CN113373442B - Zinc-cadmium alloy composite coating of aerospace electrical appliance accessory and preparation method thereof - Google Patents

Zinc-cadmium alloy composite coating of aerospace electrical appliance accessory and preparation method thereof Download PDF

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CN113373442B
CN113373442B CN202110653496.2A CN202110653496A CN113373442B CN 113373442 B CN113373442 B CN 113373442B CN 202110653496 A CN202110653496 A CN 202110653496A CN 113373442 B CN113373442 B CN 113373442B
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zinc
component
cadmium
coating
layer
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CN113373442A (en
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赖奂汶
郭崇武
陈媚
夏亮
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Guangzhou Ultra Union Chemicals Ltd
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
    • C23C28/32—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer
    • C23C28/322—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer only coatings of metal elements only
    • C23C28/3225—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer only coatings of metal elements only with at least one zinc-based layer
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • 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
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/31—Coating with metals
    • C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
    • C23C18/34—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • 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
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/48—Coating with alloys
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • 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
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • 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
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/82—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
    • C23C28/32—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer
    • C23C28/321—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer with at least one metal alloy layer
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
    • C23C28/34—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
    • C23C28/34—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates
    • C23C28/345—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates with at least one oxide layer
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/12—Electroplating: Baths therefor from solutions of nickel or cobalt
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/56—Electroplating: Baths therefor from solutions of alloys
    • C25D3/565—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of zinc
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • 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
    • C23C2222/00—Aspects relating to chemical surface treatment of metallic material by reaction of the surface with a reactive medium
    • C23C2222/20—Use of solutions containing silanes

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Electrochemistry (AREA)
  • Electroplating Methods And Accessories (AREA)

Abstract

The invention provides a zinc-cadmium alloy composite coating of an aerospace electrical appliance accessory and a preparation method thereof, and relates to the technical field of protective materials. The zinc-cadmium alloy composite coating provided by the invention comprises a chemical zinc deposition layer, a nickel coating, a zinc-cadmium alloy coating, a silane chromium-free passivation layer and a graphene sealing layer which are sequentially arranged on the surface of an aluminum alloy substrate. According to the invention, the chemical zinc deposition layer and the nickel coating are arranged on the surface of the aluminum alloy matrix, so that the bonding strength of the zinc-cadmium alloy coating and the aluminum alloy matrix is improved; the zinc-cadmium alloy plating layer has excellent corrosion resistance, replaces a cadmium plating layer of the traditional aerospace part, and can greatly reduce the pollution of cadmium to the environment; the invention adopts the silane chromium-free passivation layer to replace the hexavalent chromium passivation layer with high toxicity, thereby avoiding the pollution of hexavalent chromium to the environment; according to the invention, the graphene sealing layer is arranged on the surface of the silane chromium-free passivation layer, so that the technical defect of poor weather resistance of the silane chromium-free passivation layer can be overcome.

Description

Zinc-cadmium alloy composite coating of aerospace electrical appliance accessory and preparation method thereof
Technical Field
The invention relates to the technical field of protective materials, in particular to a zinc-cadmium alloy composite coating of aerospace electrical fittings and a preparation method thereof.
Background
Aerospace electrical fittings are usually processed and manufactured by adopting aluminum alloy materials, and cadmium plating and hexavalent chromium passivation are needed to prepare a high-corrosion-resistance protective layer. The adoption of trivalent chromium passivation for civil zinc plating and zinc-nickel alloy has made great progress, but the trivalent chromium passivation layer has no self-repairing property and can not meet the technical requirements of military products. Therefore, in the past, cadmium plating and other plating layers of aerospace products are passivated by hexavalent chromium, but the hexavalent chromium passivation has the problem of high pollution and has great destructive effect on human health and natural environment.
A passivation layer prepared by adopting the solvent type silane chromium-free passivator has self-repairing property (see tenacious, guo Chongwu, high-performance chromium-free passivation technology, electroplating and environmental protection, 6 th stage of 2012: 35-37), but the passivation layer has the defect of poor weather resistance, and white powder appears on the surface after the passivation layer is placed in a natural environment for one year, so that the corrosion resistance is reduced, and therefore, the passivation layer prepared by adopting the passivator for aerospace products can not meet the requirement of the aerospace industry.
Disclosure of Invention
The invention aims to provide a zinc-cadmium alloy composite coating of an aerospace electrical appliance accessory and a preparation method thereof. The zinc-cadmium alloy composite coating provided by the invention has excellent weather resistance and corrosion resistance, and the adoption of the silane chromium-free passivation layer can avoid the pollution of hexavalent chromium to the environment.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a zinc-cadmium alloy composite coating of an aerospace electrical appliance accessory, which comprises a chemical zinc deposition layer, a nickel coating, a zinc-cadmium alloy coating, a silane chromium-free passivation layer and a graphene sealing layer which are sequentially arranged on the surface of an aluminum alloy substrate.
Preferably, the thickness of the nickel plating layer is 1-8 μm; the thickness of the zinc-cadmium alloy plating layer is 8-28 mu m; the thickness of the silane chromium-free passivation layer is 0.5-2 mu m; the thickness of the graphene sealing layer is 2-4 mu m.
The invention provides a preparation method of a zinc-cadmium alloy composite coating of an aerospace electrical appliance accessory in the technical scheme, which comprises the following steps:
a chemical zinc deposition layer, a nickel coating, a zinc-cadmium alloy coating, a silane chromium-free passivation layer and a graphene sealing layer are sequentially prepared on the surface of an aluminum alloy substrate.
Preferably, the zinc-cadmium alloy coating is prepared by an electroplating process; the electroplating liquid adopted by the zinc-cadmium alloy plating layer comprises 30-50 g/L of zinc chloride, 10-25 g/L of cadmium chloride, 140-180 g/L of potassium chloride, 100-160 g/L of coordination agent, 1.5-2.5 mL/L of brightening agent and 25-35 mL/L of auxiliary agent.
Preferably, the preparation raw material of the complexing agent comprises a component A and a component B; the mass ratio of the component A to the component B is 7:6 to 10;
the component A comprises nitrilotriacetic acid and glycine; the mass ratio of the nitrilotriacetic acid to the glycine is 7:4 to 6;
the component B comprises one or two of citric acid, tartaric acid, gluconic acid and malic acid.
Preferably, the raw materials for preparing the brightener comprise a component C, a component D, a component E, a component F and a component G; the mass ratio of the component C to the component D to the component E to the component F to the component G is 30-60: 30 to 50:100 to 150:20 to 30:40 to 70 percent;
the component C is one or two of 2, 3-dimethylbenzaldehyde, 2, 5-dimethylbenzaldehyde, 2, 6-dimethylbenzaldehyde, 3, 4-dimethylbenzaldehyde and 3, 5-dimethylbenzaldehyde;
the component D comprises one or two of 3-methoxy-4-hydroxybenzaldehyde, 3, 4-dimethoxybenzaldehyde and 4-methoxybenzaldehyde;
the component E comprises one or two of propargyl alcohol ethoxy ether, propargyl alcohol propoxy ether, N-diethyl propargyl amine, N-diethyl propargyl amine formate, N-diethyl propargyl amine sulfate and propiolic salt;
the component F is o-chlorobenzaldehyde;
the component G is butyl ether humate.
