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
• • 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
  • C23C2222/00—Aspects relating to chemical surface treatment of metallic material by reaction of the surface with a reactive medium
  • C23C2222/20—Use of solutions containing silanes

Definitions

• the present invention relates to non-chrome containing coatings for metals. More particularly, the present invention relates to rinsable, non-chromate, non-metal phosphate coatings for steel, zinc coated steel, and aluminum surfaces to improve the adhesion of siccative coatings to the surface and provide enhanced corrosion protection.
• Acidic, aqueous solutions or dispersions are provided for contact with the requisite metal surfaces such as steel, zinc coated steel, and aluminum surfaces.
• the solutions and dispersions are chromate free and provide enhanced corrosion protection and adherence of siccative coatings on the metal surface.
• siccative coatings typically include paints, lacquers, inks, varnishes, resins, etc.
• the methods of the invention comprise contacting the requisite metal surface with an effective amount of an acidic aqueous composition or dispersion to enhance corrosion protection and adherence of siccative coatings.
• the chromate and inorganic phosphate free composition or dispersion comprise (a) a material or materials including a Group IV B element; (b) a fluoride source; and (c) phosphonic acid or phosphonate.
• the coating may be rinsed and dried in place. The surface is then ready for application of a paint, lacquer, varnish, resin, or other siccative coating thereto.
• the acidic aqueous compositions or dispersions comprise (a) a material or materials comprising one or more elements selected from the Group IV B elements as set forth in the CAS version of the Periodic Table of Elements. Such elements comprise Zr, Ti, and Hf. Mixtures of these elements may be included. Zr and Ti containing materials are preferred.
• Exemplary Zr sources are adapted to provide Zr anions in an acidic medium and include a soluble fluozirconate, zirconium fluoride (ZrF 4 ), or water soluble zirconium salt such as zirconium nitrate or sulfate.
• the zirconium source can comprise an ammonium or alkali zirconium salt.
• Zirconium oxides and Zr metal itself may be used provided it ionizes to Zr anion in an acidic medium.
• the Zr source comprises fluozirconic acid, H 2 ZrF 6 .
• organic Zr containing compounds may be utilized provided they liberate Zr in the acidic aqueous medium.
• the Group IV B element may also comprise Ti.
• the preferred Ti source is H 2 TiF 6 , but titanium fluorides such as TiF 3 and TiF 4 may also be mentioned. Nitrate, sulfate, ammonium or alkali titanium salts can also be used as well as Ti metal itself. Additionally, organic Ti compounds can be used if they liberate Ti in the acidic medium. Preliminary tests have included use of Ti(iv) isopropoxide as a Ti source component especially if it is reacted with an acidic solution such as H 2 ZrF 6 .
• the fluoride source (b) that is used as a component of the acidic treatment or composition may most preferably be the same fluozironic or fluotitiantic acid that may be employed to provide the Ti and/or Zr. It is most preferred that the treatment comprise H 2 ZrF 6 and H 2 TiF 6 which combination will adequately serve as a source of the Zr, Ti, and fluoride.
• Other suitable F sources include hydrofluoridic acid and salts thereof, alkali metal bifluorides, H 2 SiF 6 and HBF 4 . Again, the source must be capable of liberating F in the medium. Most preferably, the combined Zr, Ti, and F sources liberate fluotitanate and fluozinconate, i.e., (TiF 6 ) ⁇ 2 and (ZrF 6 ) ⁇ 2 , in the medium.
• the desirable fluoride concentration is that which will combine with the Zr and Ti to form a soluble complex therewith, for example, a fluozirconate and fluotitanate.
• a fluozirconate and fluotitanate for example, at least about 4 moles of fluoride is provided per mole of Zr and Ti present.
• Zirconium and titanium may be present in the treatment medium in amounts up to slightly greater that their solubility limits.
• the phosphonic acids and phosphonates these may be mentioned as including any compounds having the formula wherein X is H or a cation; R is any organic moiety including alkyl, cycloalkyl, substituted and unsubstituted N and/or P containing heterocyles, aryl, substituted aryl including halogenated aryl and alkyl substituted aryl, substituted alkyl such as aminoalkyl, carboxyalkyl, phosphonoalkyl, alkylimino, hydroxyalkyl, silane substituted alkyl, etc.
• the phosphonate may more particularly be selected from phosphonic acids and phosphonates having formulas as per II, III, and IV, as follows whereas phosphonate (II) has the formula: wherein R 1 is PO 3 X 2 or R 2 PO 3 X 2 , wherein X 2 is independently chosen from H or a cation, and R 2 is a C 1 -C 5 alkylene, preferably methylene.
• Z is a member selected from H, halo, C 1 -C 5 alkyl, NO 2 , and COOH. Preferably Z is located in the para position.
• Exemplary members of this group include 4-bromobenzylphosphonic acid, 4-tertbutylbenzylphosphonic acid, phenylphosphonic acid, 4-hydroxybenzylphosphonic acid, 4-nitrobenzylphosphonic acid, 4-methylbenzylphosphonic acid, 4-carboxybenzylphosphonic acid, and 4-bromobenzyl phosphonate ethyl ester.
• Phosphonates having the formula (III) may also be mentioned wherein X is as defined above in the formulation (I) and R 3 is C 1 -C 5 alkyl, C 1 -C 5 carboxyalkyl, C 1 -C 5 phosphonoalkyl, C 1 -C 5 siloxyalkyl, C 1 -C 5 iminoalkyl, and C 1 -C 5 phosphonoiminoalkyl.
