CN115433483A - High-hardness chromium-free Dacromet coating, anticorrosive coating and preparation method of anticorrosive coating - Google Patents
High-hardness chromium-free Dacromet coating, anticorrosive coating and preparation method of anticorrosive coating Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
- C09D5/08—Anti-corrosive paints
- C09D5/10—Anti-corrosive paints containing metal dust
- C09D5/106—Anti-corrosive paints containing metal dust containing Zn
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05C11/00—Component parts, details or accessories not specifically provided for in groups B05C1/00 - B05C9/00
- B05C11/02—Apparatus for spreading or distributing liquids or other fluent materials already applied to a surface ; Controlling means therefor; Control of the thickness of a coating by spreading or distributing liquids or other fluent materials already applied to the coated surface
- B05C11/08—Spreading liquid or other fluent material by manipulating the work, e.g. tilting
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- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
- B05D5/08—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
- B05D7/24—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials for applying particular liquids or other fluent materials
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- C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
- C09D5/08—Anti-corrosive paints
- C09D5/10—Anti-corrosive paints containing metal dust
- C09D5/103—Anti-corrosive paints containing metal dust containing Al
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
- C09D7/40—Additives
- C09D7/60—Additives non-macromolecular
- C09D7/61—Additives non-macromolecular inorganic
Abstract
The invention discloses a high-hardness chromium-free Dacromet coating, an anticorrosive coating and a preparation method thereof, and relates to the technical field of anticorrosive treatment of metal material surfaces. The raw materials comprise: metal pastes, chromate substitutes and auxiliaries; the metal powder slurry comprises zinc-aluminum alloy powder, a first wetting dispersant, a protective agent and water; the chromate substitute comprises a corrosion inhibition/passivation combination agent, a silane coupling agent, a second wetting dispersant and water; the auxiliary agent comprises a thickening agent and a defoaming agent. According to the invention, the rare earth oxide/graphene nanosheet is adopted to carry out composite modification on the chromium-free Dacromet coating, so that the corrosion resistance of the coating is improved, the hardness of the coating is also improved, and the wear resistance of the coating is greatly improved. The zinc-aluminum alloy powder is used for replacing zinc-aluminum mixed powder, and the dispersibility and uniformity of the metal powder are greatly improved. The invention makes a spin coating device by self and can obtain a coating with a parallel lap joint structure of flaky powder.
Description
Technical Field
The invention relates to the technical field of metal material surface anti-corrosion treatment, in particular to a high-hardness chromium-free Dacromet coating, an anti-corrosion coating and a preparation method thereof.
Background
The Dacromet coating is a mixed solution consisting of flake zinc powder, flake aluminum powder, chromic anhydride, a wetting agent, a dispersing agent, a reducing agent, deionized water and other additives, is uniformly stirred to obtain a coating solution, is coated on the surface of a workpiece, and is baked at about 300 ℃ to form a coating with excellent corrosion resistance on the surface of a metal matrix. The Dacromet coating is mainly formed by regularly overlapping flaky zinc powder and aluminum powder in a coating solution on the surface of a fastener, chromic acid in the coating solution and a reducing agent are subjected to oxidation-reduction reaction during baking and sintering to generate a complex oxide to mutually bond the zinc powder and the aluminum powder, the chromic acid in the coating solution can oxidize the zinc and the aluminum to generate a flocculent chromate passivation film, and the film layer is tightly combined with a substrate after curing. The Dacromet coating has excellent corrosion resistance, no hydrogen embrittlement and high thickness controllability which is generally 10-20 mu m, does not influence the connection and matching of workpieces, and can obviously improve the corrosion resistance of the fastener.
Dacromet technology is an excellent corrosion protection technology, but the coating has a Cr content of about 2% 6+ The ion has carcinogenic effect and does not meet the relevant environmental protection requirements of the automobile industry. Under the background, the chromium-free Dacromet technology is developed, the pollution problem is solved well by the chromium-free Dacromet technology, but the coating is low in hardness and wear resistance and easy to scratch, the pencil hardness is only 1H-2H, and the chromium-free Dacromet technology cannot be adopted for workpieces needing wear resistance. Due to the low hardness of the film layer, the wear resistance is poor, workpieces are often scratched and scratched in the processes of transportation, assembly and use, and meanwhile, the corrosion resistance is weakened in the high-salt-mist and high-humidity environment relative to Dacromet coating, so that the corrosion resistance of the coating is influenced, and the appearance of the product is also influenced. Thus, by eliminating chromiumIt is imperative to add reinforcing phases to the Kraft coating to increase the hardness and corrosion resistance of the coating.