Preferably, the preparation raw materials of the auxiliary agent comprise polyacrylamide, sodium benzoate, sodium dimethyl benzene sulfonate, a condensate of ethylenediamine and epichlorohydrin and polyoxyethylene ether phosphate; the mass ratio of the polyacrylamide, sodium benzoate, sodium dimethyl benzene sulfonate, the condensate of ethylenediamine and epoxy chloropropane and polyoxyethylene ether phosphate is 50-80: 30 to 60: 50-80: 30 to 70:30 to 70.
Preferably, the electroplating conditions of the zinc-cadmium alloy coating comprise: the pH value of the electroplating solution is 6.5-7.5; the electroplating temperature is 15-35 ℃; the cathode current density is 0.5-2.5A/dm 2 (ii) a The anode is a zinc plate for electroplating and a cadmium plate for electroplating; what is needed isThe area ratio of the zinc plate for electroplating to the cadmium plate for electroplating is 5:1 to 2.
Preferably, the passivating agent adopted for preparing the silane chromium-free passivation layer is a zinc prociol Z-Caot 888FL solvent type silane chromium-free passivating agent; the passivation time is 50-70 s.
Preferably, the graphene sealing layer is prepared by adopting a hydroxyl graphene modified plating layer sealing agent.
The invention provides a zinc-cadmium alloy composite coating of an aerospace electrical appliance accessory, which comprises a chemical zinc deposition layer, a nickel coating, a zinc-cadmium alloy coating, a silane chromium-free passivation layer and a graphene sealing layer which are sequentially arranged on the surface of an aluminum alloy substrate. According to the invention, the chemical zinc deposition layer and the nickel coating are arranged on the surface of the aluminum alloy matrix, so that the bonding strength of the zinc-cadmium alloy coating and the aluminum alloy matrix is improved; in the invention, the zinc-cadmium alloy plating layer has excellent corrosion resistance, replaces a cadmium plating layer of the traditional aerospace part, and can greatly reduce the pollution of cadmium to the environment; according to the invention, a silane chromium-free passivation layer is adopted to replace a high-toxicity hexavalent chromium passivation layer, so that the pollution of hexavalent chromium to the environment can be avoided; according to the invention, the graphene sealing layer is arranged on the surface of the silane chromium-free passivation layer, so that the technical defect of poor weather resistance of the silane chromium-free passivation layer can be overcome. The zinc-cadmium alloy composite coating provided by the invention has excellent weather resistance and corrosion resistance, and can meet the use requirements of aerospace electrical fittings.
Drawings
FIG. 1 is a schematic structural diagram of a zinc-cadmium alloy composite coating of an aerospace electrical fitting provided by the invention; wherein 1 is an aluminum alloy matrix, 2 is a chemical zinc deposition layer, 3 is a nickel coating, 4 is a zinc-cadmium alloy coating, 5 is a silane chromium-free passivation layer, and 6 is a graphene sealing layer;
FIG. 2 is a salt spray test result chart of the Zn-Cd alloy composite coating of the aerospace electrical parts prepared in examples 1-3.
Detailed Description
The invention provides a zinc-cadmium alloy composite coating of an aerospace electrical appliance accessory, which comprises a chemical zinc deposition layer, a nickel coating, a zinc-cadmium alloy coating, a silane chromium-free passivation layer and a graphene sealing layer which are sequentially arranged on the surface of an aluminum alloy substrate as shown in figure 1.
The invention has no special requirements on the specific components of the aluminum alloy matrix, and the aluminum alloy known by the technicians in the field can be adopted.
The zinc-cadmium alloy composite coating of the aerospace electrical appliance accessory provided by the invention comprises a chemical zinc deposition layer arranged on the surface of an aluminum alloy substrate. In the invention, the chemical precipitation zinc layer is used as a pre-plating layer of the nickel plating layer.
In the present invention, the composition of the electroless zinc plating layer preferably includes zinc and copper or zinc and nickel; in the invention, when the chemical zinc deposition layer comprises zinc and copper, the mass content of the copper in the chemical zinc deposition layer is preferably 10-20%, and more preferably 12-15%; when the chemical zinc deposition layer comprises zinc and nickel, the mass content of the nickel element in the chemical zinc deposition layer is preferably 10-20%, and more preferably 13-16%.
The zinc-cadmium alloy composite coating of the aerospace electrical appliance accessory provided by the invention comprises a nickel coating arranged on the surface of the chemical deposition zinc layer. In the invention, the nickel plating layer can make the zinc-cadmium alloy plating layer become an anode plating layer, and the corrosion resistance of the zinc-cadmium alloy plating layer is improved.
In the present invention, the thickness of the nickel plating layer is preferably 1 to 8 μm, more preferably 2 to 6 μm, and still more preferably 3 to 5 μm.
The zinc-cadmium alloy composite coating of the aerospace electrical appliance accessory comprises a zinc-cadmium alloy coating arranged on the surface of the nickel coating. In the invention, the zinc-cadmium alloy plating layer has excellent corrosion resistance, and can obviously improve the corrosion resistance of the aluminum alloy parts.
In the present invention, the thickness of the zinc-cadmium alloy plating layer is preferably 8 to 28 μm, more preferably 10 to 16 μm, and still more preferably 10 to 14 μm. In the invention, the mass content of cadmium element in the zinc-cadmium alloy coating is preferably 20-40%, and more preferably 25-35%; the balance being zinc.
The zinc-cadmium alloy composite coating of the aerospace electrical appliance accessory provided by the invention comprises a silane chromium-free passivation layer arranged on the surface of the zinc-cadmium alloy coating. In the invention, the silane chromium-free passivation layer has self-repairing property, and can improve the corrosion resistance of the aluminum alloy part by matching with the arrangement of other layers.
In the present invention, the thickness of the silane chromium-free passivation layer is preferably 0.5 to 2 μm, more preferably 0.8 to 1.1 μm, and still more preferably 0.9 to 1.0 μm.
The zinc-cadmium alloy composite coating of the aerospace electrical appliance accessory provided by the invention comprises a graphene sealing layer arranged on the surface of the silane chromium-free passivation layer. According to the invention, the silane chromium-free passivation layer is sealed by the graphene sealant, so that the technical defect of poor weather resistance of the silane chromium-free passivation layer can be overcome; but also can improve the wear resistance and the corrosion resistance of the aluminum alloy parts.
In the present invention, the thickness of the graphene sealing layer is preferably 2 to 4 μm, more preferably 2.8 to 3.2 μm, and still more preferably 2.9 to 3.1 μm.
The invention also provides a preparation method of the zinc-cadmium alloy composite coating of the aerospace electrical appliance fitting, which comprises the following steps:
a chemical zinc deposition layer, a nickel coating, a zinc-cadmium alloy coating, a silane chromium-free passivation layer and a graphene sealing layer are sequentially prepared on the surface of an aluminum alloy substrate.
The chemical zinc deposition layer is prepared on the surface of the aluminum alloy substrate. According to the invention, the aluminum alloy matrix is preferably placed in the zinc deposition solution for zinc deposition. The invention preferably carries out pretreatment on the aluminum alloy matrix before preparing the chemical zinc deposition layer. In the present invention, the method of pretreatment preferably includes wax removal, oil removal, and activation, which are performed in this order. The present invention has no special requirements for the specific processes of dewaxing, degreasing and activation, and can be carried out by processes well known to those skilled in the art.
