Metal treatment – Process of modifying or maintaining internal physical... – Processes of coating utilizing a reactive composition which...
Reexamination Certificate
1999-12-22
2001-02-27
Sheehan, John (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Processes of coating utilizing a reactive composition which...
C148S243000, C148S279000, C148S280000
Reexamination Certificate
active
06193814
ABSTRACT:
BACKGROUND OF THE INVENTION
1) Field of the Invention
The present invention relates to the preparation of activated metal, particularly tinplate, and the activated metal itself. The activated metal is highly reactive with oxygen and can be used as a pyrophoric decoy material or as a catalyst.
2) Description of the Prior Art
The closest prior art known to the applicant is commonly owned U.S. Pat. No. 4,895,609, the entire disclosure of which is expressly incorporated by reference into the present patent application. This U.S. Patent issued on Jan. 23, 1990, to the inventor of the present invention, and generally describes the preparation of activated metals by several techniques. One of those techniques is the activation of metal foil where the metal can be steel. However, this U.S. Patent does not expressly teach that the metal foil can be tin-plated steel, commonly known as “tinplate”.
SUMMARY OF THE INVENTION
The present invention relates to the preparation of activated metal, particularly activated “tinplate”, and the activated metal itself. The activated metal is highly reactive with oxygen and can be used as a pyrophoric decoy material or as a catalyst.
In the method of the present invention, tin-plated steel, sometimes referred to herein as “tinplate”, is pyrophorically activated by depositing aluminum on the surface of the tinplate, either alone or as a mixture with other metal powders (e.g., iron powder), to form a coating on the tinplate and then heating the coated tinplate to cause the aluminum to react with iron and diffuse into the tinplate to form an aluminide coating on the tinplate followed by the removal of at least a portion of the aluminum that is contained in the coating. The aluminum can be applied to the tinplate as a powder dispersion, foil laminate or electrolytic deposit of aluminum. Upon heating the aluminum coated tinplate to temperatures of about 700° to 930° C., the lower melting tin (mp about 232° C.) on the surface of the steel enables excellent wetting and uniform diffusion of the higher melting aluminum (mp about 660° C.) into the tin-plated steel surface to form the aluminide coating.
Upon exposure to oxygen, the activated tinplate provides self-igniting pyrophoric elements which are very suitable for decoying heat seeking missiles.
The superior lubricity, corrosion and oxidation resistance of tinplate as well as the presence of a small amount of tin in the aluminide coating enables a more effective and more economically produced pyrophoric material than uncoated steel. Aluminide coated tinplate is also desirable in that it demonstrates a unique combination of high temperature oxidation resistance and corrosion resistance in comparison to either uncoated tinplate or aluminide coated steel (i.e., uncoated steel that has been coated with an aluminide).
DEFINITIONS
A “mil” is a unit of measurement equal to one thousandth of an inch.
The term “Sn—Fe intermetallic” or “tin-iron intermetallic” as used herein is intended to encompass any combination of tin and iron where the tin molecules are bound, either chemically or physically, to iron molecules.
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Alloy Surfaces Company
Connolly Bove & Lodge & Hutz LLP
Oltmans Andrew L.
Sheehan John
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