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
  • C23C22/82—After-treatment
  • C23C22/83—Chemical after-treatment

Definitions

• ABSTRACT This invention provides a new sealing rinse and process for sealing phosphate coated metals against porosity and to promote the adhesion of subsequent paint coatings.
• the new sealing rinse is an acidic aqueous solution containing simple or complex fluoride ions.
• steel, galvanized steel, aluminum or zinc are given a phosphate coating and then wetted with an acid aqueous solution containing fluoride ion.
• Phosphate coatings on metals are widely known as useful adhesion promoters for paint, varnish, lacquer and the like, and their application is one of the standard procedures of the metal finishing industry. Besides adhesion, the phosphate coatings also provide some protection against underpaint corrosion, but normally not enough. It was found long ago that the underpaint corrosion protection of phosphate coatings is greatly enhanced when the phosphate coated metal is wetted with a dilute acid chromate rinse solution prior to paint application, and almost every proprietary phosphate coating process specifies these chromate rinses which are also called sealing rinses or chromate seals.
• chromate sealing rinses have two disadvantages. Since chromates are toxic to animal life, depleted chromate solutions must now be treated before they can be discharged into streams or waste systems to render them non-toxic. A major short-coming of the chromate rinse is that uneven accumulations of the chromate rinse, when dried on the metal surface, cause discloloration under the paint or cause blister-type failures of the painted surfaces. Water rinsing alleviates the blistering but removes most of the chromate coating along with most of its sealing ability.
• the fluoride sealing rinses which are the subject of this invention do not contain chromates and hence do not suffer from the above disadvantages.
• the fluoride sealing rinse also has the advantage that the chemical ingredients are relatively inexpensive.
• the fluorides useful in forming the fluoride sealing rinses of our invention are obtained from calcium fluoride, zinc fluoride, zinc aluminum fluoride, titanium fluoride, zirconium fluoride, chromic fluoride, chromic zirconium fluoride, nickel fluoride, ammonium fluoride, hydrofluoric acid and fluoboric acid. Mixtures of one or more fluorides can also used.
• the useful concentration of the above fluorides in water as sealing rinses ranges from about 0.01 gram/- liter to about 25 grams/liter expressed as fluoride.
• De ionized water is a preferred source of water.
• the fluorides are useful as sealing rinses for phosphate coated metals at a pH ranging from about 3 to about 7.
• the application temperature of the sealing rinses may range from ambient to about 200F.
• the time of contact with the metal can range from about 2 seconds to about 1 hour.
• the metal may then be washed with water, preferably deionized water an then the metal is dried.
• the metal wetted with the fluoride sealing rinse is dried without any water rinse, or the metal wetted with the fluoride sealing rinse is first dried, then rinsed with water, preferably deionized water and then redried.
• the latter two procedures give better under-paint corrosion resistance than the first procedure embodying the water rinse prior to drying.
• the drying of the rinsed panels is done by any conventional way currently employed in the metal treating industry. The drying temperatures are not critical and will vary from room temperature to about 180F. or higher as measured on the treated metal surfaces.
• the phosphate coated metals which have been sealed with our fluoride sealing rinse are then ready for the application of siccative organic coatings such as plastic coatings, paints, enamels and the like.
• the fluoride rinses of our invention are useful in sealing phosphate coatings on any metal substrate which carries a phosphate coating to increase resistance to corrosion and to enhance the bonding of paint or lacquer coatings.
• the substrate will be steel, galvanized steel, zinc or aluminum.
• the metal substrates must be clean for application of the phosphating solutions and the metal surfaces are first cleaned by physical and/or chemical means well known in the art to remove surface dirt, grease or oxides.
• the fluoride sealing rinses of this invention are applicable to either the heavy-weight coating phosphates derived from aqueous zinc or manganese phosphate solutions or the light-weight phosphate coatings, generally called iron phosphate coatings, derived from aqueous solutions of acid sodium, potassium, and ammonium phosphates.
• the heavy-weight zinc phosphate coatings may be prepared and applied to steel, galvanized steel, zinc and aluminum metals as is disclosed in U.S. Pat. Nos. 3,203,835 and 3,619,300 and these patents are incorporated by reference.
• the use and application of the iron phosphate coatings to these metals are shown in US. Pat. Nos. 3,l29,121 and 3,152,018 and these patents are incorporated by reference.
• the phosphating solutions described above are applied by immersion, spraying, wiping and/or by roller coating as is well known in the art.
• the coated metal is rinsed with water and then wetted with the fluoride sealing rinse of our invention. If it is necessary to store the phosphate coated metal before sealing, it is preferable to dry the water rinsed metal rinsed metal by conventional methods.
• the fluorides useful in sealing the phosphate coated metals are obtained from calcium fluoride, titanium fluoride, zirconium fluoride, chromic fluoride, chromic zirconium fluoride, nickel fluoride, ammonium fluoride, hydrofluoric acid and fluoboric acid. Mixtures of the above fluorides are also useful.
• the acids When the fluorine acids are used as the source of fluoride ion, the acids must be adjusted with a base to bring them within the proper pH range. Ammonia and water soluble amines such as triethanolamine and nmethyl morpholine are desirable for this purpose since the amines are volatilized at the paint curing temperatures.
• the fluoride materials useful in forming the sealing rinses of our new process are obtainable from commercial sources or else they can be prepared by processes well known in the art.
• the sealing rinses are prepared by adding the fluorine containing material to water. If the fluorine containing material is a solid, agitation of the water will assist in solution of the material. For best sealing results deionized water is preferred because of the absence of water impurities which could interfere with the sealing process.
• the pH of the sealing rinse is adjusted within the range of about 3 to about 7.
• a preferred pH range is from about 4 to about 6 for the metal fluorides and fluorine acids while the preferred range for ammonium fluoride is about 4 to about 7.
• Adjustments in pH can be made with suitable acids and/or bases such as ammonia, zinc oxide, n-methyl morpholine, triethanolamine, hydrofluroic acid fluoboric acid.
• the concentration of the fluoride in the sealing rinse and the thickness of the fluoride coating on the metal surfaces will be the same as for the conventional chromic acid sealing rinse and coating as taught in US. Pat. Nos. 3,116,178 and 2,882,189 and the teachings of these patents are incorporated by reference. Generally, the concentration will vary from about 0.01 grams to about 25 grams per liter expressed as fluoride. Higher amounts than 25 grams/liter can be used without any significant benefit in corrosion prevention or paint adhesion.
