EP3562976A1 - Revêtements électrocéramiques de couleur sombre pour le magnésium - Google Patents

Revêtements électrocéramiques de couleur sombre pour le magnésium

Info

Publication number
EP3562976A1
EP3562976A1 EP17889436.6A EP17889436A EP3562976A1 EP 3562976 A1 EP3562976 A1 EP 3562976A1 EP 17889436 A EP17889436 A EP 17889436A EP 3562976 A1 EP3562976 A1 EP 3562976A1
Authority
EP
European Patent Office
Prior art keywords
inorganic
layer
magnesium
based coating
coating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP17889436.6A
Other languages
German (de)
English (en)
Inventor
Shawn E. Dolan
Jr. Michael A. Murphy
James P. Golding
Andrew M. Dahl
Eric C. KUHNS
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Henkel AG and Co KGaA
Original Assignee
Henkel AG and Co KGaA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Henkel AG and Co KGaA filed Critical Henkel AG and Co KGaA
Publication of EP3562976A1 publication Critical patent/EP3562976A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/30—Anodisation of magnesium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/024—Anodisation under pulsed or modulated current or potential
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/026—Anodisation with spark discharge
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/18—After-treatment, e.g. pore-sealing
    • C25D11/24—Chemical after-treatment
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D9/00—Electrolytic coating other than with metals
    • C25D9/04—Electrolytic coating other than with metals with inorganic materials
    • C25D9/06—Electrolytic coating other than with metals with inorganic materials by anodic processes

Definitions

  • This invention relates to articles having metal surfaces of magnesium which have been provided with a dark colored, electroceramic coating that is chemically bonded to the metal surfaces, desirably a black, brown or bronze electroceramic coating.
  • dark colored means black, brown, bronze or gray.
  • Articles having a composite coating comprising first sectors of the electroceramic coating and second sectors comprising organic and/or inorganic components different from the electroceramic coating are also provided.
  • the invention further relates to processes of making and using the articles.
  • magnesium or magnesium alloy susceptibility to corrosion, generally taking place on Mg in the presence of oxygen, moisture and other environmental agents, such as human fingerprint constituents.
  • a variety of coating products have been used on magnesium or magnesium alloy surfaces to provide them with desired dark colors and attempting to improve corrosion resistance, but none has met needs for both corrosion resistance and dark color.
  • One method used to improve corrosion resistance of metal surfaces is anodization, where a metal (M) surface is oxidized electrically to form a metal oxide (MOx) layer from molecules of the metal surface, see for example U.S. Pat. No. 4,978,432, U.S. Pat. No. 4,978,432 and U.S. Pat. No. 5,264, 113.
  • Anodization of magnesium or magnesium alloy affords some protection against corrosion, but U.S. Pat. No. 5,683,522, indicates that conventional anodization often fails to form a protective layer on the entire surface of a complex workpiece, and can contain cracks, some down to the metal surface, at sharp corners. This lack of coverage negatively affects corrosion, and also fails to provide a uniform colored surface.
  • PEO Plasma Electrolytic Oxidation
  • MAO Micro Arc Oxidation
  • Spark Anodizing and Microplasma Oxidation referred to herein collectively as "PEO”
  • PEO Plasma Electrolytic Oxidation
  • MAO Micro Arc Oxidation
  • Spark Anodizing and Microplasma Oxidation referred to herein collectively as "PEO”
  • PEO Plasma Electrolytic Oxidation
  • MAO Micro Arc Oxidation
  • Spark Anodizing and Microplasma Oxidation referred to herein collectively as "PEO”
  • PEO Plasma Electrolytic Oxidation
  • PEO processing of magnesium or magnesium alloy produces a crystalline oxide (60-80 vol. %) coating with minor amounts of silicates and/or phosphates, depending on the content of the PEO bath.
  • PEO processes have disadvantages including lack of uniformity in the coating structure between crystalline and amorphous, cratered areas, and thicker and thinner coating areas which can negatively impact color uniformity making it unsuitable for show surfaces. Further, PEO produces a brittle sub-layer with a porosity of more than 15%, which is removed by an additional polishing step.
  • Polishing has the disadvantages of additional processing and, often, manual labor, as well as loss of dimensional integrity of the article and challenges in uniformly polishing complex articles or those having non-uniform coating layers due to throw-power limitations of PEO. More importantly, colored features of the coating can be negatively affected, e.g. made uneven, by removal of coating layers containing color.
  • the inorganic-based coating may have additional layers deposited thereon, may form a composite coating comprising the inorganic-based coating and a second component distributed throughout or in contact with at least a portion of the inorganic-based coating and/or the coating on the magnesium or magnesium alloy surface may comprise a reaction product the inorganic-based coating and a second component.
  • It is also an object of the invention to provide a method of depositing a dark colored coating that improves corrosion resistance of magnesium or magnesium alloy metal substrates comprising: A) providing an alkaline electrolyte, which may be a solution or dispersion, comprising water, an organic amine, a source of phosphorus, and one or more additional components selected from the group consisting of: water-soluble transition metal oxides, water-soluble transition metal salts and mixtures thereof; and a cathode in contact with the alkaline electrolyte;
  • an alkaline electrolyte which may be a solution or dispersion, comprising water, an organic amine, a source of phosphorus, and one or more additional components selected from the group consisting of: water-soluble transition metal oxides, water-soluble transition metal salts and mixtures thereof; and a cathode in contact with the alkaline electrolyte;
  • step 1) after step 1) if present, applying to the first layer of the inorganic-based coating, a
  • polymeric composition thereby forming a second layer comprising organic polymer chains and/or inorganic polymer chains having a layer thickness of 0.1 micron to 15 microns;
  • the post-treating step E) is present as a step of contacting the first layer of inorganic-based coating with a second component different from the inorganic-based coating; distributing the second component throughout at least a portion of the first layer, in particular the pores; and depositing a second layer that is different from the inorganic-based coating and is adhered to at least external surfaces of the inorganic-based coating,
  • step E) i) is present and comprises a step of introducing at least one Ti, Zr, Hf or combinations thereof- containing composition as the second component to the second sub-layer of inorganic-based coating, contacting at least the external surfaces and desirably at least some of the internal surfaces of the second sub-layer, whereby the second component forms a thin inorganic-based coating in contact with the external surfaces of the inorganic- based coating and lining at least a portion of the pores in the inorganic-based coating.
