Application of plasma ferrophosphorus powder in epoxy zinc-rich anticorrosive paint and corresponding epoxy zinc-rich anticorrosive paint

Abstract

The invention belongs to the technical field of new materials, particularly relates to the field of anti-corrosion materials, and particularly relates to application of plasma ferrophosphorus powder in epoxy zinc-rich anti-corrosion paint and the epoxy zinc-rich anti-corrosion paint added with the plasma ferrophosphorus powder. Wherein the ferrophosphorus powder is selected from one or a mixture of more of FeP, Fe2P and Fe3P, and the median particle size of the ferrophosphorus powder is 1-30 [mu] m. The ferrophosphorus powder obtained after plasma treatment is higher in conductivity and higher in zinc powder connecting capacity. Compared with zinc-rich paint using unmodified ferrophosphorus powder, the epoxy zinc-rich paint prepared by replacing part of zinc powder with the modified ferrophosphorus powder has the advantages of stronger barrier ability, longer cathode protection period and better salt spray corrosion resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of new materials, especially the field of anti-corrosion materials. Specifically, it relates to the application of plasma-treated phosphorus iron powder in zinc-rich anti-corrosion coatings, and also relates to zinc-rich anti-corrosion coatings added with plasma-treated phosphorus iron powder. Background Art

[0002] Among numerous steel anti-corrosion technologies, organic coatings are one of the most economical and widely used corrosion protection methods. Especially epoxy zinc-rich primer, due to its excellent anti-corrosion performance, is widely used in the fields of ships, oceans, roads and bridges, buildings, automotive industry, chemical industry, etc.

[0003] Generally, to ensure that the zinc-rich primer has excellent anti-corrosion performance, its zinc powder content is usually 60% - 90% of the dry film mass. However, a high zinc content in the coating leads to high product costs, difficult leveling during the curing process, and also affects the storage of the coating. In addition, zinc oxide fumes released during welding and cutting may cause workers to suffer from "zinc fever".

[0004] Research reports by the International Lead and Zinc Study Group indicate that there is no obvious direct correlation between the zinc powder content of zinc-rich paints and the anti-corrosion ability of the paint film. The actual anti-corrosion effect must be used as the evaluation criterion. Moreover, reports show that when cathodic protection fails, only about 30 wt% of the zinc in the paint film is consumed as a sacrificial anode. Therefore, how to improve the utilization rate of zinc powder, reduce the cost of zinc-rich paints, and at the same time ensure the original anti-corrosion performance is a hot topic of current research.

[0005] Researchers have proposed two strategies: One is to use conductive fillers to connect zinc powder, such as iron phosphide, aluminum powder, carbon black, graphene, carbon nanotubes, zinc nanoparticles, flaky zinc, polypyrrole, polyaniline, and two-dimensional transition metal carbon / nitrogen compounds (MXene), etc. Such additives can improve the utilization rate of zinc powder and form a more efficient cathodic protection circuit network. The other is to add barrier-type additives, such as micaceous iron oxide, nano-montmorillonite, etc., to form a maze effect and slow down the diffusion of erosive particles, thereby reducing the corrosion rate. However, among these additives, few conductive additives can replace more than 10 wt% of zinc powder while maintaining the original cathodic protection ability of the paint film. Although graphite, graphene, carbon nanotubes, and MXene have high electrical conductivity, their preparation processes are complex and the prices are relatively high. Moreover, these carbon-based conductive agents will accelerate the corrosion of iron after cathodic protection fails, which is not conducive to long-term corrosion protection.

