Rare earth aluminum magnesium alloy powder coating and preparation method thereof

Abstract

The invention discloses a rare earth aluminum magnesium alloy powder coating which comprises the following components in parts by mass: 50-55 parts of epoxy resin, 10-13 parts of an epoxy curing agent, 0.3-0.8 part of dimethylimidazole, 2-3 parts of a toughening agent, 3-5 parts of mica powder, 2-3 parts of an auxiliary agent and 14-20 parts of flaky rare earth aluminum magnesium alloy powder. The invention further discloses a preparation method of the rare earth aluminum magnesium alloy powder coating. The preparation method comprises two stages of preparing the scaly rare earth aluminum magnesium alloy powder and preparing the scaly rare earth aluminum magnesium alloy powder-containing coating. The rare earth metal and the magnesium metal are added during aluminum alloy smelting, the electric corrosion resistance of the scaly rare earth aluminum magnesium alloy powder can be improved, the metal powder is added step by step through extrusion and external mixing, the scale shape of the metal powder can be kept to the maximum extent, and the effects of sacrificial anode protection and corrosion ion blocking of the metal powder scale are fully exerted; the prepared powder coating containing the rare earth aluminum magnesium alloy powder and a weather-proof protective coating are cooperatively applied to corrosion prevention of a steel structure, and long-acting corrosion prevention can be achieved for 25 years or above.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and in particular relates to a rare earth aluminum-magnesium alloy powder coating and a preparation method thereof. Background Art

[0002] Corrosion and protection involve many industries in the development of the national economy. Correctly selecting corrosion control technology can effectively prevent and slow down corrosion damage and minimize the economic losses and social harm caused by corrosion. The most common method of corrosion protection for steel structures is to use paint coatings. The principles of corrosion protection of paint coatings mainly include physical shielding isolation and sacrificial anode protection. Zinc-rich primers or aluminum powder paints prepared by adding metal zinc powder or aluminum powder with sacrificial anode protection to the coating have become the most common and important anti-corrosion coatings for protecting steel structures. They are widely used in bridges, ships, offshore oil platforms, oil pipelines, port terminal facilities, indoor and outdoor steel structure protection, etc. in the atmosphere and marine environment.

[0003] In industrial areas with high humidity and harsh atmosphere, coastal areas with high salinity, or offshore areas with high salinity and tropical and subtropical industrial areas with extremely high humidity and corrosive atmosphere, the corrosion protection period of steel components such as bridges, docks, and offshore platforms is generally required to be 30 years, 50 years, or even more than 100 years. Frequent coating maintenance not only greatly increases operating costs, but also seriously affects the normal use of facilities. Due to the fast sacrificial speed of zinc, the protection period of zinc-rich primers prepared with zinc powder as anti-corrosion pigment can only reach 3 to 15 years under atmospheric and marine climate conditions, and most of them are overhauled and maintained in about 10 years. Aluminum powder paint with aluminum powder as anti-rust pigment has good durability, but because a layer of poorly conductive oxide film is easily formed on the surface of aluminum powder, the sacrificial anode effect of the coating is weak, and the purpose of sacrificial anode protection of the steel substrate cannot be achieved. The flaky zinc powder is arranged in parallel and overlapped in the coating. In addition to the sacrificial anode protection function, it can also reduce defects such as pinholes and cracks in the coating, block the penetration path of corrosive ions, and improve the anti-corrosion effect of the coating. Patent CN105602415 discloses a VCI powder zinc-rich coating for steel structure surface protection. It uses flaky zinc powder, VCI vapor phase corrosion inhibitor, aluminum tripolyphosphate, zinc phosphate and other anti-rust pigments to prepare powder coatings through one-time extrusion and grinding process. It is used for steel structure corrosion protection, and the protection period can exceed 10 years. Patent CN103421989 discloses a flaky multi-component aluminum-zinc-silicon alloy powder containing Ce, Pr and Nd and its preparation method. The flaky multi-component aluminum-zinc-silicon alloy powder containing Ce, Pr and Nd is used in Dacromet coatings and zinc-rich paints. The passivation effect of aluminum is used to slow down the consumption rate of zinc, thereby increasing the anti-corrosion time of the coating.