  • step E) 1) comprises reacting the composition and elements of the inorganic-based coating to thereby form a portion of the second component, which is different from the inorganic-based coating and the composition.
  • step E) ii) is present and comprises contacting the first layer of an inorganic-based coating with a polymeric composition thereby forming a second layer comprising organic polymer chains and/or inorganic polymer chains; and optionally applying a layer of paint after the post-treating step.
  • materials containing the element silicon e.g. silicates, and/or fluorine, e.g. metal fluorides, nonmetal fluorides, fiuorometallates, on the metal surface.
  • neither Si nor F are present in the electrolyte or the coating, other than trace amounts from the metal substrate and electrolyte raw materials.
  • the electrolyte may be an alkaline electrolyte, which may be a solution or dispersion, which comprises; desirably consists essentially of; or optionally consists of water, an organic amine, a source of phosphorus, and at least one water soluble source of at least one transition metal, e.g. one or more additional components selected from: water-soluble transition metal oxides, water-soluble transition metal salts and mixtures thereof.
  • the organic amine is monoethanolamine and the at least one transition metal element comprises one or more of iron, vanadium and tungsten.
  • the alkaline electrolyte contains less than 100 ppm silicon or aluminum and is essentially free of fluorine and tertiary amines.
  • the organic amine is a primary monoamine in the absence of cyclic amines, and the at least one transition metal element consists of iron or vanadium or tungsten.
  • the organic amine is monoethanolamine, the source of phosphorus is phosphoric acid, and the at least one transition metal element comprises iron and vanadium and the alkaline electrolyte has a pH of at least 10.2.
  • the organic amine is monoethanolamine, the source of phosphorus is phosphoric acid, and the at least one transition metal element comprises tungsten.
  • the alkaline electrolyte is vanadium free
  • the organic amine is monoethanolamine
  • the source of phosphorus is phosphoric acid
  • the at least one transition metal element comprises iron and optionally a second transition metal element other than vanadium.
  • the organic amine is a primary monoamine in the absence of cyclic amines
  • the at least one water-soluble or dispersible source of at least one transition metal element comprises iron citrate.
  • the composition may be provided as a storage-stable two pack system wherein Part A contains water; a source of phosphorus, for example phosphoric acid, phosphorous acid, pyrophosphate, phosphonate; one or more water soluble salts of transition metals, for example iron, vanadium, tungsten and the like; wherein the mass ratio of phosphorus to total amount of transition metal is 4: 1 to 1 : 1 ; and Part B contains organic amine, preferably monoethanolamine, Part A and Part B being provided in amounts such that the mass ratio of Part A to Part B be ranges from 1 : 1 to 2: 1.
  • a source of phosphorus for example phosphoric acid, phosphorous acid, pyrophosphate, phosphonate
  • transition metals for example iron, vanadium, tungsten and the like
  • the mass ratio of phosphorus to total amount of transition metal is 4: 1 to 1 : 1
  • Part B contains organic amine, preferably monoethanolamine, Part A and Part B being provided in amounts such that the
  • the inorganic-based coating has
  • the article further comprises a second layer that is different from the inorganic-based coating and is adhered to at least external surfaces of the inorganic-based coating.
  • the anti-fingerprint coating comprises uncoalesced spray droplets forming a series of flattened, cured globules which form a cured refractive surface.
  • an article having an inorganic-based coating comprising a first sub-layer directly bonded to the bare, meaning a clean surface with no coating applied thereto, metallic magnesium or magnesium alloy surface at a first interface, the first sub-layer comprising Mg, O, C, P and at least one transition metal; and a second sub-layer integrally connected to the first sublayer at a second interface, the second sub-layer comprising external surfaces at the outer boundary of the inorganic-based coating, and internal surfaces defined by pores in the second sub-layer lying interior to the outer boundary of the inorganic-based coating and in communication therewith, the second sub-layer comprising Mg, O, C, P and the at least one transition metal and the second sub-layer having a composition such that the O exhibits a concentration gradient wherein O is greatest at the second interface and decreases to about 30 - 50 wt.
  • each of Mg, P and C exhibit a concentration gradient in the second sub-layer such that concentration of each element in the second sub-layer is greatest proximate the external surfaces and decreases to its lowest concentration in the second-sub-layer proximate to the second interface.
  • inorganic-based coating means that the organic-based coating
  • electroceramic coating comprises substantial amounts of inorganic compounds and/or inorganic glasses, and the inorganic-based coating may additionally include some organic material, sourced from the raw materials, generated in situ or the like.
  • Organic material will be understood to describe molecules that are made up of at least one carbon atom with hydrogen(s) bonded thereto, the carbons may form chains or cyclic structures and may optionally include additional atoms and functional groups (e.g. oxygen, silicon, phosphorus and nitrogen) attached.
  • an inorganic-based coating may contain less than 50, 40, 30, 20, 10, 8, 6, 4, 2, 1 wt. %, the units more preferably being amounts in parts per thousand, most preferably parts per million, of organic material.
  • paint includes all like materials that may be designated by more specialized terms such as lacquer, enamel, varnish, shellac, topcoat, and the like; and, unless otherwise explicitly stated or necessarily implied by the context.
  • metal or “metallic' will be understood by those of skill in the art to mean a material, whether it be an article or a surface, that is made up of atoms of metal elements, e.g.
  • magnesium the metal elements present in amounts of at least, with increasing preference in the order given, 55, 65, 75, 85, or 95 atomic percent
  • the simple term "magnesium” includes pure magnesium and those of its alloys that contain at least, with increasing preference in the order given, 55, 65, 75, 85, or 95 atomic percent of magnesium atoms.
  • Figure 1 is a graph of elemental composition, in weight percent, of an inorganic-based electrolytically deposited coating according to the invention, measured by GDOS, showing varying chemical composition of a coating of the invention, as a function of distance from the magnesium alloy surface.
  • Figure 2 is a drawing of a cross-section of a panel of AZ-31 coated according to Example 1, prior to post-treating, showing the inorganic-based coating and sub-layers thereof.
  • Figure 3 shows photographs of Comparative Example 2, 3 and 4.
