesium hydroxide, ortho-phosphoric a'cid, concentrated aqueous ammonium hydroxide and chromium trioxide.
• the magnesium, ammonium,.chromate and phosphate ions are proportionately present in the aqueous solutionas 0.01 28 mole percent magnesium ion, 5 22 mole percent'ammonium ion, 4 26 mole percent chromate ion and 33 67 mole percent phosphate ionand preferably as 16 26 mole percent magnesium ion, 7 mole percent ammonium ion, 7 21 mole percent chromate ion and 45 65 mole percent phosphate ion.
• Magnesium is needed in order to render the cured coating substantially water insoluble and to decrease curing times to reasonable periods.
• a lower limit of 0.01 mole percent magnesium ion is imposed as cured coatings formed from solutions with less than 0.01 mole percent are not water insoluble.
• An upper limit of 28 mole percent magnesium'ion is imposed as 28 mole percent is the limit-of the solubility for magnesium brain the coating solution.
• Chromate ion assists in giving the coating its transparency and is required to render the coating substantially water insoluble after curing. Solutions with less than 4 percent chromate ion produce opaque cured coatingsland. solutions with more than 26.mole percent chromate ion produce blotchy coatings which require excessivecuring *times'. .Ammonium ion also assistsv in giving the coating its transparency.
• the concentration of magnesium, ammonium; chromate and.phosphate. ions inthewater shouldbe no-greater than about iii-moles of ionsper ml. of water and preferably should be no greater than 0.8 moles of ions per 100ml. of water.
• 'Solutions'with concentrations in excess of L5 have too high a solid level and produce a cloudy, bubbly coat.
• Any composition which gives a transparentcoating will continue to give a transparent coating as the amount of water is increased. The only effect of dilution is'to decrease the coating thickness.
• a lower limit of 0.01 moles'of'ions per 100 ml. of water has been set.
• a preferred lower limit is 0.25 moles of ions per 100 ml. of water.
• a wetting. agent can be added to the coating solution to insure'the best possible wetting action at the metal surface.
• wetting agents are optional'and by no means necessary.
• Typical wetting. agents are Wetanol (Glyco Products, Inc., New York, NY.) and Alkanol HCS (E. l. du Pont de Nemours & Company, .Wilmington, Del.
• the invention is not dependent upon the use of any particular coating'method.
• Illustrative. coating methods are clip coating, flow coating, spray coating, roll coating and spin coating.
• The. coating should be cured so as to render it substantially water insoluble.
• Curing. is atime and temperaturedependent process. Shorter times are required at higher temperatures and longer'times are required at lower temperatures. Curing temperatures; i.e., the temperatures at: the metallic surfaces, rangingfrom 400" to 1,900" F. have been successfully employed at timesrangingfrom two seconds to four hours.
• Various colors and tints can begiven'to the coating by varying'the curing temperature..Thisenables certain metals; e.g.,. stainless steel, to take. on' the appearance of. color without treating;.e.g., heat tinting, themetal. Color' can also be varied by adjusting the relative proportion-of magnesium, ammonium, chromate and phosphate ions which are present in the aqueous coating solution and/or by adjusting the thickness of the cured coating. It is also withinthe scope of this invention to add pigments, dies and other chemical agents to alter the colorof the coating.
• the article of thisinvention is comprised of a layer of metal having a decorative surface disposed to be visible and at least one layeroia substantially water insoluble, transparent, cured coating which offers protection from marring,.marking and staining-disposed in adhering relation on the decorative surface.
• the coating is comprised. of magnesium cations and anionic polymeric chains of chromium, oxygen and phosphorous atoms. No limit is placed on the thickness of the coating although each individual layer should not exceed 0.0005 inches. Layers thicker than 0.0005 inches require an excessive amount of coating solution and acquire a frosty appearance during curing.
• Stainless steel has a strikingly noticeable tendency to show scratches and marks which cannot be easily removed by any known commercial means without destroying its uniform appearance.
• Stainless steel trim members e.g., automotive trim members, having a contact surface which abuts a metallic body member less noble in the electromotive series than stainless steel; e.g., a carbon steel automotive body, and an exposure surface subject to view, constitute a particular embodiment of this invention.
• assemblies comprised of stainless steel trim members and metallic body members.
• Stainless steel is known to serve a particularly good purpose in those applications where brightness and corrosion resistance is required and is ideally suited for use as automotive trim.
• the use of stainless steel can result in galvanic corrosion.
