JP2011515587A - Aluminum treatment composition - Google Patents

Abstract

An aqueous chemical conversion film treatment composition for treating a metal substrate such as aluminum, aluminum alloy, zinc, zinc alloy, magnesium, magnesium alloy, and steel to provide a chemical conversion film on the metal substrate.
The chemical conversion film treatment composition is selected from the group consisting of a) an aluminum ion source, b) a fluoro compound, c) at least one pH adjuster, and d) tungstate ion and trivalent chromium ion. A group VIB metal ion source, and e) optionally a preservative. The conversion coating composition provides a corrosion resistant coating on the metal surface and improves adhesion of subsequently applied layers.
[Selection figure] None

Description

  The present invention generally relates to compositions and methods for forming protective, corrosion-inhibiting films on metals or other materials coated with metals.

  Metals such as aluminum, zinc, magnesium, titanium, cadmium, silver, copper, tin, lead, cobalt, zirconium, beryllium, or indium, alloys thereof, and articles coated with these metals are oxidized-reduced (redox ) It tends to corrode rapidly in the presence of water because of its low potential or because of the easy formation of oxides. Typically, these metal non-alloy materials form a natural oxide film that slightly protects the non-alloy material and reduces the overall corrosion rate. However, these metal alloys are particularly susceptible to corrosive action. In addition, these metal alloys may also have significant problems with paint adhesion. The reason for this is that the metal surface on which the oxide film is formed as described above is typically very smooth and tends to be weakly bonded to the surface oxide. This is because the paint that is subsequently applied onto the base does not provide a robust base that can fix the paint itself.

  One way to enhance the corrosion resistance of metal alloys is to use a conversion coating, which is formed during the intentional exposure of the metal or metal alloy to a chemical reaction solution. It is a corrosion-inhibiting layer. Conversion coatings are particularly useful in the surface treatment of metals such as steel, zinc, aluminum, and magnesium. In the conversion coating treatment process, an adhesive surface is formed that contains an integral corrosion inhibitor that can protect the damaged portion of the coating. The metal is exposed to a compound that chemically modifies the surface and forms a film that imparts high corrosion resistance. Thus, a conversion coating applied to the surface of a less noble alloy can reduce the extent and extent of corrosion by water, impart long-term stability of properties, and extend the useful life of the product.

  An important feature of an effective conversion coating is the ability to protect base metals from corrosion even when the coating is damaged. The chemical conversion film forms an oxide film on the metal without applying an electric potential from the outside. The protective film is formed by a chemical redox reaction between the metal surface and the chemical conversion film treatment solution. The film is composed of oxides and global corrosion inhibiting species that are formed during exposure to the conversion coating solution.

  Application of these chemical conversion films or pretreatment films using a hexavalent chromium-containing solution is already common. These coatings provide excellent corrosion resistance, but hexavalent chromium, which is known to be a highly toxic and carcinogenic substance, is more tolerable due to problems with work, safety, health and environmental impacts. Attempts have been made to provide non-chromium-derived films or trivalent chromium-derived films. Various efforts have been made to develop such coatings and examples of these coatings can be found in US Pat.

  The surface that has been subjected to the chemical conversion film treatment may remain exposed or may be further protected by applying a further film or film. The conversion coating must adhere to the substrate and must provide a surface that promotes the formation of a strong bond with the coating applied later. Adhesion with a subsequently applied film depends on the form and chemical composition of the conversion film. The adhesion promoting surface treatment may exhibit corrosion inhibition. Depending on the intended use, a conversion coating as described herein may be considered an “adhesion promoter” and vice versa.

  Usually, a chemical conversion film is formed by applying a chemical conversion film treatment solution to a metal surface. The solution can be applied by dipping, spraying, spraying, wiping, or other similar means, depending on the surface complexity of the substrate being treated.

  Various chemical substances for chemical conversion film treatment have been proposed, but the present inventors thought that further improvements were desired in order to approach the protection level of the hexavalent chromium chemical conversion film.

US Pat. No. 7,294,362 (Tanaka et al.) US Pat. No. 6,375,726 (Matzdorf et al.) US Pat. No. 6,521,029 (Matzdorf et al.) US Pat. No. 6,669,764 (Matzdorf et al.) US Pat. No. 7,294,211 (Sturgill et al.)

  It is an object of the present invention to provide an improved conversion coating composition that does not contain toxic hexavalent chromium but imparts improved corrosion protection to the metal surface.

