# US 2021/0340686 A1 · Aluminum and aluminum alloy electroplated coatings > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0340686 A1 - Document ID: US20210340686A1 - Status: Published application - Kind: A1 - Application number: 16/863,282 - Filed: 2020-04-30 - Published: 2021-11-04 - Earliest claimed: 2020-04-30 - Assignees: The Boeing Company - Applicants: The Boeing Company - Inventors: Vijaykumar S. IJERI; Om PRAKASH; Stephen P. GAYDOS - Web page: https://patentgrep.com/patent/US20210340686A1 ## CPC - C25D 3/44: Aluminium - C23C 22/24: containing hexavalent chromium compounds - C23C 22/34: containing fluorides or complex fluorides - C23C 22/37: containing also hexavalent chromium compounds - C25D 3/10: characterised by the organic bath constituents used - C25D 3/665: {from ionic liquids} - C25D 5/18: Electroplating using modulated, pulsed or reversing current - C25D 5/623: {Porosity of the layers} - C23C 2222/10: Use of solutions containing trivalent chromium but free of hexavalent chromium - C25D 5/36: of iron or steel - C25D 7/00: Electroplating characterised by the article coated - Y10T 428/12764: Next to Al-base component - C25D: PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR - 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) - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract In certain aspects, a coated steel substrate comprises a single or multiple-layer electroplated aluminum coating over a steel substrate. The multiple-layer electroplated aluminum coating comprises one or more porous layers and one or more compact layers. The one or more porous layers comprise a material selected from a group consisting of aluminum and aluminum alloys. The one or more compact layers comprise a material selected from a group consisting of aluminum and aluminum alloys. In certain aspects, a method of depositing a multiple-layer aluminum coating over a steel substrate includes electroplating one or more porous aluminum layers over the steel substrate. The one or more porous aluminum layers comprise a material selected from a group consisting of aluminum and aluminum alloys. One or more compact aluminum layers are electroplated over the steel substrate. The one or more compact aluminum layers comprise a material selected from a group consisting of aluminum and aluminum alloys. ## Claims ### Claim 1 A coated steel substrate, comprising: a steel substrate; and a multiple-layer electroplated aluminum coating over the steel substrate, the multiple-layer electroplated aluminum coating comprising at least one porous layer and at least one compact layer, the at least one porous layer comprising a material selected from a group consisting of aluminum and aluminum alloys and the at least one compact layer comprising a material selected from a group consisting of aluminum and aluminum alloys. ### Claim 2 (depends on 1) The coated steel substrate of claim 1, wherein the at least one porous layer has a plurality of pores having a pore size of about 2 μm or more and wherein the at least one compact layer has a plurality of pores having a pore size of about 0.2 μm or less. ### Claim 3 (depends on 1) The coated steel substrate of claim 1, wherein the at least one porous layer has a thickness from about 0.3 μm to about 3 μm and the at least one compact layer has a thickness from about 0.3 μm to about 3 μm. ### Claim 4 (depends on 1) The coated steel substrate of claim 1, wherein the multiple-layer electroplated aluminum coating comprises from one to fifty porous layers and from one to fifty compact layers. ### Claim 5 (depends on 1) The coated steel substrate of claim 1, wherein the multiple-layer electroplated aluminum coating is configured to provide sacrificial corrosion protection of over 1,000 hrs under ASTM B 117. ### Claim 6 (depends on 1) The coated steel substrate of claim 1, wherein the multiple-layer electroplated aluminum coating passes a hydrogen embrittlement (HE) test performed according to ASTM F 519 using Type 1a.1 specimens having a notch. ### Claim 7 (depends on 1) The coated steel substrate of claim 1, wherein the multiple-layer electroplated aluminum coating provides sacrificial corrosion protection to the steel substrate in neutral water and in salt water. ### Claim 8 A method of depositing a multiple-layer aluminum coating over a steel