Compositions: coating or plastic – Coating or plastic compositions – Corrosion inhibiting coating composition
Patent
1997-04-14
1998-05-12
Green, Anthony
Compositions: coating or plastic
Coating or plastic compositions
Corrosion inhibiting coating composition
106 1415, 106 1431, 106 1437, 106285, 252394, 208 14, C09D 508, C23F 1114, C23F 1110
Patent
active
057499470
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to oil-based corrosion inhibitors for metallic surfaces, more particularly iron-based surfaces, which are preferably used in the form of oil-in-water emulsions. The invention provides alkylamine-free corrosion inhibitors which are distinguished by good oil solubility and which, at the same time, emulsify the oil phase in water.
RELATED ART
Rust-control emulsions are used for temporarily protecting metals against atmospheric corrosion-inducing influences. They essentially contain nonpolar or polar oils, emulsifiers, corrosion inhibitors and water. Their effect is based on the adsorption of inhibitor molecules to the metal surface and on the formation of a protective film of emulsion components which acts as a diffusion barrier against atmospheric oxygen and water. In "Oberflache-Surface" 1989, No. 4, pages 8-12, T. Forster et al. report on modes of action of and tests for rust-control emulsions.
Conventional corrosion-control formulations contain such components as, for example, petroleum sulfonates, salts of alkyl sulfonamidocarboxylic acids and amine or other salts of partial esters of alkyl or alkenyl succinic acid. For example, EP-A-566 956 describes corrosion-control formulations based on an amine-free salt of a semiester of an alkyl or alkenyl succinic acid.
Sulfur-containing corrosion inhibitors such as, for example, alkyl aryl sulfonic acids, petroleum sulfonates or salts of alkyl sulfonamidocarboxylic acids have the disadvantage that they can readily be degraded by micro-organisms, such as sulfur-reducing bacteria, which can lead to serious odor emission problems. Alkylamine-containing corrosion-control formulations, particularly those containing secondary amines, are attracting increasing criticism on account of the risk of the formation of health-endangering nitrosamines. Accordingly, there is a need for sulfur-free and alkylamine-free corrosion inhibitors. Stearic acid derivatives have been described as corrosion inhibitors for purely oil-based systems, for example lubricating oils and lubricating greases (DE-C-32 03 491). Examples of the stearic acid derivatives in question are 9,10-dihydroxystearic acid and alkali metal salts and oligomeric condensates thereof, 9,10-epoxystearic acid, alkali metal salts and oligomeric "Estolids" thereof and, finally, mixed oligomers of 9,10-epoxy and 9,10-dihydroxystearic acid.
Corrosion-control formulations intended to be used in the form of oil-in-water emulsions may be marketed as purely oil-based, i.e. water-free, concentrates so that they may be brought into the ready-to-use emulsion form by addition of water at the point of use. These oil concentrates contain the corrosion inhibitors which, accordingly, have to be oil-soluble. To ensure that the oil concentrates are able spontaneously to form an emulsion on dilution with water, i.e. are self-emulsifying, it has hitherto been necessary for the concentrates to contain emulsifiers in addition to the corrosion inhibitors. Possible interactions between the surface-active emulsifiers and the polar corrosion inhibitors often have an adverse effect on emulsifying behavior and on the corrosion-control effect and, as a result, complicate formulation of the product. This problem could be eliminated if oil-soluble corrosion inhibitors with emulsifying properties could be made available.
Guanidinium salts of unsaturated fatty acids and processes for their production are known from U.S. Pat. No. 2,978,415. These guanidine soaps of unsaturated fatty acids are used as so-called boosters in the cleaning of textiles with solvents, i.e. in dry cleaning. A corrosion-inhibiting effect and emulsifying power are of no significance for this particular application which takes place in purely organic phase. Accordingly, the US patent in question does not contain any data on a corresponding effect of the guanidine soaps of unsaturated fatty acids.
BRIEF DESCRIPTION OF THE INVENTION
The problem addressed by the present invention was to provide new sulfur-free and alkylamine-free
REFERENCES:
patent: 2978415 (1961-04-01), Chamberlain
patent: 5286397 (1994-02-01), Schmid et al.
patent: 5318954 (1994-06-01), Mueller et al.
patent: 5403822 (1995-04-01), Mueller et al.
Chemical Abstract No. 115:118225 which is an abstract of the Hori et al article entitled "Corrosion Prevention By Guanidine Salts" (1991).
Oberflache -- Surface, 1989, 4, pp. 8-12.
Geke Juergen
Speckmann Horst-Dieter
Stedry Bernd
Westfechtel Alfred
Green Anthony
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Ortiz Daniel S.
Szoke Ernest G.
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