According to the invention, the aluminum alloy substrate is preferably subjected to primary zinc deposition, water washing, zinc removal, water washing, secondary zinc deposition and water washing in sequence, so that a chemical zinc deposition layer is formed on the surface of the aluminum alloy substrate. In the invention, the zinc precipitating liquid adopted by the first zinc precipitating and the second zinc precipitating is preferably the same; the zinc stripping is preferably carried out by adopting a nitric acid solution with the volume fraction of 10%.
In the invention, the zinc precipitating solution is preferably an aqueous solution of a zinc precipitating agent. In the present invention, the zinc precipitating agent preferably comprises a cyanide-free aluminum zinc-precipitating agent or an acidic aluminum zinc-precipitating agent. In the present invention, the cyanide-free aluminum zinc-plating agent preferably comprises zinc ions and copper ions; the concentration of zinc ions in the cyanide-free aluminum zinc-plating agent is preferably 6-9 g/L, and more preferably 7-8 g/L; the concentration of copper ions is preferably 0.16 to 0.20g/L, more preferably 0.18 to 0.19g/L. In the present invention, the acidic aluminum zinc-plating agent preferably includes zinc ions and nickel ions; the concentration of zinc ions in the acidic aluminum zinc-plating agent is preferably 5-10 g/L, and the concentration of nickel ions is preferably 0.5-1.5 g/L.
In a specific embodiment of the invention, the cyanide-free aluminum zinc-plating agent is an ALBUMEAS-699 cyanide-free aluminum zinc-plating agent produced by Guangzhou ultra-Pont chemical Co., ltd; the acid aluminum zinc-plating agent is AZIN-113 acid aluminum zinc-plating agent produced by Guangzhou Chaobang chemical industry Co.
In the invention, when the zinc precipitating agent is a cyanide-free aluminum zinc-up precipitating agent, the concentration of the zinc precipitating agent in the zinc precipitating solution is preferably 160-200 mL/L, and more preferably 180-190 mL/L; the working temperature of the zinc deposition is preferably 20-30 ℃, and more preferably 25 ℃; the time for depositing the zinc is preferably 60 to 120s, and more preferably 80 to 100s. In the invention, when the zinc precipitating agent is an acidic aluminum zinc-up precipitating agent, the concentration of the zinc precipitating agent in the zinc precipitating solution is preferably 50-250 mL/L, and more preferably 150-200 mL/L; the pH value of the zinc precipitation solution is preferably 3.4-4.2, and more preferably 3.6-3.8; the working temperature of the zinc deposition is preferably 15-30 ℃, and more preferably 20-25 ℃; the time for depositing the zinc is preferably 20 to 80s, and more preferably 40 to 50s.
After the chemical zinc deposition layer is obtained, the nickel coating is prepared on the surface of the chemical zinc deposition layer. The invention preferably adopts a watt nickel plating process or a low-phosphorus chemical nickel plating process to prepare the nickel plating layer.
In the present invention, the nickel plating solution used for preparing the nickel plating layer by the watt nickel plating process preferably includes: 200-250 mL/L of nickel sulfate, 45-55 mL/L of nickel chloride and 30-35 mL/L of boric acid. In the specific embodiment of the invention, the nickel plating solution comprises 220-230 mL/L nickel sulfate and is chloridized50-53 mL/L of nickel and 33-34 mL/L of boric acid. In the present invention, the plating parameters for preparing the nickel plating layer by the watt nickel plating process preferably include: the temperature is 25 to 40 ℃, and more preferably 30 ℃; the pH value of the nickel plating solution is 4.1-4.5, and more preferably 4.2-4.3; the current density is 1.5-4A/dm 2 More preferably 1.8 to 2A/dm 2 (ii) a The moving speed of the cathode is 4 to 6m/min, and more preferably 5m/min.
In the invention, the low-phosphorus chemical nickel plating process is preferably adopted to prepare the nickel plating layer, and the GG-178 alkaline chemical nickel plating process of Guangzhou ultra-Pont chemical Co., ltd is preferably adopted to prepare the nickel plating layer; the chemical nickel plating solution for preparing the nickel plating layer by adopting the low-phosphorus chemical nickel plating process preferably comprises the following components: GG-178A additive 25-50 mL/L, more preferably 30-40 mL/L; GG-178B reducing agent 25-40 mL/L, more preferably 30-35 mL/L; GG-178C stabilizer is 30-60 mL/L, and more preferably 40-50 mL/L. In the present invention, the parameters for preparing the nickel plating layer by the low-phosphorus chemical nickel plating process preferably include: the operating temperature is 25-38 ℃, and more preferably 30-35 ℃; the pH of the electroless nickel plating solution is in the range of 8.5 to 9.5, more preferably 9.0.
After the nickel coating is obtained, the zinc-cadmium alloy coating is prepared on the surface of the nickel coating. In the invention, the zinc-cadmium alloy plating layer is preferably prepared by adopting an electroplating process, more preferably a potassium chloride zinc-cadmium alloy electroplating process, and particularly preferably a potassium chloride zinc-cadmium alloy electroplating process of Guangzhou ultra-Pont chemical Co. In the invention, the zinc-cadmium alloy plating layer is formed by electroplating in a plating tank containing electroplating solution by taking the aluminum alloy plating piece deposited with the nickel plating layer as a cathode and taking a zinc plate for electroplating and a cadmium plate for electroplating as anodes. In the present invention, the area ratio of the zinc plate for plating to the cadmium plate for plating is preferably 5:1 to 2, more preferably 5: 1.5. In the present invention, the purity of the zinc plate for plating is preferably more than 99.99% by mass, and the purity of the cadmium plate for plating is preferably more than 99.97% by mass.
In the invention, the electroplating solution adopted by the zinc-cadmium alloy plating part preferably comprises 30-50 g/L of zinc chloride, and more preferably 40g/L; 10-25 g/L of cadmium chloride, more preferably 18-20 g/L; 140-180 g/L of potassium chloride, more preferably 150-170 g/L, and 100-160 g/L of complexing agent, more preferably 130-150 g/L; 1.5-2.5 mL/L of brightener, more preferably 2-2.3 mL/L; the adjuvant is 25 to 35mL/L, and more preferably 30 to 32mL/L.
In the present invention, the raw materials for preparing the complexing agent preferably include component a and component B; the mass ratio of the component A to the component B is preferably 7:6 to 10, more preferably 7:8 to 9; the component A preferably comprises nitrilotriacetic acid and glycine; the mass ratio of the nitrilotriacetic acid to the glycine is preferably 7:4 to 6, more preferably 7:5; the component B preferably comprises one or two of citric acid, tartaric acid, gluconic acid and malic acid. In the present invention, the preparation method of the complexing agent preferably comprises: and mixing the component A and the component B to obtain the complexing agent.