  • Figure 3a shows a photograph of an AZ-31 Mg alloy panel treated with a pH of 5.7 for 45 seconds and Figure 3b shows a photograph of an AZ-31 Mg alloy panel treated with a pH of 6.6 for 45 seconds, both panels are bright shiny metallic in appearance with no coating deposited.
  • Figure 3c shows a photograph of an AZ-31 Mg alloy panel treated with a pH of 6.1 for 10 minutes, showing etching but no coating.
  • Figure 3d shows a photograph of an AZ-31 Mg alloy panel treated at pH 9.9 for 10 minutes, showing etching, but no coating.
  • Articles according to the invention include magnesium-containing articles having a coating, which may be an electrolytically deposited coating, chemically bonded to one or more metal surfaces of the article, said coating having a dark appearance, e.g. black, brown, bronze, gray and the like, to the unaided human eye.
  • Such articles are useful as for example, parts for motor vehicles, aircraft, and electronic devices, including handheld electronic devices, and other products where the light weight and strength of magnesium is desired.
  • the articles generally have at least one metal surface, which comprises magnesium or magnesium alloy and chemically bonded directly to that metal surface is an inorganic- based coating.
  • the inorganic-based coating is post treated and/or painted.
  • At least a portion of the article has a metal surface that contains not less than 50% by weight, more preferably not less than 70% by weight, magnesium or magnesium alloy.
  • magnesium- containing article as used in the specification and the claims, means an article having at least one surface that may be in whole or in part metallic magnesium or a magnesium alloy.
  • the body of the article may be formed of metallic magnesium or a magnesium alloy or may be formed of other materials, e.g. metals other than magnesium, polymeric materials, refractory materials, such as ceramics, that have a layer of magnesium or magnesium alloy on at least one surface.
  • the other materials may be other metals different from magnesium, non-metallic materials or combinations thereof, such as composites or assemblies.
  • the article may comprise at least one surface of metallic magnesium or a magnesium alloy comprising, in order of increasing preference, at least about 51, 60, 65, 70, 75, 80, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98 or 99 wt. % magnesium.
  • the coated metal surface has an appearance different from the uncoated metal surface.
  • the coated metal surface may have a black, brown, bronze or gray colored appearance, and is generally darker than the bare metal surface and MOx coated surfaces where M is magnesium or magnesium alloying elements.
  • the coating may have a uniform thickness or may be selectively deposited, e.g. using sealed chambers restricting electrolyte contact to only selected surfaces, masking and the like, such that the thickness of the coating is greater in selected areas of the metal surface.
  • An inorganic-based coating may include some organic material, but contains a greater mass of inorganic material than of organic molecules.
  • the inorganic material may act as a matrix in which any organic constituent may be distributed.
  • organic molecules may be absent.
  • carbon is present in the coating and organic molecules are not detected.
  • the inorganic-based coating may be applied by an electrolytic deposition process as described herein.
  • the inorganic-based coating contains carbon, oxygen, phosphorus, one or more transition metals, and magnesium.
  • the inorganic-based coating contains oxygen, at least one alloying element from the metal substrate in addition to at least one of magnesium or magnesium alloy, and at least one element from the bath.
  • the inorganic-based coating comprises carbon, oxygen, phosphorus, two or more transition metals, and magnesium.
  • GDOES Glow Discharge Optical Emission Spectroscopy
  • the inorganic-based coating may comprise carbon. Both the carbon and alloying elements, if present, may be dispersed in a ceramic layer. Even with inclusion of carbon and alloying elements in the inorganic-based coating, a uniform thickness can be generated which provides uniform paint and adhesive bonding, as well as corrosion resistance, which is improved as compared to the bare surface of the magnesium containing substrate. This feature of the invention is beneficial in reducing scrap rate where substrates and the inorganic-based coatings deposited thereon achieve good coating quality even in the presence of carbon and alloying elements in the inorganic-based coating.
  • the inorganic-based coating comprises C, O, P, Al, Mg, and at least one transition metal.
  • the inorganic-based coating may have a bi-layer morphology, as shown in Figure 1 and Figure 2.
  • Figure 1 is a graph of an elemental depth profile taken of inorganic-based coatings according to the invention using glow discharge optical emission spectroscopy (GDOES). Amounts of various elements are shown in weight percent at particular distances from the metal surface.
  • Figure 1 shows that the first sub-layer and the second sub-layer are different in morphology and elemental content.
  • Figure 2 shows a cross-section of a magnesium alloy panel coated according to Example 1 , prior to application of a post-treatment.
  • the inorganic-based coating 100 has a bilayer structure, despite being deposited in a single processing step: a first sub-layer 120 directly bonded to the magnesium article 200 and having an interface 110 with the metal surface (first interface 1 10); and a second sublayer 140 in direct contact with the first sub-layer and spaced away from the metal surface by the first sub-layer lying there between.
  • the second sub-layer is directly bonded with the first sub-layer at an interface 130 with the first sub-layer (second interface).
  • the second sub-layer of the inorganic-based coating comprises pores 160, and has internal surfaces 170 and external surfaces 150.
  • the internal surfaces 170 are defined by pores 160 in the second sub-layer and lie interior to the outer boundary of the inorganic-based coating, which comprises the external surfaces 150 of the second sub-layer.
  • the external surfaces of the second sub-layer lie in a boundary between inorganic-based coating and an external environment or a secondary layer applied to the outer boundary and are not in direct contact with a metallic surface of the magnesium-containing article.
  • the first sub-layer may have few or no pores and has a more dense composition than the second sub-layer. Any pores present in the first sub-layer are desirably not contiguous between the metallic surface of the article and the external surface of the inorganic-based coating layer, and optionally smaller than the pores of the second sublayer. Some of the pores of the second sub-layer are open pores in communication with the external surface.
  • the second sub-layer may comprise open and closed cell pore structure.
  • Pore size may range from about 0.1 microns to 5 microns and may make up as much as 50 % or more of the volume of the deposited coating.
  • the electrolytically applied inorganic-based coating may have a surface area that is about 75 - 150X that of the uncoated substrate surface. [0045.] At least a portion of the inorganic-based coating has an amorphous structure. Physical morphology of the inorganic-based coating may comprise non-crystalline compounds of magnesium and one or more of elements. In one embodiment, the inorganic-based coating shows amorphous structure by X-ray crystallography (XRD).