• exemplary members of this group include 2-carboxyethylphosphonic acid, trihydroxysilylpropylmethyl phosphonate, 1,2,-diethylenediphosphonic acid, iminobis (methylphosphonic acid) and tert-butylphosphonic acid.
• the phosphonate can also be chosen from formula IV. wherein X is as defined above in formula I.
• R 4 and R 5 are independently chosen from hydrogen, C 1 -C 5 alkyl, C 1 -C 5 hydroxyalkyl, and C 1 -C 5 phosphonoalkyl, with the proviso that R 4 and R 5 may, together as covalently bonded, form a cyclic structure, R 6 may or may not be present and, when present, is chosen from C 1 -C 5 alkylene;
• Q is N or N oxide (i.e., N ⁇ O + ).
• Exemplary members of this Group IV include phosphonic acid [[(2-hydroxyethyl)imino]bis (methylene) bis-, N oxide referenced to herein as—linear EBO—CAS 137006-87-2; and [tetrahydro-2-hydroxy-4H-1,4,2-oxaza phosphorin-4-yl) methyl]-N,P-dioxide CAS 133839-05-01—referred to herein as cyclic EBO.
• both linear EBO and cyclic EBO are present at once in the form of mixed solution. Based upon preliminary data, a mixture of linear EBO and cyclic EBO is preferred for use. These phosphonates may be prepared via the following preparatory route.
• the batch is cooled and adjusted to pH 9-10 by addition of 50% aqueous sodium hydroxide (3.73 mole).
• the batch temperature is then adjusted to 40 ⁇ 2° C. and 35% aqueous hydrogen peroxide (1.07 mole) is charged drop wise over approximately a 1-hour period with cooling to maintain the batch temperature between 38-52° C.
• the batch is held at 50 ⁇ 2° C. for 2 hours.
• the batch is then cooled to room temperature and collected. During the cool down, 50% aqueous gluconic acid (0.005 mole) is charged to the batch.
• the product as produced is characterized by 13P NMR as a nominal 1:1 molar ratio of the sodium salts of Linear EBO and Cyclic EBO and is referred collectively hereinafter as EBO.
• the material is also composed of traces of the sodium salts of residual phosphorous acid, oxidized byproduct phosphoric acid, and byproduct methylenediphosphonic acid. It is a preferred embodiment of the invention to utilize the product as produced without any purification.
• exemplary phosphonates may be prepared as follows:
• TABPA 4-tert-Butylbenzylphosphonic Acid
• the other substituted benzyl phosphonates of class II are similarly prepared. That is, the corresponding benzyl bromide is used as the starting reactant and then reacted with triethylphosphonate to form the desired substituted benzylphosphonate ester.
• the ester may be converted to the acid form via conventional techniques or used in its so produced ester form.
• a silane (d) may be included in the acidic treatment composition.
• Representative silanes include, but are not limited to, alkoxysilane, aminosilane, ureidosilane, glycidoxysilane, or mixtures thereof.
• Preferred alkoxysilanes and aminosilanes are taught in U.S. Pat. No. 6,203,854. At present, most preferred is ureidopropyltrimethoxy silane available from GE Silicones-OSI under the designation Silquest A 1524.
• Preferred acidic, aqueous compositions in accordance with the invention are chromate free and include:
• a1 a zirconium source present in an amount of from about 0.01 wt % to about 10 wt % above its solubility limit;
• a fluoride source wherein fluoride is present in a molar excess relative to the total moles of Zr and Ti present, preferably in a molar excess of at least about four times the total molar amount of Zr and Ti present;
• the remainder of the composition comprises water and pH adjustment agent to regulate the pH within the range of about 0.5-6.
• the weight of the acidic aqueous composition is 100 wt %.
• the acidic, aqueous compositions comprise:
• the composition, in total, including water is 100 wt %.
• compositions include
• H 2 ZrF 6 in an amount of about 0.01-40 wt %
• H 2 TiF 6 in an amount of about 0.01-40 wt %
• a phosphonic acid or phosphonate selected from the group of (i) Linear EBO and (ii) Cyclic EBO and mixtures of (i) and (ii). These phosphonates are present in a combined amount of about 0.01-50 wt %. The remainder of the composition is optional silane (4) in an amount of about 0.00-20 wt %, water and pH adjustment agent.
• the requisite metal surface may be contacted by the treatment in spray, immersion, or other application forms.
• the treatment may be rinsed and dried with the thus prepared metal surface then ready for application of a siccative coating thereto.
• the acidic aqueous solution or dispersion in accordance with the invention is applied to the metal surface to result in a coating weight of greater than about 1 milligram per square foot to the treated surface with a weight of about 2-500 milligrams per square foot being more preferred.
• working solutions comprising about 3-100 wt %, preferably 10-100 wt % concentration, of the above formulations may be used to contact the desired metal surfaces.
• additives can be included in the formulation to facilitate formation of the conversion coating.
• Oxidizing agents such as nitrate, nitrites, chlorates, bromates, and nitro aromatic compounds can be added to speed up and maintain coating formation.
• Inorganic or organic acids and bases can be added to maintain pH of the working bath.
• Betz Kleen 132 commercially available from GE Water & Process Technologies 140° F., 90 second spray
• Pretreat immersion for 2 minutes at 140° F.
• Example 1 Additional phosphonates were evaluated as in Example 1.
• a base formulation of Ti and Zr components was prepared as follows:

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• 2005
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