Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-11-04
2001-11-27
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S459000, C523S466000, C525S107000
Reexamination Certificate
active
06323264
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a corrosion barrier coating composition, and more particularly to a corrosion barrier coating composition comprising an admixture of (1) a one-component epoxy resin composition, (2) polytetrafluoroethylene (TEFLON) powder, and (3) glass powder. The present invention is also directed to a substrate coated with the corrosion barrier coating composition of the invention, and a method of coating a substrate with the corrosion barrier coating composition of the invention.
2. Brief Description of the Art
Corrosion barrier coatings are useful in a wide variety of industrial applications to provide metal parts with protection from natural elements such as water, carbon dioxide, salts spray, oxygen, ozone, UV radiation, and the like. In particular, corrosion barrier coatings have proven useful in aircraft and industrial equipment, where severe environmental conditions can occur. For example, aircraft fuel and oil pump housings frequently require repair because they corrode during use. This corrosion reduces the longevity of the housings and results in costly rebuilding, repair, or replacement.
The prior art is replete with corrosion-inhibiting compositions for use in a variety of purposes. However, most of these compositions provide only a thin coating of corrosion barrier to the substrate. While thin coatings may offer adequate protection against corrosion, the thin nature of the barrier makes them more susceptible to damage and corresponding loss of corrosion protection in the damaged area.
Representative patents describing corrosion inhibiting coatings include the following:
U.S. Pat. No. 4,996,085 discloses coating a pump housing surface with a composition comprising a hardenable epoxy resin, a reinforcing filler, and an agent having a lower coefficient of friction than the epoxy resin. Graphite may function as the reinforcing filler, and the frictional reducing agent may be either graphite, in fibrous or granulated form; fluorinated carbon (i.e., —(CF
x
)— wherein x<2); or molybdenum disulfide. Further, the preferred class of epoxy resin is a diglycidyl ether of a dihydric phenol (e.g., the diglycidyl ether of bisphenol A).
U.S. Pat. No. 5,316,790 discloses a lubricative coating and filler material for restoring metal surfaces that have become scratched, scored, grooved, or otherwise damaged to a functional condition. This coating and filler material is a mixture of an epoxy resin, tungsten disulfide, and isopropyl alcohol in a ratio of 9:1:1.6.
U.S. Pat. Nos. 5,603,818 and 5,385,655 disclose a method of producing an adherent and corrosion-inhibiting multilayer coating on metal parts by electrolizing a first composition made from water emulsions, dispersions, or solutions based on water-dispersible or emulsifiable synthetic resin such as alkyd resins, acrylic polymers, melamine resins, and the like. A second coating, comprising at least one film-forming organic resin, is applied over the first coating.
U.S. Pat. No.5,753,316 discloses a method of treating metal surfaces by coating those surfaces with a film-forming sealcoat containing at least one organic resin and at least one torque modifier. The organic resin is made from water emulsions, dispersions, or solutions based on water-dispersible or emulsifiable synthetic resin such as alkyd resins, acrylic polymers, melamine resins, and the like. The torque modifier may be one or more fluoroalkene polymers, polyethylene, polypropylene, mica, talc, or calcium carbonate.
U.S. Pat. No. 5,312,491 discloses a rust-inhibiting composition containing oxime-based rust converter compounds formulated with a latex based paint to provide a flexible film coating that acts as a barrier to oxygen and water vapor diffusion to the metal surface.
Copending U.S. patent application Ser. No. 08/568,114 discloses a curable composition useful for repairing worn surfaces on housings comprising an admixture of (1) a mixture of (a) at least one one-component epoxy resin, (b) at least one solvent and (c) at least one reactive diluent, wherein the epoxy resin is present in a major (i.e., at least 50% by weight) amount in the mixture; (2) graphite powder; and (3) polytetrafluoroethylene powder.
Copending U.S. patent application Ser. No. 09/413,566 discloses a low friction coating composition, comprising about 60 wt % to about 95 wt % of a high temperature epoxy, comprising (1) about 30 wt % to about 60 wt % of N,N′-m-phenylene dimaleimide; (2) about 30 wt % to about 60 wt % of bisphenol epoxy resin; and (3) about 1 wt % to about 5 wt % of amorphous silicon dioxide; (B) about 1 wt % to about 30 wt % of molybdenum disulfide; and (C) about 1 wt % to about 20 wt % of polyimide powder.
While these corrosion-inhibiting and low-friction coating materials may be satisfactory for certain applications, there is still need for improved corrosion barrier compositions that are useful on a wide variety of substrates, such as housings of various aircraft and machinery parts, that are exposed to severe environmental conditions. The present invention is believed to be an answer to that need.
BRIEF SUMMARY OF THE INVENTION
In one aspect, the present invention is directed to a corrosion barrier coating composition, comprising an admixture of: (1) about 60 to about 95 wt % of a one-component epoxy resin composition comprising (a) about 10-30% by weight of 4-glycidyloxy, n,n-diglycidyl aniline; (b) about 30-60% by weight of an epoxy resin, wherein the epoxy resin is epichlorohydrin ether of bisphenol A; and (c) about 3-7% by weight of strontium chromate; (2) about 1 to about 30 wt % of polytetrafluoroethylene; and (3) about 1 to about 20 wt % of glass powder; wherein all weight percents are based on the total weight of the composition.
In another aspect, the present invention is directed to a substrate coated with the corrosion barrier coating composition of above composition.
In yet another aspect, the present invention is directed to a method of coating a substrate with a corrosion barrier coating composition, comprising the steps of: (A) coating the substrate with the above corrosion barrier composition; and (B) curing the corrosion barrier composition onto the substrate at a temperature of between 250 and 350° F. for between 0.5 and 5 hours.
These and other aspects will become apparent from the following written description.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a corrosion barrier composition made from selected components that provides a thicker layer of corrosion protection than the corrosion coatings of the prior art. The composition of the present invention has also been found to bond strongly to the substrate, and together with the thicker nature of the coating, provides for excellent corrosion barrier to protect the underlying substrate, particularly under harsh conditions of salt spray, ozone, oxygen, and the like, found in commercial aircraft and industrial equipment. The corrosion barrier composition of the present invention is particularly useful on magnesium, aluminum or stainless steel aircraft fuel or oil pump housings.
As indicated above, the preferred corrosion barrier composition of the present invention comprises (1) about 60 to about 95 wt % of a one-component epoxy resin composition, such as HYSOL EA929NA, (2) about 1 to about 30 wt % of polytetrafluoroethylene powder; and (3) about 1 to about 20 wt % of glass powder. Each of these components are discussed below.
As mentioned above, the preferred one-component epoxy resin composition used in the composition of the invention is HYSOL EA929NA epoxy resin. As defined herein, the term “one-component” refers to an epoxy resin composition that is pre-catalyzed. The HYSOL EA929NA product is available commercially from the Dexter Aerospace Materials Division of Hysol Aerospace Products (Pittsburg, Calif.). This product contains 4-glycidyloxy, n,n-diglycidyl aniline (Chemical Abstract No. 5026-74-4), which constitutes about 10 to 30% by weight of the epoxy resin composition; a bisphenol A epichloroh
Greenberg Glen
Nazaryan Nikolay
Orkin Stanley S.
Aylward D.
Dawson Robert
Garabedian Todd E.
Simons William A.
Turbine Controls, Inc.
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