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
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/14—Cleaning or pickling metallic material with solutions or molten salts with alkaline solutions
  • C23G1/19—Iron or steel
• • 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
  • C23C22/78—Pretreatment of the material to be coated
  • C23C22/80—Pretreatment of the material to be coated with solutions containing titanium or zirconium compounds

Definitions

• This invention relates to methods and compositions for treating ferrous and zinc surfaces to improve their corrosion resistance and paint adhesion properties. It is particularly concerned with improvements in the formation of crystalline phosphate coatings on steel and galvanized steel. .Such coatings are here termed zinc phosphate coatings, although it should be understood that manganese and calcium are included in some zinc phosphating systems and that the coatings formed from these systems include manganese phosphate or calcium phosphate along with zinc phosphate.
• ferrous metal surface used herein includes a wide variety of steels, iron, and iron alloys, including alloys of iron with chromium and/or nickel
• zinc surface used herein includes zinc and zinc alloys in which zinc is the principal constitiTent, as well as galvanized surfaces, including both hot-dipped and electrogalvanized surfaces.
• step 4 the rinse of step 4 is omitted.
• the present invention is most directly concerned with improvements in the cleaning stage and in the activating and grain refining stage of the zinc phosphating process.
• these two stages can be successfully combined, and the two functions performed .anited States Patt O 3,741,747 Patented June 26, 1973 "ice simultaneously under highly alkaline conditions.
• the combining of these two stages permits the elimination of one set of treating equipment and one set of rinsing equipment, thus reducing the process to a five stage treating sequence capable of performance in plants having only five stage equipment.
• the alkaline cleaning stage of a zinc phosphating process has been shown by experience to be important to the overall success of the treatment because good quality, uniform, corrosion resistant, paint adherent, zinc phosphate coatings are not satisfactorily obtained unless the metal being treated is cleaned.
• the kinds of soils commonly encountered include dust, grease, and oil.
• Alkaline cleaners that is, cleaners with a pH in the range above 10, have been found to be effective and economical in removing the kinds of soil which interfere with the formation of a good zinc phosphate coating.
• activation and grain-refining have been found to be important operations in the process of producing a good zinc phosphate coating.
• activation refers to the conditioning of the metal surface so that a zinc phosphate coating will form on it readily and quickly.
• the need for surface activation varies somewhat with the particular type of zinc phosphating system employed. Some systems, such as the chlorate-nitrite accelerated systems disclosed in US. Patent 3,333,988, produce zinc phosphate coatings with a highly desirable set of properties, but require a highly activated surface to do so. Other zinc phosphating systems can be operated on less activated surfaces, but substantially all of them produce better coatings when the surface is highly activated.
• Grain-refining is a term employed to describe the conditioning of the surface to be treated so that the crystalline zinc phosphate coating when formed is made up of very fine closely packed crystals, as distinguished from relatively large, coarse, elongated and loosely arranged crystals.
• a fine grained zinc phosphate coating has been found by experience to be superior, both in its corrosion resistant and paint adherent properties, to a coarse grained surface. While the present invention is not intended to be limited by any theoretical explanation of this phenomenon, or any other phenomenon related to the invention, it can be pointed out that it is thought that large coarse crystals which are loosely packed leave significant areas of bare metal exposed in the interstices between crystals and that these exposed areas are very susceptible to rusting and corrosion.
• the most widely used method for obtaining activation and grain-refining is to apply certain colloidal titanium salts to the surface prior to zinc phosphating.
• the salts are termed Jernstedt salts, as disclosed in US. Pats. 2,310,239 and 2,322,349, among others. It is thought that the Jernstedt salts act as activators and grain refiners by adhering to the surface, upon being contacted with it, in a multitude of closely spaced sites, thus providing a large number of crystallization nuclei on the surface. The large number of crystallization nuclei both activate the surface and grain refine it, because they make it possible for many zinc phosphate crystals to start to grow simultaneously.
• the coating is formed quickly, and the individual crystals remain desirably small because they grow into one another before any can become very large.
• the Jernstedt salts undo the damage caused by efiicient cleaning.
• a good cleaner in the course of removing soils, also removes the naturally occurring crystallization nuclei, thus deactivating the surface.
• the Jernstedt salts replace the crystallization nuclei.
• Another object of this invention is to provide a method for stabilizing Jernstedt salts in a high pH environment, thus rendering them capable of use in eflicient alkaline cleaners.
• a further object of the invention is the provision of improved metal treating compositions containing Jernstedt salts, which compositions are highly effective cleaners, activators, and grain-refiners, and are characterized by their high alkalinity.
• a concomitant object of the invention is to provide a zinc phosphate coating process for ferrous and zinc metals which is a five-stage process, rather than six or seven stages, and which can be satisfactorily performed in plants having five-stage equipment.
