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
  • C25D11/026—Anodisation with spark discharge

Definitions

• the present invention concerns surface chemical treatment, in particular to surface chemical treatment for metal material.
• the ceramic materials have become the third generation engineering materials because of their special performances, superiority of rich resources.
• the whole ceramic materials are brittle, not easy to process, their wide application has been limited all the time.
• Creating ceramic layers on the surface of metals and alloys we may use cheap metal materials instead of expensive metal materials with the prerequisite for guaranteeing the use performance, at the same time endow with the substrate metal material some special performances that can not be obtained by the other surface treatment methods and enlarge its suitable range.
• using easy-processing materials as the substrate to apply surface ceramic coating can increase the shaping and processing performances for the ceramic materials, providing guarantee for making complicated shape spares with ceramic coating, and carving out a new way for widely using ceramic products.
• surface ceramic coating for the surface of metal and alloy can be carried out by using both plasma spraying and solid powder applying in addition to laser melt-coating, i.e., sintering on the metal surface by using additional powder material or part of powder material itself under high-density energy so as to obtain ceramic coating.
• Technique for plasma spraying and laser melt-coating generally use solid powder as metal and carbonate, oxygenate and boronate compound powder. After high energy sintering, ceramic layer forms on surface of substrate. Its hard particle mostly consists in the carbonate, oxygenate and boronate compound of metal (transitional group), in an amount of about 40-90%, and about 10-60% of solid component.
• the surface ceramic layer produced by plasma spraying and laser melt-coating has a topography of irregular mosaic stacking with higher porosity and less defectives in macrostate. Each component exhibits un-uniform distribution in the coating layer, and the binding between each coating layer are of mechanical with clear boundary. Following are some shortcomings in these methods.
• a common process for metal or alloy (such as aluminum alloy) surface treatment is anodic oxidation.
• the process is anodic oxidizing the work piece which is anode in acidic electrolyte (such as sulfuric acid solution).
• aluminum oxide is formed on the anode surface by combining the primary oxygen and the anode (work piece), and the aluminum oxide provides an internal oxide film which is of high density and high hardness with its thickness being 0.01-0.05 ⁇ m.
• Such oxide film is not easy to be permeated by eletrolyte so to be called as a barrier.
• the outer oxide which contacts to the electrolyte consists with aluminum oxide and monohydrate aluminum oxide.
• Such oxide film has large amount of pore, and make electrolyte easily permeate their between. So, upon energizing, it is continuous to increase the amount of micropore and deepen and thicken the micropore, so as called film-forming.
• Such coating layer obtained by using conventional process shows a topography of capillary porous structure, in which components distributes uniformly in the layer and the binding between layer and substrate is high.
• the chemical components of the film general are Al 2 O 3 and Al 2 O 3 ⁇ H 2 O in the amount of 95.0-99.0, and other impurity in the amount of 1.0-5.0%.
• Such conventional oxidation technique has following shortcomings:
• the object of the invention is to overcome the above defects in the prior art, and provide a process for surface ceramic-coating on metal substrate and a product thereof.
• Another object of the invention is to provide a kind of metal products coated by ceramic layer.
• the present invention is a process for electrochemical anodic oxidation on a metal substrate as anode through plasma are discharging and sintering the electrolyte on the surface of the substrate so as to form a ceramic structure layer.
• the growing course of the ceramic layer is in electrochemical oxidizing electrolytic bath, the metal workpiece is as anode, adding direct current electrical field between the cathode and the anode, there will be following anodic oxidation reaction on the surface of the workpiece.
• the process of the present invention also comprises the steps of cleaning the substrate metal before anodic oxidization, and rinsing, then sealing the surface after anodic oxidation. Therefore, the process of the present invention comprises following steps:
• alkaline clean liquid which is formulated as Na 3 PO 4 ⁇ 12H 2 O 50-60g/l, Na 2 SiO 3 10-15g/l, Na 2 CO 3 10-20g/l and surfactant 0.1-10ml/l. It is required that the clean liquid must be forced to be stirred or to be sprayed to the surface of workpiece in the bath,to make it clean up at the temperature of 40-60°C for 20-30 min. Then the workpiece is immersed in a potcher containing clean water at the temperature of 15-20°C and rinsed until there are no clean liquid aforementioned remained on the surface of the workpiece.
• Products with different colors, pattern, designs and properties, which can be applied in various field, can be obtained by using various electrolyte solutions, controlling various operation current, voltage, temperature of the solutions, stirring strength and pattern.
• the voltage for arc discharging is usually between 100-400V, the current density is 0.5-20A/dm 2 , and the temperature of the solution is 10-50°C.
• the decorative film with various dots patterns or homogeneous dark pink film can be obtained by using the method of ⁇ 2 ⁇ .
• the oxidizing time is 5-25 min, the thickness is 5-25 ⁇ m.
• the film thus obtained is in light pink to dark pink.
• the method for combining is as same as ⁇ 1 ⁇ .