The corrosion resistance of the environment-friendly Dacromet coating prepared by replacing chromate with film-forming substances (oxysalts and oxides, rare earth salts and rare earth oxides, silane coupling agents + corrosion inhibitors and resin + corrosion inhibitors) is remarkably improved, but the hardness of the coating is not improved.
Disclosure of Invention
The invention aims to provide a high-hardness chromium-free Dacromet coating, an anticorrosive coating and a preparation method thereof, which are used for solving the problems in the prior art, so that the chromium-free Dacromet coating has excellent corrosion resistance and higher hardness.
In order to achieve the purpose, the invention provides the following scheme:
according to one technical scheme of the invention, the high-hardness chromium-free Dacromet coating comprises the following raw materials: metal pastes, chromate substitutes and auxiliaries;
the metal powder slurry comprises, by mass, 6-10 parts of zinc-aluminum alloy powder, 3-5 parts of a first wetting dispersant, 4-6 parts of a protective agent and 10-15 parts of water; the chromate substitute comprises 0.5-0.8 part of corrosion inhibition/passivation combined agent, 5-10 parts of silane coupling agent, 2-4 parts of second wetting dispersant and 8-12 parts of water; the auxiliary agent comprises 0.05-0.2 part of thickening agent and 0.1-0.3 part of defoaming agent. The contents of the respective components are designed by orthogonal experiments, and more or less than this range affects the corrosion resistance, appearance, adhesion and hardness of the coating.
The role of the silane coupling agent includes: the function of bonding the rare earth oxide and the graphene nanosheet is achieved; the base layer is passivated; the adaptability of the rare earth oxide and graphene nanosheet to the substrate is improved; has a small amount of passivation effect on zinc-aluminum alloy powder.
Further, the mass ratio of zinc element to aluminum element in the zinc-aluminum alloy powder is 5:1-2:1; the particle size of the zinc-aluminum alloy powder is 10-20 μm.
Further, the first wetting and dispersing agent is Span20; the second wetting dispersant is PEG400; the protective agent is PEG200; the thickening agent is hydroxyethyl cellulose ether; the antifoaming agent is dow kangning; the silane coupling agent is one or more of epoxy silane AC66, AC66E, AC67 or vinyl silane AC 77.
The selection of the dispersant is based on: the coating is volatile in the heating and curing process, so that the adhesive force of the coating can be improved, the dispersion effect of Span20 on the metal powder slurry is more excellent, and the dispersion effect of PEG400 on a silane coupling agent and a corrosion-inhibition/passivation combination agent is better; the thickener is selected according to the following: the thickening effect is excellent, the stability of the coating liquid is not influenced, and the effect of the hydroxyethyl cellulose ether is more excellent; the selection of the defoaming agent is based on: the defoaming capability is optimal, the appearance and the bonding force of the coating are not affected (the addition amount cannot be excessive, the excessive addition can blacken the coating liquid and reduce the glossiness and the adhesive force of the coating), and the dow corning effect is more excellent; the selection of the silane coupling agent is based on: the aqueous solution has good compatibility with a metal powder coating system, presents a silver gray bubble-free slurry shape, and one or more of epoxy silane AC66, AC66E, AC67 or vinyl silane AC77 can meet the requirement.
Further, the corrosion inhibition/passivation combined agent is a mixture of rare earth oxide and graphene nanosheets; the rare earth oxide accounts for 60-70% of the mass of the corrosion inhibition/passivation combined agent. Beyond this range the corrosion resistance of the coating will decrease.
Further, the rare earth oxide is yttrium oxide. In the technical scheme of the invention, the corrosion inhibition effect of the yttrium oxide is more excellent than that of other rare earth oxides.
In the second technical scheme of the invention, the preparation method of the high-hardness chromium-free Dacromet coating comprises the following steps:
step 1, adding a first wetting dispersant into water, uniformly stirring, adding zinc-aluminum alloy powder and a protective agent, and uniformly dispersing to obtain uniform slurry A;
step 2: mixing and dissolving a silane coupling agent, a corrosion inhibition/passivation combination agent and water, removing impurities, adding a second wetting dispersant, and uniformly dispersing to obtain uniform slurry B;
and step 3: and mixing the uniform slurry A and the uniform slurry B, adding a thickening agent and a defoaming agent, and stirring until the pH value and the viscosity are stable to obtain the high-hardness chromium-free Dacromet coating.
