Compositions – Preservative agents – Anti-corrosion
Reexamination Certificate
2000-06-30
2004-04-20
Thexton, Matthew A. (Department: 1714)
Compositions
Preservative agents
Anti-corrosion
C252S389310, C106S014150, C524S183000, C524S185000
Reexamination Certificate
active
06723258
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to pretreating metal surfaces to minimize the formation of rust and to improve the adhesion of subsequently applied decorative finishes, such as paint, to the metal surfaces.
BACKGROUND OF THE INVENTION
Minimizing the formation of rust and improving the adhesion of a decorative finish to a metal surface can be effected by pretreating the metal surface. Certain metals, such as steel, (including galvanized steel and electro galvanized steel), zinc alloys, and aluminum alloys, tend to rust in the absence of a pretreating step. Even with the application of a pretreatment, certain metals will form rust if the decorative finish (such as paint) is not applied within a few days after application of the pretreatment.
Pretreating a metal surface results in the formation of a coating or film layer over a metal surface which improves the ability of a subsequently applied decorative finish to adhere to the metal surface. Such a coating or film also decreases the reactivity of the metal surface to minimize the formation of an oxide layer (i.e., rust) over the metal surface. It is desirable, however, that the coating or film does not decease the reactivity of the metal to such an extent that the subsequently applied paint does not adhere well to the metal surface. (For convenience, paint will be identified in some places herein as the particular decorative finish to be applied, but the statements made herein referring specifically to paint can apply equally to other decorative finishes, such as lacquers.)
In general, some coating compositions serve to adequately passivate (i.e., minimize rust formation of) metal surfaces while others improve the adhesion of a subsequently applied paint or other decorative layer. One problem with known compositions, however, is that no single composition appears to form a coating on many metal surfaces (especially those metals which tend to rust easily) which functions adequately to both minimize rust formation and improve paint adhesion. In particular, steel and zinc coated steel are often not adequately passivated by many compositions.
A problem with many known compositions is that steel or zinc-coated steel must be painted very soon after the composition is applied. This is because many compositions used to passivate steel or zinc-coated steel form protective films that are hydrophobic and therefore are not readily paintable. In some cases, paint adhesion performance drops off quickly over time, and the steel or zinc coated steel must be painted within a few hours (up to about 24 hours at the most). Otherwise, the paint will not adhere well to the metal surface. For other pretreatment compositions, although paint adhesion remains adequate even if more time elapses between the application of the pretreatment and painting, the metal surface tends to rust. Depending on a number of conditions, rust can form as quickly as two days after pretreating and becomes even more problematic as more time elapses, such as between 4 to 6 days. Rust formation becomes even more likely and occurs more quickly in environments having high humidity or salt content.
The present invention is directed to a method and composition which both improves the ability of a metal surface to prevent rust formation prior to painting, while still providing good adhesion of paint to the metal surface.
SUMMARY OF THE INVENTION
To achieve these and other objectives, and in view of its purposes, the present invention provides a method and composition for pretreating a metal surface to minimize rust prevention prior to the application of the paint while still providing good paint adhesion. The pretreating composition is a blend of water, an organo-functional silane, and a borate ester. According to the method for pretreating a metal surface, a cleaned metal surface is pretreated with a pretreating composition of the present invention, then dried in preparation for application of a decorative coating to the dried metal surface.
A method for treating a metal surface according to the present invention involves first contacting the metal surface with a cleaning solution to remove soils to form a cleaned metal surface then rinsing with water. The metal surface is subsequently contacted with a pretreating solution comprising a blend of water, an organo-functional silane, and a borate ester to form a pretreated metal surface then dried. After drying, a decorative coating is applied to the dried metal surface. Using a pretreating composition according to the present invention allows for extended storage times, such as at least 8 to 12 days or more, to elapse between the pretreatment step and the painting step, with minimal or no rust forming.
The present invention also contemplates use of the composition as a final seal for a metal surface which has already been contacted with another pretreatment solution. For example, in a three stage process, a metal surface is first contacted with a combined cleaning/phosphatizing bath, rinsed, then contacted with a final rinse comprising a blend of water, an organo-functional silane, and a borate ester. Alternatively, a five stage process involves cleaning, rinsing, pretreating (such as by using an iron phosphate bath), rinsing, then applying a final seal by contacting the rinsed metal surface with a blend of water, an organo-functional silane, and a borate ester.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention pertains to a method for treating and a method and composition for pretreating metal surfaces. As used herein, the term “treating” shall include all processing of metal surfaces and include cleaning, pretreating, sealing, and applying a decorative finish to the metal surface, as well as any intermediate rinsing or drying steps. In some cases, metal surfaces are precleaned prior to the “cleaning step” referred to herein. Such precleaning typically involves mechanically abrading the metal surface, such as by sandblasting the metal surface. The term “pretreating” is directed specifically to the step in which a pretreating composition (such as a composition of the present invention or known iron phosphate pretreating compositions) is applied to the metal. The pretreating composition of the present invention serves to minimize rust formation while still allowing for good paint adhesion, even if an extended period of time such as at least eight to twelve days (or more), elapses between the pretreating step and the painting step. Even if a known pretreating composition (such as an iron phosphate bath) is used, the composition of the present invention may be applied as final seal to increase the potential storage time before painting while minimizing rust formation during this storage time. Thus, by virtue of the composition of the present invention having the ability to pretreat and to seal, it can be said that the composition of the present invention is used in the treatment of metal surfaces.
The pretreating composition of the present invention can be used to pretreat any metal surface. Preferably, the composition is used to pretreat metal surfaces which tend to rust easily, namely those forming some visible evidence of rust in a typical atmosphere after two or three days with no protective film formed thereon. Such metals are typically ferrous metals, such as steel. Other metals particularly suitable for pretreatment by the composition of the present invention include zinc and aluminum alloys, galvanized steel, and electrogalvanized steel. Also, the form of the metal to be treated can be any known form of metal, such as cold-rolled metal, extrusions, coil, or cast parts.
The treatment method is carried out in order in the following stages:
1) Clean—The metal surface is contacted with a cleaning solution to form a cleaned metal surface;
2) Water rinse;
3) Pretreatment—The metal surface is contacted with a pretreating solution which is a bl
Bulk Chemicals, Inc.
RatnerPrestia
Thexton Matthew A.
LandOfFree
Method and composition for minimizing rust formation and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and composition for minimizing rust formation and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and composition for minimizing rust formation and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3245386