  Another object of the present invention is to provide an improved conversion coating composition that imparts improved corrosion protection to aluminum, aluminum alloys, zinc, zinc alloys, magnesium, magnesium alloys, and steels. .

  Still another object of the present invention is to provide a chemical conversion film treatment composition containing a stable solution for treating a metal substrate.

For this purpose, in general, the present invention is an aqueous conversion coating composition,
a) an aluminum ion source;
b) a fluoro compound;
c) at least one pH adjuster;
d) a Group VIB metal ion source selected from the group consisting of tungstate ions and trivalent chromium ions;
e) optionally preservatives;
It relates to the aqueous | water-based chemical conversion film processing composition containing this.

  The present invention also relates to a method for treating a metal substrate such as an aluminum substrate and an aluminum alloy substrate with the aqueous chemical conversion film treatment composition of the present invention to provide an improved chemical conversion film on the substrate. In one embodiment, the aqueous chemical conversion film treatment composition of the present invention is substantially free of phosphorus and / or chromium.

  In one embodiment, in general, the present invention provides an acidic aqueous conversion coating treatment for pretreating metals such as aluminum, aluminum alloys, zinc, zinc alloys, magnesium, magnesium alloys, and steel, and the corrosion resistance of such metal substrates. And process for improving.

  In one embodiment, in general, the present invention provides compositions for pretreating aluminum and aluminum alloy substrates and aluminum and aluminum alloy substrates at temperatures up to about 200 F ° from ambient temperature. It relates to the preprocessing process. Typically these pretreatment compositions comprise an acidic aqueous solution having a pH of about 0.5 to about 6, preferably about 3-5.

The pretreatment composition of the present invention typically comprises
a) an aluminum ion source;
b) a fluoro compound;
c) at least one pH adjuster;
d) at least one Group VIB metal ion source selected from the group consisting of tungstate ions and trivalent chromium ions;
e) optionally preservatives;
An aqueous solution containing

  In one preferred embodiment, the aluminum ion source is ammonium hexafluoroaluminate. Typically ammonium hexafluoroaluminate is preferred, but alkali hexafluoroaluminates such as sodium hexafluoroaluminate may be used in the practice of the invention. In another preferred embodiment, the aluminum ion source is pure aluminum powder used in combination with hexafluorotitanic acid, and the aluminum powder is dissolved in the solution due to the acidity of hexafluorotitanic acid.

Fluoro compounds useful in the practice of the present invention include, for example, ammonium hexafluoroaluminate and hexafluorotitanic acid. Other similar fluoro compounds may be used. The potassium, lithium, sodium, and ammonium salts of hexafluorotitanate function particularly effectively in this application and the performance of the ammonium salt is best. Other fluoro complexes include, but are not limited to, fluoroaluminic acid (eg AlF ₆ ^-3 or AlF ₄ ^-1 ), fluoroboric acid (eg BF ₄ ^-1 ), fluorogallic acid (eg GaF ₄ ^-1 ), fluoroindium Acids (eg InF ₄ ⁻¹ ), fluorogermanic acids (eg GeF ₆ ⁻² ), fluorostannic acids (eg SnF ₆ ⁻² ), fluorophosphoric acids (eg PF ₆ ⁻¹ ), fluoroarsenic acids (eg AsF ₆ ⁻¹ ) , Fluoroantimonic acid (eg SbF ₆ ^-1 ), fluorobismasic acid (eg BiF ₆ ^-1 ), fluorosulfuric acid (eg SF ₆ ^-2 ), fluoroselenic acid (eg SeF ₆ ^-2 ), fluorotauric acid (eg TEF ₆ ^-2 or teOF ₅ ^-1), fluoro cuprate (e.g. _CuF ^{3 -1} or C F ₄ ^-2), fluoro Ginsan (e.g. _AgF ^{3 -1} or _AgF ^{4 -2),} fluoro zincate (e.g. _ZnF ^{4 -2),} hafnic acid (e.g. _HfF ^{6 -2),} fluoro vanadate (e.g. VF ₇ ^-2), fluoro niobate (e.g. _NbF ^{7 -2),} fluoro tantalate (e.g. _TaF ^{7 -2),} fluoro molybdate (e.g. _MoF ^{6 -3),} fluoro tungstate (e.g. _WF ^{6 -1),} fluoro Yttrium acid (eg, YF ₆ ⁻³ ), fluorolantanic acid (eg, LaF ₆ ⁻³ ), fluoroceric acid (eg, CeF ₆ ⁻³ or CeF ₆ ⁻² ), fluoromanganic acid (eg, MnF ₆ ⁻² ), fluoroiron acid (e.g., _FeF ^{6 -3),} can be mentioned fluoro nickelate (e.g. _NiF ^{6 -2),} off Orokobaruto acid (e.g. _CoF ^{6 -2)} is also a suitable fluoride source, fluoroaluminate is preferred. Water-soluble potassium salts, sodium salts, lithium salts, or ammonium salts of these anions are typical, and ammonium salts of these anions are preferred. One particularly preferred compound for use in the composition of the present invention is ammonium hexafluoroaluminate.