In the present invention, the preparation raw material of the brightener preferably includes component C, component D, component E, component F, and component G; the mass ratio of the component C, the component D, the component E, the component F and the component G is preferably 30-60: 30 to 50:100 to 150:20 to 30:40 to 70, more preferably 45 to 50:40 to 45: 125-130: 25 to 28:55 to 65; the component C is preferably one or two of 2, 3-dimethylbenzaldehyde, 2, 5-dimethylbenzaldehyde, 2, 6-dimethylbenzaldehyde, 3, 4-dimethylbenzaldehyde and 3, 5-dimethylbenzaldehyde; the component D preferably comprises one or two of 3-methoxy-4-hydroxybenzaldehyde, 3, 4-dimethoxybenzaldehyde and 4-methoxybenzaldehyde; the component E preferably comprises one or two of propargyl alcohol ethoxy ether, propargyl alcohol propoxy ether, N-diethyl propargyl amine, N-diethyl propargyl amine formate, N-diethyl propargyl amine sulfate and propiolic salt; the component F is preferably o-chlorobenzaldehyde; the component G is preferably a butyl ether humate. According to the invention, dimethylbenzaldehyde is adopted as a component of the brightener, and the brightness of the zinc-cadmium alloy coating can be effectively improved under the synergistic effect of dimethylbenzaldehyde and other components.
In the present invention, the method for preparing the brightener preferably includes: and (3) taking water and isopropanol as a mixed solvent, and dissolving the component C, the component D, the component E, the component F and the component G in the mixed solvent to obtain the brightener. In the present invention, the volume content of isopropyl alcohol in the brightener is preferably 40%; the total concentration of the component C, the component D, the component E, the component F and the component G in the brightener is preferably 22 to 36 percent, and more preferably 29 to 33 percent. In the present invention, the water is preferably deionized water.
In the present invention, the preparation raw materials of the adjuvant preferably include polyacrylamide, sodium benzoate, sodium dimethyl benzenesulfonate, condensate of ethylenediamine and epichlorohydrin, and polyoxyethylene ether phosphate. In the invention, the mass ratio of the polyacrylamide, sodium benzoate, sodium dimethyl benzene sulfonate, condensate of ethylenediamine and epichlorohydrin to polyoxyethylene ether phosphate is preferably 50-80: 30 to 60: 50-80: 30 to 70:30 to 70, more preferably 65 to 70:45 to 50:65 to 70: 50-60: 50 to 60 percent. In the present invention, the polyacrylamide is preferably a low molecular weight polyacrylamide, the molecular weight range is preferably less than 8000; the invention has no special requirements on the condensation degree and the molecular weight of the condensation compound of the ethylenediamine and the epichlorohydrin, and can be used as a commercially available product; the polyoxyethylene ether phosphate is preferably polyoxyethylene ether phosphate with the product model of PE 600.
In the present invention, the preparation method of the adjuvant preferably includes: and dissolving the polyacrylamide, sodium benzoate, sodium dimethyl benzene sulfonate, a condensation product of ethylenediamine and epoxy chloropropane and polyoxyethylene ether phosphate in water to obtain the auxiliary agent. In the present invention, the total concentration of polyacrylamide, sodium benzoate, sodium dimethylbenzenesulfonate, a condensate of ethylenediamine and epichlorohydrin, and polyoxyethylene ether phosphate in the adjuvant is preferably 19 to 36%, more preferably 27.5 to 33%.
In the present invention, the plating conditions of the zinc-cadmium alloy plating layer preferably include: the pH value of the electroplating solution is 6.5-7.5, and more preferably 6.7-7.3; the electroplating temperature is 15-35 ℃, and more preferably 25-30 ℃; the cathode current density is 0.5-2.5A/dm 2 More preferably 1.0 to 2.0A/dm 2 。
After the zinc-cadmium alloy coating is obtained, the silane chromium-free passivation layer is prepared on the surface of the zinc-cadmium alloy coating. Preferably, before the silane chromium-free passivation layer is prepared, the aluminum alloy plating part deposited with the zinc-cadmium alloy plating layer is subjected to light extraction, oxide film removal and drying in sequence. The invention has no special requirements on the specific processes of light extraction, oxide film removal and drying, and can adopt the processes known by the technical personnel in the field. In the specific embodiment of the invention, the light is extracted by using a nitric acid solution with the volume fraction of 1%; and removing an oxidation film by adopting a sulfuric acid solution with the mass fraction of 5%.
In the invention, the passivating agent used for preparing the silane chromium-free passivation layer is preferably a zinc PROMICO Z-Caot 888FL solvent type silane chromium-free passivating agent. The invention preferably uses a passivating agent stock solution for passivation.
According to the invention, the aluminum alloy plated part deposited with the zinc-cadmium alloy coating is preferably placed in the passivating agent for passivation. In the present invention, the temperature of the passivation is preferably room temperature, and the time of the passivation is preferably 50 to 70s, and more preferably 60s.
According to the invention, after the passivation, the obtained passivation layer is preferably baked to form the silane chromium-free passivation layer. In the invention, the baking temperature is preferably 80-100 ℃, and more preferably 85-95 ℃; the baking time is preferably 18 to 25min, and more preferably 20 to 22min.
After the silane chromium-free passivation layer is obtained, the graphene sealing layer is prepared on the surface of the silane chromium-free passivation layer, and the zinc-cadmium alloy composite coating of the aerospace electrical appliance fitting is obtained. In the invention, the graphene sealing layer is preferably prepared by using a hydroxyl graphene modified plating layer sealing agent. In the present invention, the preparation method of the graphene sealing layer preferably includes: and placing the aluminum alloy plated part with the silane chromium-free passivation layer in a hydroxyl graphene modified plating layer sealant solution, dipping, taking out, baking and curing to form a graphene sealing layer on the surface of the silane chromium-free passivation layer.
In the invention, the hydroxyl graphene modified plating layer sealant in the hydroxyl graphene modified plating layer sealant solution preferably comprises, by mass, 20-30 parts of silica sol, 20-30 parts of PU 113 water-soluble silane polymer (produced by Taiwan Dajin chemical industry, china), 6-20 parts of nano-scale hydroxyl graphene aqueous solution with 1% of carbon element by mass, 0.6 part of TANAOAMS organic silicon defoamer (produced by Dutch Nay Co., ltd.), 0.8 part of LA13-863 organic silicon leveling agent (produced by Dutch Tael Co., ltd.), and 35-45 parts of deionized water. In the invention, the hydroxyl graphene modified coating sealant more preferably comprises 23-27 parts by mass of silica sol, 23-27 parts by mass of PU 113 water-soluble silane polymer, 10 parts by mass of nano-level hydroxyl graphene aqueous solution with 1% of carbon element, 0.6 part by mass of TANAOAMS organic silicon defoamer, 0.8 part by mass of LA13-863 organic silicon flatting agent and 40 parts by mass of deionized water.
In the present invention, the preparation method of the nano-scale graphene hydroxide aqueous solution preferably includes: adding concentrated sulfuric acid and graphite into a reactor, using potassium permanganate as an oxidant, preparing graphene oxide through low-temperature oxidation, medium-temperature oxidation and high-temperature oxidation in sequence, reducing excessive potassium permanganate with hydrogen peroxide, removing acid and salt in a reaction product by using an electrodialysis method, then adding 20wt% of sodium hydroxide solution until the pH value is 11-12, converting sulfate-based graphene into hydroxyl graphene, removing excessive sodium hydroxide by using an electrodialysis method, and enabling the pH value of the hydroxyl graphene pasty solution to be 8.0-9.5 to obtain a nanoscale hydroxyl graphene aqueous solution; the temperature of the low-temperature oxidation is preferably 2-10 ℃, and the time is preferably 115-125 min; the temperature of the medium-temperature oxidation is preferably 30-40 ℃, and the time is preferably 25-35 min; the high-temperature oxidation temperature is preferably 90-100 ℃, and the time is preferably 25-35 min.