• an aqueous alkaline solution comprising a colloidal titanium salt and a stabilizing composition consisting of silicate and a condensed phosphate selected from the group consisting of tripolyphosphate and pyrophosphate can be maintained in a stable state as it is utilized to clean and activate a plurality of metallic surfaces prior to the application of a zinc phosphate coating thereon.
• the cleaning and activating solutions are highly alkaline, having a pH above about and contain the Jernstedt salt as a stable colloid.
• the amount of Jernstedt salt in the solution can be varied within wide limits in accordance with the general teachings of the above referred to Jernstedt patents.
• the concentration of the Jernstedt salt, expressed as titanium ion at the use dilution, may be varied between 0.005% by weight and 0.05% by weight.
• the Jernstedt salt is maintained as a stable colloid in the highly alkaline cleaning solution by a stabilizing composition, which is itself a combination of materials contributing to the cleaning action of the solution.
• the stabilizing composition suitable for use in accordance with the present invention are those which are themselves stable in the alkaline cleaning bath having a pH above 10, under the temperature conditions normally obtained in a cleaning stage, that is, between about F. and about F.
• the concentration of the stabilizing composition can be from about .03% weight/volume to about 1.5% weight/volume.
• the preferred use concentration for the stabilizing composition is between about .2% weight/volume and 1.0% weight/volume. Since the stabilizing composition also contributes to the cleaning action of the working solution as well as promoting the stability of the Jernstedt colloid, the amount required to be present is somewhat flexible, since one level of performance may be satisfactory for some operations, while a higher level is desired for others.
• aqueous cleaning, activating grain-refining solution We mean the aqueous bath containing the Jernstedt salt and stabilizing composition, wherein said bath contains finely divided and colloidally dispersed particles which possess a certain stability resulting in no settling or precipitation and no loss in cleaning and activating effect.
• cleaning and activating concentrate or cleaning and activating composition means the combination of stabilizing composition, Jernstedt salt, other alkaline ingredients, and surface activators, said composition or concentrate employed to prepare the aqueous cleaning, activating, and grain-refining solution.
• the materials which have been found to act as stabilizing compositions for the Jernstedt salt are a combination of silicate and condensed phosphate selected from the group consisting of tripolyphosphate and pyrophosphate.
• the silicate should be present as a combination of orthosilicate and metasilicate in certain proportions.
• the silicate and tripolyphosphate or pyrophosphate cooperate with each other to produce stabilizing results better than each of the materials produces alone.
• not all blends or mixtures of silicate and tripolyphosphate or pyrophosphate yield the desirable results described herein.
• the beneficial effects are dependent upon the proportions of silicate and condensed phosphate which are present. Such proportions can be conveniently expressed as weight ratios.
• the weight ratio of silicate to tripolyphosphate should be within the range of between about .4 and about 6 to 1.
• the silicate portion of the stabilizing composition is comprised of orthosilicate and metasilicate and the proportions of each present should be such that for each part by weight of orthosilicate there is from about 1 part to about 5 parts by weight of metasilicate.
• Pyrophosphate can be substituted for tripolyphosphate thereby producing a substantially equivalent stabilizing composition, in which case the ratios of silicate and pyrophosphate should correspond to those specified hereinabove when tripolyphosphate is employed.
• the foregoing weight ratios are calculated on the basis of the sodium form of each material.
• the sodium salts are selected for use, but the other alkali salts, such as potassium salts can be substituted.
• silicate and tripolyphosphate or pyrophosphate stabilizing composition contributes to the cleaning action of the alkaline cleaner in addition to protecting the Jernstedt salt.
• These materials in various combinations, have been employed in the past to clean metals, although it has not been regarded as good practice to use silicates as cleaners for steel because of the difliculty in removing the silicate if it dries on the surface.
• the aqueous cleaning and activating solution of the present invention can also contain ingredients such as soda ash, trisodium phosphate, and caustic soda, and any other high alkaline ingredients contributing to the alkalinity of the cleaning bath and to its cleaning action.
• the cleaning and activating composition or concentrate of the present invention is prepared by adding a Jernstedt salt to an alkaline cleaner concentrate comprising the stabilizing composition and desirable alkaline cleaning ingredients, said Jernstedt salt added in an amount from about 1% to about 20% by weight.
• concentration of the stabilizing composition in the cleaning and activating concentrate can be from about 50% by weight to about 80% by weight, depending upon the amounts of the additional alkaline cleaning ingredients present.
• the cleaners and activators of this invention can be added to an aqueous bath as two separate component concentrates the cleaner concentrate as one component and the Jernstedt salt added as a separate component to form the stable aqueous cleaning, activating, and grain-refining solution at concentrations for use.