• the time of contact or wetting of the sealing rinse with the phosphated coated metal will vary with the temperature of the solution, the type of phosphate coating and the desired thickness of the fluoride coating. Contact or wetting time may vary from 2 seconds as in spraying to about 1 hour as by immersion. Coating weight will range from less than about 0.5 milligrams per square foot to as high as about 10 milligrams per square foot. The coating weight can be influenced by many factors including the nature of the phosphate undercoat. A heavy zinc phosphate coating will absorb more of the fluoride rinse than an iron phosphate coating. Also, if the fluoride rinse is followed by a water rinse without drying of the fluoride rinse, the coating weight will be quite low.
• the temperature of the sealing rinse may range from room temperature to boiling temperatures, that is, from about F. to about 212F. Where the sealing rinse is to be dried on the phosphate coating without intermediate water rinse, a hot fluoride solution will leave a substantial amount of heat in the metal which will assist in the drying operation. Bath temperatures of about to F. are generally encountered in the processing lines and this range is preferred.
• the best manner of applying the fluoride sealing rinses is to contact the phosphate coated substrate with the sealing rinse, dry the metal wetted with fluoride containg solution, then water rinse the sealed phosphate coating, preferably with deionized water, and then redry the metal. This manner of sealing the phosphate coatings gives the highest ratings in the salt spray and paint adhesion tests.
• the fluoride rinse is allowed to dry without any water rinse.
• the fluoride sealing rinse is followed by a water rinse, preferably a deionized water rinse and then the metal is dried. This last procedure gives the lowest ratings in the salt spray and paint adhesion tests.
• the fluoride sealing rinse may be sold as an aqueous acid concentrate which can be diluted with water for application to the phosphate coated metal substrate. These concentrates will contain from 20 to about 200 grams per liter of fluoride ion.
• Mild steel panels (SAE-l0l0) were cleaned in a proprietary alkaline hot soak cleaner, water rinsed, spray coated with a proprietary chlorate accelerated zinc phosphate coating compound and water rinsed again. The coated panels were then divided into three equal parts. The first part was dried immediately. The panels of the second part were rinsed with a proprietary chromate rinsing compound before drying. This compound consisted mainly of acid calcium chromates, having a CrO (crhomic acid) concentration of 0.47 g./l. The third part of the panels received a rinse of chromic fluoride (CrF before drying. This rinse was adjusted to a concentration of 0.27 g./l. fluoride.
• CrF chromic fluoride
• the rinse solution was prepared by placing an excess of a commercial grade chromium trifluoride (CrF .3 /2 H O) into cold water, stirring for three days and then filtering the solution from the undissolved excess.
• the concentrated solution contained 43.6 g./l. Cr (chromium) and 47.9 g./l. F (fluorine) and was diluted further prior to application.
• the panels were then painted with one coat of a proprietary high bake alkyd enamel spray paint and exposed to 5% salt spray according to A.S.T.M. B117. After 240 hours, the panels were inspected and rated according to A.S.T.M. D1654 with the results shown in Table l.
• Mild steel panels were cleaned as above.
• One series of panels was coated with the chlorate accelerated zinc phosphate compound of the first example.
• a second series was coated with a proprietary nitrite accelerated zinc phosphate coating compound.
• the coated panels were again divided into three parts. The first part received only a deionized water rinse prior to drying. The second and third parts were again rinsed respectively with the chromate and chromic fluoride rinse of the first example, but this time one-half of the panels were washed off with deionized water immediately following the rinse application and then dried. On the other half, the rinse was dried on first and then rinsed with deionized water and then dried again. Finally the panels were painted and tested as in Example 1. The observations are set forth in Table 2.
• EXAMPLE 3 the chromic fluoride sealing rinse was dried on the pan- Mild steel panels were cleaned as before and coated with the nitrite accelerated zinc phosphate compound of the second example. After water rinsing, the followingsealing rinses were applied: NH F, HF, CaF ZnF AlF TiF... ZrF Cr (ZrF NiF The concentrations were 0.27 g./l. fluoride, except rinse CaF (calcium fluoride) which was a saturated solution (0.016 g./l.). After application, the sealing rinse was washed immediately with deionized water, the panels dried, painted and salt spray tested as in Example 1. Rinses NH F and els and then they were rinsed with deionized water. In the third set of panels the fluoride sealing rinse was dried without any water rinse. The pH of the rinse solutions at the various concentrations are shown in C01- umn 2 of;Table 4.
• Example 4 After the steel panels were treated as described above, the panels were spray painted as in Example 1 and one-half of the panels were exposed to salt spray as in Examples 1 to 3. The other half was exposed for 500 hours to humidity at F. The results appear in Table 4.
• EXAMPLE 7 taining fluoride ion at a concentration ranging from Various simple and complex fluorides were tested as sealing rinses using the procedure and test panels as described in Example 3. The fluoride rinse solutions were adjusted to a fluoride concentration of 0.27 grams/liter. The pH of all solutions was at 4.2 after adjustment with hydrofluoric acid or zinc oxide. All of the sealing rinses failed in the salt spray evaluation tests. The results appear in Table 7.
• Table 7 about 0.01 to about grams/liter which is supplied by at least one of the members selected from the group consisting of calcium fluoride, zinc fluoride, aluminum fluoride, titanium fluoride, zirconium fluoride, chromic fluoride, chromic zirconium fluoride, nickel fluoride, ammonium fluoride, hydrofluoric acid and fluoboric acid and then drying the said fluoride solution on the said wetted metal.
• Fluoboric acid and zinc fluoborate were tested on mild steel panels using the procedure of Example 3.
• the fluoride concentration was 0.5 grams/liter.
• the pH of the fluoboric acid was adjusted with N-methyl morpholine to 6.7 and the zinc fluoborate to 4.3.
• the panels were spray painted as in the prior examples and then subjected to the salt spray tests. The results appear in Table 8.
• the process of sealing a phosphate coating on a metal comprising wetting the phosphate coated metal with the composition consisting essentially of an acidic aqueous fluoride solution free of chromates and having a pH within the range of about 3 to about 7 and conconsisting of calcium fluoride, zinc fluoride, aluminum fluoride, titanium fluoride, zirconium fluoride, chromic fluoride, chromic zirconium fluoride, nickel fluoride, ammonium fluoride, hydrofluoric acid and fluoboric acid, drying the said fluoride solution on the said wettaining fluoride ion at a concentration ranging from about 0.01 to about 25 grams/liter which is supplied by at least one of the members selected from the group consisting of calcium fluoride, zinc fluoride, aluminum fluoride, titanium fluoride, zirconium fluoride, chromic fluoride, chromic zirconium fluoride, nickel flu