• the homogeneous color film in light grey to dark grey or dots patterns film in grey can be obtained.
• the thickness is 5-20 ⁇ m.
• any two kinds of them can be mixed together to produce different color film.
• the white film oxidized in electrolyte ⁇ 1 ⁇ can be overlapped by blue dots in electrolyte ⁇ 2 ⁇ with the above stirring manner, and become another kind of product.
• the details show in the following examples.
• Temperature of water is 15-60°C. The requirement is cleaning up the workpiece until there are no electrolyte solution remaining on the surface of it.
• the workpiece After rinsing, the workpiece can be sealed by using the process of dip coating, pour coating, spray coating and etc. to improve the luster. Paints of water-soluble acrylic acid resin or water-soluble amino resin, and etc. can be used, and according to the requirements of the paint, be baked at 150-250°C for 5-30min in the case when the water-soluble acrylic acid is used. After baking, the products must be inspected to be standard, and then packed.
• the content of the material from the electrolyte in the layer by using the process of the present invention is higher than that of traditional anodic oxide film lay, and there are no oxide hydrate of the substrate Metal in the film.
• the products obtained by using the process of the present invention are composed of substrate metal and the ceramic layer on the surface of the substrate.
• the content of the substrate metal oxide is 70.0-95.0% by weight
• the content of the other metal oxides, non-metal oxides, inorganic salts or their mixture is 5.0-3.0% by weight.
• Said ceramic layer is formed by using the process of anodic oxidation enhanced plasma arc discharge.
• the described other metal oxides, non-metal oxides, inorganic salts or their mixture come from the electrolyte solution.
• the layer's appearance of the products is stacked in regular mosaic manner, and the rate of holes is very low, which is less than 0.5%. There are little macroscopic defect.
• Each composition is uniformly the layer. Because the metal atoms on the substrate surface take part in the reaction directly, the layer and the substrate are combined closely, and have no obvious boundary.
• the homogeneity of the ceramic layer of the products in the present invention is good, and the combination strength between the layer and the substrate is higher.
• the holes in the layer are little. Both ram resistance and corrosion resistance are good, and the colors are bright and there are many patterns, as well as the decorative effect is great.
• the process of the present invention is suitable for surface treatment of the substrate workpiece of any dimension, shape and construction.
• the oxidization treatment began when the solution in the bath was stirred in the case of the workpiece as anode and a stainless steel plate as cathode. Keeping the current being constant 1A, the voltage was slowly raised to 160-180V, on the surface of the workpiece, there was the phenomenon of plasma arc discharge. When the voltage raised to 210-240V, the current decreased. The duration for oxidization was 10 min, then the oxidization was stopped by adjusting the current to 0, the voltage to 0 and shutting off the power source. The workpiece was taken out form the bath and a white film was thus obtained. After cleaning, the holes was closed, and the workpiece was dip coated in water-soluble acrylic acid resin, and then baked for 5 min. at 220°C, and then taken out to be an end product. The thickness of the film was measured as 10 ⁇ m, microhardness (HV) was 310kg/mm 2 (5g), and wear resistance was judgement the time of spraying sands was 300 second.
• the sections was put into the cleaning bath, dipped for 25 min. After raised by a shop traveler, the sections were dropped water freely, then was put into a potcher. After raised, they were put into the second potcher and then to the oxide bath to begin electrifying and oxidizing.
• the current was 1A/dm 2 , the voltage was raised slowly. Stirring the solution, cooling, when the voltage was raised to 150V, small arc light on the surface of the workpieces occurred.
• the operation conditions described ahead was kept for 10min, the end voltage was 230V. Then the workpieces were put into potcher to rinse again, and dipped into resin bath, and baked in an oven. After unloading from the hanging, products was packed.
• the color of the film was coffee-color, and the thickness was measured as 8-11 ⁇ m.
• the appearance of the end products was homogeneous, and the microhardness (HV) was 260-480kg/mm 2 (0.049N), and wear resistance was judgement the time of spraying sands was 300-500 second.
• the oxidizing time was controlled to 15min, voltage 150V, then current was decreased and the power source be shut off.
• the workpiece was taken out and rinsed. After baking, the color of the workpiece was grey.
• the thickness of the film was measured as 15 ⁇ m, CASS test: class 9.
• the workpiece was taken out from the bath, rinsed and baked until to be an end product.
• the thickness of the film was measured as 50-70 ⁇ m, the time for wear resistance of spray sands was 720-800 second, microhardness was 900-1300HV (0.098N), and the combination strength with substrate was 25.6-35.0kg/mm 2 .

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Detergent Compositions (AREA)

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• 1995
  • 1995-04-18 CN CN95114880A patent/CN1034522C/zh not_active Expired - Fee Related
  • 1995-09-11 EP EP95930367A patent/EP0823496B1/fr not_active Revoked
  • 1995-09-11 JP JP8531384A patent/JP2937484B2/ja not_active Expired - Fee Related
  • 1995-09-11 DE DE69526256T patent/DE69526256T2/de not_active Expired - Fee Related
  • 1995-09-11 AU AU33788/95A patent/AU3378895A/en not_active Abandoned
  • 1995-09-11 WO PCT/CN1995/000072 patent/WO1996033300A1/fr not_active Ceased

Non-Patent Citations (3)

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