# US 6,297,208 B1 · Rust stain removal formula > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,297,208 B1 - Document ID: US6297208B1 - Status: Granted - Kind: B1 - Application number: 09/416,170 - Filed: 1999-10-11 - Granted: 2001-10-02 - Earliest claimed: 1999-10-11 - Assignees: Iron Out, Inc. - Inventors: Robert F. Crist - Web page: https://patentgrep.com/patent/US6297208B1 ## CPC - C03C 15/00: Surface treatment of glass, not in the form of fibres or filaments, by etching (etching or surface-brightening compositions, in general C09K13/00) - C03C 23/0075: {Cleaning of glass (specially adapted to plate glass B08B11/00)} - C04B 41/5315: {Cleaning compositions, e.g. for removing hardened cement from ceramic tiles} - C11D 3/042: {Acids} - C11D 3/046: {Salts} - C11D 3/2082: {Polycarboxylic acids-salts thereof} - C11D 2111/16: Metals - C03C: CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS - C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE - C11D: DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL ## Abstract A rust stain removal formula using fluoboric acid as the active ingredient and a method of making same. The inventive formula does not etch glazed, glass or enamel surfaces to which the formula is applied. Further, the inventive formula reduces other problems caused by the hydrofluoric acid used as the active ingredient in prior art rust stain removal formulas. The formula is initially formed by adding ammonium bifluoride, and then boric acid to a solution of heated water. Oxalic acid is then added. The ammonium bifluoride reacts with the boric acid to form fluoboric acid. Optional ingredients such as a thickener and perfume may also be included in the inventive rust stain removal formula. ## Claims ### Claim 1 A composition for removal of rust stains, said composition comprising: about 1 to 5 percent by weight of ammonium bifluoride; about 1 to 5 percent by weight of boric acid; about 1 to 5 percent by weight of oxalic acid; and fluoboric acid, said fluoboric acid formed by reaction of said ammonium bifluoride with said boric acid; the remainder of said composition being substantially water and, optionally, one or both of a surfactant and a thickening agent. ### Claim 2 (depends on 1) The composition of claim 1, further comprising about 1 to 5 percent by weight of citric acid. ### Claim 3 (depends on 1) The composition of claim 1, wherein said ammonium bifluoride comprises about 2.5 to 3.5 percent by weight, said boric acid comprises about 2 to 3 percent by weight and said oxalic acid comprises about 3 to 4 percent by weight. ### Claim 4 (depends on 3) The composition of claim 3, further comprising about 3 percent by weight of citric acid. ### Claim 5 (depends on 4) The composition of claim 4, wherein said surfactant comprises about 0.1 to 1.0 percent by weight and said thickening agent comprises about 0.1 to 0.5 percent by weight. ### Claim 6 A composition for removal of rust stains, said composition consisting essentially of: about 1 to 5 percent by weight of ammonium bifluoride; about 1 to 5 percent by weight of boric acid; about 1 to 5 percent by weight of oxalic acid; and the remainder of said composition being substantially water and, optionally, one or both of a surfactant and a thickening agent; whereby said ammonium bifluoride and said boric acid react in said composition to form fluoboric acid. ### Claim 7 A method of treating rust stains comprising the following steps: (a) combining a predetermined amount of ammonium bifluoride with water in a container and dissolving the ammonium bifluoride; (b) after step (a), adding a predetermined amount of boric acid to the container; (c) mixing the contents of the container, whereby the boric acid and the ammonium bifluoride react to form a formula including fluoboric acid; and (d) applying the formula to an article having a rust stain thereon, said formula removing at least a portion of the rust stain. ### Claim 8 (depends on 7) The method of claim 7, wherein the predetermined amount of ammonium bifluoride is about 1 to 5 percent by weight of the formula and the predetermined amount of boric acid is about 1 to 5 percent by weight of the formula. ### Claim 9 (depends on 8) The method of claim 8, wherein the predetermined amount of ammonium bifluoride is about 2.5 to 3.5 percent by weight of the formula and the predetermined amount of boric acid is about 2 to 3 percent by weight of the formula. ### Claim 10 (depends on 9) The method of claim 9, further comprising adding predetermined amounts of oxalic acid and optionally, citric acid, after step (b). ### Claim 11 (depends on 7) The method of claim 7, further comprising adding predetermined amounts of oxalic acid and optionally, citric acid, after step (b). ### Claim 12 (depends on 7) The method of claim 7, further comprising adding an effective amount of thickener. ### Claim 13 (depends on 12) The method of claim 12, further comprising adding predetermined amounts of detergent and perfume after step (b). ### Claim 14 (depends on 8) The method of claim 8, further comprising heating and maintaining the container contents while mixing. ### Claim 15 (depends on 14) The method of claim 14, wherein the contents are heated and maintained at about 40 to 50 degrees Celsius. ### Claim 16 (depends on 7) The method of claim 7, further comprising adding water to bring the formula to a desired final weight. ### Claim 17 A method of forming a rust stain removal formula comprising the following steps: (a) adding a thickener to a container having water therein; (b) adding a predetermined amount of ammonium bifluoride to the container; (c) after step (b), adding a predetermined amount of boric acid to the container, the boric acid reacting with the ammonium bifluoride to form fluoboric acid; and (d) after step (c), adding predetermined amounts of oxalic acid and optionally, citric acid. ### Claim 18 (depends on 17) The method of claim 17, wherein the predetermined amount of ammonium bifluoride comprises about 1 to 5 percent by weight of the formula. ### Claim 19 (depends on 18) The method of claim 18, wherein the predetermined amount of boric acid comprises about 1 to 5 percent by weight of the formula. ### Claim 20 (depends on 19) The method of claim 19, further comprising adding effective amounts of detergent and perfume. ### Claim 21 (depends on 19) The method of claim 19, wherein the predetermined amount of ammonium bifluoride is about 2.5 to 3.5 percent by weight of the formula and the predetermined amount of boric acid is about 2 to 3 percent by weight of the formula.