CN115433483B - High-hardness chromium-free Dacromet coating, anti-corrosion coating and preparation method thereof - Google Patents
High-hardness chromium-free Dacromet coating, anti-corrosion coating and preparation method thereof Download PDFInfo
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- 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
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- 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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- 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 anti-corrosion coating and a preparation method thereof, and relates to the technical field of anti-corrosion treatment of metal material surfaces. The raw materials comprise: metal slip, chromate substitute and adjuvant; the metal powder slurry comprises zinc-aluminum alloy powder, a first wetting dispersant, a protective agent and water; the chromate substitute includes a corrosion inhibition/passivation composition, 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 nano-sheet 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 improved, and the wear resistance of the coating is greatly improved. The invention uses zinc-aluminum alloy powder to replace zinc-aluminum mixed powder, and the dispersibility and uniformity of the metal powder are greatly improved. The invention self-controls the spin coating device, and can obtain the coating with the flaky powder parallel lap joint structure.
Description
Technical Field
The invention relates to the technical field of corrosion prevention treatment of metal material surfaces, in particular to a high-hardness chromium-free Dacromet coating, a corrosion prevention coating and a preparation method thereof.
Background
The Dacromet coating is a mixed solution composed of flaky zinc powder, flaky aluminum powder, chromic anhydride, a wetting agent, a dispersing agent, a reducing agent, deionized water and other auxiliary agents, the mixed solution is uniformly stirred to obtain a coating solution, the coating solution is coated on the surface of a workpiece, and a coating with excellent corrosion resistance is formed on the surface of a metal matrix after baking at about 300 ℃. The Dacromet coating is mainly formed by regularly superposing flaky zinc powder and aluminum powder in a coating liquid on the surface of a fastener to form a film, wherein chromic acid in the coating liquid and a reducing agent undergo oxidation-reduction reaction during baking and sintering, the generated complex oxide bonds the zinc powder and the aluminum powder with each other, chromic acid in the coating liquid can oxidize the zinc aluminum to form a flocculent chromate passivation film, and the film layer and a matrix are tightly combined after solidification. The Dacromet coating has excellent corrosion resistance, no hydrogen embrittlement and high thickness controllability, is generally 10-20 mu m, does not influence the connection and coordination of workpieces, and can obviously improve the corrosion resistance of the fastener.
Dacromet technology, although an excellent corrosion protection technology, has a Cr content of about 2% in the coating 6+ The ion has carcinogenic effect and does not meet the environmental protection requirements related to the automobile industry. Under the background, the chromium-free Dacromet technology has been developed, the pollution problem is better solved by the chromium-free Dacromet technology, but the coating has lower hardness and wear resistance, is easy to scratch, has pencil hardness of only 1H-2H, and cannot be adopted for workpieces requiring wear resistance. Because the film hardness is low, the abrasion resistance is poor, workpieces are often scratched and scratched in the transportation, assembly and use processes, and meanwhile, the corrosion resistance is weakened relatively to Dacromet coating in a high-salt-fog and high-humidity environment, so that the corrosion resistance of the coating is influenced, and the appearance of a product is also influenced. Therefore, it is urgent to improve the hardness and corrosion resistance of the coating by adding a reinforcing phase to the chrome-free dacromet coating.
The corrosion resistance of the environment-friendly dacromet coating prepared by replacing chromates with film-forming substances (oxysalts and oxides, rare earth salts and oxides, silane coupling agents + corrosion inhibitors and resins + corrosion inhibitors) is significantly 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 anti-corrosion coating and a preparation method thereof, so that the problems existing in the prior art are solved, and the chromium-free Dacromet coating has excellent corrosion resistance and higher hardness.
In order to achieve the above object, the present invention provides the following solutions:
according to one of the technical schemes, the high-hardness chromium-free Dacromet coating comprises the following raw materials: metal slip, chromate substitute and adjuvant;
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 composition, 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 content of each component is designed by orthogonal experiments, and more or less than the range influences the corrosion resistance, appearance, adhesion and hardness of the coating.
The silane coupling agent has the following functions: plays a role in bonding rare earth oxide and graphene nano-sheets; passivation effect is performed on the basal layer; the suitability of rare earth oxide and graphene nano sheets with a matrix 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, a step of; the particle size of the zinc-aluminum alloy powder is 10-20 mu m.