In the invention, the hydroxyl graphene modified plating layer sealant solution is preferably an aqueous solution of a hydroxyl graphene modified sealant; the concentration of the hydroxyl graphene modified sealant in the hydroxyl graphene modified plating layer sealant solution is preferably 300-400 mL/L, and more preferably 330-350 mL/L. In the present invention, the operation temperature is preferably room temperature; the time for the immersion is preferably 10 to 30 seconds, more preferably 15 to 25 seconds. Preferably, the dipped plated piece is taken out, and the residual hydroxy graphene modified plating layer sealant solution on the plated piece is removed. In the invention, the residual hydroxyl graphene modified plating layer sealant solution on the plated part is preferably blown off by high-pressure air.
In the invention, the temperature of the baking and curing is preferably 70-100 ℃, and more preferably 80-90 ℃; the time for baking and curing is preferably 30-60 min, and more preferably 35-55 min.
The zinc-cadmium alloy composite coating of the aerospace electrical appliance accessory prepared by the invention has high wear resistance and corrosion resistance, has excellent weather resistance, and is suitable for being used in a strong corrosive environment. The preparation method provided by the invention is simple, convenient and easy to operate, and is suitable for popularization and application.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
The structural schematic diagram of the zinc-cadmium alloy composite coating of the aerospace electrical appliance accessory prepared in the embodiment is shown in fig. 1, and a chemical zinc deposition layer 2, a nickel coating layer 3, a zinc-cadmium alloy coating layer 4, a silane chromium-free passivation layer 5 and a graphene sealing layer 6 are sequentially prepared on an aluminum alloy substrate 1 from inside to outside.
The method comprises the steps of sequentially carrying out chemical dewaxing, water washing, ultrasonic dewaxing, water washing, chemical oil removal, water washing, activation and water washing on an aluminum alloy matrix to obtain the pretreated aluminum alloy matrix.
Sequentially carrying out primary zinc deposition, water washing, zinc removing, water washing, secondary zinc deposition and water washing on the pretreated aluminum alloy matrix to form a chemical zinc deposition layer on the surface of the aluminum alloy matrix; the zinc precipitating solution adopted by the first zinc precipitation and the second zinc precipitation is an aqueous solution of an ALBUMEAS-699 cyanide-free aluminum zinc-precipitating agent produced by Guangzhou ultra-Pont chemical Co., ltd, and the concentration of the zinc-precipitating agent in the zinc-precipitating solution is 180mL/L; the working temperature of the zinc deposition is 25 ℃, and the zinc deposition time is 80s; the zinc precipitating agent contains 8g/L of zinc ions and 0.18g/L of copper ions, and the prepared chemical zinc precipitating layer contains two components of zinc and copper; the zinc stripping adopts a nitric acid solution with the volume fraction of 10% to strip the zinc.
The chemical is carried out by adopting a watt nickel plating processPreparing a nickel coating on the surface of the zinc layer; the thickness of the nickel coating is 3-5 μm. The nickel plating solution comprises the following components and electroplating parameters: 220mL/L of nickel sulfate, 50mL/L of nickel chloride and 33mL/L of boric acid; the operation temperature is 30 ℃, the pH value is 4.3, and the current density is 2A/dm 2 The moving speed of the cathode was 5m/min.
Electroplating in a plating tank filled with electroplating solution by taking the aluminum alloy plated part deposited with the nickel plating layer as a cathode and taking a zinc plate for electroplating and a cadmium plate for electroplating as anodes, and forming a zinc-cadmium alloy plating layer on the surface of the nickel plating layer; the thickness of the zinc-cadmium alloy plating layer is 10-12 mu m, and the zinc-cadmium alloy plating layer is prepared by adopting a potassium chloride zinc-cadmium alloy electroplating process of Guangzhou ultra-Pont chemical industry Co.Ltd; the electroplating solution is as follows: 40g/L of zinc chloride, 18g/L of cadmium chloride, 160g/L of potassium chloride, 130g/L of coordination agent, 2mL/L of brightening agent, 30mL/L of auxiliary agent, pH 7, the temperature of the plating bath is 25 ℃, and the cathode current density is 1.5A/dm 2 And the area ratio of the zinc plate for electroplating to the cadmium plate for electroplating is 5:1.5;
the complexing agent consists of a component A and a component B, wherein the component A is nitrilotriacetic acid and glycine, and the mass ratio of the nitrilotriacetic acid to the glycine is 7:5, the component B is malic acid, and the mass ratio of the component A to the component B is 7:8, uniformly mixing the component A with the component B to obtain the coordination agent;
the preparation method of the brightener comprises the following steps: uniformly mixing 200mL of deionized water and 400mL of isopropanol, adding 45G of the component C, 40G of the component D, 125G of the component E, 25G of the component F and 55G of the component G, stirring until all the components are completely dissolved, and adding water to 1000mL to obtain a brightener; wherein the component C is 2, 3-dimethylbenzaldehyde, the component D is 3-methoxy-4-hydroxybenzaldehyde, the component E is propiolic alcohol ethoxy ether, the component F is o-chlorobenzaldehyde, and the component G is butyl ether humate;
the preparation method of the adjuvant comprises the following steps: adding 65g of low-molecular-weight polyacrylamide (the molecular weight is less than 8000), 45g of sodium benzoate, 65g of sodium dimethyl benzene sulfonate, 50g of condensation product of ethylenediamine and epichlorohydrin and 50g of polyoxyethylene ether phosphate with the product model of PE 600 into 600g of water, stirring to dissolve the condensation product, and adding water to 1000mL to obtain the auxiliary agent.
Sequentially carrying out brightening and washing on the aluminum alloy plated part deposited with the zinc-cadmium alloy plating layer by using a nitric acid solution with the volume fraction of 1%, removing an oxidation film by using a sulfuric acid solution with the mass fraction of 5%, and washing to obtain a pretreated zinc-cadmium alloy plating layer;
placing the pretreated zinc-cadmium alloy coating in a passivating agent for passivation, and forming a silane chromium-free passivation layer on the surface of the zinc-cadmium alloy coating after baking; the thickness of the silane chromium-free passivation layer is 0.8-0.9 mu m; the passivating agent is a zinc PRODICO Z-Caot 888FL solvent type silane chromium-free passivating agent; the passivation temperature is room temperature, and the passivation time is 60s; the baking temperature is 90 ℃, and the baking time is 22min.