  • XRD X-ray crystallography
  • the inorganic-based coating may be a hard (5-6 Moh hardness), amorphous coating comprising non-stoichiometric magnesium compounds.
  • Nonstoichiometric glasses of Mg and transition metals as disclosed herein, with or without oxygen, may be present.
  • the inorganic-based coating is an inorganic composition comprising Mg, O & Fe, including stoichiometric and non-stoichiometric compounds of said elements with each other.
  • the inorganic composition comprises crystalline and non-crystalline compounds comprising magnesium, with more than 50 atomic percent of the composition comprising non-crystalline compounds.
  • Coating thickness of the inorganic-based electrolytically deposited coating may range from 0.1 microns to about 50 microns, desirably 1-20 microns depending upon the desired use of the coated article. Coating thickness of the inorganic-based electrolytically deposited coating desirably is at least, in increasing order of preference 0.5, 1, 3, 5, 7, 9, 10 or 11 microns thick, and no more than, if only for economic reasons, in increasing order of preference, 50, 30, 25, 20, 15, 14, 13, or 12 microns thick. As a decorative layer, the coating may range from 2- 5 microns. In one embodiment, the coating thickness ranges from 3 to 10 microns.
  • electrolytically applied inorganic-based coatings according to the invention perform better than commercially available conversion coatings for magnesium in unpainted and painted corrosion testing, as well as providing improved corrosion resistance when compared to PEO coatings on magnesium alloys typically used in the automotive industry, e.g. magnesium casting alloys and forged alloys.
  • the electrolytically applied inorganic-based coatings perform better than commercially available conversion coatings for magnesium in unpainted and painted corrosion testing, as well as providing improved corrosion resistance when compared to PEO coatings on magnesium alloys typically used in the automotive industry, e.g. magnesium casting alloys and forged alloys.
  • magnesium-containing article may have a composite coating wherein the inorganic-based coating may act as a matrix.
  • This embodiment may include a coating comprising:
  • the coating on the magnesium containing article may comprise:
  • the second component may have the same composition as the second layer. In another embodiment of the invention, the second component may be different from both A) and C). In one embodiment, the second component and/or the second layer may form reaction products with elements in the inorganic-based coating. In one embodiment, the inorganic-based coating has a layer of paint deposited thereon, which may comprise the second layer or may be in addition to the second layer.
  • inorganic-based coatings according to the invention and aqueous compositions for depositing the inorganic-based coatings, as defined above, may be substantially free from many ingredients used in compositions for similar purposes in the prior art.
  • aqueous compositions according to the invention when directly contacted with metal in a process according to this invention, contain no more than 1.0, 0.5, 0.35, 0.10, 0.08, 0.04, 0.02, 0.01, 0.001, or 0.0002 percent, more preferably said numerical values in grams per liter, of each of the following constituents: chromium, cyanide, nitrite ions, organic surfactants, formaldehyde, formamide, urea, hydroxylamines, ammonia, tertiary amines, cyclic amines, e.g. hexamethylene tetraamine; silicon, e.g.
  • siloxanes organosiloxanes, silanes, silicate; rare earth metals; alkali metals, e.g. sodium, potassium; sulfur, e.g. sulfate; permanganate; perchlorate; boron, e.g. borax, borate; strontium, fluorine, e.g. free or bound fluoride; and/or free chloride.
  • as-deposited inorganic- based coatings and inorganic secondary layers according to the invention contain no more than 1.0, 0.5, 0.35, 0.10, 0.08, 0.04, 0.02, 0.01, 0.001 , or 0.0002 percent, more preferably said numerical values in parts per thousand (ppt), of each of the following constituents: chromium, cyanide, nitrite ions, organic surfactants, formaldehyde, formamide, urea, hydroxylamines, ammonia and hexamethylene tetraamine; silicon, e.g.
  • siloxanes organosiloxanes, silanes, silicate; rare earth metals; alkali metals, e.g. sodium, potassium; sulfur, e.g. sulfate; permanganate; perchlorate; boron, e.g. borax, borate; strontium, fluorine, e.g. free or bound fluoride; and/or free chloride.
  • Inorganic-based coatings can be produced by a variety of processes capable of generating hard, amorphous coatings chemically bonded to magnesium-containing metals.
  • the inorganic-based coating may be formed using electrolytic deposition according to the inventive process described herein.
  • compositions for forming a second layer comprising organic polymer chains and/or inorganic polymer chains include, by way of non-limiting example aqueous compositions comprising (A) a component of a dissolved fluoroacids of one or more metals and metalloid elements selected from the group of elements consisting of titanium, zirconium, hafnium, boron, aluminum, germanium, and tin; and/or (B) a component of one or more of (i) dissolved or dispersed finely divided forms of metals and metalloid elements selected from the group of elements consisting of titanium, zirconium, hafnium, boron, yttrium, lithium, aluminum, germanium, and tin and (ii) the oxides, hydroxides, and carbonates of such metals and metalloid; plus
  • (C) a component that is either (i) a water soluble or dispersible polymer and/or copolymer, preferably selected from the group consisting of (i.l) polymers and copolymers of one or more x-(N--R'— N--R 2 - aminomethyl)-4-hydroxy-styrenes, where x 2, 4, 5, or 6, R 1 represents an alkyl group containing from 1 to 4 carbon atoms, preferably a methyl group, and R 2 -represents a substituent group conforming to the general formula H(CHOH) friendship C3 ⁇ 4 --, where n is an integer from 1 to 7, preferably from 3 to 5, (i.2) epoxy resins, particularly polymers of the diglycidylether of bisphenol-A, optionally capped on the ends with non-polymerizable groups and/or having some of the epoxy groups hydrolyzed to hydroxyl groups; (i.3) polymers and copolymers of acrylic and methacrylic acids and their salts; and (
  • the treating may consist either of coating the surface of the first layer of an inorganic-based coating with a liquid film of the composition and then drying this liquid film in place on the surface of the first layer, or simply contacting the first layer of an inorganic-based coating with the composition for a sufficient time to produce an improvement in the resistance of the coated article to corrosion, and subsequently rinsing before drying.