• Carbonsteel is anodic to stainless steel and generally corrodes in the vicinity of stainless steel in the presence of an electrolyte, such as moisture. Galvanic corrosion can, however, be precluded if an insulating material is placed between the carbon steel and the stainless steel; e.g., on the contact surface of the stainless steel trim member.
• the coating described in this application is particularly appropriate since it will serve as an insulator and will also provide the exposure surface with protection from marring, marking and staining.
• EXAMPLE I A.I.S.I. Type 434 stainless steel samples 0.0185 inches thick were dip coated in an aqueous solution containing ions of magnesium, ammonium, chromate and phosphate. The ions were proportionately present in the solution as 22.5 mole percent magnesium ion, 9.5 mole percent ammonium ion, 12.5 mole percent chromate ion and 55.5 mole percent phosphate ion. The molar concentration of the specified ions in the solution was 0.420 moles of ions per I ml. of water. Half of the samples had a bright anneal finish and half had a matte finish. All the samples were cured for one minute in a furnace at temperatures ranging from 550' F. up to l,200 F.
• the bright annealed samples had coatings ranging from 0.000040 inches to 0.000l68 inches and the matte finished samples had coatings ranging from 0.000043 inches to 0.000209 inches.
• Table I found below, gives the appearance of the coating. Note how the appearance changes with the curing temperature.
• Tan Tint 900 Substantially Gray-Green Colorless Tint 950
• Substantially Gray-Green Colorless Tint l I00 Light Cloudy Gray Gray I200 Cloudy Blue Gray Gray-Tan Tint
• the bright annealed and the matte finished samples which were cured at 900 F. and l,000 F. were subjected to a number of tests. The favorable results of the tests are reported below.
• the continuity; e.g., electrical resistance, of the coating was not, however, afiected after 24 hours of testing.
• a bright annealed sample was tested with an abrasion tester. Two one-half inch wide X 2% inch diameter rubberized carborundum wheels, each causing a 1,000 gram drag on the coated surface, traveled over a 3% inch diameter circle while being driven by the samples which were revolved. Any coating that will withstand cycles of this test is considered to be very good. The tested coating withstood 800 cycles without having its continuity impaired. This indicates that it is very hard and should offer high resistance to marking and marring.
• Ammonium ion The molar concentration of the ions in solutions A and B were respectively 0.91 and 1.05 moles of the specified ions per 100 ml. of water.
• the coated strips were divided into a number of samples which were cured at temperatures ranging from 630 to 1,030 F. for a period of 2 minutes. The samples were subsequently measured for color. Color values were obtained using a Hunter Associates (Mclean, Va.), Laboratory Sphere Color and Color Difference Meter, Model D25.
• Table Ill found below, gives the finish of the samples prior to coating, the coating solution used, the curing temperature, the calculated coating thickness after curing and the color values.
• marring, marking and staining comprising the steps of: coating said metallic surface with an aqueous solution of magnesium, ammonium, chromate and phosphate ions, said aqueous solution having a molar concentration of said ions of between about 0.0l and 1.5 moles of said ions per 100 ml. of water, said ions being proportionately present in said aqueous solution as 0.01-28 mole percent magnesium ion, 522 mole percent ammonium ion, 4-26 mole percent chromate ion and 33-67 mole percent phosphate ion; and curing said coating at an elevated temperature so as to render it substantially water insoluble.
• the L term refers to the lightness of color and corresponds to the lightness scale used in the Munsell Color System. Low values of L are associated with dull surfaces while bright surfaces give numerically large L values. L indicates the quantity of black or white contained in the hue (color). Higher L values are closer to white and lower L values are closer to black.
• the a term requires a positive or negative prefix sign to indicate whether red or green hues are present. The positive prefix is for red hues and the negative prefix is for green hues. The size of the number indicates the strength or amount of the particular hue present in the total color.
• the b" term is similar with the positive prefix indicating yellowness and the negative prefix indicating blueness.
• the size of the number indicates the strength or amount of yellow or blue present in the total color.
• the A E value is a calculated color difference that exists between the selected standard and the sample being examined. It is equal to the square root of (A L) (A a) (A b)? Uncoated samples 1 and 11 were used as the selected standard.
• the haze value is a ratio of the intensity of diffused light to reflected light times 100. Standard rhodium mirrors have a haze value of l 1.0 while sandblasted surfaces have haze values near l00.