  The pH may be adjusted by adding one or more organic acids, inorganic acids, fluoro complexes, alkali metal salts, ammonia, or pH adjusting agents that can include these salts. Examples of these additives include, but are not limited to, acetic acid, benzoic acid, citric acid, lactic acid, malic acid, propionic acid, succinic acid, tartaric acid, adipic acid, 1,2,3,4-butanetetracarboxylic acid, Fluoroboric acid, sulfuric acid, sulfonic acid, methanesulfonic acid, methanedisulfonic acid, nitric acid, silicic acid, hydrosilicofluoric acid, hydrofluoric acid, phosphoric acid, fluorozirconic acid, fluorotitanic acid, sodium hydroxide, ammonia, bicarbonate Ammonium, ammonium carbonate, sodium carbonate, sodium bicarbonate, and combinations of one or more of these. Other compounds are known to those skilled in the art. In one preferred embodiment of the invention, the pH adjusting agent includes an organic acid, ammonium bicarbonate, and / or ammonium carbonate. In a preferred embodiment, the organic acid is benzoic acid.

  The composition of the present invention includes at least one VIB group metal compound selected from the group consisting of a tungstic acid compound and a trivalent chromium compound.

In one embodiment of the invention, the Group VIB metal compound is chromium, in particular trivalent chromium, which may be added to the solution as any water-soluble trivalent chromium compound, preferably as a trivalent chromium salt. . A preferred trivalent chromium compound useful in the compositions of the present invention comprises basic chromium (III) sulfate (chromane), which has the formula CrOHSO ₄ .Na ₂ SO ₄ xH ₂ O, and is about 17.2% Contains chromium. Other trivalent chromium compounds that may be useful in the practice of the present invention include, for example, chromium (III) thiocyanate complexes described in US Pat. No. 4,062,737 (Barclay et al.); Trivalent chromium ions in low pH solutions described in US Pat. No. 4,612,091 (Tardy et al.); Trivalent chromium described in US Pat. No. 4,804,446 (Lashmore et al.) Chloride salts; and the chromium complexes described in US Pat. No. 4,460,438 (Benaben et al.), Which are incorporated herein by reference in their entirety. Other specific trivalent chromium salts useful in the practice of the present invention include chromium (III) formate, chromium (III) acetate, chromium (III) bromide hexahydrate, chromium (III) chloride hexahydrate. , Chromium (III) iodide hydrate, chromium (III) nitrate, chromium oxalate (III), chromium (III) orthophosphate, chromium (III) sulfate, hexamine chromium (III) chloride, hexaurea fluorosilicate In these various technical fields, chromium (III), chromium fluoride (III) tetrahydrate, chromium iodide (III) nine hydride, chromium nitrate (III) hexaammonide, potassium chromium oxalate (III) The known equivalents, and combinations of one or more of these are included.

  In another embodiment, the Group VIB metal is tungsten. Typically, tungsten is added to the composition as a tungstate ion source. The tungstate ion source includes all tungstates, but most specifically all orthotungstates, metatungstates, paratungstates, polytungstates, heteropolytungstates, isopolytungsten. Acid salts, peroxytungstates, and combinations thereof. Metatungstate or paratungstate is preferred. Suitable tungstate ion sources include sodium tungstate, tungstic acid, such as ammonium metatungstate, potassium metatungstate, sodium metatungstate, tungstic acid, sodium tungstate, potassium tungstate, and ammonium tungstate. Examples include potassium salt, lithium tungstate, calcium tungstate, cerium tungstate, barium tungstate, magnesium tungstate, strontium tungstate, tungstate, and ammonium tungstate.

  Another optional ingredient that may be beneficial to be included in some formulations prepared in accordance with the present invention is a preservative. One preferred preservative is hexahydro-1,3,5-tris (2-hydroxyethyl) -s-triazine sold under the trade name Surcide P (available from Surety Laboratories, Cranford, NJ). Other similar preservatives are known to those skilled in the art.