[0006] Ferrophosphorus powder is a by-product of the metallurgical industry. It is inexpensive and has good electrical conductivity, and can be added to inorganic silicate zinc-rich paint [Feliu Jr S, Morcillo M, Bastidas J M, et al. Zinc reactivity in zinc-rich coatings co-pigmented with di-iron phosphide[J]. Journal of Coatings Technology, 1991, 63(793): 31-34.]. The literature discloses that 12 wt% of ferrophosphorus powder can reduce the zinc powder content of ethyl silicate zinc-rich paint from 84 wt% to 77 wt%, while the cathodic protection ability of the paint film only decreases by about 20%. It can be seen that ferrophosphorus powder is inexpensive and highly efficient, and is an ideal zinc-reducing additive. The research by Xie et al. [Xie D M, Huang K, Feng X, et al. Improving the performance of zinc-rich coatings using conductive pigments and silane[J]. Corrosion Engineering, Science and Technology, 2020, 55(7): 539-549.] shows that in an epoxy polyamide system with a zinc content of 84 wt%, adding 6 wt% of Fe2P can hardly affect the original cathodic protection performance, while 12% of Fe2P reduces the cathodic protection ability by about 20%. However, the addition of ferrophosphorus powder causes porosity in the coating, reducing the barrier property and long-term passive defense ability of the paint film. Although using a silane coupling agent can increase the interfacial affinity and weaken this negative effect, the modification with a silane coupling agent inevitably causes a decrease in the electrical conductivity of ferrophosphorus powder, which is not conducive to ferrophosphorus powder fully exerting its own electrical conductivity and connecting with zinc powder to form a more complete conductive network system. Summary of the Invention

[0007] The purpose of the present invention is to provide a new idea different from chemical modification. By subjecting ferrophosphorus powder to plasma treatment and then adding it to an epoxy zinc-rich coating, better anti-corrosion and zinc-reducing effects can be obtained.

[0008] Based on this purpose, the present invention provides the following solutions: In the first aspect, Application of plasma-treated ferrophosphorus powder in an epoxy zinc-rich anti-corrosion coating.

[0009] The ferrophosphorus powder is selected from one or a mixture of more than one of FeP, Fe2P, and Fe3P.

[0010] The median particle size of the ferrophosphorus powder is 1 μm to 30 μm.

[0011] The plasma treatment is to place the ferrophosphorus powder in a plasma processor and treat it for 5 s to 1 h at a power of 30 - 300 W. During the treatment process, the ferrophosphorus powder is in a vacuum or atmospheric pressure state, and the atmosphere can be one or any combination of H2, Ar, N2, O2, and air.

[0012] The plasma processor is equipped with a radio frequency or microwave plasma emitter.

[0013] The plasma processor is of a drum type, a disc type (DBD) or a torch type.

[0014] In a second aspect, An epoxy zinc - rich anti - corrosion coating containing plasma - treated ferrophosphorus powder includes a conductive filler, a film - forming substance, and necessary solvents; the film - forming substance is a water - borne epoxy resin, a solvent - based epoxy resin, or an epoxy resin powder coating; the conductive filler is composed of zinc powder and plasma - treated ferrophosphorus powder, and the total addition amount of the conductive filler accounts for 70 - 90% of the total weight of the dry film, and the plasma - treated ferrophosphorus powder accounts for 5 - 30% of the total weight of the dry film.

[0015] In the epoxy zinc - rich anti - corrosion coating containing plasma - treated ferrophosphorus powder, the ferrophosphorus powder is selected from one or a mixture of more than one of FeP, Fe2P, and Fe3P.

[0016] In the epoxy zinc - rich anti - corrosion coating containing plasma - treated ferrophosphorus powder, the median particle size of the ferrophosphorus powder is 1 μm to 30 μm.

[0017] The plasma treatment is to place the ferrophosphorus powder in a plasma processor and treat it for 5 s to 1 h at a power of 30 - 300 W.

[0018] In the present invention, the ferrophosphorus powder is modified by plasma activation. The prepared modified ferrophosphorus powder has higher electrical conductivity and stronger ability to connect zinc powder. When it is used to replace part of the zinc powder in the zinc - rich paint, it can show a longer cathodic protection period, stronger barrier ability, and better salt - spray corrosion resistance than the unmodified ferrophosphorus powder. Compared with the chemical modification method such as adding a coupling agent, which will reduce the electrical conductivity of the ferrophosphorus powder, the plasma - treated ferrophosphorus powder can fundamentally eliminate the influence of the chemical modifier on the electrical conductivity of the ferrophosphorus powder.

