CA1090029A

CA1090029A - Metal surface treatment

Info

Publication number: CA1090029A
Application number: CA227,651A
Authority: CA
Inventors: Kakuro Muro; Kuniji Yashiro; Hideaki Kaneko; Kiyoichi Yamazaki
Original assignee: Oxy Metal Industries Corp
Current assignee: Oxy Metal Industries Corp
Priority date: 1975-05-23
Filing date: 1975-05-23
Publication date: 1980-11-18

Abstract

Disclosed is a method and composition useful in the treatment of a metal surface. The composition contains a dissolved or dispersed resin and a dissolved titanium compound. Preferably, the composition also contains fluoride.

Description

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This invention relates to a process for the treatment of a metal surface and a process for the aftertreatment of metal surface containing a chemical conversion coating.
In conventional processes ~or treating metal surfaces ` in order to improve the corrosion resistance and adhesion of paints, there have been used acids and salts containing cations such as chromium, iron, manganese, aluminum, zinc, nickel and ; anions such as phosphates, borates, nitrates, chromates, bi-` chromates to precipitate the insoluble salts on the metal sur-face. Coatings containing a titanium compound as an essential component have not provided satisfactory properties both for the corrosion resistance and for the adhesion with paints. In addition, the use of treating solutions containing ions such as chromium, zinc, manganese and the like have been restricted in ~' view of the undesirability of their control and environmental pollution.
It has now been found that a coating having an :' ' :
-~ improved corrosion resistance and good paint adhesion can be formed by applying an aqueous treating solution or emulsion comprising a solution or emulsion of a water soluble ~r water emulsifiable type resin, a water soluble titanium compound, and -iw luding fluoride ion, onto a metal surface.
In another aspect of the invention there is provided an aqueous composition which comprises the water soluble or water emulsifiable resin and the dissolved titanium compound :- together with fluoride.
,,~, Metals capable of being treated according to this invention include, for example, iron, zinc and aluminum. The ;`1 metal may be treated with a conversion coating by any suitable ~ 30 zinc-based phosphating process, iron-based phosphating process, or chromating process such as those disclosed in the Metal Finishing Guidebook.