Further, the first wetting dispersant is Span20; the second wetting dispersant is PEG400; the protective agent is PEG200; the thickener is hydroxyethyl cellulose ether; the antifoaming agent is dakangning; the silane coupling agent is one or more of epoxy silane AC66, AC66E, AC67 or vinyl silane AC 77.
The basis for selecting the dispersing agent is as follows: the coating is easy to volatilize in the heating and curing process, the adhesive force of the coating can be improved, the dispersion effect of Span20 on metal powder slurry is more excellent, and the dispersion effect of PEG400 on a silane coupling agent and a corrosion/passivation composition agent is better; thickener selection is based on: the thickening effect is excellent, the stability of the coating liquid is not affected, and the hydroxyethyl cellulose ether effect is more excellent; the defoamer is selected according to the following steps: the defoaming capability is optimal, the appearance and the binding force of the coating are not adversely affected (but the addition amount cannot be excessive, the excessive addition can blacken the coating liquid, the glossiness and the adhesive force of the coating are reduced), and the daokanning effect is more excellent; the selection of the silane coupling agent is based on the following: the aqueous solution has good compatibility with a metal powder coating system, presents silver gray bubble-free paste, and one or more of epoxy silane AC66, AC66E, AC67 or vinyl silane AC77 can be satisfied.
Further, the corrosion inhibition/passivation composition is a mixture of rare earth oxide and graphene nano sheets; the rare earth oxide accounts for 60-70% of the mass of the corrosion inhibition/passivation combination agent. The corrosion resistance of the coating layer is lowered beyond this range.
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.
The second technical scheme of the invention is that 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, and then adding zinc-aluminum alloy powder and a protective agent for uniform dispersion to obtain uniform powder slurry A;
step 2: mixing and dissolving a silane coupling agent, a corrosion inhibition/passivation composition agent and water, removing impurities, and adding a second wetting dispersant for uniform dispersion to obtain uniform slurry B;
step 3: and mixing the uniform powder slurry A and the uniform powder slurry B, adding a thickening agent and a defoaming agent, and stirring until the pH and the viscosity are stable, thus obtaining the high-hardness chromium-free Dacromet coating.
Further, in step 3, the pH is 6.0-8.5 and the viscosity is 20-80s.
The third technical scheme of the invention is the application of the high-hardness chromium-free Dacromet coating in the preparation of an anti-corrosion coating.
When the high-hardness chromium-free Dacromet coating is used for spraying, the viscosity is controlled to be 20-50s, and when the high-hardness chromium-free Dacromet coating is used for dip coating, the viscosity is controlled to be 40-80s.
According to the fourth technical scheme, the anti-corrosion coating is obtained by spraying or dip-coating the high-hardness chromium-free Dacromet coating on the surface of a substrate.
The fifth technical scheme of the invention is that the spin coating device for preparing the anti-corrosion 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 anti-corrosion 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 the removal of redundant coating on the sample is realized.
The invention discloses the following technical effects:
(1) According to the invention, the rare earth oxide/graphene nano-sheet 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 improved, and the wear resistance of the coating is greatly improved.
(2) The invention uses zinc-aluminum alloy powder to replace zinc-aluminum mixed powder, and the dispersibility and uniformity of the metal powder are greatly improved.
(3) The invention self-controls the spin coating device, and can obtain the coating with the flaky powder parallel lap joint structure.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are 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 other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a graph of the microscopic morphology of the corrosion protection coating prepared in example 3 and comparative example 3; wherein, (a) represents example 3 and (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 of 1000 hours; wherein the left graph represents example 3 and the right graph represents comparative example 3;
FIG. 3 is a schematic view of a spin-on apparatus for producing an anti-corrosive coating according to the present invention.
Detailed Description
Various exemplary embodiments of the invention will now be described in detail, which should not be considered as limiting the invention, but rather as more detailed descriptions 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. In addition, for numerical ranges in this disclosure, it is understood that each intermediate value between the upper and lower limits of the ranges is also specifically disclosed. Every smaller range between any stated value or stated range, and any other stated value or intermediate value within the stated range, is also encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.
Unless otherwise defined, 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 by reference for the purpose of disclosing and describing the methods and/or materials associated with the documents. 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 invention described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from consideration of the specification of the present invention. The specification and examples of the present invention are exemplary only.
