Compositions – Preservative agents – Anti-corrosion
Reexamination Certificate
2001-10-25
2004-12-21
Toomer, Cephia D. (Department: 1714)
Compositions
Preservative agents
Anti-corrosion
C252S389610, C252S396000, C252S397000, C252S399000, C252S400100, C252S400610, C252S407000
Reexamination Certificate
active
06833087
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
NONE
BACKGROUND OF THE INVENTION
Corrosion is a serious problem that affects and undermines the quality of everyday social life and the endurance of industrial products. Extensive efforts have been undertaken to design and fabricate products such as steam generators, heat exchangers, bridges, oil drilling platforms and motor vehicles that can resist the destructive effects of corrosion. For many traditional products, however, corrosion continues to be a serious destructive problem. In addition to traditional products, new developments in energy sources, advances in material sciences, microprocessing technology and miniaturization of new devices to the micron scale all reassert the demands for effective anti-corrosion technologies that avert device failures.
Corrosion is typically understood as an electrochemical reaction that involves loss of electrons from metals, a reaction more generally described as oxidation. The definition of oxidation in electrochemical terms is independent of whether or not oxygen is present when the process of electron loss from a metal occurs. The loss of one or more electrons from a metal requires the acquisition of the electron(s) by another agent. Thus, the metal that serves as an electron donor in this case is termed a reducing agent, while the electron acceptor serves as an oxidizing agent. One practical example illustrating such an electrochemical event typically involves metallic iron. Electrons lost from an iron atom (reducing agent) can be acquired by oxygen (oxidizing agent) to produce a new combined iron and oxygen derivative identified as iron oxide, or rust, which is an inorganic, low density (flaky) product commonly associated with metal corrosion. Although oxygen is used as a model of iron oxidation in this case, the same oxidizing agent effect could be demonstrated by sulfur and the resulting product could have been iron sulfide instead of iron oxide.
Apart from rust involving metal corrosion, the formation of scale presents another illustrative model tied to principles of oxidation. Scale is defined as a thin coating, layer or encrustation of material that is rich in complex oxides of sulfur, magnesium and/or calcium. These and other insoluble materials are typically developed and observed as mineral deposits on the inside diameters of pipes, chambers or containment vessels when water plus its dissolved constituents. or solutes, are heated in the process of making hot water.
The transfer of electrons between oxidizing agents and reducing agents cannot occur without the presence of an electrically conductive medium. Water typically serves as the electrically conductive universal solvent medium that supports metal oxidation, consequential corrosion and rusting as well as scale formation in the foregoing models.
Efforts to halt water-mediated metal oxidation and corrosion typically rely on superficial passivation of the metal with toxic materials such as chromic acid, sacrificial coatings (e.g., zinc or galvanized coatings), electroplated metals, polymeric coatings or related efforts that produce a protective barrier between the reactive metal surface and water. Implementation of such strategies usually produces an inflexible anti-corrosion barrier on metal surfaces, and once applied, its removal may be difficult or impossible. For those situations where micro-mechanical or circuit-based devices display corrosion tendencies, aggressive industrial anti-corrosion methods may be totally unsuitable and physically damaging. Thus, there is a significant need for new, simple-to-execute anti-corrosion barrier possibilities.
BRIEF SUMMARY OF THE INVENTION
The invention described herein is directed to preventing the oxidative corrosion of metal surfaces. The invention relies on the exposure of a metal surface to an anti-corrosion agent characterized as 2,4-trans, trans-hexadienoic acid (2,4-HDA), its alkali salt identified as potassium sorbate (KHDA), or other derivatives that conserve or embody the 2,4-trans, trans-hexadiene-type moiety present in their molecular structures, as an active anti-corrosion agent (ACA) in combination with a material, as hereinafter defined, capable of forming a moisture retentive barrier on the surface of the metal. In certain applications, the anti-corrosion agent alone is sufficient to achieve the desired anti-corrosive effect.
In preferred embodiments, the material capable of forming a moisture retentive barrier film over a surface of the metal is selected from the group consisting of a polar liquid, a non-polar liquid, a viscous material, an organic liquid, a polymeric material and a petroleum-based substance; and the composition further comprises any one of a polar liquid, a non-polar liquid, a surfactant, an antioxidant, an organic liquid, a polymeric material, a petroleum-based substance, a buffering material, or graphite or particulate carbon in a suspension. The anti-corrosion agent in the composition of the invention may be packaged for delayed release, e.g., by encapsulation. Preferably, the anti-corrosion agent is present in the composition at a concentration of between 0.2 and 58 percent by weight. Most preferably, the composition is first prepared in concentrated form and then diluted prior to use. The anti-corrosion agent spontaneously adsorbs or chelates to metal surfaces from water solutions so as to produce an organometallic barrier coating. In addition, the residual anti-corrosion agent, after having had an opportunity to adsorb to the metal surface, remains as an aqueous solution where it effectively alters the normal dielectric properties of available water that could contribute to the water's ordinary corrosion properties.
The compositions and methods of the invention provide a practical, non-toxic way of ensuring anti-corrosion protection for metals, or devices containing exposed metals, stored or operated in water or in the presence of water vapor. Exemplary, non-inclusive uses include employing the composition as a lubricant for the surface of a metal or as a pump oil or brake fluid; using the composition as an undercoating for painting, electro-plating or electro-polishing procedures; and providing a protective coating for any metal or metal-containing machine or device, from automotive assembly plant metal press machines to electronic circuit boards.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to the use of 2,4-trans, trans-hexadienoic acid (HDA or sorbic acid), KHDA (a potassium salt of sorbic acid), or their derivatives that structurally conserve the characteristic 2,4-trans, trans-diene moiety as an active anti-corrosion agent (ACA), in combination with a material, as hereinafter defined, chosen, e.g., for its low dielectric constant (D-value) and/or for its lubrication properties and capable of forming a moisture retentive barrier to provide anti-corrosion protection for metal surfaces. In certain applications, e.g., if the protected metal object remains immersed in a KHDA solution, the anti-corrosion agent alone is sufficient to achieve the desired anti-corrosive effect. However, most preferably, the anti-corrosion agent is used in combination with a material capable of forming a moisture retentive barrier on the surface of the article to be protected. This composition not only achieves superior results during immersion but also permits the protected article to be dried and to still retain long term anti-corrosion protection.
The invention disclosed here provides a practical, non-toxic method that ensures anti-corrosion protection for metals, or devices containing exposed metals, stored or operated in water or in the presence of water vapor. Preparations of 2,4-trans, trans-hexadienoic acid (HDA) present as its potassium salt (KHDA), hereinafter designated as the active anti-corrosion agent (ACA), will inhibit the corrosion of metals for indefinite periods of time in a variety of venues as hereinafter described, e.g., while the metals remain immersed in a KHDA-solution, following coating w
Beck Robert A.
Manos Paul D.
Toomer Cephia D.
Weingarten Schurgin, Gagnebin & Lebovici LLP
Wonders of Water, LLC
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