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Solution or emulsion resins usable in this invention , may be those having an activity as a binder, but should prefer-ably also be those having high corrosion resistance and high stability in the presence of a water soluble titanium compound.
Solution or emulsion of resins may be conventional resins which include, for example, polymers or copolymers based on vinyl such as vinyl acetate, vinylidene chloride and vinyl chloride, ~ acrylic such as acrylates, acrylic acid, and methacrylic acid, ; polyesters, polymers or copolymers based on monomers of amino-alkyl, epoxy, urethane, or styrene, polyethylene polymer or copolymers, natural or synthetic rubber, natural high mole-cular weight resins and the like.
These solution and emulsion resins are used in a con-; centration of 0.1 to 6C% by weight of solid resin, depending on the type of resin, viscosity and application procedure.
Water-soluble titanium compounds usable in the invention include K2TiF6, Na2TiF6, (~H4 ~iF6, TiF4, Ti(S04)2, TiOS04, acid soluble titanium compounds, for example, TiO, ; `Ti203, TiO3, H2TiO3, H4TiO4 can also be employed. The concent-ration of the water-soluble titanium compound depends on the solubility, stability in the presence of the resin, type and viscosity o~ the resin solution or emulsion and application procedure. In general, the compound is used as a solution con-taining 0.1 to l~/o by weight.
In order to improve the solubility of the titanium compound, to adjust the pH of solution or to stabilize the resin solution or emulsion, there may be used amines such as ethylamine, dimethylamine, trimethylamine, hexylamine and the like, alkaline bases such as ammonia, caustic soda, caustic potash and the like, inorganic acids, for example, phosphoric acid, nitric !' ~; acid, sulfuric acid, hydrofluoric acid and the salts thereof, and organic acids, for example, oxalic acid, citric acid, malic acid, maleic acid, phthalic acid, acetic acid and the salt~
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.i ' ~O~Ol~Z9 `~ thereof. If desired, the solution or emulsion may contain a pigment.
The composition in a preferred embodiment may contain ' a fluoride, in particular the fluoride being present as fluoride ion in an amount sufficient to complex at least a ~,; , ; portion of the titanium present. The fluoride may conveniently form part of the water-soluble titanium compound as indicated above, however, it may be added independently as hydrofluoric acid or a salt thereof, as indicated above.
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In order to prepare the treating solution or emulsion -comprising a solution or emulsion of a resin and a water-soluble , ;:
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,, : i ` P-10~2 iO90~29 ' titanium compound, the titanium compound may be dissolved in water and then ~he resin added to form the solution or emulsion, or the resin may be dissolved or dispersed into water to form the isolution or emulsion and then the water-soluble titanium compound added as solid product as such or as the solution, or both the water-soluble titanium compound and the resin may be added concurrently to form the solution or emulsion. The proportion on the basis of weight of said resin to water-soluble titanium compound may be 100:1 to 1:10, preferably 20:1 to 1:1.
The treating solution or emulsion may be applied onto metal surace to be treated by any conventional technique, ...
such as immersiny, pouring, brushing or spreading by means of a roller and allowed to stand as such or dried to form a tough coating haviny an improved corrosion resistance. The coating or immersion procedure may be conducted at a temperature ranging from room temperatures to 80C or higher. The i drying operation may be carried out at a temperature suitable for the resin employed and normally ranging from 80 to 250C
~20 for 0.2 to 10 minutes.
The coating formed according to this invention ` provides excellent corrosion resistance and adhesion with paints.
This invention will now be illustrated by the ~25 following examples, in which all percentages are by weight.
~- EXAMPLE 1 Potassium titanium fluoride (K2TiF6, 1 yram) was dissolved in water (500 ml). To the solution was added an aqueous 46~ emulsion o~ acrylic resin ~50 grams, Primal ~30 E-269 prepared by Nippon Acryl CoO) and water to make 1 liter.
The resulting treating emulsion contained the acrylic solid -3~
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P-10~2 ~ 2 g resin in a concentration o~ 2~3~ and potassium titanium fluoride in a concentxation of 0.1~. This treating emulsion was applied to degreased and cleaned alu~inum plate of 2S
- type by the immersion procedure and the coated aluminum ; 5 plate was dried at 120C for 3 minutes. The treated plate was subjected to a corrosion test based on the salt spray test according to JIS Z-2371 (referred to hereinafter as the salt spray test~. For comparison, identical panels were treated with the same solution without titanium. Results are given in Table 1.
- Table 1 Salt Spray Test .~.
Test Period Resin Only Resin with Titanium 100 hrs. 60 - 80% white stain No Stain ~15 200 hrs. 100% white stain No Stain Coating Weight 300 - 350 mg/m2 300 - 350 mg/m2 ,: EXAMPLE 2 ,,:, Various amounts of ammonium titanium fluoride 1 (NH4)2TiF6, 1 ~ram, 3 grams and 5 grams ] were dissolved in water (500 ml.) and to each solution was added an aqueous 40% emulsion of acrylate resin (50 grams, Tocryl N-142~
prepared by Toyo Ink Co.) and the compositions were made up :., to 1 liter with water. The pH of each resulting emulsion was adjusted to a value from 1 to 2 by adding 75% phosphoric acid (10 grams). Degreased and cleaned aluminum plates of ~ 2S-type were brushed separately with the treating emulsion `~ and dried under the same conditions to those disclosed in EXAMPLE 1. The coated Al plate was subjected to the corrosion resistance test based on the salt spray test.
Additionally, degreased and cleaned aluminum plates treated as above were coated with a conventional paint solution for protecting cans by means of a barcoatex and dried at 180C
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for 6 minutes to prepare coat~cl specimens having a ~ilm ~. .
~ thickness of 3 microns. The specimens were immersed in pure ., .
,jj water at 80C for 30 minutes to simulate can processing conditions and the whitening of the ~ilm was compared. Table 2 shows the results of these tests.
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Table 2 Salt Spra~
(NH4)2TiF6 75~ H3POa g/l g/l 168 hrs 500 hrs Whitening test .... . _ .. _ .. .
.I0 0 0 100% stained - lO0~ whitened 0 lO lO0~ stained - 100~ whitened 1 lO No Stain 50% stained 100% whitened . :; , . :
3 lO No Stain No Stain No Stain , 5 lO No Stain No Stain No Stain __ Iron of SPC-l was degreased, cleaned and treated with a zinc-based phosphating solution (Bonderite 137 prepared by Nihon Parkerizing Co.). The thus-treated plate was -20 immersed into an aqueous emulsion containing ammonium titanium fluoride [ (NH4)2TiF6] in a concentration of lO grams/liter acrylate resin emulsion (Tocryl ~-2009 prepared by Toyo Ink Co.) in a solid resin concentration of 3% and dried at 120C
for 3 minutes. The treated plate was subjected to the salt i25 spray corrosion resistance test. Table 3 shows the reswlts obtained.