Further, in step 3, the pH is 6.0-8.5 and the viscosity is 20-80s.
In the third technical scheme of the invention, the high-hardness chromium-free Dacromet coating is applied to preparation of an anticorrosive coating.
When the high-hardness chromium-free Dacromet coating is used for spraying, the control viscosity is 20-50s, and when the high-hardness chromium-free Dacromet coating is used for dip coating, the control viscosity is 40-80s.
In the fourth technical scheme of the invention, the anticorrosive coating is obtained by spraying or dip-coating the high-hardness chromium-free Dacromet coating on the surface of the substrate.
The invention adopts the fifth technical scheme that the spin coating device for preparing the anticorrosive coating comprises a rotating speed regulator and an electric stirrer; the rotating speed regulator is connected with the electric stirrer.
When the spin coating device is used for preparing an anticorrosive coating, a sample is placed on the electric stirrer, and the rotating speed of the electric stirrer is controlled by adjusting the rotating speed regulator, so that redundant coating on the sample is removed.
The invention discloses the following technical effects:
(1) According to the invention, the rare earth oxide/graphene nanosheet is adopted to carry out composite modification on the chromium-free Dacromet coating, so that the corrosion resistance of the coating is improved, the hardness of the coating is also improved, and the wear resistance of the coating is greatly improved.
(2) The zinc-aluminum alloy powder is used for replacing zinc-aluminum mixed powder, and the dispersibility and uniformity of the metal powder are greatly improved.
(3) The invention makes a spin coating device, and can obtain a coating with a parallel lap joint structure of flaky powder.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a micro-topography of the corrosion protection coatings prepared in example 3 and comparative example 3; wherein (a) represents example 3, (b) represents comparative example 3;
FIG. 2 is a photograph of corrosion morphology of the anticorrosive coatings prepared in example 3 and comparative example 3 after a neutral salt spray test for 1000 h; wherein the left hand side represents example 3 and the right hand side represents comparative example 3;
FIG. 3 is a schematic view of a spin coating apparatus for preparing an anticorrosive coating according to the present invention.
Detailed Description
Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but rather as a more detailed description of certain aspects, features and embodiments of the invention.
It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the documents are cited. In case of conflict with any incorporated document, the present specification will control.
It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The description and examples are intended to be illustrative only.
As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.
The first wetting and dispersing agent used in the examples of the present invention is Span20; the second wetting dispersant is PEG400; the protective agent is PEG200; the corrosion inhibition/passivation combined agent is a mixture of yttrium oxide and graphene nanosheets; the particle size of the zinc-aluminum alloy powder is 10 mu m, and the mass ratio of zinc element to aluminum element is 3:1.
the spin coating device for preparing the anticorrosive coating in the embodiment of the invention is shown in fig. 3.
Example 1
Preparing raw materials:
the component A comprises: 6g of zinc-aluminum alloy powder, 3g of first wetting dispersant, 4.8g of protective agent and 10g of deionized water;
and B component: 0.5g of corrosion inhibition/passivation combined agent, 5g of silane coupling agent (AC 66), 2g of second wetting dispersant and 8g of deionized water;
and C, component C: 0.1g of hydroxyethyl cellulose ether and 0.15g of Dow Corning.
The preparation method specifically comprises the following steps:
step 1, adding 3g of first wetting dispersant into 10g of deionized water, uniformly stirring on an electromagnetic stirrer to obtain a uniformly dispersed solution, then adding 6g of zinc-aluminum alloy powder and 4.8g of protective agent, continuously stirring, ultrasonically dispersing the powder slurry for 5min, and then stirring by the electromagnetic stirrer to obtain uniform powder slurry A.
And 2, step: stirring 5g of silane coupling agent, 0.3g of yttrium oxide, 0.2g of graphene nanosheet and 8g of deionized water on a magnetic stirrer at normal temperature for 4 hours (the technical effect of 3-5 hours is equivalent to that of 4 hours), fully hydrolyzing the silane coupling agent, adding a second wetting dispersant for uniform dispersion after the yttrium oxide and the graphene nanosheet are completely dissolved and uniformly dispersed, removing impurities by using a centrifugal machine, and performing ultrasonic dispersion again by using an ultrasonic cell crusher to obtain uniform slurry B.