[0004] Zinc and its alloys have low corrosion potential and strong cathodic protection for steel substrates, but their sacrificial rate is fast. According to the international standard ISO12944 "Paints and varnishes - Corrosion protection of steel structures by protective coating systems - Part 2: Environmental classification", the corrosion rate of zinc can reach 8.4μm / year in industrial areas with high humidity and harsh atmosphere and coastal areas with high salinity; in offshore areas with high salinity and tropical and subtropical industrial areas with extremely high humidity and corrosive atmosphere, the corrosion rate of zinc can reach 25μm / year, and its durability is obviously insufficient. The sacrificial rate of aluminum and its alloy coatings is slow, only 1.85μm / year in marine corrosion environments, and its corrosion resistance is good. A large number of application practices have proved that aluminum coatings are prone to pitting in marine environments, and the sacrificial anode protection is weak, which has defects in protecting steel substrates. In addition, a large amount of metal powder is melted and mixed with resin from a screw extruder. The scale shape of the metal powder is easily deformed and curled under the shearing action of the screw, and the parallel arrangement in the coating is affected, thereby reducing the anti-corrosion effect. Summary of the invention

[0005] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a rare earth aluminum-magnesium alloy powder coating and a preparation method thereof.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A rare earth aluminum-magnesium alloy powder coating comprises the following components by mass: 50-55 parts of epoxy resin, 10-13 parts of epoxy curing agent, 0.3-0.8 parts of dimethylimidazole, 2-3 parts of toughening agent, 3-5 parts of mica powder, 2-3 parts of auxiliary agent and 14-20 parts of flaky rare earth aluminum-magnesium alloy powder.

[0008] The flaky rare earth aluminum-magnesium alloy powder is composed of 0.01% to 0.5% cerium or lanthanum rare earth elements, 2% to 5% magnesium, and the rest is aluminum. The epoxy resin is a mixture of one or two of bisphenol A epoxy resin and phenolic epoxy resin. The epoxy curing agent is a phenolic epoxy curing agent. The auxiliary agent is a leveling agent, a brightener, and a degassing agent.

[0009] The present invention also discloses a method for preparing a rare earth aluminum-magnesium alloy powder coating, comprising the following steps: S1, preparing flaky rare earth aluminum-magnesium alloy powder;

[0010] First, preheat the smelting furnace to 400-450°C, and evenly apply a layer of KCl-NaCl molten salt covering agent on the inner wall of the furnace. After the KCl-NaCl molten salt is completely melted, weighed aluminum ingots and a formula amount of rare earth aluminum intermediate alloy are sequentially put into the smelting furnace, and then the temperature is increased for smelting, and the smelting temperature is controlled at 870°C. After complete melting, a formula amount of magnesium ingot is put into the furnace, and the magnesium ingot is quickly pressed into the bottom of the furnace for melting. After the magnesium ingot is completely melted, compressed air deslagging is performed, and a deslagging refining agent is pressed into the bottom of the melt for refining treatment. The refining process is controlled within about 10-15 minutes until the surface of the melt presents a bright mirror surface; after refining, stir for about 15 minutes, and then stand for about 30 minutes to remove the slag, and at the same time, sample and analyze the components of each alloy. After passing the test, put it into a holding furnace and control the temperature at 760°C, and then cast it into a rare earth aluminum-magnesium alloy bar;

[0011] Then, the rare earth aluminum-magnesium alloy rod is placed in a vacuum atomization powder making device to be atomized into a spherical rare earth aluminum-magnesium alloy powder of 300-500 meshes, and then the obtained spherical rare earth aluminum-magnesium alloy powder, a grinding aid and a ball milling medium are added to a ball mill for ball milling. The ball milling medium is a stainless steel ball or a zirconium oxide ball with a diameter of 0.8-2 mm. Before ball milling, vacuum must be drawn and then an inert gas is introduced. A cooling liquid is introduced into the interlayer of the ball mill to control the temperature not to exceed 50° C. during the ball milling process. The ball milling time is 10-15 hours, and the ball mill speed is maintained at 30-50 rpm, so that the spherical rare earth aluminum-magnesium alloy powder is ball milled into a flaky alloy powder, and then the flaky rare earth aluminum-magnesium alloy powder is prepared after sieving.