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• Chemical Treatment Of Metals (AREA)
• Application Of Or Painting With Fluid Materials (AREA)

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• 1973
  • 1973-06-11 US US365019A patent/US3895970A/en not_active Expired - Lifetime
  • 1973-09-21 AR AR250202A patent/AR197352A1/es active
  • 1973-09-24 ES ES419011A patent/ES419011A1/es not_active Expired
  • 1973-09-27 BR BR7529/73A patent/BR7307529D0/pt unknown
  • 1973-09-28 JP JP10859773A patent/JPS5637312B2/ja not_active Expired
  • 1973-10-30 CA CA184,668A patent/CA999220A/en not_active Expired
• 1974
  • 1974-01-08 GB GB84174A patent/GB1414274A/en not_active Expired
  • 1974-01-14 ZA ZA740231A patent/ZA74231B/xx unknown
  • 1974-02-22 FR FR7406061A patent/FR2232615B3/fr not_active Expired
  • 1974-03-29 IT IT42578/74A patent/IT1010855B/it active
  • 1974-05-29 NL NLAANVRAGE7407232,A patent/NL178799C/xx not_active IP Right Cessation
  • 1974-06-10 SE SE7407646A patent/SE391345C/xx unknown
  • 1974-06-11 DE DE2428065A patent/DE2428065C2/de not_active Expired
  • 1974-06-11 BE BE2053675A patent/BE816148A/xx not_active IP Right Cessation

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