And 3, step 3: adding the uniform slurry A and the uniform slurry B into a container, mixing, adding 0.1g of hydroxyethyl cellulose ether and 0.15g of Dow Corning, rapidly stirring for 7h at room temperature (the technical effect is equivalent to that of 7h in 6-8 h), and testing the pH and viscosity of the coating per hour in the continuous stirring process; the pH value of the coating liquid is controlled to be 6.0-8.5; the viscosity is controlled to be 20-50s during spraying and 40-80s during dip coating; after the parameters are stable, the coating is placed in a water bath kettle at 40 ℃ for standing to obtain the high-hardness chromium-free Dacromet coating, which is called the coating for short.
Dipping a substrate sample (metal Q235 steel) in the coating, throwing away excessive coating in a throwing coating device shown in figure 3 to obtain a coating with a flaky powder parallel lap joint structure, then sintering and curing the coating sample in an oven, pre-baking for 9min (the technical effect is equivalent to 9min in 8-10 min) at 100 ℃ (90-110 ℃ and 100 ℃), and sintering for 20min (the technical effect is equivalent to 20min in 20-25 min) at 280 ℃ (240-300 ℃ and 280 ℃). And preparing the coating by adopting a two-coating and two-baking mode.
In this example, the thickness of the anticorrosive coating was 14 μm.
The corrosion resistant coating prepared in this example is labeled coating No. 1.
Example 2
The component A comprises: 8g of zinc-aluminum alloy powder, 4g of first wetting dispersant, 5g of protective agent and 12g of deionized water;
and B component: 0.6g of corrosion inhibition/passivation combined agent, 6g of silane coupling agent (AC 66), 3g of second wetting dispersant and 10g of deionized water;
and C, component C: 0.1g of hydroxyethyl cellulose ether and 0.15g of Dow Corning.
The preparation method specifically comprises the following steps:
step 1, adding 4g of first wetting dispersant into 12g of deionized water, uniformly stirring on an electromagnetic stirrer to obtain a uniformly dispersed solution, then adding 8g of zinc-aluminum alloy powder (and 5g of protective agent, continuously stirring, ultrasonically dispersing the powder slurry for 5min, and then stirring by the electromagnetic stirrer to obtain uniform powder slurry A.
Step 2: stirring 6g of silane coupling agent, 0.4g of yttrium oxide, 0.2g of graphene nanosheet and 10g of deionized water on a magnetic stirrer at normal temperature for 4 hours (the technical effect is equivalent to that of 4 hours) to fully hydrolyze the silane coupling agent, adding a second wetting dispersant for uniform dispersion after the yttrium oxide and the graphene nanosheet are completely dissolved and uniformly dispersed, removing impurities by using a centrifugal machine, and performing ultrasonic dispersion again by using an ultrasonic cell crusher to obtain uniform slurry B.
And step 3: adding the uniform slurry A and the uniform slurry B into a container, mixing, adding 0.1g of hydroxyethyl cellulose ether and 0.15g of Dow Corning, rapidly stirring for 7 hours at room temperature (the technical effect is equivalent to that of 7 hours after 6-8 hours), and testing the pH and viscosity of the coating per hour in the continuous stirring process; the pH value of the coating liquid is controlled to be 6.0-8.5; the viscosity is controlled to be 20-50s during spraying and 40-80s during dip coating; after the parameters are stable, the coating is placed in a water bath kettle at 40 ℃ for standing to obtain the high-hardness chromium-free Dacromet coating, which is called the coating for short.
The coating was prepared in the same manner as in example 1.
In this example, the thickness of the anticorrosive coating was 14 μm.
The corrosion protection coating prepared in this example is labeled coating No. 2.
Example 3
And (2) component A: 10g of zinc-aluminum alloy powder, 5g of first wetting dispersant, 5.5g of protective agent and 15g of deionized water;
and B component: 0.8g of corrosion inhibition/passivation combined agent, 10g of silane coupling agent (AC 66), 4g of second wetting dispersant and 12g of deionized water;
and (C) component: 0.1g of hydroxyethyl cellulose ether and 0.15g of Dow Corning.