  • Such contact may be achieved by spraying, immersion, and the like as known per se in the art.
  • the process may comprise optional steps of: cleaning, etching, deoxidizing and desmutting with or without intervening steps of rinsing with water.
  • a rinse water may be counterflowed into a preceding bath.
  • a step 5) of masking or closing off portions of the article to limit or prevent contact with the electrolyte may be performed prior to contacting the magnesium containing article with the electrolyte.
  • masking may be applied to magnesium containing portions of the article where no coating is desired or may be applied to protect article components or surfaces that might be damaged by the electrolyte, likewise hollow portions of an article, e.g. the lumen of a pipe, may be closed off or plugged to prevent electrolyte contact of interior surfaces.
  • the inorganic-based coating is not physically or chemically removed or etched.
  • no more than 1000, 500, 100, 50, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 or 0.5 mg/m2 of the inorganic- based coating may be removed from the article.
  • the surface to be electrolytically coated has sufficient magnesium metal or other light metal in combination with magnesium, desirably in the zero oxidation state, to permit coating generation and the non-magnesiferous surfaces are not negatively affected by the treatments.
  • Masking of selected surfaces to prevent contact with electrolyte can be accomplished by methods known in the art.
  • the electrolytic treatment is advantageously applicable to magnesium-base alloys containing one or more other elements such as Al, Zn, Mn, Zr, Si and rare earth metals.
  • the magnesium containing surfaces to be coated are contacted with an alkaline electrolyte, as described herein.
  • the electrolyte may have a pH of 10 or more, desirably greater than 10, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 1 1, 11.1, 1 1.2, 11.3, 11.4, 1 1.5, 1 1.6, 1 1.7, 11.8, 11.9, 12, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6, 12.7, 12.8, 12.9 or 13.
  • an electrolyte is employed which may be maintained at a temperature between about 5° C. and about 90° C, desirably from about 20° to about 45°C.
  • the electrolyte is an alkaline solution or dispersion, which comprises; desirably consists essentially of; or optionally consists of water, an organic amine, a source of phosphorus, and at least one water soluble source of at least one transition metal, e.g. one or more additional components selected from: water-soluble transition metal oxides, water-soluble transition metal salts and mixtures thereof.
  • the organic amine is soluble or dispersible in the electrolyte.
  • the organic amine may be a primary amine, desirably a monoamine, such as by way of non-limiting example monoethanolamine. Desirably the organic amine is present in the absence of cyclic amines or tertiary amines. Primary monoamines are preferred; secondary amines or diamines may be present provided that they do not interfere with deposition of the coating or corrosion resistance.
  • the source of organic amine is generally present in an amount, in increasing order of preference, of about 50, 60, 70, 80, 90, 100, 105, 1 10, 1 15, 120, 125, 130, or 140 g/1 and at most in increasing order of preference about 500, 400, 350, 300, 275, 250, 225, 200, 190, 180, 170, 160, 150, 145, 143 or 141 g/1.
  • Suitable sources of phosphorus include water-soluble acids and salts thereof, desirably oxy acids.
  • the source may be inorganic or organic. Non-limiting examples include phosphoric acid, phosphorous acid, phosphonic acid, phosphates, pyrophosphate, phosphonates, and combinations thereof.
  • the source of phosphorus is generally present in an amount, in increasing order of preference, of about 10, 15, 17, 19, 20, 21 , 22, 23, 24, 25, 26, 28, 30, 32, 34, 36, 38 or 40 g/1 and at most in increasing order of preference about 85, 80, 75, 70, 65, 60, 55, 50, 45, 44, 43, 42 or 41 g/1, calculated as PO x .
  • Water soluble sources of at least one transition metal include sources of the transition metal such as transition metal oxides, acids and salts of the metal oxides; non-oxidic transition metal salts and mixtures thereof. Salts may be inorganic or may include organic counterions. Examples of suitable sources include metal oxides e.g. oxides of vanadium and oxide salts thereof, acids and salts of the metal oxides include e.g. tungstic acid and ammonium metatungstate; and non-oxidic transition metal salts, e.g. iron citrate, iron acetate, iron acetylacetonate and the like; and combinations thereof.
  • suitable sources include metal oxides e.g. oxides of vanadium and oxide salts thereof, acids and salts of the metal oxides include e.g. tungstic acid and ammonium metatungstate; and non-oxidic transition metal salts, e.g. iron citrate, iron acetate, iron acetylacetonate and the like; and combinations thereof.
  • Water-soluble as used herein includes sources of the transition metals that may be insoluble or only slightly soluble in H 2 0, but are soluble in the alkaline electrolyte as described herein.
  • Preferred transition metals include iron, tungsten, vanadium and mixtures thereof.
  • Suitable sources of iron are water soluble or alkali soluble salts of iron, such as by way of non-limiting example iron nitrate, iron sulfate, iron ammonium citrate, iron citrate, iron ammonium sulfate, iron acetate, iron acetylacetonate, and the like. Iron acetate and iron citrate are preferred.
  • the source of transition metal is present as ions dissolved in the electrolyte, and the amount utilized in the electrolyte depends on the transition metal selected and the color desired. For black, each transition metal may be present in an amount up to the solubility limit of the transition metal ion, provided that amount present does not interfere with deposition of the coating, corrosion resistance or bath maintenance.
  • iron ions may be present in an amount, in increasing order of preference, of about 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.00, 1.1, 1.2, 1.3, 1.4 g/1 and at most in increasing order of preference about 5.0, 4.0, 3.5, 3.0, 2.5, 2.4, 2.3, 2.2, 2.1, 2.0, 1.9, 1.8, 1.7, 1.6, or 1.5 g/1.
  • vanadium may be present in an amount, in increasing order of preference, of about 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.00, 1.1 , 1.2, 1.3, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, or 1.85 g/1 and at most in increasing order of preference about 10, 9,8,7,6, 5.5, 5.0, 4.5, 4.25, 4.0, 3.9, 3.8, 3.7, 3.6, 3.5, 3.4, 3.3, 3.2, 3.1 , 3.0, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2, 2.15, 2.1, 2.05, 2.0, 1.95, 1.9 or 1.875 g/1.