As used herein, the terms "comprising," "including," "having," "containing," and the like are intended to be inclusive and mean an inclusion, but not limited to.
The first wetting dispersant 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 composition agent is a mixture of yttrium oxide and graphene nano-sheets; 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 anti-corrosion coating in the embodiment of the invention is shown in fig. 3.
Example 1
Preparing raw materials:
and (3) a component A: 6g of zinc-aluminum alloy powder, 3g of first wetting dispersant, 4.8g of protective agent and 10g of deionized water;
and the component B comprises the following components: 0.5g of corrosion inhibition/passivation combination agent, 5g of silane coupling agent (AC 66), 2g of second wetting dispersant and 8g of deionized water;
and C, component: hydroxyethyl cellulose ether 0.1g and dakangning 0.15g.
The preparation method comprises the following steps:
step 1, adding 3g of a first wetting dispersant into 10g of deionized water, uniformly stirring on an electromagnetic stirrer to obtain a uniform dispersion solution, then adding 6g of zinc-aluminum alloy powder and 4.8g of a protective agent, continuously stirring, ultrasonically dispersing the slurry for 5min, and then stirring by the electromagnetic stirrer to obtain uniform slurry A.
Step 2: 5g of silane coupling agent, 0.3g of yttrium oxide, 0.2g of graphene nano-sheets and 8g of deionized water are stirred on a magnetic stirrer for 4 hours at normal temperature (3-5 hours are equivalent to 4 hours in technical effect), so that the silane coupling agent is fully hydrolyzed, the yttrium oxide and the graphene nano-sheets are completely dissolved and uniformly dispersed, a second wetting dispersant is added for uniform dispersion, then the centrifugal machine is used for removing impurities, and an ultrasonic cell grinder is used for ultrasonic dispersion again, so that uniform slurry B is obtained.
Step 3: adding the uniform powder slurry A and the uniform powder slurry B into a container, mixing, adding 0.1g of hydroxyethyl cellulose ether and 0.15g of dakangning, and rapidly stirring for 7 hours at room temperature (6-8 hours are equivalent to 7 hours in technical effect), wherein the pH and viscosity of the coating must be tested every hour in the continuous stirring process; the pH 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; and after the parameters are stable, placing the coating in a water bath kettle at 40 ℃ for standing to obtain the high-hardness chromium-free Dacromet coating, which is called as the coating for short.
After immersing the substrate sample (metal Q235 steel) in the above coating, superfluous coating is thrown off in a spin-coating apparatus as shown in fig. 3 to obtain a coating with a flaky powder parallel lap structure, and then the coating sample is sintered and solidified in an oven, and is prebaked for 9min (8-10 min is equivalent to 9min in technical effect) at 100 ℃ (90-110 ℃ is equivalent to 100 ℃) and sintered for 20min (20-25 min is equivalent to 20min in technical effect) at 280 ℃ (240-300 ℃ is equivalent to 280 ℃). And preparing the coating by adopting a two-coating and two-baking mode.
In this example, the thickness of the corrosion-resistant coating was 14. Mu.m.
The corrosion-resistant coating prepared in this example is designated as coating No. 1.
Example 2
And (3) a component A: 8g of zinc-aluminum alloy powder, 4g of first wetting dispersant, 5g of protective agent and 12g of deionized water;
and the component B comprises the following components: 0.6g of corrosion inhibition/passivation combination agent, 6g of silane coupling agent (AC 66), 3g of second wetting dispersant and 10g of deionized water;
and C, component: hydroxyethyl cellulose ether 0.1g and dakangning 0.15g.
The preparation method comprises the following steps:
and step 1, adding 4g of a first wetting dispersant into 12g of deionized water, uniformly stirring on an electromagnetic stirrer to obtain a uniform dispersion solution, then adding 8g of zinc-aluminum alloy powder (and 5g of a protective agent, continuously stirring, ultrasonically dispersing the slurry for 5min, and then stirring by the electromagnetic stirrer to obtain uniform slurry A.