• a method according to claim 1 for providing a colored coating which includes the step of adding pigments or dies to the aqueous coating solution.
• a method according to claim 1 wherein said coating is cured by heating said metallic surface at a temperature of from about 400 F. to about l,900 F. for a period of from 2 seconds to about 4 hours.
• a method according to claim 1 adapted to protect a metallic surface selected from the group consisting of stainless steel, brass, aluminum, silver, zinc, copper, plain carbon steel, lead, chromium, nickel, gold, platinum, and alloys of said metals.
• a composite article comprising a layer of metal having a decorative exposed surface and at least one layer of a substantially water insoluble, cured coating of magnesium cations and anionic polymeric chains of chromium, oxygen, and phosphorus atoms, adhered to said surface; said coating having been formed from an aqueous solution of magnesium, amrnonium, chromate and phosphate ions having a molar concentration of between 0.01 and 1.5 moles of said ions per 100 ml.
• each layer of said coating is less than about 0.0005 inches thick.
• metal is selected from the group consisting of stainless steel, brass, aluminum, silver, zinc, copper, plain carbon steel, lead, chromium, nickel, gold, platinum and alloys of said metals.
• the improvement which comprises: coating said contact surface with an aqueous solution of magnesium, ammonium, chromate and phosphate ions, said aqueous solution having a molar concentration of said ions of between about 0.01 and 1.5 moles of said ions per l ml.
• said ions being proportionately present in said aqueous solution as 0.01 28 mole percent magnesium ion, 22 mole percent ammonium ion, 4 26 mole percent chromate ion and 33 67 mole percent phosphate ion; and curing said coating at an elevated temperature so as to render it substantially water insoluble.
• a method according to claim including the steps of coating said exposure surface with said aqueous solution and curing said coating on said exposure surface.
• An assembly comprising a stainless steel trim member in combination with a metallic body member less noble in the electromotive series than stainless steel; said stainless steel trim member having an exposed surface, a contact surface abutting said metallic body member and at least one layer of a substantially water insoluble cured coating of magnesium cations and anionic polymeric chains of chromium, oxygen and phosphorus atoms, adhered to said contact surface; said coating having been formed from an aqueous solution of magnesiurn, ammonium, chromate and phosphate ions having a molar concentration of between 0.0l and 1.5 moles of said ions per 100 ml. water and having said ions proportionately present as 0.01 28 mole percent magnesium ion, 5 22 mole percent ammonium ion, 4 26 mole percent chromate ion and 33 67 mole percent phosphate ion.
• each layer of said coating is less than about 0.0005 inches thick.
• a method of providing an exposed metallic surface from the group consisting of stainless steel, brass, aluminum, silver, zinc, copper, plain carbon steel, lead, chromium, nickel, gold, platinum, and alloys of said metals with protection against marring, marking, staining, and corrosion which comprises the steps of: coating said metallic surface with an aqueous solution of magnesium, ammonium, chromate and phosphate ions, said aqueous solution having a molar concentration of said ions of between about 0.01 and 1.5 moles of said ions per 100 ml.
• said ions being proportionately present in said aqueous solution as 0.01 28 mole percent magnesium ion, 5 22 mole percent ammonium ion, 4 26 mole percent chromate ion and 33 67 mole percent phosphate ion; and curing said coating by heating saidmetallic surface at a temperature of from about 400 F. to about l,900 F. for a period of from 2 seconds to about 4 hours, so as to render it substantially water insoluble.

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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)
• Laminated Bodies (AREA)

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Cited By (5)

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Citations (5)

• 1970
  • 1970-01-02 US US3658603D patent/US3658603A/en not_active Expired - Lifetime
  • 1970-11-18 AU AU22416/70A patent/AU2241670A/en not_active Expired
  • 1970-12-21 FR FR7046097A patent/FR2075068A5/fr not_active Expired
  • 1970-12-22 CA CA101223A patent/CA931449A/en not_active Expired
  • 1970-12-23 GB GB6109070A patent/GB1298410A/en not_active Expired
  • 1970-12-23 BE BE760723A patent/BE760723A/xx unknown
  • 1970-12-29 SE SE1767370A patent/SE368035B/xx unknown
  • 1970-12-30 ES ES386935A patent/ES386935A1/es not_active Expired
  • 1970-12-31 DE DE2064770A patent/DE2064770C3/de not_active Expired
• 1971
  • 1971-01-04 JP JP1171A patent/JPS551987B1/ja active Pending

Patent Citations (5)

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