Rust removal process

Details Rust removal process Rust removal process

1983-09-27

1985-06-04

Caroff, Marc L.

Cleaning and liquid contact with solids

Processes

For metallic, siliceous, or calcareous basework, including...

134 4, 134 41, 25217424, C23G 102

Patent

active

045212538

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention relates to removal of rust from metal surfaces.


BACKGROUND OF THE INVENTION

Adequate removal of rust from metal surfaces in preparation for the application of paint or other protective coatings is a long standing problem. Mechanical cleaning techniques such as sand blasting, wire brush scrubbing, etc. are messy and time consuming. Previous attempts to chemically clean rusty surfaces have not been entirely satisfactory.
One particularly difficult type of metal surfaces to clean is the irregular surfaces found on ships, i.e., high-temperature valves, pipes, and the like. Frequently, the only cleaning method feasible is the lengthy and tiresome process of wire brushing the surface to be cleaned and then subsequently applying a solution of a wetting agent mixed with a cleaning agent to the metal surface. Such a technique suffers from the difficulty of keeping the cleaning fluid in contact with the surface to be cleaned, such as overhead objects, as well as the subsequent disposal of liquid wastes. Additionally, these solutions are often toxic, non-economical, and require large volumes of water for washing purposes.
Previous attempts to chemically remove rust have involved the use of chemicals such as inhibited hydrochloric acid, ethylenediaminetetraacetic acid (EDTA), EDTA/citric acid, etc. More recently it has been suggested that a paste of water-soluble polymer such as polyvinylpyrrolidone (PVP) and a chelating agent such as EDTA be coated onto a rusty metal surface to be cleaned. After application the paste is said to harden into a thick crust which encapsulates the rust and may be peeled from the cleaned surface and disposed of as solid waste. This process is more fully described in U.S. Pat. No. 4,325,744.


SUMMARY OF THE INVENTION

The invention is a process for removing rust from a rusty metal surface which comprises: composition consisting essentially of an aqueous solution or dispersion of water soluble or water dispersible copolymer of maleic acid and unsaturated monomer; and incorporated into said layer and the layer containing the rust detaches itself from the surface.
Suitable copolymers for use in practicing the invention include but are not limited to copolymers of maleic acid with one or more monomers of the formulas ##STR1## where R is H, CH.sub.3 or C.sub.2 H.sub.5 ; ##STR2##


DETAILED DESCRIPTION OF THE INVENTION

Water soluble or water dispersible copolymers suitable for use in the process of the invention are copolymers of maleic acid with one or more unsaturated monomers. Such maleic acid copolymers may be formed by hydrolysis of precursor copolymer of maleic anhydride and one or more unsaturated monomers capable of forming water soluble or water dispersible copolymers of maleic acid. The precursor copolymer may be obtained by any of the conventional methods known for making such copolymers as exemplified for instance in U.S. Pat. Nos. 3,553,183, 3,794,622 and 3,933,763 the disclosures of which are incorporated herein by reference.
Suiable monomers for copolymerization with maleic anhydride precursor to form copolymers for use in the invention include for instance:


______________________________________ Formula Name ______________________________________ 1. CH.sub.2CH.sub.2 ethylene 2. CH.sub.2CHCH.sub.3 propylene 3. CH.sub.2CHCHCH.sub.2 butadiene 4. CH.sub.2CHC.sub.2 H.sub.5 butylene 5. CH.sub.2CHCOOCH.sub.3 methylacrylate 6. CH.sub.2CHCOOC.sub.2 H.sub.5 ethylacrylate ##STR3## dimethylamino- ethylacrylate 8. CH.sub.2CHCN acrylonitrile 9. CH.sub.2CHOCOCH.sub.3 vinylacetate 10. CH.sub.2CHOCOC.sub.2 H.sub.5 vinylpropionate 11. CH.sub.2CHCHO acrolein 12. CH.sub.2CHOCH.sub.3 vinylmethylether 13. CH.sub.2CHOC.sub.2 H.sub.5 vinylethylether 14. ##STR4## dimethylamino- ethylvinylether 15. CH.sub.2CHCONH.sub.2 acrylamide 16. CH.sub.2CHSCH.sub.3 vinylmethylthioether 17. CH.sub.2CHSC.sub.2 H.sub.5 vinylethylthioether 18. CH.sub.2CHNCO vinylisocyanate 19. CH.

REFERENCES:
patent: 3085916 (1963-04-01), Zimmie et al.
patent: 3277008 (1966-10-01), Heit
patent: 3696498 (1972-10-01), Leontaritis et al.
patent: 3793222 (1974-02-01), Haschke et al.
patent: 3922394 (1975-11-01), Lozier
patent: 4200671 (1980-04-01), Krajewski et al.
patent: 4325744 (1982-04-01), Panayappan et al.
patent: 4351673 (1982-09-01), Lawson
patent: 4424079 (1984-01-01), Barabas

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