The first formulation (Formulation A) determined to improve the corrosion protection of metal substrates such as aluminum, aluminum alloys, zinc, zinc alloys, magnesium, magnesium alloys, and steels prepared according to the present invention is:
a) organic acids,
b) ammonium bicarbonate,
c) preservative,
d) ammonium hexafluoroaluminate,
e) methanesulfonic acid,
f) trivalent chromium compound, and g) balance: water.

Table 1 lists one of the preferred compositions of Formulation A prepared according to the present invention.

Table 2 lists various alternative use concentration examples for Formulation A solutions prepared according to the present invention.

Another formulation (Formulation B) determined to improve the corrosion protection of metal substrates such as aluminum, aluminum alloys, zinc, zinc alloys, magnesium, magnesium alloys, and steels prepared according to the present invention is:
a) hexafluorotitanic acid (50%),
b) pure aluminum powder,
c) ammonium bicarbonate,
d) ammonium metatungstate, and e) balance: water.

Table 3 lists one preferred composition of Formulation B prepared according to the present invention.

Finally, Table 4 lists various alternative use concentration examples for Formulation B solutions prepared according to the present invention.

  The metal substrate for use in the process of the present invention may be any substrate having at least a metal surface. Examples of useful substrates include substrates having a surface formed of iron, aluminum, magnesium, zinc, copper, tin, or an alloy containing any of these metals. A steel sheet substrate, an aluminum substrate or an aluminum alloy substrate is particularly preferred.

  Examples of the steel sheet substrate include a hot dip galvanized steel sheet, an electrogalvanized steel sheet, an iron-zinc alloy plated steel sheet, a nickel-zinc alloy plated steel sheet, and an aluminum-galvanized steel sheet. A zinc-based metal-plated steel sheet that has been subjected to a chemical conversion film treatment such as a chromate treatment, a zinc phosphate treatment, or a composite oxide film treatment is also useful as a steel sheet substrate. Furthermore, a steel sheet assembly may be used as a steel sheet substrate.

  The coating composition of the present invention may be applied to a metal substrate by any known process such as dip coating, shower coating, spray coating, roll coating, and electrodeposition coating. The contact time is from about 30 seconds to about 5 minutes, but longer contact may be required, such as when the concentration of the solution is low or when the temperature of the solution is relatively low. The temperature of the aqueous solution is usually less than 100 ° C., for example, 15 ° C. to 75 ° C., more preferably about ambient temperature (eg about 25 ° C.).

  In general, it is preferred to dry the composition for about 2 seconds to about 30 minutes by heating the substrate under conditions that reach a maximum temperature of about 60 ° C to 250 ° C.

  Prior to performing the trivalent chromium pretreatment, the substrate may be treated by washing and / or activation as is well known in the art. The composition of the present invention may then be contacted with the substrate for a sufficient time to form a conversion coating layer on the substrate surface, and then the substrate may be dried.

  The composition of the present invention can also be used to improve the adhesion and corrosion resistance of metal coated substrates, such as in US Pat. Nos. 6,511,532 and 6,527,841. , And 6,663,700 (both are Matzdorf et al.) And are incorporated herein by reference in their entirety. Since these “post-treatment” coatings typically come into contact with the metal to be treated after the initial coating is formed, the post-treatment usually does not involve the possibility of contacting through several holes in the metal coating. There is no direct contact with the substrate.

  Although the invention has been described with reference to particular embodiments of the invention, it will be apparent that many changes, modifications, and substitutions may be made without departing from the inventive concepts disclosed herein. Accordingly, the present invention is intended to embrace all such alterations, modifications and variations that fall within the spirit and broad scope of the appended claims. All patent applications, patents, and other publications cited herein are incorporated by reference in their entirety.

Claims (27)

