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
  • C23C22/05—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 using aqueous solutions
  • C23C22/06—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 using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/24—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 using aqueous solutions using aqueous acidic solutions with pH less than 6 containing hexavalent chromium compounds
  • C23C22/33—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 using aqueous solutions using aqueous acidic solutions with pH less than 6 containing hexavalent chromium compounds containing also phosphates
• • 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
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12535—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.] with additional, spatially distinct nonmetal component
  • Y10T428/12583—Component contains compound of adjacent metal
  • Y10T428/1259—Oxide
• • 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
  • Y10T428/27—Web or sheet containing structurally defined element or component, the element or component having a specified weight per unit area [e.g., gms/sq cm, lbs/sq ft, etc.]
  • Y10T428/273—Web or sheet containing structurally defined element or component, the element or component having a specified weight per unit area [e.g., gms/sq cm, lbs/sq ft, etc.] of coating

Definitions

• This invention resides in a process and solution for treating alloyed zinc coatings, that is, zinc-iron and/or iron-zinc alloyed surfaces, to prevent white rust corrosion (storage stain) under mildly corrosive conditions, and to provide suitable substrate for organic coatings such as paint, lacquer and enamels.
• Zincgrip Another similar type of material was developed and became known as Zincgrip.
• the zinc coating metal has a small percentage of aluminum in it which prevents much alloy formation between the zinc and steel.
• United States Patent 2,487,137 it was taught that this Zincgrip could be made paintable by treating the material with certain phosphate solutions containing fluorine but without actually producing coatings which contained fluorine in anything but very small amounts.
• Zincgrip has the typical galvanize coating spangle, and upon aging it was found that phosphate coated Zincgrip would corrode at the spangle boundaries and cause organic coatings to blister in this area.
• the alloyed zinc coating (with aluminum) which was heat treated so as to produce from a Zincgrip type of alloy, 2. final product in which all the coating metal is in the single phase alloy stage.
• the alloyed zinc coating after heat treating, is substantially homogeneous and is made up of zinc plus about 8 to 12% iron and about .13% aluminum.
• the treating solution of the instant invention is applied to the alloyed surface at temperatures below the boiling point of water.
• the solution is dried on the treated surface by any convenient means at any temperature below 325 Fahrenheit.
• the temperature of application of the solution may be varied from room temperature up to the boing point of water and the optimum temperature is about Fahrenheit. Room temperature, however, will suffice, but if the solution is hotter, the solution will dry itself rather than necessitating the use of hot air blowers and the like to dry the solution.
• the reason for drying below 325 Fahrenheit is to prevent the loss of some of the chrome which is believed would occur if the temperature were above this. It is thought that the hexavalent chromium will go over to trivalent chromium if the temperatures go very much above this range.
• the solution may be applied straight off of the zinc coating line or after or during the temper rolling of the zinc coated material. Temper rolling accomplishes a slight reduction in thickness of the coated material, and this reduction causes heating up of the strip.
• this phosphoric acid-chromic acid solution is applied in or during the temper rolling step, the solution itself does not have to be heated above room temperature because the heat in the strip will cause a rapid drying.
• Equal parts of phosphoric acid and chromic acid have produced satisfactory results but the preferred range is 2 parts phosphoric acid and 1 part chromic acid.
• the preferred concentration of acid is 1% phosphoric acid and /t chromic acid, by weight. With respect to these percentages of the acids in the water solution, it is preferred that they do not go above substantially 10% phosphoric acid and chromic acid. Also, as a low limit, there should be about /2% phosphoric acid and fit% chromic acid.
• the solution may also be applied to the alloyed zinc coating surface to be treated by spray, brush immersion, or by coating rolls.
• the solution of phosphoric acid and chromic acid reacts with the alloyed surface to produce a mixture of phosphates and chromates.
• the phosphates, determined as zinc phosphate, ZN (PO should be in the range of .028 gram per square foot of sheet to .200 gram per square foot of sheet.
• the chromium content of the film (determined as chromium) should be in the range .0005 gram to .004 gram per square foot of sheet (2 square feet of surface). It is possible that a solution more dilute than that above indicated might be used so long as the residue (film obtained) is within the ranges just set forth.
• the ratio of 1 part chromic acid to 2 parts phosphoric acid works well. This ratio may even be more important than the actual amounts used, assuming, of course, that the film' obtained is in the specified ranges. As indicated, however, equal parts have been used.
• the percentage of chromic acid gets too high, the phosphoric acid reaction will slow down. Consequently the use of too much chromic acid produces an oxidizing effect which inhibits the effectiveness of the phosphoric acid.
• the amount of phosphate deposited is preferably about three times that of the chromate. And, if the percentage of phosphoric acid gets too high, it will tend to pickle rather than to carry out the chemical reduction of chromium on the sheet.
• the final result of the reaction of the phosphoric acid and the chromic acid on the alloyed zinc coated surface is to produce a Zn (PO -CrPO complex.
• a process of treating a sheet having a substantially single phase, alloyed zinc coating containingaluminum to prevent white rustand improve paintability which comprises the steps of: preparing a water solution of phosphoric acid and chromic acid in which the" concentration of acid is /2 to 10% phosphoric acid and to 5% chromic acid, the percentages being" by weight, and in which the quantity of phosphoric acid is at least substantially as great as the quantity of chromic acid; applying the solution to the zinc coated sheet at a temperature below the boiling point of water and in sufficient quantity to form phosphates in the range of .028 gram to .200 gram per square foot of sheet, and to form chromates on the coating in the range of .0005 gram to .004 gram of chromium per square foot of sheet; and drying the solution on the coating at a temperature below 325 Fahrenheit. 7

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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)

Priority Applications (5)

Applications Claiming Priority (1)

Publications (1)

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Cited By (2)

Citations (4)

Family Cites Families (1)

• 1960
  • 1960-03-22 US US16657A patent/US3074827A/en not_active Expired - Lifetime
• 1961
  • 1961-02-07 GB GB4591/61A patent/GB914797A/en not_active Expired
  • 1961-02-09 DE DEA36691A patent/DE1258703B/de active Pending
  • 1961-03-02 BE BE600837A patent/BE600837A/fr unknown

Patent Citations (4)

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