  • tungsten may be present in an amount calculated as tungstic acid, in increasing order of preference, of about 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9.00, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10.00, 10.1, 10.2, 10.3, 10.45g/l and at most in increasing order of preference about 20, 19, 18, 17, 16, 15, 14, 13, 12, 12.5, 12.4, 12.3, 12.2, 12.1, 12.0, 11.9, 1 1.8, 11.7, 1 1.6, 1 1.5, 1 1.4, 1 1.3, 11.2, 11.1, 11.0, 10.9, 10.8, 10.7, 10.6, or 10.5 g/1.
  • the electrolyte may contain at least one additive such as a ligand, a chelant or the like capable of forming coordination complexes with the transition metals in the electrolyte bath for example acetylacetone.
  • a ligand such as a ligand, a chelant or the like capable of forming coordination complexes with the transition metals in the electrolyte bath for example acetylacetone.
  • the organic amine is monoethanolamine and the at least one transition metal element comprises one or more of iron, vanadium and tungsten.
  • the alkaline electrolyte contains less than 100 ppm silicon or aluminum and is essentially free of fluorine and tertiary amines.
  • the organic amine is a primary monoamine in the absence of cyclic amines, and the at least one transition metal element consists of iron or vanadium or tungsten.
  • the organic amine is monoethanolamine, the source of phosphorus is phosphoric acid, and the at least one transition metal element comprises iron and vanadium and the alkaline electrolyte has a pH of at least 10.2.
  • the organic amine is monoethanolamine, the source of phosphorus is phosphoric acid, and the at least one transition metal element comprises tungsten.
  • the alkaline electrolyte is vanadium free, the organic amine is monoethanolamine, the source of phosphorus is phosphoric acid, and the at least one transition metal element comprises iron and optionally a second transition metal element other than vanadium.
  • the organic amine is a primary monoamine in the absence of cyclic amines, and the at least one water-soluble or dispersible source of at least one transition metal element comprises iron citrate.
  • the composition may be provided as a storage-stable two pack system wherein Part A contains water; a source of phosphorus, for example phosphoric acid, phosphorous acid, pyrophosphate, phosphonate; one or more water soluble salts of transition metals, for example iron, vanadium, tungsten and the like; wherein the mass ratio of phosphorus to total amount of transition metal is 4: 1 to 1 : 1 ; and Part B contains organic amine, preferably monoethanolamine, Part A and Part B being provided in amounts such that the mass ratio of Part A to Part B be ranges from 1 : 1 to 2: 1.
  • a method wherein a magnesium or magnesium alloy surface is contacted with, desirably immersed in, an aqueous electrolyte and electrolyzed as the anode in the circuit.
  • One such process comprises immersing at least a portion of the article in the electrolyte, which is preferably contained within a bath, tank or other such container.
  • a second article that is cathodic relative to the anode is also placed in the electrolyte.
  • the electrolyte is placed in a container which is itself cathodic relative to the article (anode). Voltage is applied across the anode and cathode for a time sufficient to form an inorganic-based electrolytic coating.
  • the time required to produce a coating in an electrolytic process according to the invention may range from about 30, 60, 90, 120 seconds, up to about 150, 180, 210, 240, 300 seconds. Longer deposition times may be utilized but are considered commercially undesirable. Electrolytic processing time can be varied to maximize efficiency by reducing time to Vmax and to control coating weight.
  • Alternating current, direct current or a combination may be used to apply the desired voltage, e.g. straight DC, pulsed DC, AC waveforms or combinations thereof.
  • pulsed DC current is used.
  • a period of at least 0.1, 0.5, 1.0, 3.0, 5.0, 7.0, 9.0, or 10 millisecond and not more than 50, 45, 40, 35, 30, 25, 20, or 15 millisecond may be used, which period may be held constant or may be varied during the immersion period.
  • Waveforms may be rectangular, including square;
  • Peak voltage potential desirably may be, in increasing order of preference, up to about 800, 700, 600, 500, 400 volts, and may desirably is at least in increasing order of preference 200, 250, 300, 350, 375 or 395 volts. Lower voltages generate thinner films that are generally lighter in color, which may be acceptable for gray or to obtain a tan color.
  • Average voltage may be in increasing order of preference at least 300, 310, 320 330, 350, or 375 volts and independently preferably may be less than 600, 550, 500, 450, 425 or 400 volts. In one embodiment, average voltage can range from about 300-450 volts. In another embodiment, average voltage may be selected to be in a higher range of 400-550 volts.
  • Voltage is applied across the electrodes until a coating of the desired thickness is formed on the surface of the article. Generally, higher voltages result in increased overall coating thickness. Higher voltages may be used within the scope of the invention provided that the substrate is not damaged and coating formation is not negatively affected.
  • magnesium-containing surfaces Prior to electrolytic coating, magnesium-containing surfaces may be subjected to one or more of cleaning, etching, deoxidizing and desmutting steps, with or without rinsing steps. Cleaning may be alkaline cleaning and a cleaner may be used to etch the surfaces. A suitable cleaner for this purpose is Parco Cleaner 305, an alkaline cleaner commercially available from Henkel Corporation. Desirably, the magnesium-containing surfaces may be etched by at least in increasing order of preference 1, 3, 5, 7, 10, or 15 g/m2 and independently preferably, at least for economy, not more than 20, 25, 30, 35, 40, 45 or 50 g/m2. Etching can be accomplished using commercially available etchants and/or deoxidizers for magnesium.
  • a desmutting step may also be included in processing.
  • Suitable desmutters include acids such as carboxylic acids, e.g. hydroxyacetic acid, alone or in combination with chelators and nitrates. If any of the above- described steps is utilized, the magnesium-containing surfaces are typically rinsed as a final step to reduce introduction of the prior steps' chemistries into the electrolyte. [0075.] Additional processing steps may be used after deposition of the inorganic-based coating, such as rinsing with water, alkaline solutions, acid solutions and combinations of such steps.
  • the process may include steps of applying at least one post-treatment, which may be dispersed in the inorganic-based coating, may form reaction products therewith, and/ or may form an additional layer and combinations thereof.
  • the additional layer may be an inorganic layer, an organic layer or a layer that comprises inorganic and organic components.