[0019] At the same time, the modified ferrophosphorus powder has good compatibility with the coating system. After electrochemical experimental tests, it can still maintain a relatively high impedance value in the low - frequency region, indicating that the coating has better barrier ability and effectively avoids the problem that the cathodic protection ability and barrier performance of the zinc - rich paint film are greatly reduced due to the addition of ferrophosphorus powder.

[0020] In addition, the plasma treatment of the powder is simple in method, mild in conditions, low in energy consumption but high in treatment efficiency. It does not require chemical reagent modification anymore, can reduce the zinc powder addition amount in the anticorrosive coating to a certain extent, improve the utilization rate of zinc powder, and does not weaken the original anticorrosive performance while reducing the coating cost. This is extremely attractive for the market promotion of the product. Description of the Drawings

[0021] Figure 1 are the digital photos of the coating samples of Comparative Sample 1 and Modified Sample 1 after the salt spray test; Figure 2 are the digital photos of the coating samples of Comparative Sample 4 and Modified Sample 4 after the salt spray test. Detailed Description of the Invention

[0022] The inventors have conducted research and experiments on the present invention. Some of the embodiments are listed below to further illustrate the present invention.

[0023] Example 1 Take 500 g of Fe2P particles with a medium particle size of 1 μm, transfer them to the treatment chamber of a drum-type low-pressure plasma device, evacuate to 0.2 mbar, introduce an Ar atmosphere, turn on the stirring and radio frequency plasma switches, with a power of 100 W, carry out plasma treatment, the stirring speed is 60 rpm, and the time is 30 min, thus obtaining surface-activated modified Fe2P particles, namely plasma-modified phosphorus iron powder. The resistivity of the powder is significantly reduced compared with that before the plasma treatment, changing from 5.0×10 - ³ Ω·m to 6.7×10 -4 Ω·m, having better conductivity.

[0024] Take 5 g of Fe2P without plasma treatment and 5 g of Fe2P after the above plasma treatment respectively, and add them together with 80 g of zinc powder to the mixed solution of waterborne epoxy polyamide resin, and prepare Comparative Sample 1 and Modified Sample 1 according to the ratio in Table 1. The mixed solution uses water as the solvent and dissolves a total of 15 g of epoxy resin and its curing agent (Table 1, excluding the solvent).

[0025] Stir at 3000 rpm for 10 min to obtain a uniform slurry, spray it onto the Q235 carbon steel plate polished with sandpaper through a spray gun, and wait for it to be completely cured to obtain a zinc-rich epoxy anticorrosive coating with a Fe2P addition amount of 5% and a pure zinc content of 80%, and the spraying film thickness is about 50 μm.

[0026] Use a standard cross-cutting instrument to cross-cut on the coating sample with a width of 0.5 mm, and then place the coating sample in a salt spray chamber with a 5% salt water concentration and 35 °C for 1000 h. After the salt spray test, the digital photos of the two groups of coating samples are as Figure 1 shown, Figure 1Specimen a is a coated sample of epoxy resin added with unmodified phosphorus iron powder. The average corrosion width on the specimen is 1.22 mm, and there are a small number of pitting corrodions; while for the specimen of the zinc-rich paint film added with modified phosphorus iron powder ( Figure 1 b), there are no bubbles, peeling, or pitting corrodions, and the average corrosion width (the average width of the corrosion boundary of the scratch boundary) is 0.83 mm. It can be seen that plasma treatment of phosphorus iron powder can improve the anti-corrosion performance of the zinc-rich coating system.

[0027] Table 1. Composition and properties of epoxy zinc-rich coatings added with 5% phosphorus iron powder

[0028] Example 2 Take 200 g of Fe3P phosphorus iron powder with a medium particle size of 20 μm, place it in an atmospheric pressure DBD disk-type plasma generator, the atmosphere is air, the plasma treatment power is 30 W, and the time is 1 min, then the plasma-activated and modified phosphorus iron powder is obtained.

