Corrosion inhibited runway deicing fluid

Details Corrosion inhibited runway deicing fluid Corrosion inhibited runway deicing fluid

2001-07-13

2003-04-01

Green, Anthony (Department: 1755)

Compositions

Frost-preventing, ice-thawing, thermostatic, thermophoric,...

C106S014130, C106S014140, C106S014410, C106S014420, C106S014440, C106S013000, C252S388000, C252S394000, C252S396000

Reexamination Certificate

active

06540934

ABSTRACT:

The present invention relates to a deicing fluid. More particularly the present invention relates to a runway deicing fluid. Most particularly the present invention relates to a novel corrosion inhibited runway deicing fluid.
BACKGROUND OF THE INVENTION
The prior art for the products and manufacture of compositions which are useful for deicing and protection from ice formation as well as for prevention of corrosion on various metallic and metal containing surfaces has become quite well developed in the past. Such protection is necessary in many areas, for example, in metal containing equipment exposed to water or steam or water containing mixtures and emulsions. More particularly, the protection is of top priority importance in connection with deicing of areas where mechanical equipment is employed, such as runways and in the care and safety of aircraft surfaces. Exemplary of some of the prior art teachings are as follows.
Ayres et al., U.S. Pat. No. 3,711,409 describes ice-preventative and deicing compositions, which are viscous, stable, oil-in-water emulsions and which consist of a mineral oil as a disperse phase, an emulsifying agent which is a cationic or non-ionic surface-active agent, and an aqueous solution as a continuous phase containing a water absorbing, viscosity maintaining compound and a freezing point depressant.
Darden et al., U.S. Pat. No. 4,647,392 describes corrosion inhibitor compositions for use in aqueous systems and include corrosion inhibitor anti-freeze compositions for use in water-cooled internal combustion engines. The ingredients of the composition are alleged to exercise a synergistic protection effect.
Himmrich et al., U.S. Pat. No. 5,387,359 describes a deicing agent of an alkaline earth metal potassium acetate consisting of calcium, magnesium, potassium, acetate and water. Chan et al., U.S. Pat. No. 5,435,930 describes liquid deicer/anti-icer compositions for use on the exterior surfaces of aircraft which comprises aqueous mixtures of an alkali metal acetate, phosphate, a silicate, an aromatic triazole, a water soluble surfactant and a water soluble dye.
Caupin et al., U.S. Pat. No. 5,507,861 describes corrosion inhibiting compositions which comprise at least one monocarboxylic acid from the group heptanoic acid, nonanoic acid and undecanoic acid and alkali metal and alkaline earth metal salts thereof and a perborate oxidizing agent.
Sapienza, U.S. Pat. No. 5,876,621 describes deicing compositions which are environmentally benign prepared from recovered industrial waste streams comprising hydroxycarbolic acids by alcoholizing at least part of the hydroxycarboxylic acids in the recovered waste stream with an alkyl alcohol, thus converting that part of the hydroxycarboxylic acids to water soluble hydroxycarboxylic acid esters. Sapienza, U.S. Pat. No. 5,980,774 describes a method for making deicing compositions from a variety of organic compounds including but not limited to hydrocarbyl aldosides.
The Homepage publication designed and maintained by Adam Zimmer Copyright 1996 (3 Pages) (Vigoro—Aug. 30, 1998) has a description and listing of “Common Ice Melter Ingredients.” The listing is very extensive. It states that the ice melter ingredients can be categorized as pure or blended. The list includes ten specific ingredients and also includes “corrosion inhibitors” and simple blends in general terms.
From a more industrial perspective, deicing fluids for airport runways traditionally have been formulated from ethylene glycol, propylene glycol, urea and mixtures thereof, but these materials have come under scrutiny due to the Clean Water Act. Ethylene glycol-based fluids are toxic and require expensive treatment and disposal. Propylene glycol, although non-toxic, biodegrades too rapidly imposing excess oxygen demand on the environment or the waste treatment facility. As a consequence of these factors, new and more environmentally benign deicing/anti-icing compounds based on potassium acetate (KAc) have begun to replace these traditional fluids in recent years. Potassium acetate is considered to be more environmentally friendly in that it is nontoxic and exerts a low oxygen demand on the environment. Low-molecular weight monocarboxylic acids were recommended as antifreezing compounds, i.e., the alkali salts of formic, acetic, propionic and butyric acids as per U.S. Pat. No. 2,233,185. However, a number of the larger airports in the United States have resisted the conversion to KAc fluids due to concerns over materials compatibility issues with these fluids. Compared to the glycols, the KAc fluids tend to be more corrosive toward certain metals, particularly galvanized steel, used in the construction of in-ground runway light fixtures. Unlike the glycols, potassium acetate is also an electrolyte, and KAc fluids exhibit high conductivity. Because metal corrosion is an electrochemical process, fluids of high conductivity may facilitate corrosion more than low conductivity fluids, and they can have additional detrimental effects on electrical connections within the light fixtures themselves.
Thus, it would represent a notable advance in the state of the art if one could develop a deicing fluid based on potassium acetate which solved the problems of the prior art potassium acetate compositions.
SUMMARY OF THE INVENTION
In solving the problems of the prior art, the present invention embraces and includes novel and highly effective combinations of additives for use as a part of and in conjunction with known and currently used commercial deicing fluids containing monocarboxylic acid salts such as, and particularly potassium acetate and related salts. The novel liquid products of the resulting combinations have unexpected improved characteristics in use. They are particularly useful, as they have combined deicing as well as other desirable properties.
For instance, the advantages of the resulting modified potassium acetate formulations having present the additive fluid of the invention, include reduced conductivity, and improved corrosion protection for metals, especially for galvanized steels such as those used in construction of ground runway lighting fixtures on or near airport runways. These surfaces are especially susceptible to corrosion and damage from atmospheric attack.
In particular the present invention provides a corrosion and conductivity inhibitor used in deicing and/or anti-icing composition comprising aqueous monocarboxylic acid salts, said inhibitor comprising: (a) from about 1 to about 25 weight percent of an organic deicing agent composition selected from the group consisting of glycols, hydrocarbyl aldosides, glycerol, sorbitol and mixtures thereof, and (b) from about 0.1 to about 30 weight percent of (i) a C
5
-C
16
aliphatic monobasic acid or the alkali metal, ammonium or amine salt of said monobasic acid, or (ii) a C
5
-C
16
hydrocarbyl dibasic acid or the alkali metal, ammonium or amine salt of said acid, or (iii) a mixture of (i) and (ii); and, optionally, (c) from about 0.1 to about 0.5 weight percent of a hydrocarbonyl triazole.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a novel corrosion and conductivity inhibitor used in deicing and/or anti-icing composition comprising aqueous monocarboxylic acid salts, said inhibitor comprising: (a) from about 1 to about 25 weight percent of an organic deicing agent composition selected from the group consisting of glycols, hydrocarbyl aldosides, glycerol, sorbitol and mixtures thereof and (b) from about 0.1 to about 30 weight percent of (i) a C
5
-C
16
aliphatic monobasic acid or the alkali metal, ammonium or amine salt of said monobasic acid, or (ii) a C
5
-C
16
hydrocarbyl dibasic acid or the alkali metal, ammonium or amine salt of said acid, or (iii) a mixture of (i) and (ii); and, optionally, (c) from about 0.1 to about 0.5 weight percent of a hydrocarbonyl triazole.
The aqueous solutions for which the novel corrosion and conductivity inhibitor of the present invention provides corrosion and conductivity inhibition contain carboxylic acids. The carboxylic acid

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