  • any post-treatments including for example additional layers described herein, are durably bound to the inorganic-based coating; while other removable layers for masking during manufacture or for shipping after coating may be applied.
  • the porous structure of the electrolytically deposited inorganic-based coatings on the magnesium containing article was a particular challenge for post-treatments that are not pore closing due to the significant surface area present on the internal surfaces of inorganic-based coatings, Surface area of inorganic-based coatings according to the invention is generally 75 to 100 times that of the original metal surface, by BET measurement. Such surface area is typically not found in conventional conversion coatings.
  • the Ti, Zr and the like -containing post-treatment step, described above was surprisingly found to be a suitable method for introducing a second component for additional corrosion protection, in processes according to the invention, despite other post-treatments useful for anodized layers having little or no positive effect on corrosion resistance.
  • At least one post-treatment composition is desirably introduced to the second sub-layer of inorganic-based coating, contacting at least the external surfaces and desirably at least some of the internal surfaces thereof.
  • the second component may comprise the post-treatment composition and/or may comprise reaction products of the post-treatment composition and elements of the inorganic-based coating.
  • the post-treatment composition reacts with elements of the inorganic-based coating to thereby form a second component, which is different from the inorganic-based coating at least in that the second component comprises a metal or polymer from the posttreatment.
  • the second component may form a thin inorganic-based coating in contact with the external surfaces of the inorganic- based coating and lining at least a portion of the pores in the inorganic-based coating.
  • the post-treatment compositions may also contact internal surfaces of the inorganic-based coating and/or react with elements of the internal surfaces rendering the inorganic- based coating more resistant to corrosion producing agents reaching the magnesium containing surface.
  • Depth of penetration of second components into the inorganic-based coating matrix may include up to 70, 65, 60, 55 or 50% of total thickness of the porous second sub-layer of the inorganic-based coating, said total thickness being measured from the second interface to the external surface of the inorganic-based coating.
  • the post-treatment composition may be reactive with elements in the inorganic-based coating. Contacting the inorganic-based coating with a post-treatment composition provides improved corrosion resistance and does not cover up the pores in external surfaces of the inorganic-based coating. This is beneficial if a subsequent paint step is to be used because the pores provide anchoring sites for adhering paint to the surface.
  • Another post-treatment step which may be employed is depositing an additional layer comprising a polymer, preferably this may be done using a thermosetting resin which may or may not react with the inorganic-based coating.
  • Average thickness of the polymeric second layer as measured from an external surface of the inorganic-based coating to an outer surface of the second layer, may range from, in order of increasing preference, at least about 0.1, 0.25, 0.5, 0.75, 1, 2, 3, 4, or 5 microns and in order of increasing preference, not more than about 14, 12, 10, 8 or 6 microns.
  • typical paint thicknesses are at least 25 microns thick.
  • Use of either a thin polymeric layer, as described above, or a paint generally covers the pores in the external surfaces of the inorganic-based coating, the pores providing improved adhesion of the polymer or paint and surprisingly resulting in a uniform surface.
  • polymers forming the second layer may comprise organic polymer chains or inorganic polymer chains.
  • polymers suitable for an additional layer include by way of non- limiting example, silicone, epoxy, phenolic, acrylic, polyurethane, polyester, and polyimide.
  • organic polymers selected from epoxy, phenolic and polyimide are utilized.
  • Preferred polymers forming additional layers include phenol-formaldehyde-based polymers and copolymers generated from, for example novolac resins, which have a formaldehyde to phenol molar ratio of less than one, and resole resins having a formaldehyde to phenol molar ratio of greater than one.
  • Such polyphenol polymers can be made as is known in the art for example according to US Patent No. 5,891,952.
  • Novolac resins are desirably used in combination with a crosslinking agent to facilitate curing, In one
  • a resole resin having a formaldehyde to phenol molar ratio of about 1.5 is utilized to form a polymer additional layer on the inorganic-based coating.
  • Phenolic resins useful in forming polymeric layers desirably have molecular weights of about 1000 to about 5000 g/mole, preferably 2000 to 4000 g/mole.
  • At least one of the above-described resins is desirably introduced to the first layer of inorganic-based coating, contacting at least the external surfaces thereof, and crosslinking to thereby form a polymeric layer on external surfaces of the inorganic-based coating.
  • This polymeric second layer is different from the inorganic-based coating and is adhered to the inorganic-based coating.
  • the resin may also contact internal surfaces of the inorganic-based coating and upon curing form a polymeric second component that is different from the inorganic-based coating and distributed throughout at least a portion of the inorganic-based coating.
  • Analysis of inorganic-based coatings according to the invention that have been contacted with a resole resin having a formaldehyde to phenol molar ratio of 1.5 showed the polymeric components present in the inorganic- based coating matrix thereby forming a composite coating.
  • Depth of penetration of polymeric second components into the inorganic-based coating matrix may range in increasing order of preference from 1, 2, 5, 10, 15, 20 or 25% and in increasing order of preference may be not more than 70, 65, 60, 55 or 50, 45, 40 or 35% of total thickness of the inorganic-based coating, said total thickness being measured from the first interface to the external surface of the inorganic-based coating.
  • the resin may comprise functional groups reactive with elements in the inorganic-based coating, which may form bonds between the resin and the inorganic-based coating.
  • uncured novolac and resole resins comprise OH functional groups which may react with metals in the inorganic-based coating thereby linking the polymer to the inorganic-based coating.
  • Coated substrates according to the invention are useful in motor vehicles; aircraft and electronics where the combination of the inorganic-based coating and post-treatment layers can provide more corrosion protection than paint or anodizing alone, while ceramic-type hardness of the combination imparts additional toughness to external layers because sharp objects have greater difficulty in deforming a harder substrate prime layer than magnesium, which is relatively soft as compared to ceramic. Coatings according to the invention also can be beneficial in keeping the topcoat gloss and color readings relatively consistent by providing a relatively uniform paint base.
  • the process and coated articles of the invention provide a more uniform dark colored surface on magnesium and magnesium alloys, by way of non-limiting example AZ-3 IB, AZ-91B, AZ-91D, AM- 60, AM-50, AM-20, AS-41 , AS-21, AE-42, LZ-91, WS-82 and AM-lite®, a proprietary Mg-Zn-Al alloy.