• Surfactants and foaming agents are desirably included in the cleaning and activating composition or concentrate. Such materials enhance the cleaner performance but are not of the essence of the invention since they are used to perform functions substantially similar to the function they perform in prior art solutions. It can be observed, however, that nonionic surfactants and foam control agents operate best in cleaning baths of the invention.
• a suitable solid concentrate when added to water that is capable of both cleaning, activating and grain-refining ferrous and zinc
• solid concentrates for simultaneously cleaning, activating, and grain-refining surfaces utilizing the stabilizing compositions of this invention and formulated in accordance with the present invention:
• Nonionic surfactants 7 FORMULA 2 Percent by weight Sodium tripolyphosphate (anhydrous) 20 Sodium metasilicate (anhydrous) 40 Sodium orthosilicate (anhydrous) Soda ash l0 Jernstedt salt 13
• Nonionic surfactants 7 FORMULA 3 Percent by weight Sodium tripolyphosphate (anhydrous) 10 Sodium metasilicate (anhydrous) 50 Sodium orthosilicate (anhydrous) 10 Soda ash 1O Jernstedt salt 13
• Nonionic surfactants 7 FORMULA 4 Percent by weight Sodium tripolyphosphate (anhydrous) 50 Sodium metasilicate (anhydrous) 10 Sodium orthosilicate (anhydrous) 10 Soda ash 10 Jernstedt salt 13
• Nonionic surfactants 7 6 FORMULA 5 Percent by weight Sodium tripolyphosphate (anhydrous) 40 Sodium metasilicate (anhydrous) 20 Sodium orthosilicate
• the treating solutions of this invention when employed in the cleaning and activating process can be applied to the substrate utilizing any of the contacting techniques known to the art.
• application will be effected by conventional spray or immersion methods.
• the time of treatment of a metal surface with the cleaning and activating solution need only be long enough to ensure complete Wetting of the surface and can be as long as 5 minutes.
• the surface should be treated for a time from about 15 seconds to about 1 minute.
• the treating bath can be operated at temperatures as high as 180 F. It is preferred that the cleaning and activating process be operated at temperatures from about F. to about F.
• the final passivating rinse may be any one of the variety of solutions which are known to perform this function well, operated under the conditions regarded by the art as good practice.
• a dilute chromate solution can be utilized as the final passivating rinse following application of the zinc phosphate coatmg.
• EXAMPLE 1 A series of tests were performed utilizing Formulas 1 through 5, at a concentration of 5.6 grams/liter, in order to illustrate the cooperation of orthosilicate, metasilicate, and tripolyphosphate for protceting the Jernstedt salt under highly alkaline conditions while cleaning is effected concurrently.
• aqueous cleaning, activating, and grain-refining solutions prepared by adding 5.6 grams of concentrate per liter of water were evaluated by treating cold rolled steel panels. The panels were sprayed with the baths for one minute at about 160 F. The solutions, as made up, had a pH as listed in Table 1 which remained substantially constant throughout.
• This phosphate coating bath was formed from a concentrate having the following composition:
• This concentrate was diluted with water to about 1% by volume for use.
• Sodium nitrite was added as a separate accelerating component in amounts sufficient to maintain a concentration of about .006% by weight.
• the bath temperature was maintained at about 130 F. and the treating time was about 1 minute.
• the coating weights obtained when the pretreated panels were subjected to the phosphate coating bath are noted in Table 1.
• the zinc phosphated panels were visually evaluated to determine whether the solutions adequately grainrefined and activated the surfaces.
• a thin non-uniform and powdery phosphate coating indicated a lack of activation, and coarse crystals visible to the naked eye or under a low power microscope indicated a lack of refinement.
• the results are reported in Table 1.
• coating weight data provides a measure of the degree to which grain refinement is obtained.
• a high coating weight is an indication of the presence of coarse crystals, while a lower coating weight indicates that the crystals are refined and that the coating is more dense.
• Coating weight determinations are not an absolute measure of grain refinement and coating quality, since the optimum coating weight is strongly dependent on the particular kind of zinc phosphating solution employed.
• a good coating weight for the steel panels is in the neighborhood of to about 225 mg./ft. with a coating weight from about mg./ft. to about 180 mg./ft. being preferred.
• EXAMPLE 2 A series of tests were performed utilizing Formula 1 and formulas based on Formula 1 in which the tripolyphosphate or silicates were deleted and replaced by inert fillers.
• the treating solutions were prepared by adding the compositions to water at a concentration of 4/ 10% weight per volume.
• the various solutions were evaluated by spraying cold-rolled steel panels with each of the aqueous baths for one minute at about F- Test panels were sprayed in each test bath at each two hour interval. In order to determine the activating and cleaning qualities as well as the colloidal suspension qualities of the treating solutions in this test, the baths resistance to degradation caused by shear stresses within pumping systems and spray nozzles was observed.