Placing the aluminum alloy plated part with the silane chromium-free passivation layer in a hydroxyl graphene modified coating sealant solution, dipping, taking out, baking and curing to form a graphene sealing layer on the surface of the silane chromium-free passivation layer to obtain a zinc-cadmium alloy composite coating of the aerospace electrical appliance fitting; the thickness of the graphene sealing layer is 3.0-3.2 mu m;
the preparation method of the hydroxyl graphene modified plating layer sealant in the hydroxyl graphene modified plating layer sealant solution comprises the following steps: adding 115mL of concentrated sulfuric acid into a 1000mL beaker, reducing the temperature of the concentrated sulfuric acid by 3 ℃ in an ice water bath, adding 5g of 300-mesh crystalline flake graphite powder with the mass fraction of more than 99%, slowly adding 18g of potassium permanganate while stirring, controlling the reaction temperature at 6 ℃, and carrying out low-temperature oxidation reaction for 120min while stirring; changing the ice water bath into warm water bath, controlling the reaction temperature at 35 ℃, and performing medium-temperature oxidation reaction for 90min under stirring; after the medium-temperature oxidation reaction, taking the beaker out of the water bath, heating the paste in the beaker to 90 ℃, slowly adding 100mL of water, controlling the reaction temperature to be 95 ℃, stirring for 30min, slowly adding 15mL of hydrogen peroxide with the mass fraction of 30% into the beaker, and continuously reacting for 30min; removing acid and salt in the reaction product by using an electrodialysis method, then adding a sodium hydroxide solution with the mass fraction of 20% to the pH value of 11 to convert the sulfate-based graphene into the hydroxyl graphene, and removing excessive sodium hydroxide by using an electrodialysis method to ensure that the pH value of the hydroxyl graphene pasty liquid is 9.0 to obtain a nano-scale hydroxyl graphene aqueous solution;
according to the mass parts, 27 parts of silica sol, 23 parts of PU 113 water-soluble silane polymer, 10 parts of nano-grade hydroxyl graphene aqueous solution with 1% of carbon element mass fraction, 0.6 part of TANAOAMS organic silicon defoamer, 0.8 part of LA13-863 organic silicon flatting agent and 40 parts of deionized water are mixed and stirred uniformly to obtain a hydroxyl graphene modified sealing agent;
the solvent of the hydroxyl graphene modified plating layer sealant solution is water; the concentration of the hydroxyl graphene modified sealant in the hydroxyl graphene modified coating sealant solution is 350mL/L; the temperature of the impregnation is room temperature; the time for the impregnation is 20s; dipping the workpiece out of the tank, dripping the workpiece dry, and blowing off the residual hydroxyl graphene modified plating layer sealant solution at the bottom of the plated workpiece by using high-pressure air; the temperature for baking and curing is 90 ℃; the baking and curing time is 40min.
Example 2
The structural schematic diagram of the zinc-cadmium alloy composite coating of the aerospace electrical appliance accessory prepared in the embodiment is shown in fig. 1, and a chemical zinc deposition layer 2, a nickel coating layer 3, a zinc-cadmium alloy coating layer 4, a silane chromium-free passivation layer 5 and a graphene sealing layer 6 are sequentially prepared on an aluminum alloy substrate 1 from inside to outside.
The method comprises the steps of sequentially carrying out chemical dewaxing, water washing, ultrasonic dewaxing, water washing, chemical degreasing, water washing, activation and water washing on an aluminum alloy matrix to obtain the pretreated aluminum alloy matrix.
Sequentially carrying out primary zinc precipitation, water washing, zinc removing, water washing, secondary zinc precipitation and water washing on the pretreated aluminum alloy matrix to form a chemical zinc precipitation layer on the surface of the aluminum alloy matrix; the zinc precipitating solution adopted by the first zinc precipitation and the second zinc precipitation is an aqueous solution of AZIN-113 acidic aluminum zinc-precipitating agent produced by Guangzhou ultra-Pont chemical Co., ltd, the concentration of the zinc-precipitating agent in the zinc-precipitating solution is 200mL/L, and the pH value of the zinc-precipitating solution is 3.6; the working temperature of the zinc deposition is 25 ℃, and the zinc deposition time is 40s; the zinc precipitating agent contains 8g/L of zinc ions and 0.6g/L of nickel ions, and the prepared chemical zinc precipitating layer contains two components of zinc and nickel; the zinc stripping adopts a nitric acid solution with the volume fraction of 10% to strip the zinc.
Preparing a nickel coating on the surface of the chemical precipitation zinc layer by adopting a GG-178 alkaline chemical nickel plating process of Guangzhou ultra-high chemical company Limited; the thickness of the nickel plating layer is 2-4 μm. The chemical nickel plating solution comprises the following components and operating parameters: 40mL/L of GG-178A additive, 35mL/L of GG-178B reducing agent and 50mL/L of GG-178C stabilizer; the operating temperature is 35 ℃; the pH of the nickel plating solution was 9.0.
Electroplating in a plating tank filled with electroplating solution by taking the aluminum alloy plated part deposited with the nickel plating layer as a cathode and taking a zinc plate for electroplating and a cadmium plate for electroplating as anodes, and forming a zinc-cadmium alloy plating layer on the surface of the nickel plating layer; the thickness of the zinc-cadmium alloy plating layer is 12-14 mu m, and the zinc-cadmium alloy plating layer is prepared by adopting a potassium chloride zinc-cadmium alloy electroplating process of Guangzhou ultra-Pont chemical industry Co.Ltd; the electroplating solution is as follows: 30g/L of zinc chloride, 10g/L of cadmium chloride, 160g/L of potassium chloride, 100g/L of coordination agent, 2mL/L of brightening agent, 30mL/L of auxiliary agent, 6.7 of pH, 25 ℃ of temperature of plating bath and 1.0A/dm of cathode current density 2 And the area ratio of the zinc plate for electroplating to the cadmium plate for electroplating is 5:1.5; the compositions of the complexing agent, the brightening agent and the auxiliary agent are the same as that of the embodiment 1.
Sequentially carrying out brightening and washing on the aluminum alloy plated part deposited with the zinc-cadmium alloy plating layer by using a nitric acid solution with the volume fraction of 1%, removing an oxidation film by using a sulfuric acid solution with the mass fraction of 5%, and washing by using water to obtain a pretreated zinc-cadmium alloy plating layer;
placing the pretreated zinc-cadmium alloy coating in a passivating agent for passivation, and forming a silane chromium-free passivation layer on the surface of the zinc-cadmium alloy coating after baking; the thickness of the silane chromium-free passivation layer is 0.9-1.0 mu m; the passivating agent is a zinc PRODICO Z-Caot 888FL solvent type silane chromium-free passivating agent; the passivation temperature is room temperature, and the passivation time is 60s; the baking temperature is 95 ℃, and the baking time is 20min.