[0029] Take 10 g of phosphorus iron powder without plasma treatment and the above-mentioned plasma-treated phosphorus iron powder respectively, and add them to a mixed solution of waterborne epoxy polyamide resin together with 60 g of zinc powder (800 mesh) to prepare Comparative Specimen 2 and Modified Specimen 2 according to the ratio in Table 2. The mixed solution uses water as a solvent and dissolves a total of 30 g of epoxy resin and its curing agent (Table 2, excluding the solvent).

[0030] Stir at 3000 rpm for 10 min to obtain a uniform coating slurry, spray it onto a Q235 carbon steel plate, the spray film thickness is about 60 μm, and after complete curing, a zinc-rich anti-corrosion coating with a phosphorus iron powder addition of 10% and a zinc content of 60% is obtained.

[0031] In the electrochemical experiment, the specimen was immersed in a 3.5% NaCl solution and tested by electrochemical experiment. The cathodic protection period of Modified Specimen 2 was measured to be 65 days; while the cathodic protection period of Comparative Specimen 2 was 57 days.

[0032] When the cathodic protection fails, the impedance value of the coating of Modified Specimen 2 at 0.01 Hz in the low-frequency region is 4.3×10 4 Ω·cm 2 , while the impedance value of the coating of Comparative Specimen 2 containing the same concentration of unmodified phosphorus iron powder in the low-frequency region is 9.3×10 3 Ω·cm 2 . This shows that compared with ordinary Fe3P phosphorus iron powder, adding plasma-modified Fe3P phosphorus iron powder to the anti-corrosion coating has better barrier ability.

[0033] Table 2. Composition and properties of epoxy zinc-rich coatings added with 10% phosphorus iron powder

[0034] Example 3 Take 250 g of FeP phosphorus iron powder particles with a medium particle size of 10 μm and place them in an open container equipped with a stirring device, about 5 cm below the torch nozzle of a torch-type atmospheric plasma device. Introduce air into the torch plasma device, turn on the stirring, and start the plasma treatment for 10 min to obtain surface-activated and modified phosphorus iron powder particles.

[0035] Take 15 g of unplasma-treated phosphorus iron powder and the above-mentioned plasma-treated phosphorus iron powder, 60 g of zinc powder (500 mesh), and 25 g of epoxy resin powder coating respectively. After mixing evenly, extrude at 100 °C, and obtain an anticorrosive powder coating with an average particle size of 35 μm through crushing and screening. Mark them as Comparative Sample 3 and Modified Sample 3 (Table 3) respectively. Spray them onto a Q235 carbon steel plate with an electrostatic spray gun at a voltage of -70 kV and a spraying distance of 20 cm, and heat and cure in an oven at 200 °C for 15 min to obtain a zinc-containing epoxy anticorrosive coating with a film thickness of 60 μm, 15% modified phosphorus iron powder, and a zinc content of 60%.

[0036] In the electrochemical experiment, immerse the sample in a 3.5% NaCl solution and conduct electrochemical experiment tests. The measured cathodic protection period is 69 days; while the cathodic protection period of the epoxy resin coating sample containing unmodified phosphorus iron powder with the same concentration is 61 days. When the cathodic protection fails, the impedance value of the modified Sample 3 coating at 0.01 Hz in the low-frequency region is 6.5×10 5 Ω·cm 2 , while the impedance value of Comparative Sample 3 with the same addition amount of phosphorus iron powder is 8.2×10 4 Ω·cm 2 .

[0037] This shows that compared with ordinary FeP phosphorus iron powder particles, after plasma modification of FeP and then adding it to the anticorrosive coating, it can endow the zinc-rich coating with better barrier ability.