The preparation method specifically comprises the following steps:
step 1, adding 54g of first wetting dispersant into 15g of deionized water, uniformly stirring on an electromagnetic stirrer to obtain a uniformly dispersed solution, then adding 10g of zinc-aluminum alloy powder and 5.5g of protective agent, continuously stirring, ultrasonically dispersing the powder slurry for 5min, and then stirring by the electromagnetic stirrer to obtain uniform powder slurry A.
Step 2: stirring 10g of silane coupling agent, 0.5g of yttrium oxide, 0.3g of graphene nanosheet and 12g of deionized water on a magnetic stirrer at normal temperature for 4 hours (the technical effect of 3-5 hours is equivalent to that of 4 hours), fully hydrolyzing the silane coupling agent, adding a second wetting dispersant for uniform dispersion after the yttrium oxide and the graphene nanosheet are completely dissolved and uniformly dispersed, removing impurities by using a centrifugal machine, and performing ultrasonic dispersion again by using an ultrasonic cell crusher to obtain uniform slurry B.
And 3, step 3: adding the uniform slurry A and the uniform slurry B into a container, mixing, adding 0.1g of hydroxyethyl cellulose ether and 0.15g of Dow Corning, rapidly stirring for 7 hours at room temperature (the technical effect is equivalent to that of 7 hours after 6-8 hours), and testing the pH and viscosity of the coating per hour in the continuous stirring process; the pH value of the coating liquid is controlled to be 6.0-8.5; the viscosity is controlled to be 20-50s during spraying and 40-80s during dip coating; after the parameters are stable, the coating is placed in a water bath kettle at 40 ℃ for standing to obtain the high-hardness chromium-free Dacromet coating, which is called the coating for short.
The coating was prepared in the same manner as in example 1.
In this example, the thickness of the anticorrosive coating was 14 μm.
The corrosion resistant coating prepared in this example is labeled coating No. 3.
Example 4
The corrosion inhibition/passivation combination agent is different from the corrosion inhibition/passivation combination agent in example 3 only in that 0.8g of the corrosion inhibition/passivation combination agent is composed of 0.6g of yttrium oxide and 0.2g of graphene nano sheets, and other parameters and steps are the same as those in example 3.
The coating was prepared in the same manner as in example 1.
In this example, the thickness of the anticorrosive coating was 14 μm.
The corrosion resistant coating prepared in this example is labeled coating No. 4.
Example 5
The corrosion inhibition/passivation combination agent is different from the corrosion inhibition/passivation combination agent in example 3 only in that 0.8g of the corrosion inhibition/passivation combination agent is composed of 0.55g of yttrium oxide and 0.25g of graphene nano sheets, and other parameters and steps are the same as those in example 3.
The coating was prepared in the same manner as in example 1.
In this example, the thickness of the anticorrosive coating was 14 μm.
The corrosion resistant coating prepared in this example is labeled coating No. 5.
Comparative example 1
The corrosion inhibition/passivation combined agent is different from the corrosion inhibition/passivation combined agent in example 3 only in that 0.8g of yttrium oxide is replaced by 0.5g of yttrium oxide, the addition of graphene nanosheets is omitted, and other parameters and steps are the same as those in example 3.
The coating was prepared in the same manner as in example 1.
In this comparative example, the thickness of the anticorrosive coating was 14 μm.
The corrosion protection coating prepared in this example is labeled coating No. 6.
Comparative example 2
The corrosion inhibition/passivation combined agent is different from the corrosion inhibition/passivation combined agent in example 3 only in that 0.8g of the corrosion inhibition/passivation combined agent is replaced by 0.5g of graphene nano-sheets, the addition of yttrium oxide is omitted, and other parameters and steps are the same as those in example 3.
The coating was prepared in the same manner as in example 1.
In this comparative example, the thickness of the anticorrosive coating was 14 μm.
The corrosion protection coating prepared in this example is labeled coating No. 7.
Comparative example 3
The difference from example 3 was only that 10g of the zinc-aluminum alloy powder was replaced with 7.5g of zinc powder and 2.5g of aluminum powder, the particle size of the zinc powder was 10 μm, the particle size of the aluminum powder was 10 μm, and other parameters and steps were the same as in example 3.
The coating was prepared in the same manner as in example 1.
In this comparative example, the thickness of the anticorrosive coating was 14 μm.
The corrosion protection coating prepared in this example is labeled coating No. 8.