Placing the aluminum alloy plated part with the silane chromium-free passivation layer in a hydroxyl graphene modified coating sealant solution, dipping, taking out, baking and curing to form a graphene sealing layer on the surface of the silane chromium-free passivation layer to obtain a zinc-cadmium alloy composite coating of the aerospace electrical appliance fitting; the thickness of the graphene sealing layer is 2.8-3.0 mu m;
the preparation method of the hydroxyl graphene modified plating layer sealant in the hydroxyl graphene modified plating layer sealant solution comprises the following steps: adding 115mL of concentrated sulfuric acid into a 1000mL beaker, reducing the temperature of the concentrated sulfuric acid by 3 ℃ in an ice water bath, adding 5g of 300-mesh crystalline flake graphite powder with the mass fraction of more than 99%, slowly adding 18g of potassium permanganate while stirring, controlling the reaction temperature at 3 ℃, and carrying out low-temperature oxidation reaction for 120min while stirring; changing the ice water bath into warm water bath, controlling the reaction temperature at 38 ℃, and performing medium-temperature oxidation reaction for 90min under stirring; after the medium-temperature oxidation reaction, taking out the beaker from the water bath, heating the paste in the beaker to 90 ℃, slowly adding 100mL of water, controlling the reaction temperature to be 93 ℃, stirring for 30min, slowly adding 15mL of hydrogen peroxide with the mass fraction of 30% into the beaker, and continuously reacting for 30min; removing acid and salt in the reaction product by using an electrodialysis method, then adding a sodium hydroxide solution with the mass fraction of 20% to the pH value of 12, converting the sulfate-based graphene into the hydroxyl graphene, and removing excessive sodium hydroxide by using an electrodialysis method to ensure that the pH value of the hydroxyl graphene pasty liquid is 9.0, so as to obtain a nano-grade hydroxyl graphene aqueous solution;
according to the mass parts, 23 parts of silica sol, 27 parts of PU 113 water-soluble silane polymer, 10 parts of nano-grade hydroxyl graphene aqueous solution with 1% of carbon element mass fraction, 0.6 part of TANAOAMS organic silicon defoamer, 0.8 part of LA13-863 organic silicon flatting agent and 40 parts of deionized water are mixed and stirred uniformly to obtain a hydroxyl graphene modified sealing agent;
the solvent of the hydroxyl graphene modified plating layer sealant solution is water; the concentration of the hydroxyl graphene modified plating layer sealant solution is 330mL/L; the temperature of the impregnation is room temperature; the time for the immersion was 15s; dipping and draining the workpiece out of the tank, and blowing off the residual hydroxy graphene modified plating layer sealant solution at the bottom of the workpiece by using high-pressure air; the baking and curing temperature is 85 ℃; the baking and curing time is 55min.
Example 3
The structural schematic diagram of the zinc-cadmium alloy composite coating of the aerospace electrical appliance accessory prepared in the embodiment is shown in fig. 1, and a chemical zinc deposition layer 2, a nickel coating layer 3, a zinc-cadmium alloy coating layer 4, a silane chromium-free passivation layer 5 and a graphene sealing layer 6 are sequentially prepared on an aluminum alloy matrix 1 from inside to outside.
The method comprises the steps of sequentially carrying out chemical dewaxing, water washing, ultrasonic dewaxing, water washing, chemical degreasing, water washing, activation and water washing on an aluminum alloy matrix to obtain the pretreated aluminum alloy matrix.
Sequentially carrying out primary zinc precipitation, water washing, zinc removing, water washing, secondary zinc precipitation and water washing on the pretreated aluminum alloy matrix to form a chemical zinc precipitation layer on the surface of the aluminum alloy matrix; the zinc precipitating solution adopted by the first zinc precipitation and the second zinc precipitation is an aqueous solution of AZIN-113 acidic aluminum zinc-precipitating agent produced by Guangzhou ultra-high chemical company, the concentration of the zinc precipitating agent in the zinc precipitating solution is 150mL/L, and the pH value of the zinc precipitating solution is 3.8; the working temperature of the zinc deposition is 30 ℃, and the time of zinc deposition is 50s; the zinc precipitating agent contains 9g/L of zinc ions and 1.1 g/L of nickel ions, and the prepared chemical zinc precipitating layer contains two components of zinc and nickel; and the zinc is removed by adopting a nitric acid solution with the volume fraction of 10%.
Preparing a nickel coating on the surface of the chemical zinc deposition layer by adopting a watt nickel plating process; the thickness of the nickel coating is 4-6 μm. The nickel plating solution comprises the following components and electroplating parameters: 230mL/L of nickel sulfate, 45mL/L of nickel chloride and 32mL/L of boric acid; the operation temperature is 25 ℃, the pH value is 4.5, and the current density is 1.8A/dm 2 The moving speed of the cathode was 5m/min.
Electroplating in a plating tank filled with electroplating solution by taking the aluminum alloy plated part deposited with the nickel plating layer as a cathode and taking a zinc plate for electroplating and a cadmium plate for electroplating as anodes, and forming a zinc-cadmium alloy plating layer on the surface of the nickel plating layer; the thickness of the zinc-cadmium alloy plating layer is 14-16 mu m, and the zinc-cadmium alloy plating layer is prepared by adopting a potassium chloride zinc-cadmium alloy electroplating process of Guangzhou ultra-Bang chemical industry Co., ltd; the electroplating solution is as follows: 50g/L of zinc chloride, 25g/L of cadmium chloride, 160g/L of potassium chloride, 160g/L of coordination agent, 2mL/L of brightening agent, 30mL/L of auxiliary agent, 7.3 of pH, 30 ℃ of plating bath temperature and 2.0A/dm of cathode current density 2 The area ratio of the zinc plate for electroplating to the cadmium plate for electroplating is 5:1.5; the compositions of the complexing agent, the brightening agent and the auxiliary agent are the same as that of the embodiment 1.
Sequentially carrying out brightening and washing on the aluminum alloy plated part deposited with the zinc-cadmium alloy plating layer by using a nitric acid solution with the volume fraction of 1%, removing an oxidation film by using a sulfuric acid solution with the mass fraction of 5%, and washing by using water to obtain a pretreated zinc-cadmium alloy plating layer;
placing the pretreated zinc-cadmium alloy coating in a passivating agent for passivation, and forming a silane chromium-free passivation layer on the surface of the zinc-cadmium alloy coating after baking; the thickness of the silane chromium-free passivation layer is 1.0-1.1 mu m; the passivating agent is a zinc PRODICO Z-Caot 888FL solvent type silane chromium-free passivating agent; the passivation temperature is room temperature, and the passivation time is 60s; the baking temperature is 85 ℃, and the baking time is 25min.
Placing the aluminum alloy plated part with the silane chromium-free passivation layer in a hydroxyl graphene modified coating sealant solution, dipping, taking out, baking and curing to form a graphene sealing layer on the surface of the silane chromium-free passivation layer to obtain a zinc-cadmium alloy composite coating of the aerospace electrical appliance fitting; the thickness of the graphene sealing layer is 2.9-3.1 mu m;
the preparation method of the hydroxyl graphene modified plating layer sealant in the hydroxyl graphene modified plating layer sealant solution comprises the following steps: adding 115mL of concentrated sulfuric acid into a 1000mL beaker, reducing the temperature of the concentrated sulfuric acid by 5 ℃ in an ice water bath, adding 5g of 300-mesh crystalline flake graphite powder with the mass fraction of more than 99%, slowly adding 18g of potassium permanganate while stirring, controlling the reaction temperature at 2 ℃, and carrying out low-temperature oxidation reaction for 120min while stirring; changing the ice water bath into warm water bath, controlling the reaction temperature at 32 ℃, and performing medium-temperature oxidation reaction for 90min under stirring; after the medium-temperature oxidation reaction, taking the beaker out of the water bath, heating the paste in the beaker to 90 ℃, slowly adding 100mL of water, controlling the reaction temperature to be 95 ℃, stirring for 30min, slowly adding 15mL of hydrogen peroxide with the mass fraction of 30% into the beaker, and continuously reacting for 30min; removing acid and salt in the reaction product by using an electrodialysis method, then adding a sodium hydroxide solution with the mass fraction of 20% to the pH value of 11.5 to convert the sulfate-based graphene into the hydroxyl graphene, and removing excessive sodium hydroxide by using an electrodialysis method to ensure that the pH value of the hydroxyl graphene pasty liquid is 8.8 to obtain a nano-grade hydroxyl graphene aqueous solution;
mixing 25 parts of silica sol, 25 parts of PU 113 water-soluble silane polymer, 10 parts of nano-grade hydroxyl graphene aqueous solution with 1% of carbon element by mass, 0.6 part of TANAOAMS organic silicon defoamer, 0.8 part of LA13-863 organic silicon flatting agent and 45 parts of deionized water in parts by mass, and uniformly stirring to obtain a hydroxyl graphene modified sealing agent;
the solvent of the hydroxyl graphene modified plating layer sealant solution is water; the concentration of the hydroxyl graphene modified plating layer sealant solution is 350mL/L; the temperature of the impregnation is room temperature; the time for the impregnation was 25s; dipping the workpiece out of the tank, dripping the workpiece dry, and blowing off the residual hydroxyl graphene modified plating layer sealant solution at the bottom of the plated workpiece by using high-pressure air; the baking and curing temperature is 95 ℃; the baking and curing time is 35min.
