# US 5,704,823 A · Method for removing at least one coating from metal scrap parts > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,704,823 A - Document ID: US5704823A - Status: Granted - Kind: A - Application number: 08/603,216 - Filed: 1996-02-20 - Granted: 1998-01-06 - Earliest claimed: 1995-02-17 - Assignees: Hoogovens Staal BV - Inventors: Adrianus Jacobus Wittebrood - Web page: https://patentgrep.com/patent/US5704823A ## CPC - C22B 7/005: {Separation by a physical processing technique only, e.g. by mechanical breaking} - B24B 31/00: Machines or devices designed for polishing or abrading surfaces on work by means of tumbling apparatus or other apparatus in which the work and/or the abrasive material is loose; Accessories therefor (abrasive blasting machines B24C3/26) - B24B 31/14: Abrading-bodies specially designed for tumbling apparatus, e.g. abrading-balls - C22B 1/005: {Preliminary treatment of scrap (C22B1/02 - C22B1/26 take precedence)} - C22B 19/30: from metallic residues or scraps - C23F 1/40: for etching other metallic material - C23F 1/44: Compositions for etching metallic material from a metallic material substrate of different composition - Y02P 10/20: Recycling - C22B: PRODUCTION AND REFINING OF METALS (electrolytic C25); PRETREATMENT OF RAW MATERIALS - B24B: MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING (grinding of gear teeth B23F, of screw-threads B23G1/36; by electro-erosion B23H; abrasive or related blasting B24C; tools for grinding, buffing or sharpening B24D; polishing compositions C09G1/00; abrasives C09K3/14; electrolytic etching or polishing C25F3/00; grinding arrangements for use on assembled railway tracks E01B31/17); DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS - C23F: NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE (working metal by laser beams B23K26/00; desurfacing by applying flames B23K7/00; working of metal by electro-erosion B23H; producing decorative effects by removing surface material, e.g. by engraving, by etching, B44C1/22; electrolytic etching or polishing C25F); INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25 - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## Abstract Method for removing at least one coating from metal scrap parts covered with a coating. The scrap parts are brought into motion in a vessel containing abrasive elements in such a way that multiple collisions occur within the vessel. In further embodiments a liquid, and a metal powder are added to the scrap parts. ## Claims ### Claim 1 A method of removing a coating layer selected from the group consisting of zinc, a plastic material and a metal alloy from coated scrap metal parts having a composition different from the composition of the coating layer comprising the steps of introducing a mixture comprising said coated parts, an aqueous alkaline solution and a sufficient amount of a metal powder selected from the group consisting of Pt, Pd, Ir, Co, Ni and Fe to increase the evolution of hydrogen and thereby accelerate coating removal, into a vessel and tumbling said parts, said aqueous alkaline solution and said metal powder in said vessel whereby said coating layer is at least partly removed. ### Claim 2 (depends on 1) A method according to claim 1, where said scrap metal is steel scrap. ### Claim 3 (depends on 1) A method according to claim 1, wherein said abrading stones are made of at least one of Al.sub.2 O.sub.3, SiC, mullite and Fe.sub.3 Si. ### Claim 4 (depends on 1) A method according to claim 1, wherein said abrading stones have a maximum dimension of 100 mm. ### Claim 5 (depends on 4) A method according to claim 4, wherein said abrading stones have a maximum dimension of 20 mm. ### Claim 6 (depends on 1) A method according to claim 1, wherein said alkaline solution contains at least 75 g/l NaOH. ### Claim 7 (depends on 1) A method according to claim 1, wherein said scrap metal parts are steel parts with a coating layer made of zinc, and a metal powder is introduced to said vessel along with said abrading stones so as to be additionally present in said vessel during said tumbling step. ### Claim 8 (depends on 1) A method according to claim 1, wherein said metal powder is Fe. ### Claim 9 (depends on 7) A method according to claim 7, wherein said metal powder has a particle size of less than 500 .mu.m, preferably less than 50 .mu.m. ### Claim 10 (depends on 1) A method according to claim 1, wherein said scrap metal parts have a maximum dimension of 200 mm. ### Claim 11 (depends on 1) A method according to claim 1, including the step of reducing the size of the scrap metal parts mechanically, prior to the step of introducing said parts into said vessel. ### Claim 12 (depends on 1) A method according to claim 1, wherein said vessel is a drum, said drum having an axis of rotation, and the method including rotating said drum about said axis of rotation to cause said tumbling, said axis being at an angle of at most 45.degree. relative to a horizontal position. ### Claim 13 (depends on 12) A method according to claim 12, wherein said drum has inward projections on its inner surface which lift the scrap metal parts during rotation. ### Claim 14 (depends on 1) A method in accordance with claim 1 wherein said mixture which is introduced to said vessel further comprises abrading stones and said abrading stones are tumbled in said vessel with said parts, said aqueous solution and said metal powder.