  • the uniformity aids in adhesion of any subsequently applied layers which provides improved corrosion resistance.
  • the AZ-31 Mg alloy panels were about-93-97 wt.% Mg, the remainder being made up of Al, Zn, Mn, and less than 0.5 wt.% of other metal and metalloid impurities.
  • the AZ-91 Mg alloy panels had less magnesium, about 87-91 wt.% Mg, with the remainder being made up of Al, Zn, Mn, and less than 1.2 wt.% of other metal and metalloid impurities.
  • Example 1 BLACK Electroceramic Coating On Magnesium
  • AZ-31 Mg alloy panels were immersed in an electrolyte bath containing:
  • the electrolyte pH was measured at 10.55.
  • the panels were electrolytically coated as the anode for 30 seconds at a peak voltage of 350 volts utilizing a square DC waveform of 25 milliseconds on and 9 milliseconds off generating an edge-covering, inorganic-based coating.
  • the coated panels were removed from the electrolyte bath and rinsed with Deionized water for 300 sec. [0092.]
  • the resulting coating appeared uniformly black to the unaided human eye.
  • Color was measured with a Minolta Cr 300 color meter: the coating had color values of L, a, b of: 29.93, -2.14 and +2.33 respectively.
  • the inorganic-based coating had a uniform texture and surface appearance.
  • the coating thickness was measured and had a thickness of 10.01 microns. Coating was corrosion tested under e-coat paint and passed 504 hours of B-l 17 ASTM NSS testing.
  • AZ-31 Mg alloy panels were immersed in an electrolyte bath, as described below, and coated under the same conditions as Example 1 :
  • the resulting coating appeared uniformly black to the unaided human eye.
  • the coating was measured with a Minolta Cr color meter and had an L, a, b of: 28.18, -2.68, +2.33 respectively, the inorganic-based coating had a uniform texture and surface appearance, and the coating thickness was measured to be 10.22 microns.
  • AZ-31 Mg alloy panels were immersed in an electrolyte bath, as described below, and coated under the same conditions as Example 1 :
  • the pH of the bath was measured at 10.26.
  • the resulting coating appeared uniformly black to the unaided human eye.
  • the resulting coating was measured with a Minolta Cr color meter and had an L, a, b of: 28.87, -2.66 and +2.70 respectively.
  • the inorganic-based coating had a uniform texture and surface appearance and had a thickness of 9.29 microns.
  • AZ-31 Mg alloy panels were immersed in an electrolyte bath, as described below, and coated under the same conditions as Example 1 :
  • the pH of the bath was measured at 10.30.
  • the resulting coating appeared uniformly black to the unaided human eye.
  • the coating was measured with a Minolta Cr color meter and had an L, a, b of: 32.59, -1.62 and +6.13 respectively.
  • the inorganic-based coating had a uniform texture and surface appearance and had a thickness of 10.06 microns.
  • Example 5 BROWN Electroceramic Coating On Magnesium
  • AZ-31 Mg alloy panels were immersed in an electrolyte bath, as described below, and coated under the same conditions as Example 1 :
  • the pH of the bath was measured at 10.33.
  • the resulting coating appeared uniformly brown to the unaided human eye.
  • the coating was measured with a Minolta Cr color meter and had an L, a, b of: 42.19, -1.89 and +1 1.90 respectively.
  • the inorganic-based coating had a uniform texture and surface appearance and had a thickness of 15.76 microns.
  • AZ-31 Mg alloy panels were immersed in an electrolyte bath according to Example 3, and coated under the same conditions as Example 1, except a higher peak voltage of 420 volts was used.
  • the resulting coating was measured with a Minolta Cr color meter and had an L, a, b of: 25.21, -2.75 and +1.55 respectively.
  • the inorganic-based coating was uniform and had a thickness of 14.98 microns.
  • AZ-31 Mg alloy panels were cleaned with the same cleaning used in Example 1. Thereafter, the panels were immersed in an electrolyte bath and subjected to plasma electrolytic oxidation (PEO) coating in the high concentration phosphate electrolyte, as described below, with ammonium
  • Example 8 GRAY Electroceramic Coating On Magnesium
  • AZ-31 Mg alloy panels were immersed in an electrolyte bath, as described below, and coated under the same conditions as Example 1 :
  • the resulting coating was a uniform grey color.
  • the inorganic-based coating had a thickness of 10.2 microns.
  • the electrolyte pH was measured at 10.51.
  • the inorganic-based coating was extremely uniform and had a thickness of 8.48 microns.
  • This coating had emissivity of 0.77 (on a scale of 0 to 1) which makes it useful for heat sink and heat dissipation applications, for example in electronics where light weight and uniform visual appearance are desirable.
  • GDOES depth profile was performed for this example.
  • the GDOES results, shown in Fig. 1, tend to show that the chemical composition in the outermost 0.5 microns of the electroceramic coating makes a significant contribution to imparting a desired color to the coating.
  • Example 11 Comparative Examples 2. 3 and 4
  • a standard commercial cleaning and deoxidizing process was used to prepare AZ31 panels which was identical in panels and preparation to the examples according to the invention. Panels measuring 1 inch by 2 inches (2.54 cm by 5.08 cm) were each immersed in one of the electrolytes and electrolyzed at 20 amps, 350 volts utilizing a square DC waveform of 25 milliseconds on and 9 milliseconds off, for 45 sees. Amperage and voltage were within the parameters disclosed in the '598 publication and time was selected to be comparable to the examples according to the invention.

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Abstract

La présente invention concerne des articles ayant des surfaces métalliques contenant du magnésium avec un revêtement électrocéramique noir, brun ou bronze, chimiquement lié directement aux surfaces métalliques contenant du magnésium magnésium, le revêtement ayant une couche externe de couleur sombre et une couche interfaciale sous-jacente. L'invention concerne également des articles portant un revêtement composite comprenant des premiers secteurs de revêtement électrocéramique et des seconds secteurs comprenant des composants organiques et/ou inorganiques différents du revêtement électrocéramique. En outre, l'invention concerne des procédés de production et d'utilisation des articles.
EP17889436.6A 2017-01-01 2017-12-29 Revêtements électrocéramiques de couleur sombre pour le magnésium Withdrawn EP3562976A1 (fr)

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