Comparative example 4
The difference from the example 3 is only that 10g of zinc-aluminum alloy powder is replaced by 7.5g of zinc powder and 2.5g of aluminum powder, the particle size of the zinc powder is 10 mu m, the particle size of the aluminum powder is 10 mu m, the addition of a corrosion inhibition/passivation combination agent is omitted, and other parameters and steps are the same as those of the example 3.
The coating was prepared in the same manner as in example 1.
In this comparative example, the thickness of the anticorrosive coating was 14 μm.
The corrosion protection coating prepared in this example is labeled coating No. 9.
The anticorrosive coatings (coatings No. 1 to 9) prepared in examples 1 to 5 and comparative examples 1 to 4 were subjected to performance tests, which were respectively: appearance test, thickness test, hardness test, wear resistance test, adhesion test, corrosivity test 1, corrosivity test 2.
The test criteria were as follows:
the test standard of the appearance test is GB/T18684-2002; the test standard of the thickness test is GB/T13452.2-2008; the test standard of the hardness test is GB/T6739-2006; the test standard of the wear resistance test is GB/T1768-2006; the test standard of the adhesion test is GB/T5270-2005; the test standard of the corrosivity test 1 is GB/T4334.3-2000; the test standard for the corrosivity test 2 is GB/T10125-2012.
The corrosivity test 1 is an accelerated corrosion test, the test conditions are a full immersion test of ammonium nitrate, the mass fraction of the ammonium nitrate is 20%, and the temperature is 70-80 ℃.
The corrosion test 2 is a general corrosion test, i.e., an artificial atmosphere corrosion test salt spray test.
The test results are shown in table 1:
TABLE 1
FIG. 1 is a micro-topography of the corrosion protection coatings prepared in example 3 and comparative example 3; in the figure, (a) represents example 3, (b) represents comparative example 3; as can be seen from fig. 1 (a), the coating layer made of the zinc-aluminum alloy powder has a compact and uniform surface, no obvious holes and uniform distribution of zinc-aluminum elements on the surface; and 1 (b): the zinc-aluminum mixed powder coating has local agglomeration on the surface, and the elements are not uniformly distributed, particularly the aluminum element, because the zinc powder and the aluminum powder have large specific gravity difference and are easy to be layered, so that local agglomeration of similar elements is caused.
FIG. 2 is a photograph of corrosion morphology of the anticorrosive coatings prepared in example 3 and comparative example 3 after a neutral salt spray test for 1000 h; the left-hand side of the figure represents example 3 and the right-hand side represents comparative example 3; as can be seen from fig. 2, after the neutral salt spray lasts for 1000 hours, the zinc-aluminum alloy powder coating is uniformly corroded, a layer of uniform white corrosion product covers the surface of the coating, and a layer of white corrosion product is also distributed on the surface of the corrosion morphology of the zinc-aluminum mixed powder coating, but the local area of the zinc-aluminum mixed powder coating is corroded because the zinc-aluminum mixed powder coating is locally unevenly distributed, and the number of micro-batteries in the coating is increased due to uneven components, so that the corrosion resistance of the coating is reduced to a certain extent.