[0038] Table 3. Composition and properties of epoxy zinc-rich coatings with 15% phosphorus iron powder added

[0039] Example 4 Take 100 g of FeP particles with a medium particle size of 30 μm and place them in the treatment chamber of a drum-type atmospheric plasma device. Introduce an air atmosphere and start the plasma treatment for 1 h to obtain surface-activated and modified phosphorus iron powder particles.

[0040] Take 30 g of phosphorus iron powder without isometric three-dimensional treatment and the above-mentioned plasma-treated phosphorus iron powder, 60 g of zinc powder (500 mesh), and an epoxy resin acetone solution (epoxy resin content is 10 g), and obtain a uniform slurry through sufficient stirring and grinding to prepare Comparative Specimen 4 and Modified Specimen 4 (Table 4).

[0041] Spray the obtained uniformly mixed slurry onto a Q235 carbon steel plate with a spray film thickness of about 100 μm, and then place the sample plate indoors for 7 days to fully cure, obtaining a solvent-based epoxy resin coating with a phosphorus iron powder addition of 30% and a zinc content of 60%.

[0042] Use a standard cross-cutting instrument to cross-cut on the coating specimens of Comparative Specimen 4 and Modified Specimen 4 with a width of 0.5 mm, and then place the coating specimens in a salt spray chamber with a 5 wt% salt water concentration and 35 °C for salt spray treatment for 2000 h.

[0043] After the salt spray test, the digital photos of the two groups of coating specimens are as Figure 2 shown. The average corrosion width of the paint film of the zinc-rich paint with plasma-activated phosphorus iron powder (Modified Specimen 4) is 1.09 mm; while the average corrosion width of the paint film of the zinc-rich paint with the same content of unmodified phosphorus iron powder (Comparative Specimen 4) is 1.56 mm.

[0044] Obviously, the corrosion resistance of Modified Specimen 4 is better.

[0045] Table 4. Composition and properties of epoxy zinc-rich coatings with 30% phosphorus iron powder added

Claims

1. Application of plasma-treated phosphorus iron powder in epoxy zinc-rich anti-corrosion coatings.

2. The application according to claim 1, characterized in that, The phosphorus iron powder is selected from one or a mixture of more than one of FeP, Fe2P and Fe3P.

3. The application according to claim 2, characterized in that The median particle size of the phosphorus iron powder is 1 μm to 30 μm.

4. The application according to any one of claims 1 to 3, characterized in that, The plasma treatment is to place the phosphorus iron powder in a plasma processor for treatment for 5 s to 1 h, with a power of 30 to 300 W.

5. The application according to claim 4, wherein The plasma processor is equipped with a radio frequency or microwave plasma emitter.

6. The application according to claim 4, wherein The plasma processor is of a drum type, a disc type (DBD) or a torch type.

7. An epoxy zinc-rich anti-corrosion coating containing plasma-treated iron phosphide powder, characterized in that, It includes a conductive filler, a film-forming substance and a necessary solvent; the film-forming substance is a waterborne epoxy resin, a solvent-based epoxy resin or an epoxy resin powder coating; the conductive filler is composed of zinc powder and plasma-treated phosphorus iron powder, and the total addition amount of the conductive filler accounts for 70 to 90% of the total weight of the dry film, and the plasma-treated phosphorus iron powder accounts for 5 to 30% of the total weight of the dry film.

8. The epoxy zinc-rich anti-corrosion coating containing plasmaized iron phosphide powder according to claim 7, wherein The phosphorus iron powder is selected from one or a mixture of more than one of FeP, Fe2P and Fe3P.

9. The epoxy zinc-rich anti-corrosion coating containing plasmaized ferrophosphorus powder as described in claim 8, characterized in that, The median particle size of the phosphorus iron powder is 1 μm to 30 μm.

10. The epoxy zinc-rich anti-corrosion coating containing plasmaized ferrophosphorus powder according to any one of claims 7-9, characterized in that, The plasma treatment is to place the phosphorus iron powder in a plasma processor for treatment for 5 s to 1 h, with a power of 30 to 300 W.

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