Step 2: stirring 6g of silane coupling agent, 0.4g of yttrium oxide, 0.2g of graphene nano-sheets and 10g of deionized water on a magnetic stirrer for 4 hours at normal temperature (3-5 hours are equivalent to 4 hours in technical effect), fully hydrolyzing the silane coupling agent, adding a second wetting dispersant for uniform dispersion after the yttrium oxide and the graphene nano-sheets are completely dissolved and uniformly dispersed, removing impurities by using a centrifuge, and performing ultrasonic dispersion again by using an ultrasonic cell grinder to obtain uniform slurry B.
Step 3: adding the uniform powder slurry A and the uniform powder slurry B into a container, mixing, adding 0.1g of hydroxyethyl cellulose ether and 0.15g of dakangning, and rapidly stirring for 7 hours at room temperature (6-8 hours are equivalent to 7 hours in technical effect), wherein the pH and viscosity of the coating must be tested every hour in the continuous stirring process; the pH 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; and after the parameters are stable, placing the coating in a water bath kettle at 40 ℃ for standing to obtain the high-hardness chromium-free Dacromet coating, which is called as the coating for short.
The coating was prepared in the same manner as in example 1.
In this example, the thickness of the corrosion-resistant coating was 14. Mu.m.
The corrosion-resistant coating prepared in this example is designated as coating No. 2.
Example 3
And (3) a component A: 10g of zinc-aluminum alloy powder, 5g of first wetting dispersant, 5.5g of protective agent and 15g of deionized water;
and the component B comprises the following components: 0.8g of corrosion inhibition/passivation combination agent, 10g of silane coupling agent (AC 66), 4g of second wetting dispersant and 12g of deionized water;
and C, component: hydroxyethyl cellulose ether 0.1g and dakangning 0.15g.
The preparation method comprises the following steps:
and step 1, adding 54g of a first wetting dispersant into 15g of deionized water, uniformly stirring on an electromagnetic stirrer to obtain a uniform dispersion solution, adding 10g of zinc-aluminum alloy powder and 5.5g of a protective agent, continuously stirring, ultrasonically dispersing the slurry for 5min, and then stirring by the electromagnetic stirrer to obtain uniform slurry A.
Step 2: stirring 10g of silane coupling agent, 0.5g of yttrium oxide, 0.3g of graphene nano-sheets and 12g of deionized water on a magnetic stirrer for 4 hours at normal temperature (3-5 hours are equivalent to 4 hours in technical effect), fully hydrolyzing the silane coupling agent, adding a second wetting dispersant for uniform dispersion after the yttrium oxide and the graphene nano-sheets are completely dissolved and uniformly dispersed, removing impurities by using a centrifuge, and performing ultrasonic dispersion again by using an ultrasonic cell grinder to obtain uniform slurry B.
Step 3: adding the uniform powder slurry A and the uniform powder slurry B into a container, mixing, adding 0.1g of hydroxyethyl cellulose ether and 0.15g of dakangning, and rapidly stirring for 7 hours at room temperature (6-8 hours are equivalent to 7 hours in technical effect), wherein the pH and viscosity of the coating must be tested every hour in the continuous stirring process; the pH 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; and after the parameters are stable, placing the coating in a water bath kettle at 40 ℃ for standing to obtain the high-hardness chromium-free Dacromet coating, which is called as the coating for short.
The coating was prepared in the same manner as in example 1.
In this example, the thickness of the corrosion-resistant coating was 14. Mu.m.
The anticorrosive coating prepared in this example is labeled as coating No. 3.
Example 4
The only difference from example 3 is that 0.8g of the corrosion inhibition/passivation composition is composed of 0.6g of yttrium oxide and 0.2g of graphene nanoplatelets, and other parameters and steps are the same as example 3.
The coating was prepared in the same manner as in example 1.
In this example, the thickness of the corrosion-resistant coating was 14. Mu.m.
The anticorrosive coating prepared in this example is marked as coating No. 4.
Example 5
The only difference from example 3 is that 0.8g of the corrosion inhibition/passivation composition is composed of 0.55g of yttrium oxide and 0.25g of graphene nanoplatelets, and other parameters and steps are the same as in example 3.
The coating was prepared in the same manner as in example 1.
In this example, the thickness of the corrosion-resistant coating was 14. Mu.m.
The corrosion-resistant coating prepared in this example is designated as coating No. 5.
Comparative example 1
The difference from example 3 is that 0.8g of the corrosion inhibition/passivation composition is replaced with 0.5g of yttrium oxide, the addition of graphene nanoplatelets is omitted, and other parameters and steps are 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. Mu.m.