Test example 1
The zinc-cadmium alloy composite coating of the aerospace electrical appliance accessory prepared in the embodiment 1-3 is used for measuring the binding force of an aluminum alloy matrix and a coating by a thermal shock test method according to JB 2111-1977 "method for testing the binding strength of a metal covering layer"; and (3) heating the zinc-cadmium alloy composite coating prepared by the aerospace electrical appliance fittings in a heating furnace to 190 ℃, taking out after 30min, and suddenly cooling in water at room temperature, wherein the composite coating does not foam or fall off.
Test example 2
The zinc-cadmium alloy composite coatings of the aerospace electrical fittings prepared in the embodiments 1 to 3 are subjected to a neutral salt spray test 2400h according to GB/T10125-2012 salt spray test for artificial atmosphere corrosion test, no white corrosive is generated on the surfaces of the composite coatings, and the test results are shown in FIG. 2.
Test example 3
The zinc-cadmium alloy composite coatings of the aerospace electrical fittings prepared in the examples 1-3 are placed in a natural environment for three years, and have good weather resistance and no white powder on the surfaces.
Test example 4
The wear resistance of the zinc-cadmium alloy composite coating of the aerospace electrical appliance accessory prepared in the embodiment 1-3 is detected, and the zinc-cadmium alloy composite coating is subjected to dry friction for 8000 times under the conditions of 1000g of load and 60 times of frequency/min, so that no obvious friction damage is caused. In contrast, in examples 1 to 3, the aluminum alloy without the graphene sealing layer was subjected to dry rubbing 8000 times under the same conditions, and visible rubbing damage occurred. The method has the advantage that the graphene sealing layer is arranged on the surface of the silane chromium-free passivation layer, so that the wear resistance of the composite coating can be improved.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (5)

1. A zinc-cadmium alloy composite coating of aerospace electrical fittings is characterized by comprising a chemical zinc deposition layer, a nickel coating, a zinc-cadmium alloy coating, a silane chromium-free passivation layer and a graphene sealing layer which are sequentially arranged on the surface of an aluminum alloy substrate; the mass content of cadmium element in the zinc-cadmium alloy coating is 20-40%;
the preparation method of the zinc-cadmium alloy composite coating of the aerospace electrical appliance fitting comprises the following steps:
preparing a chemical zinc deposition layer, a nickel coating, a zinc-cadmium alloy coating, a silane chromium-free passivation layer and a graphene sealing layer on the surface of an aluminum alloy substrate in sequence;
the zinc-cadmium alloy coating is prepared by adopting an electroplating process; the electroplating liquid adopted by the zinc-cadmium alloy plating layer comprises 30-50g/L of zinc chloride, 10-25g/L of cadmium chloride, 140-180g/L of potassium chloride, 100-160g/L of complexing agent, 1.5-2.5 mL/L of brightening agent and 25-35mL/L of auxiliary agent;
the raw materials for preparing the brightener comprise a component C, a component D, a component E, a component F and a component G; the mass ratio of the component C to the component D to the component E to the component F to the component G is 30 to 60:30 to 50:100 to 150:20 to 30:40 to 70;
the component C is one or two of 2, 3-dimethylbenzaldehyde, 2, 5-dimethylbenzaldehyde, 2, 6-dimethylbenzaldehyde, 3, 4-dimethylbenzaldehyde and 3, 5-dimethylbenzaldehyde;
the component D comprises one or two of 3-methoxy-4-hydroxybenzaldehyde, 3, 4-dimethoxybenzaldehyde and 4-methoxybenzaldehyde;
the component E comprises one or two of propargyl alcohol ethoxy ether, propargyl alcohol propoxy ether, N-diethyl propargyl amine, N-diethyl propargyl amine formate, N-diethyl propargyl amine sulfate and propiolic salt;
the component F is o-chlorobenzaldehyde;
the component G is butyl ether humate;
the raw materials for preparing the complexing agent comprise a component A and a component B; the mass ratio of the component A to the component B is 7:6 to 10;
the component A comprises nitrilotriacetic acid and glycine; the mass ratio of the nitrilotriacetic acid to the glycine is 7:4 to 6;
the component B comprises one or two of citric acid, tartaric acid, gluconic acid and malic acid;
the preparation raw materials of the auxiliary agent comprise polyacrylamide, sodium benzoate, sodium dimethyl benzene sulfonate, a condensation compound of ethylenediamine and epichlorohydrin and polyoxyethylene ether phosphate; the mass ratio of the polyacrylamide to the sodium benzoate to the sodium dimethyl benzene sulfonate to the ethylene diamine to the condensate of epoxy chloropropane to the polyoxyethylene ether phosphate is 50 to 80:30 to 60:50 to 80:30 to 70:30 to 70.
2. The zinc-cadmium alloy composite coating of the aerospace electrical appliance accessory according to claim 1, wherein the thickness of the nickel coating is 1 to 8 μm; the thickness of the zinc-cadmium alloy coating is 8 to 28 micrometers; the thickness of the silane chromium-free passivation layer is 0.5 to 2 mu m; the thickness of the graphene sealing layer is 2 to 4 mu m.
3. The composite zinc-cadmium alloy coating for aerospace electrical parts according to claim 1, wherein the electroplating conditions of the zinc-cadmium alloy coating comprise: the pH value of the electroplating solution is 6.5 to 7.5; the electroplating temperature is 15 to 35 ℃; the cathode current density is 0.5 to 2.5A/dm 2 (ii) a The anode is a zinc plate for electroplating and a cadmium plate for electroplating; the area ratio of the zinc plate for electroplating to the cadmium plate for electroplating is 5:1 to 2.
4. The zinc-cadmium alloy composite coating of the aerospace electrical fittings as claimed in claim 1, wherein the passivating agent used for preparing the silane chromium-free passivation layer is a zinc PRODICO Z-Caot 888FL solvent-based silane chromium-free passivating agent; the passivation time is 50 to 70s.
5. The zinc-cadmium alloy composite coating of aerospace electrical accessories as claimed in claim 1, wherein the graphene sealing layer is prepared from a hydroxyl graphene modified coating sealant.
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