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
  • C23C22/34—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 fluorides or complex fluorides
  • C23C22/36—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 fluorides or complex fluorides containing also phosphates
  • C23C22/362—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 fluorides or complex fluorides containing also phosphates containing also zinc cations

Definitions

• This invention relates to the art of coating zinciferous surfaces and involves a method and solutions for producing phosphate conversion coatings on such surfaces which coatings have highly improved characteristics, especially with respect to fineness of grain structure without serious sacrifice of coating weight, ability to promote the adhesion of siccative finishes and resistance to stresses set up by bending, folding or shaping the metal after the coating has been applied.
• zinciferous surfaces or zinc surfaces are to be understood as applying to alloys of zinc with other metals wherein zinc is the principal ingredient, to hot-dipped galvanized surfaces, to electrodeposited zinc surfaces, as well as to essentially pure zinc surfaces.
• phosphate conversion coatings to zinc surfaces, of course, is well developed and is based upon the familiar practice of subjecting the surfaces to the action of an aqueous acid phosphate coating solution until the desired coating has been deposited. Following this the surface is customarily rinsed either with water or with dilute chromic and/or phosphoric acid rinses. Probably the most familiar of the aqueous acid phosphate coating solutions is a zinc solution and the present invention is directed to the improvement of methods involving such a solution.
• the principal object of the present invention is the provision of a method and solutions for applying an improved, adhesion-promoting, zinc phosphate conversion coating on zinc surfaces which will withstand or resist to a marked extent flexing, shaping and bending operations even to an extent involving a 180 bend without failure of the siccative finish or film.
• the invention is broadly based upon the discovery that if the following agents are added to an aqueous acid zinc phosphate coating solution of generally standard characteristics and such solution is then utilized in the treatment of Zinciferous surfaces it will formon the surfaces zinc phosphate conversion coatings which are smoother, finer grained, more tightly adherent, unimpaired as to coating weight, and better suited to serve as a substrate for subsequent sicca-tive finishes than are the familiar zinc ice phosphate conversion coatings presently known to the art.
• the addition agents employed with my invention are:
• the glycerophosphoric acids or water-soluble salts there- 'of include mono and di-glycerophosphate compounds. Soluble salts are preferred over the acids in view of their greater solubility in the acid phosphate coating media. Particularly preferred salts include the alkali metal and ammonium mono and di-glycerophosphates, since these are more readily prepared, and provide an easily handled concentrated liquid solution.
• the amount of glycerophosphate, or water-soluble salt thereof, which is employed is less than the 0.1% by weight, minimum concentration, the improved paintadhesion promoting coatings will not be obtained, and subsequent bending or flexing of the phosphate coated and painted zinc surfaces will result in cracking and peeling of the siccative film.
• the amount of glycerophosphate compound in the phosphate coating solution is increased, the paint bonding qualities of subsequently produced coatings on zinc surfaces also increases up to an apparent maximum improvement at about 1% concentration, by weigh-t.
• Use of glycerophosphates in amounts greater than 1% concentration has no noticeable deleterious effect upon either the coating reaction, or upon subsequent paint adhesion on the coated surfaces.
• the phosphate ion content which yields the best results to partially exhaust solutions as a treplenisher can be ranges from about 0.5% to about 2.5% by Weight of the prepared according to the following exampl coating solution with the minimum quantity being at least sufiicient to form the dihydrogen phosphate with the zinc EXAMPLE I ions present and the content of zinc ions should be in Percent by Welght an amount which does not exceed about 0.5% by weight Zno of the coating solution.
• oxidizing agents are very familiar to those skilled in the 100-00 art and for best results with my invention the quantity h abovg f l h dil d i h watmto a of nitrate ion should be about 0.2% to about 1.0% with Strength f 4% by volume d h i dd d h m major benefits being Obtalnable when the l f 'fiy 116$ 0.25% (weight/volume) of caustic soda, has the followbetween about 0.3% to about 0.5%.
• nitrite 1s also ing analysis; included in the bath as an oxidizing agent substantially T 1 smaller amounts thereof are required in order to yield Q i i 3 0 the results which are secured by this familiar ingredient.
• i-i 0 the range of nitrite ion when used in com- 25 erwm mo bination with nitrate ion is from about 0.0002% to about The acidity referred to was determined by the method 0.008% and with my invention I have found that optimum indicated above.
• coatings are obtainable with the use of less than should then be added from 0.1% to 1.0% by weight of about 0.5% nitrate ion and less than about 0.005% of a glycerophosphate compound as hereinabove described nitrite ion. and at least 0.025% by weight of a complex fluoride as Insofar as total acidity of the solution is concerned, previously described.
• the solution should then be heated I have found that it is preferable to utilize zinc phosphate to between about 120 F. and 160 F. and preferably coating solutions which have a total acidity of less than between 130 F. and 160 F. and can then be utilized with 40 points.
• Total acidity is the milliliters of tenth normal greatest benefit in applying zinc phosphate conversion sodium hydroxide (points) required to titrate a 10 ml. coatings to zinciferous surfaces and it will be found that sample of the bath to a phenolphthalein endpoint, whereas it will produce excellent, highly flexible, smooth and finethe free acidity is the mls. of tenth normal sodium hydroxgrained, paint-bonding phosphate conversion coatings ide (points) required to neutralize a 10 ml. sample of which are ideally suitable as a substrate for siccative the bath to a brom cresol green endpoint. finishes.
• Examples 8 and 14 also contained 0.005% copper ion.
• Example 13 The panels of Example 13 were inadvertently lost and were not available for this test but visual observation thereof indicated that their coatings would be equally satisfactory as those in Examples 7 to 16, inclusive.

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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 (7)

Applications Claiming Priority (1)

Publications (1)

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Cited By (11)

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• 0
  • BE BE627337D patent/BE627337A/xx unknown
  • NL NL288062D patent/NL288062A/xx unknown
  • NL NL120662D patent/NL120662C/xx active
• 1962
  • 1962-01-26 US US169997A patent/US3109757A/en not_active Expired - Lifetime
  • 1962-11-08 GB GB42264/62A patent/GB957379A/en not_active Expired
  • 1962-12-31 DE DEA42007A patent/DE1243945B/de active Pending

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