The invention mainly realizes the following three technical effects: firstly, the chromate is prevented from causing carcinogenesis to human body and harming ecological environment. Secondly, the defect that the workpiece is not suitable for workpieces with high requirements on hardness and wear resistance because the thickness of the chromium-free Dacromet coating is about 10 mu m, the scratch resistance is poor, the hardness is only 1H-2H generally, and the wear resistance is low, so that the workpiece is easy to scratch and scratch in the assembling, transporting and using processes, and the like is overcome, the graphene nanosheet has high strength and good lubricating effect, the tribological performance of the coating is greatly improved, and the wear resistance of the coating is enhanced; meanwhile, the special two-dimensional lamellar structure and ultrathin thickness of the graphene nanosheet can be filled in gaps of the coating, so that the compactness of the coating is improved, the density of the coating is increased, the erosion process of a corrosive medium in the coating is delayed by utilizing the chemical inertia and the blocking performance of the graphene, and the corrosion resistance of the coating is enhanced. Thirdly, the traditional zinc-aluminum mixed powder is replaced by the flaky zinc-aluminum alloy powder, the traditional chromium-free Dacromet adopts the zinc-aluminum mixed powder to prepare the water-based paint, the zinc-aluminum mixed powder is easy to layer due to large specific gravity difference, so that local similar elements agglomerate, the zinc and aluminum elements in the coating are further unevenly distributed, the corrosion resistance of the coating is influenced to a certain extent, the Zn-Al alloy powder replaces the zinc-aluminum mixed powder to prepare the coating, on one hand, the single metal powder pigment has no layering phenomenon, and the problem of uneven dispersion of the metal powder pigment is solved; on the other hand, the Zn-Al alloy powder obtained by the atomization rapid solidification technology has fine crystal grainsThe composition segregation degree is small, and according to a zinc-aluminum binary alloy phase diagram, the room temperature structure of the zinc-aluminum alloy powder is extremely fine eutectoid structures, namely an aluminum-rich phase and a zinc-rich phase. Compared with Zn and Al powder mixture with macroscopic size, the Zn-Al alloy powder with the fine-scale eutectoid structure has greatly improved component uniformity. Fourthly, rare earth oxide/graphene nanosheets are adopted to modify the dacromet base liquid (the silane passivation liquid replaces chromic anhydride), the composite modification not only improves the hardness and the abrasion resistance of the coating, but also has good shielding effect on corrosive media such as water, air and the like, and can delay H 2 O、O 2 、Cl - And when corrosive media are immersed, the corrosion speed of the metal is delayed, and the corrosion resistance of the coating is improved.
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.
Claims (10)
1. The high-hardness chromium-free Dacromet coating is characterized by comprising the following raw materials: metal pastes, chromate substitutes and auxiliaries;
the metal powder slurry comprises, by mass, 6-10 parts of zinc-aluminum alloy powder, 3-5 parts of a first wetting dispersant, 4-6 parts of a protective agent and 10-15 parts of water; the chromate substitute comprises 0.5-0.8 part of corrosion inhibition/passivation combined agent, 5-10 parts of silane coupling agent, 2-4 parts of second wetting dispersant and 8-12 parts of water; the auxiliary agent comprises 0.05-0.2 part of thickening agent and 0.1-0.3 part of defoaming agent.
2. The high-hardness chromium-free Dacromet coating according to claim 1, wherein the mass ratio of zinc element to aluminum element in the zinc-aluminum alloy powder is 5:1-2:1; the particle size of the zinc-aluminum alloy powder is 10-20 μm.
3. The high hardness chromium-free Dacromet coating according to claim 1, wherein the first wetting and dispersing agent is Span20; the second wetting dispersant is PEG400; the protective agent is PEG200; the thickening agent is hydroxyethyl cellulose ether; the antifoaming agent is dow kangning; the silane coupling agent is one or more of epoxy silane AC66, AC66E, AC67 or vinyl silane AC 77.
4. The high-hardness chromium-free dacromet coating of claim 1, wherein the corrosion inhibiting/passivating combination is a mixture of rare earth oxide and graphene nanoplatelets; the rare earth oxide accounts for 60-70% of the mass of the corrosion inhibition/passivation combined agent.
5. The high hardness chromium-free Dacromet coating according to claim 4, wherein the rare earth oxide is yttria.
6. The method for preparing the high-hardness chromium-free dacromet coating according to claim 1, comprising the steps of:
step 1, adding a first wetting dispersant into water, uniformly stirring, adding zinc-aluminum alloy powder and a protective agent, and uniformly dispersing to obtain uniform slurry A;
step 2: mixing and dissolving a silane coupling agent, a corrosion inhibition/passivation combination agent and water, removing impurities, adding a second wetting dispersant, and uniformly dispersing to obtain uniform slurry B;
and step 3: and mixing the uniform slurry A and the uniform slurry B, adding a thickening agent and a defoaming agent, and stirring until the pH value and the viscosity are stable to obtain the high-hardness chromium-free Dacromet coating.
7. The method according to claim 6, wherein the pH in step 3 is 6.0 to 8.5 and the viscosity is 20 to 80 seconds.
8. Use of the high hardness chromium-free Dacromet coating according to claim 1 for the production of an anticorrosive coating.
9. An anticorrosive coating obtained by spraying or dip-coating the high-hardness chromium-free Dacromet coating material according to claim 1 on a surface of a substrate.
10. A spin coating apparatus for preparing the corrosion resistant coating of claim 9 comprising a rotational speed regulator and an electric stirrer; the rotating speed regulator is connected with the electric stirrer.
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