• the solutions were not only employed at each two hour interval to spray test panels, but were continuously being circulated through a pumping system and sprayed at 160 F. and 10 p.s.i.g. pressure upon 3" x 4" stainless steel panels suspended between dual spray nozzles mounted approximately 2 inches apart. At each two hour interval, the stainless steel panels were replaced by the cold rolled steel test panels. After treatment, the panels were rinsed in cold water and immersed in a zinc phosphate coating solution of the chlorate-nitrite type. This phosphate coating bath was formed from a concentrate having the following composition:
• This concentrate was diluted with water to about 1% by volume for use.
• Sodium nitrite was added as a separate accelerating component in amounts sufiicient to maintain a concentration of about .006% by weight.
• the bath temperature was maintained at about 130 F. and the treating time was about 1 minute.
• the zinc phosphated test panels were then visually evaluated to determine whether the solutions adequately grain-refined and adequately activated the surfaces.
• the coatings were evaluated both visually and photomicrographically at 330x magnification for both crystal size and coating density. When crystal size enlarged noticeably and coarse, elongated crystals were present, this was an indication of a lack of grain refinement and failure was considered to have occurred. In addition, a thin, nonuniform coating indicated a lack of activation.
• the solutions were evaluated by sprayfrom about Welght/Volume to about 15% Weight/ ing cold rolled steel panels employing the same method Volume, the Stabilizing composition consisting of a Siliand conditions as in Example 2 above.
• the test panels cate selected from the group consisting of orthosilicate were then zinc phosphated as in Example 2 above.
• the reand metasilicate and mixtures thereof, and a condensed sults are illustrated in Table 3.
• grain refined grain refined. grain refined. grain refined. grain refined. grain refined. grain refined. grain refined. grain refined.
• a serlcs of tests were performed utillzing Formula 1.
• the solution, as made up, had a pll 0f 50 4.
• a method for applying a zinc phosphate coating to The test panels were sprayed for one minute at each ferrous and Zinc surfaces comprising the Steps f;
• the Stainless Steel Panels were replaced y galvanized ing composition consisting essentially of a silicate test panels. selected from the group consisting of orthosilicate After treatment, the panels were rinsed in cold water and t fli at and mixtures th r of and a and p y With a Zinc P p Coating Solution of densed phosphate selected from the group consisting the chlorate-nitrite type.
• the phosphate coating bath was f tripolyphosphate d pyrophosphate, formed as in Example 2 above and was sprayed on the (2) rinsing the surfaces, test panels for 1 minute at about 130 F.
• grain refined grain refined. grain refined. grain refined. grain refined. grain refined. grain refined.
• the stabilizing composition consists of a silicate selected from the group consisting of orthosilicate and metasilicate and mixtures thereof, and a condensed phosphate selected from the group consisting of tripolyphosphate and pyrophosphate wherein the weight ratio of the silicate to the condensed phosphate is between about .4 and about 6 to 1, calculated as sodium salt.
• a composition for simultaneously cleaning, activating, and grain-refining ferrous and zinc surfaces in prep aration for the application of a zinc phosphate coating comprising basic cleaning material in an amount sufficient, upon mixing of the composition with water for use,
• a colloidal titanium salt in an amount sufficient to provide, upon dilution of the composition for use, between about .005% and about .05% by weight of said colloidal titanium salt calculated as titanium ion
• a stabilizing composition in an amount sufficient to provide, upon dilution of the composition for use, a concentration of the stabilizing composition from about .03% weight/volume to about 1.5% weight/volume, the stabilizing composition consisting of orthosilicate, metasilicate, and a condensed phosphate selected from the group consisting of tripolyphosphate and pyrophosphate.

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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)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• Detergent Compositions (AREA)

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  • BE BE789347D patent/BE789347A/xx not_active IP Right Cessation
• 1971
  • 1971-09-30 US US00185409A patent/US3741747A/en not_active Expired - Lifetime
• 1972
  • 1972-08-18 ZA ZA725686A patent/ZA725686B/xx unknown
  • 1972-08-23 AU AU45867/72A patent/AU449202B2/en not_active Expired
  • 1972-09-05 CA CA150,957A patent/CA990187A/en not_active Expired
  • 1972-09-14 BR BR006370/72A patent/BR7206370D0/pt unknown
  • 1972-09-28 GB GB4472972A patent/GB1354217A/en not_active Expired
  • 1972-09-29 SE SE7212660A patent/SE380834C/xx unknown
  • 1972-09-29 DE DE2247888A patent/DE2247888C3/de not_active Expired
  • 1972-09-29 NL NL727213204A patent/NL148952B/xx not_active IP Right Cessation
  • 1972-09-29 IT IT70077/72A patent/IT975122B/it active
  • 1972-09-30 JP JP47098557A patent/JPS4842938A/ja active Pending
  • 1972-10-02 FR FR7234881A patent/FR2154796B1/fr not_active Expired

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