substrate, comprising: electroplating one or more porous aluminum layers over the steel substrate, the one or more porous aluminum layers comprising a material selected from a group consisting of aluminum and aluminum alloys; and electroplating one or more compact aluminum layers over the steel substrate, and the one or more compact aluminum layers comprising a material selected from a group consisting of aluminum and aluminum alloys. ### Claim 9 (depends on 8) The method of claim 8, wherein the one or more compact aluminum layers are electroplated utilizing a direct current. ### Claim 10 (depends on 8) The method of claim 8, wherein the one or more compact aluminum layers are electroplated utilizing a pulsed current. ### Claim 11 (depends on 10) The method of claim 10, wherein the pulsed current is a unipolar pulsed current comprising a plurality of ON pulses and a plurality of OFF pulses, each of the plurality of ON pulses having a current density from about 5 mA/cm2 to about 25 mA/cm2, each of the plurality of ON pulses having a duration from about 100 ms to about 500 ms, and each of the plurality OFF pulses having a duration from about 100 ms to about 500 ms. ### Claim 12 (depends on 10) The method of claim 10, wherein the pulsed current is a bipolar pulsed current comprising a plurality of deposition pulses and a plurality of etching pulses, each of the plurality of deposition pulses having a current density from about 5 mA/cm2 to about 25 mA/cm2, each of the plurality of etching pulses having a current density from about 0.5 mA/cm2 to about 5 mA/cm2, each of the plurality of deposition pulses having a duration from about 100 ms to about 1,000 ms, and each of the plurality etching pulses having a duration from about 100 ms to about 1,000 ms. ### Claim 13 (depends on 8) The method of claim 8, wherein the one or more compact aluminum layers comprise an aluminum-manganese alloy electroplated in an electroplating bath including an aluminum salt and a manganese salt. ### Claim 14 (depends on 13) The method of claim 13, wherein the electroplating bath includes the aluminum salt and the manganese salt in a molar ratio from about 9:1 to about 4:1. ### Claim 15 (depends on 8) The method of claim 8, wherein the one or more porous aluminum layers are electroplated in an ionic liquid of an a-alkyl-N-alkyl′ pyrrolidinium sulfonylimide utilizing a direct current. ### Claim 16 A coated steel substrate, comprising: a high strength steel substrate; and a multiple-layer electroplated aluminum coating over the steel substrate, the multiple-layer electroplated aluminum coating comprising at least one porous layer and at least one compact layer, the at least one porous layer comprising a material selected from a group consisting of aluminum and aluminum alloys, and the at least one compact layer comprising a material selected from a group consisting of aluminum and aluminum alloys, wherein the at least one porous layer has a plurality of pores having a pore size of about 2 μm or more and wherein the at least one compact layer has a plurality of pores having a pore size of about 0.2 μm or less, wherein the at least one porous layer has a thickness from about 0.3 μm to about 3 μm and the at least one compact layer has a thickness from about 0.3 μm to about 3 μm. ### Claim 17 (depends on 16) The coated steel substrate of claim 16, wherein the multiple-layer electroplated aluminum coating is configured to provide sacrificial corrosion protection of over 1,000 hrs under ASTM B 117. ### Claim 18 (depends on 16) The coated steel substrate of claim 16, wherein the multiple-layer electroplated aluminum coating passes a hydrogen embrittlement (HE) test performed according to ASTM F 519 using Type 1a.1 specimens having a notch. ### Claim 19 (depends on 16) The coated steel substrate of claim 16, wherein the at least one porous layer is electroplated by direct current and wherein the at least one compact layer is electroplated by pulsed current, wherein the multiple-layer electroplated aluminum coating is configured to provide corrosion resistance to the steel substrate in neutral water and in salt water. ### Claim 20 (depends on 16) The coated steel substrate of claim 16, wherein the multiple layer aluminum coating has a thickness from about 10 μm to about 40 μm and provides sacrificial corrosion protection.