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;~ P-10~}~32 L0900~9 Table 3 Salt Spray Test Specimen 0.5 hrs 1 hr 2 hrs No A~tertreatment 100% red - -stain Aftertreatment by resin 10-30% red 80~ red 100~ red emulsion alone stain stain stain Atertreatment according to the invention No stain No stain No stain . _ . . v .. .. ~

` 10 EXAMPLE 4 .
Galvanized steel plate was degreased, cleaned and - pretreated with zinc-based phosphating solution. The pretreated film was then coated with an aqueous dispersion containing -~ ammonium titanium fluoride [ (NH4)2TiF6 ] in a concentration '15 of 10 grams/liter and polyvinylidene (derived from ~iophane .~. .
- 290D prepared by Petroleum Chemical Badisch Co.) in a solid resin content of 10~ by means of roller coating process, , . .
dried at 120~C for 3 minutes. The aftertreated plate was -~
subjected to the salt spray corrosion resistance test, a 20 second set of panels were treated in the same manner and painted with an aminoalkyd paint to a thickness of 20 microns.
- These panels were scribed and the corrosion creepage fxom the scribe was measured. Table 4 gives the results.

.! Table 4 ~25 Painted Panel Salt Spray Test Scribe Creepzge Specimen 1 hr 2 hrs 120 hrs No aftertreatment 50~ white 100% white rust rust 10 - 20 mm Aftertreatment with 3% white 80~ white resin emulsion only rust rust 10 mm Aftertreatment according to the No rust 20% whiteless than invention rust 3 mm `

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. A process for treating a metal surface comprising contacting the surface with an aqueous composition containing from 0.1 to 60 wt. % of a water soluble or water emulsifiable type resin, from 0.1 to 10 wt. % of a dissolved water soluble titanium compound, and including sufficient fluoride ion to complex at least a portion of the titanium present.

2. The process of claim 1, wherein the resin is a water soluble resin.

3. The process of claim 1, wherein the resin is a water emulsifiable resin.

4, The process of claim 1, 2 or 3, wherein the weight ratio of resin to titanium compound is between 0.1 to 100:1.

5. The process of claim 1, 2 or 3, wherein the weight ratio of resin to titanium compound is between 1 and 20:1.

6. The process of claim 1, wherein the resin is selected from the group consisting of acrylic-, vinyl-, polyester-, aminoalkyl-, epoxy-, urethane-, styrene- and polyethylene-based polymers and copolymers.

7. The process of claim 1, 2 or 3, wherein the metal surface is phosphatized or chromatized prior to contact with the resin composition.

8. An aqueous composition comprising from 0.1 to 60 wt. % of a water soluble or water emulsifiable type resin, from 0.1 to 10 wt. % of a dissolved water soluble titanium compound and fluoride.

9. A composition according to claim 8, wherein said resin is a water soluble resin.

10. A composition according to claim 8, wherein said resin is a water emulsifiable resin.

11. A composition according to claim 8, 9 or 10, wherein the weight ratio of resin to titanium compound is between 0.1 and 100:1.

12. A composition according to claim 8, 9 or 10, wherein the weight ratio of resin to titanium compound is between 1 and 20:1.

13. A composition according to claim 8, wherein the resin is selected from the group consisting of acrylic-, vinyl-, polyester-, aminoalkyl-, epoxy-, urethane-, styrene- and polyethylene-based polymers and copolymers.

14. A composition according to claim 8, 9 or 10, wherein said fluoride is present in an amount sufficient to complex at least a portion of the titanium present.