The corrosion-resistant coating prepared in this example is labeled as coating No. 6.
Comparative example 2
The difference from example 3 is that 0.8g of the corrosion inhibition/passivation composition is replaced with 0.5g of graphene nanoplatelets, the addition of yttrium oxide is omitted, and other parameters and steps are the same as those of 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. Mu.m.
The anticorrosive coating prepared in this example is denoted as coating No. 7.
Comparative example 3
The difference from example 3 was that 10g of zinc-aluminum alloy powder was replaced with 7.5g of zinc powder, 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 those of 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. Mu.m.
The anticorrosive coating prepared in this example is marked as coating No. 8.
Comparative example 4
The difference from example 3 was that 10g of zinc-aluminum alloy powder was replaced with 7.5g of zinc powder, 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 the addition of a corrosion inhibition/passivation composition was omitted, 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. Mu.m.
The anticorrosive coating prepared in this example is denoted as 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, and the test items were: appearance test, thickness test, hardness test, abrasion resistance test, adhesion test, corrosiveness test 1, corrosiveness test 2.
The test criteria are as follows:
the testing standard of the appearance test is GB/T18684-2002; the test standard of the thickness test is GB/T13452.2-2008; the hardness test standard is GB/T6739-2006; the test standard of the wear resistance test is GB/T1768-2006; the test standard of the adhesive force test is GB/T5270-2005; the test standard of the corrosiveness test 1 is GB/T4334.3-2000; the test standard for corrosion test 2 is GB/T10125-2012.
The corrosiveness test 1 is an accelerated corrosion test, the test condition is an ammonium nitrate total immersion test, the mass fraction of ammonium nitrate is 20%, and the temperature is 70-80 ℃.
The corrosiveness test 2 is a common corrosion test, namely an artificial atmosphere corrosion test salt spray test.
The test results are shown in Table 1:
TABLE 1
FIG. 1 is a graph of the microscopic morphology of the corrosion protection coating prepared in example 3 and comparative example 3; in the figure, (a) represents example 3 and (b) represents comparative example 3; as can be seen from fig. 1 (a), the surface of the coating layer adopting the zinc-aluminum alloy powder is compact and uniform, no obvious holes appear, and zinc-aluminum elements on the surface are uniformly distributed; and 1 (b): the zinc-aluminum mixed powder coating is adopted to locally agglomerate, the elements are unevenly distributed, and the aluminum element is particularly, because the zinc powder and the aluminum powder have large specific gravity difference and are easy to delaminate, and the locally similar elements are agglomerated.
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 of 1000 hours; the left graph in the figure shows example 3, and the right graph shows comparative example 3; as can be seen from FIG. 2, after 1000 hours of neutral salt fog, the zinc-aluminum alloy powder coating is uniformly corroded, the surface of the coating is covered with a layer of uniform white corrosion product, and the corrosion morphology surface of the zinc-aluminum mixed powder coating is also distributed with a layer of white corrosion product, but the local area of the zinc-aluminum mixed powder coating is corroded due to the phenomenon that the zinc-aluminum mixed powder coating is locally distributed unevenly, 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 technical effects of three: firstly, the cancerogenic action of chromates on human bodies and the harm to the ecological environment are overcome. Secondly, the problems that the chromium-free Dacromet coating has the thickness of about 10 mu m, poor scratch resistance, generally only 1H-2H in hardness and low wear resistance, and the workpiece is easy to scratch and scratch in the processes of assembly, transportation and use are solved, so that the chromium-free Dacromet coating is not suitable for the workpiece with high requirements on hardness and wear resistanceThe graphene nano sheet has high strength and good lubricating effect, so that 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 the ultrathin thickness of the graphene nano sheet can be filled between gaps of the coating, so that the compactness of the coating is improved, the density of the coating is increased, the chemical inertness and the barrier property of the graphene are utilized, the erosion process of a corrosive medium in the coating is delayed, and the corrosion resistance of the coating is enhanced. Thirdly, flaky zinc-aluminum alloy powder is used for replacing the traditional zinc-aluminum mixed powder, the traditional chromium-free Dacromet adopts zinc and aluminum mixed powder to prepare the water-based paint, the zinc-aluminum mixed powder is easy to laminate because of large specific gravity difference, so that local similar elements are agglomerated, zinc and aluminum elements in the coating are unevenly distributed, the corrosion resistance of the coating is affected to a certain extent, and the Zn-Al alloy powder replaces the zinc-aluminum mixed powder to prepare the coating; on the other hand, the Zn-Al alloy powder obtained by the atomization rapid solidification technology has fine crystal grains and small component segregation degree, and according to a zinc-aluminum binary alloy phase diagram, the room temperature structure of the Zn-Al alloy powder is an extremely fine eutectoid structure, namely an aluminum-rich phase and a zinc-rich phase. The Zn-Al alloy powder with fine-scale eutectoid structure has greatly improved component uniformity compared with Zn and Al powder mixture with macroscopic size. Fourthly, rare earth oxide/graphene nano-sheets are adopted to modify Dacromet base solution (silane passivation solution replaces chromic anhydride), and 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 the immersion of the corrosion medium delays the corrosion speed of the metal and improves the corrosion resistance of the coating.
