Stock material or miscellaneous articles – Composite – Of metal
Reexamination Certificate
2000-08-30
2001-11-06
Koehler, Robert R. (Department: 1775)
Stock material or miscellaneous articles
Composite
Of metal
C148S247000, C148S253000, C148S256000, C148S261000, C148S272000, C148S273000, C148S275000, C148S276000, C148S277000, C148S285000, C427S402000, C428S472000, C428S472100, C428S926000
Reexamination Certificate
active
06312821
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a coating structure for improving the corrosion resistance of aluminum alloy-made products and parts used under a water environment, such as marine screws and hulls used on sea water or a lake, water pumps and sprayers having a power such as a general-purpose engine, etc., and agricultural working machines used in a paddy field, etc.
2. Description of the Related Art
To the products and parts described above is applied rust-preventing or corrosion-resisting coating. In particular, rust-preventing coating to sea water containing salinity which is a factor of accelerating corrosion is required.
Concerning rust-preventing or corrosion-resisting coating, many techniques are proposed. For example, Japanese Patent Laid-Open Publication No. HEI-2-250997 discloses a “RUST-PREVENTING TREATMENT METHOD FOR ALUMINUM MATERIAL AND ALUMINUM-MADE OUTBOARD MOTOR FRAME” obtained by forming an anodized film on the surface of a material composed of aluminum or an aluminum alloy and subjecting the anodized film to a sealing treatment with molybdenum disulfide to form thereon a coated film. In the above-mentioned publication, it is described that in the coating structure it is desirable to first coat a primer containing a rust-preventing pigment prior to forming the coated film and also as the rust-preventing pigment which is mixed with the primer, strontium chromate is suitable.
Also, Japanese Patent Laid-Open Publication No. HEI-10-230219 discloses a “COATED FILM STRUCTURE WITH EXCELLENT CORROSION RESISTANCE TO SEAWATER” obtained by forming a formation film on the surface of an aluminum part
11
by a chromate treatment, forming an under coated layer on the surface of the formation film with a rust-preventing pigment coating material using zinc phosphate, and coating thereon a topcoat material.
However, in the coating structure of the Japanese Publication No. HEI-2-250997 described above, a coating anodizing treatment (anodized aluminum treatment) and a sealing treatment are required and these treatments increase the cost, which causes the cost up of the products.
Furthermore, because in the coated film of the Japanese Publication No. HEI-10-230219 described above, zinc phosphate is used, it is anticipated that the strength of the coated film is lowered. If the strength of the coated film is lowered, the corrosion resistance is lowered.
Particularly, because in both Japanese Patent Laid-Open Publication No. HEI-2-250997 and No. HEI-10-230219 described above, a chromic acid treatment or a chromic acid-base primer is used, the treatment of a chromic acid-base waste solution becomes inevitable and the cost for the waste solution treatment becomes a factor of increasing the product cost.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a coating structure having a sufficient corrosion resistance and capable of restraining the product cost without requiring an anodized film and a sealing treatment.
According to a first aspect of the present invention, there is provided a coating structure having a corrosion resistance, containing an aluminum alloy material, a formation film formed on the surface of the aluminum alloy material by a zirconium phosphate treatment, and a primer layer containing phosphomolybdic acid as a rust-preventing pigment, formed on the outer surface of the formation film.
As described above, according to the invention, because zirconium phosphate reacts with the oxide film of the surface of the aluminum alloy to form a zirconium boehmite layer, which gives the action of increasing the adhesion with a coating material, the corrosion resisting structure can be obtained without requiring a sealing treatment while restraining the increase of the production cost. Furthermore, because phosphomolybdic acid and zirconium phosphate are used, the cost for the water liquid treatment is not increased, whereby the increase of the production cost can be restrained.
As the aluminum alloy, there are, for example, Al—Si—Mg-based alloys. In this case, by allowing the ratio of Cu in the aluminum alloy, the occurrence of corrosion is retrained and by increasing the ratio of Mg in place of lowering Cu, the strength of the product is ensured. Accordingly, by using the above-described aluminum alloy, both the corrosion resistance and the strength can be satisfied.
In the above-described formation film, the weight thereof per unit coated area is in the range of from 5 to 30 mg/m
2
. When the weight of the formation film described above is less than 5 mg/m
2
, the film becomes too thin to keep the strength of the film, while when the weight exceeds 30 mg/m
2
, the films are overlapped each other to lower the adhesion. It is more preferred that the weight of the formation film is in the range of from 20 to 30 mg/m
2
.
The circumstance differs according to the production method and the working method, in a metal material, unevenness unavoidably forms on the surface thereof. For sufficiently cover the unevenness, as the film thickness of the primer layer, the film thickness of at least 5 &mgr;m becomes necessary. To cover the unevenness, the film thickness is thicker, the better, but because when the thickness exceeds 50 &mgr;m, it becomes uneconomical, it is preferred that the thickness of the primer layer is in the range of from 5 to 50 &mgr;m.
The above-described primer layer is composed of an epoxy resin as the basic resin added with a rust-preventing pigment composed of phosphomolybdic acid. Because an epoxy resin has a high adhesive action, phosphomolybdic acid of the primer layer is strongly adhered to zirconium phosphate of the formation layer, whereby the primer layer can be more strongly adhered to the formation film and the corrosion resistance is more improved.
When the content of the above-described epoxy resin is less than 40% by weight, the intercepting performance of the film is lowered, while the content of the epoxy resin exceeds 60% by weight, the adhesive performance of the film is lowered. Thus, in consideration of both the intercepting performance and the adhesive performance, it is preferred that the ratio of the epoxy resin in the primer is in the range of from 40 to 60% by weight. Furthermore, when the content of phosphomolybdic acid in the primer is less than 5% by weight, the rust-preventing performance is lowered, while the content thereof exceeds 13% by weight, the rust-preventing performance may be sufficient but the adhesive performance is lowered. Therefore, in consideration of both the rust-preventing performance and the adhesive performance, it is preferred that the content of phosphomolybdic acid in the primer is in the range of from 5 to 13% by weight.
By adding the topcoat layer to the formation layer and the primer layer, the whole film thickness of the corrosion resisting coatings is increased to increase the corrosion resistance. For example, even when the thickness of the primer layer may insufficient to some extent, the thickness can be supplemented by adding the topcoat layer. As the coating material constituting the topcoat layer, an acrylic resin-base or melamine-base coating material is preferred. Because an acrylic resin or melamine attaches well to phosphomolybdic acid, the topcoat layer can be strongly adhered to the primer layer.
According to a second aspect of the invention, there is provided a coating structure having a corrosion resistance, containing an aluminum alloy material subjected to a pickling treatment, a formation film formed on the surface of the aluminum alloy material by a zirconium phosphate treatment, and a primer layer using phosphomolybdic acid as a rust-preventing pigment formed on the outer surface of the formation film.
As described above, according to the invention, by applying the pickling treatment to the aluminum alloy before forming thereon the formation film, the attached amount of the formation film can be increased and the corrosion resistance can be more improved. Because zirconium phosphate has the functi
Matsuda Yoshiyuki
Murata Hiroyuki
Takasaki Norimasa
Takemura Morihiro
Adams & Wilks
Honda Giken Kogyo Kabushiki Kaisha
Koehler Robert R.
LandOfFree
Coating structure having corrosion resistance does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Coating structure having corrosion resistance, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Coating structure having corrosion resistance will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2614128