An aqueous chemical conversion film treatment composition comprising:
a) an aluminum ion source;
b) a fluoro compound;
c) at least one pH adjuster;
d) at least one Group VIB metal ion source selected from the group consisting of tungstate ions and trivalent chromium ions;
e) optionally preservatives;
An aqueous chemical conversion film treatment composition comprising:   The aqueous chemical conversion film treatment composition according to claim 1, wherein the chemical conversion film treatment composition does not contain chromium or phosphorus.   The aqueous chemical conversion film treatment composition according to claim 1, wherein the fluoro compound contains hexafluorotitanic acid, the aluminum ion source contains aluminum metal, and the group VIB metal ion contains a tungstate ion source.   The aqueous chemical conversion film treatment composition according to claim 1, wherein the one or more pH adjusting agents comprise ammonium bicarbonate or ammonium carbonate.   Group VIB metal ions selected from the group consisting of orthotungstate ions, metatungstate ions, paratungstate ions, polytungstate ions, heteropolytungstate ions, isopolytungstate ions, peroxytungstate ions, and combinations thereof The aqueous chemical conversion film treatment composition according to claim 1.   Group VIB metal ions are sodium tungstate, potassium tungstate, lithium tungstate, calcium tungstate, cerium tungstate, barium tungstate, magnesium tungstate, strontium tungstate, tungstate, And an aqueous chemical conversion film treatment composition according to claim 5, which is selected from the group consisting of ammonium tungstate.   The aqueous chemical composition of claim 6, wherein the Group VIB metal ion is selected from the group consisting of ammonium metatungstate, potassium metatungstate, sodium metatungstate, tungstic acid, sodium tungstate, potassium tungstate, and ammonium tungstate. Film treatment composition.   The aqueous chemical conversion film treatment composition according to claim 7, wherein the group VIB metal ion contains ammonium metatungstate. The ammonium ion source and the fluoro ion source comprise ammonium hexafluoroaluminate,
The composition contains a preservative,
The aqueous chemical conversion film treatment composition according to claim 1, wherein the group VIB metal ion contains a trivalent chromium ion source.   The aqueous chemical conversion film treatment composition according to claim 9, wherein the one or more pH adjusters include an organic acid, ammonium bicarbonate, and methane sulfonate.   The aqueous chemical film treatment composition according to claim 10, wherein the organic acid comprises benzoic acid.   The aqueous chemical conversion film treatment composition according to claim 9, wherein the preservative comprises hexahydro-1,3,5-tris (2-hydroxyethyl) -s-triazine.   The aqueous chemical conversion film treatment composition according to claim 9, wherein the trivalent chromium ion source contains basic chromium sulfate. A method of treating a metal substrate to form a chemical conversion film on the metal substrate,
a)
i) an aluminum ion source;
ii) a fluoro compound;
iii) at least one pH adjuster;
iv) at least one Group VIB metal ion source selected from the group consisting of tungstate ions and trivalent chromium ions;
v) optionally a preservative,
Contacting the metal substrate with a composition comprising:
b) subsequently drying the treated metal surface;
A method comprising the steps of:   15. The method of claim 14, wherein the metal substrate is selected from the group consisting of aluminum, aluminum alloy, magnesium, magnesium alloy, zinc, zinc alloy, steel, and one or more combinations thereof.   The method according to claim 14, wherein the aqueous chemical conversion film treatment composition does not contain chromium or phosphorus. The fluoro compound comprises hexafluorotitanic acid,
The aluminum ion source includes aluminum metal;
The method of claim 16, wherein the Group VIB metal ion comprises a tungsten ion source.   15. The method of claim 14, wherein the one or more pH adjusters comprises ammonium bicarbonate or ammonium carbonate.   Group VIB metal ions selected from the group consisting of orthotungstate ions, metatungstate ions, paratungstate ions, polytungstate ions, heteropolytungstate ions, isopolytungstate ions, peroxytungstate ions, and combinations thereof 15. The method of claim 14, wherein:   Group VIB metal ions are sodium tungstate, potassium tungstate, lithium tungstate, calcium tungstate, cerium tungstate, barium tungstate, magnesium tungstate, strontium tungstate, tungstate, 20. The method of claim 19, wherein the method is selected from the group consisting of: and ammonium tungstate.   21. The method of claim 20, wherein the Group VIB metal ion is selected from the group consisting of ammonium metatungstate, potassium metatungstate, sodium metatungstate, tungstic acid, sodium tungstate, potassium tungstate, and ammonium tungstate.   The method of claim 21, wherein the Group VIB metal ion comprises ammonium metatungstate. The ammonium ion source and the fluoro ion source comprise ammonium hexafluoroaluminate,
The composition contains a preservative,
15. The method of claim 14, wherein the Group VIB metal ion comprises a trivalent chromium ion source.   24. The method of claim 23, wherein the one or more pH adjusters comprises an organic acid, ammonium bicarbonate, and methane sulfonate.   25. A method according to claim 24, wherein the organic acid comprises benzoic acid.   24. The method of claim 23, wherein the preservative comprises hexahydro-1,3,5-tris (2-hydroxyethyl) -s-triazine.   24. The method of claim 23, wherein the trivalent chromium ion source comprises basic chromium sulfate.