The above embodiments are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope defined by the claims of the present invention without departing from the design spirit of the present invention.
Claims (5)
1. The high-hardness chromium-free Dacromet coating is characterized in that the raw materials consist of metal powder slurry, chromate substitutes and auxiliaries;
the metal powder slurry consists of 6-10 parts by mass of zinc-aluminum alloy powder, 3-5 parts by mass of a first wetting dispersant, 4-6 parts by mass of a protective agent and 10-15 parts by mass of water; the chromate substitute consists of 0.5-0.8 part of corrosion inhibition/passivation composition, 5-10 parts of silane coupling agent, 2-4 parts of second wetting dispersant and 8-12 parts of water; the auxiliary agent consists of 0.05-0.2 part of thickening agent and 0.1-0.3 part of defoaming agent;
the first wetting dispersant is Span20; the second wetting dispersant is PEG400; the protective agent is PEG200; the thickener is hydroxyethyl cellulose ether; the defoamer is a dakangning defoamer; the silane coupling agent is one or more of epoxy silane AC66, AC66E, AC67 or vinyl silane AC 77;
the corrosion inhibition/passivation composition agent is a mixture of yttrium oxide and graphene nano-sheets; the yttrium oxide accounts for 60-70% of the mass of the corrosion inhibition/passivation combination agent;
the mass ratio of zinc element to aluminum element in the zinc-aluminum alloy powder is 5:1-2:1, a step of; the particle size of the zinc-aluminum alloy powder is 10-20 mu m.
2. A method for preparing the high-hardness chromium-free dacromet coating of claim 1, comprising the steps of:
step 1, adding a first wetting dispersant into water, uniformly stirring, and then adding zinc-aluminum alloy powder and a protective agent for uniform dispersion to obtain uniform powder slurry A;
step 2: mixing and dissolving a silane coupling agent, a corrosion inhibition/passivation composition agent and water, removing impurities, and adding a second wetting dispersant for uniform dispersion to obtain uniform slurry B;
step 3: and mixing the uniform powder slurry A and the uniform powder slurry B, adding a thickening agent and a defoaming agent, and stirring until the pH and the viscosity are stable, thus obtaining the high-hardness chromium-free Dacromet coating.
3. The method according to claim 2, wherein in step 3, the pH is 6.0 to 8.5 and the viscosity is 20 to 80s.
4. Use of the high hardness chrome-free dacromet coating of claim 1 for preparing an anti-corrosive coating.
5. An anticorrosive coating, characterized in that it is obtained by spraying or dip-coating the high-hardness chromium-free dacromet coating according to claim 1 on the surface of a substrate.
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| CN107964351B (en) * | 2017-09-28 | 2019-12-31 | 永星化工(上海)有限公司 | Water-based composite zinc-aluminum anticorrosive paint |
| CN108192403B (en) * | 2018-01-23 | 2020-04-17 | 永星化工(上海)有限公司 | Solvent type zinc-aluminum coating |
| CN111719115B (en) * | 2020-07-08 | 2022-05-03 | 中国铁道科学研究院集团有限公司金属及化学研究所 | Composite anti-corrosion wear-resistant layer for steel substrate |
| CN112427228B (en) * | 2020-10-23 | 2022-02-11 | 安徽省振华科技工业有限公司 | Dacromet surface treatment device for complex automobile structural part |
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