# US 8,771,790 B2 · Method of reducing magnetite formation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,771,790 B2 - Document ID: US8771790B2 - Status: Granted - Kind: B2 - Application number: 13/144,422 - Filed: 2010-01-12 - Published: 2011-12-01 - Granted: 2014-07-08 - Earliest claimed: 2009-01-13 - Applicants: Michael John de Vink - Inventors: Michael John de Vink - Web page: https://patentgrep.com/patent/US8771790B2 ## CPC - F28F 19/06: of metal - B05D 7/22: to internal surfaces, e.g. of tubes - C23C 18/16: by reduction or substitution, e.g. electroless plating (C23C18/54 takes precedence) - C23C 18/1616: {interior or inner surface} - C23C 18/18: Pretreatment of the material to be coated - C23C 18/1872: {by chemical pretreatment} - C23C 18/1882: {Use of organic or inorganic compounds other than metals, e.g. activation, sensitisation with polymers} - C23C 18/31: Coating with metals - C23C 18/32: Coating with nickel, cobalt or mixtures thereof with phosphorus or boron (C23C18/50 takes precedence) - C23C 18/34: using reducing agents - C23C 18/42: Coating with noble metals - C23C 18/44: using reducing agents - C23C 18/54: Contact plating, i.e. electroless electrochemical plating - F28F 19/02: by using coatings, e.g. vitreous or enamel coatings - F28F 21/08: of metal - F28G 9/00: Cleaning by flushing or washing, e.g. with chemical solvents (appliances using jets of fluid for removing debris F28G1/16, F28G3/16) - F28F: DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION (water and air traps, air venting F16) - B05D: PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL (conveying articles or workpieces through baths of liquid B65G, e.g. B65G49/02) - C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04) - F28G: CLEANING OF INTERNAL OR EXTERNAL SURFACES OF HEAT-EXCHANGE OR HEAT-TRANSFER CONDUITS, e.g. WATER TUBES OR BOILERS (cleaning pipes or tubes in general B08B9/02; devices or arrangements for removing water, minerals, or sludge from boilers while the boiler is in operation, or which remain in position while the boiler is in operation, or are specifically adapted to boilers without any other utility F22B37/48; removal or treatment of combustion products or combustion residues F23J; removing ice from heat-exchange apparatus F28F17/00) ## Abstract A method of reducing magnetite formation in the bore of a pipe including the steps of selecting a pipe with a pre-existing oxide layer on its inner bore surface and coating the pre-existing oxide layer with an oxidation resistant metal to thereby reduce magnetite formation in the bore of the pipe. ## Claims ### Claim 1 A method of substantially preventing magnetite formation in the bore of a pipe including the steps of: (a) selecting a pipe with a pre-existing oxide layer on its inner bore surface; and (b) coating the pre-existing oxide layer with an oxidation resistant metal, to thereby substantially prevent formation of exfoliable magnetite layers in the bore of the pipe. ### Claim 2 (depends on 1) The method of claim 1 wherein the pipe is manufactured from an austenitic and/or ferritic alloy. ### Claim 3 (depends on 1, 2) The method of claim 1 or claim 2 wherein the pipe is a superheater and/or reheater pipe. ### Claim 4 (depends on 3) The method of claim 3 wherein the coating of the superheater and/or reheater pipe is carried out in situ. ### Claim 5 (depends on 3) The method of claim 3 wherein the superheater and/or reheater pipe has been in use for a sufficient period of time to develop a spinel oxide layer on its inner bore surface. ### Claim 6 (depends on 5) The method of claim 5 wherein the spinel oxide layer comprises iron and chromium. ### Claim 7 (depends on 1) The method of claim 1 wherein the pre-existing oxide layer is a spinel oxide layer. ### Claim 8 (depends on 7) The method of claim 7 wherein the spinel oxide layer is an Fe—Cr spinel oxide layer. ### Claim 9 (depends on 8) The method of claim 8 wherein the Fe—Cr spinel oxide layer comprises FeCr2O4 and/or Fe2CrO4. ### Claim 10 (depends on 1) The method of claim 1 wherein the oxidation resistant metal is oxidation and corrosion resistant at elevated temperatures. ### Claim 11 (depends on 1) The method of claim 1 wherein the oxidation resistant metal is selected from the group consisting of nickel, palladium, cobalt, platinum, ruthenium, gold, rhodium, zinc, cadmium and lead. ### Claim 12 (depends on 11) The method of claim 11 wherein the oxidation resistant metal is nickel, palladium, cobalt or an alloy thereof. ### Claim 13 (depends on 12) The method of claim 12 wherein the oxidation resistant metal is nickel or a nickel alloy. ### Claim 14 (depends on 1) The method of claim 1 wherein the coating with the oxidation resistant metal is carried out using a solution of the oxidation resistant metal. ### Claim 15 (depends on 1) The method of claim 1 wherein the coating with the oxidation resistant metal is carried out by electroless plating. ### Claim 16 (depends on 1) The method of claim 1 wherein the thickness of the oxidation resistant metal coating is between 5 micrometers to 200 micrometers. ### Claim 17 (depends on 16) The method of claim 16 wherein the coating is between 10 micrometers to 100 micrometers thick. ### Claim 18 (depends on 17) The method of claim 17 wherein the coating is between 40 micrometers to 60 micrometers thick. ### Claim 19 (depends on 18) The method of claim 18 wherein the coating is about 50 micrometers thick. ### Claim 20 (depends on 1) The method of claim 1 further comprising the step of treating the bore of the pipe to remove existing magnetite and expose an underlying spinel oxide layer substantially formed from a compound comprising iron and chromium. ### Claim 21 (depends on 20) The method of claim 20 wherein the treatment step is carried out using an EDTA solution and/or a combination of hydroxyacetic and formic acids.