[0012] S2. Preparation of powder coating containing flaky rare earth aluminum-magnesium alloy powder

[0013] First, epoxy resin, epoxy curing agent, dimethylimidazole, toughening agent, mica powder, additives and 1 / 2 to 2 / 3 of flaky rare earth aluminum-magnesium alloy powder are put into a flip mixing tank and mixed at a low speed for 30 minutes. Then, a twin-screw extruder is used for melt extrusion, and a tablet press is used for sheeting. The front temperature of the extruder is controlled at 110°C ± 5°C, the rear temperature is controlled at 80°C ± 5°C, the main engine speed is controlled at 40Hz to 50Hz, and the tablet press thickness is controlled at 0.5 to 1.5mm. Then, an ACM grading mill is used to grind the powder to control the D50 particle size at 20μm to 30μm. Finally, the powder coating obtained by ACM grinding and the remaining flaky rare earth aluminum-magnesium alloy powder are put into a binding machine for mixing and binding, and then cooled and sieved to obtain the powder coating containing flaky rare earth aluminum-magnesium alloy powder.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: adding rare earth metals and magnesium metal during aluminum alloy smelting can improve the electrolytic corrosion resistance of flaky rare earth aluminum-magnesium alloy powder, which can not only enhance the surface density of the metal powder and prevent the invasion of corrosive ions, but also improve the sacrificial anode protection capability; the metal powder is added in steps by extrusion and external mixing, which can maintain the shape of the metal powder flakes to the maximum extent and give full play to the role of the metal powder flakes in sacrificial anode protection and corrosion ion isolation; the prepared rare earth aluminum-magnesium alloy powder coating is synergistically used in steel structure corrosion protection with weather-resistant protective coating to extend the corrosion protection period. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0016] A rare earth aluminum-magnesium alloy powder coating, the main raw materials of which are as follows:

[0017] Epoxy resin: E-12, Ningbo Nanhai Chemical Co., Ltd.

[0018] Epoxy resin: GT7255, Huntsman

[0019] Epoxy curing agent: PSG-01, Xi'an Dahe Chemical Co., Ltd.

[0020] Dimethylimidazole: pharmaceutical grade, Hubei Laisi Chemical

[0021] Toughening agent: Butyral PVB, Hubei Laisi Chemical

[0022] Mica powder: Commercially available

[0023] Additives: leveling agent GLP588, brightener 701, degassing agent benzoin, Ningbo Nanhai Chemical Co., Ltd.

[0024] Flake zinc powder: D20011~13μm Hunan Jinhao New Materials Technology Co., Ltd.

[0025] Flake aluminum powder: CYH-1211~13μm Hunan Jinhao New Materials Technology Co., Ltd.

[0026] Cerium aluminum alloy block, aluminum ingot, magnesium block: all are commercially available.

[0027] Embodiment 1

[0028] Rare earth aluminum-magnesium alloy powder coating: E-1250 parts, GT72555 parts, PSG-0113 parts, dimethylimidazole 0.8 parts, PVB 3 parts, mica powder 5 parts, flaky rare earth aluminum-magnesium alloy powder 14 parts, GLP5881 parts, 7011 parts, benzoin 1 part. The formula of flaky rare earth aluminum-magnesium alloy powder: cerium 0.05g, magnesium 2g, aluminum 97.95g.

[0029] A method for preparing a rare earth aluminum-magnesium alloy powder coating comprises the following steps:

[0030] In the first stage, flaky rare earth aluminum-magnesium alloy powder is prepared.

[0031] First, the smelting furnace is preheated to 400-450°C, and a layer of KCl-NaCl molten salt covering agent is evenly coated on the inner wall of the furnace; after the KCl-NaCl molten salt is completely melted, the aluminum ingots and cerium aluminum alloy blocks calculated and weighed according to the formula are put into the smelting furnace in turn, and then the temperature is increased for smelting, and the smelting temperature is controlled at 870°C. After complete melting, the magnesium ingots of the formula amount are put into the furnace, and the magnesium ingots are quickly pressed into the bottom of the furnace for melting; after the magnesium ingots are completely melted, compressed air deslagging is carried out, and the deslagging refining agent is pressed into the bottom of the melt for refining treatment, and the refining process is controlled to be about 10-15 minutes until the surface of the melt presents a bright mirror surface; after refining, it is stirred for about 15 minutes, and then it is allowed to stand for about 30 minutes to remove the slag, and at the same time, samples are taken for analysis of the components of each alloy, and after passing the test, it is put into a holding furnace, the temperature is controlled at 760°C, and then cast into Al-Mg-Ce alloy rods. Then, the Al-Mg-Ce alloy rod is placed in a vacuum atomization powder making device and atomized into a spherical Al-Mg-Ce alloy powder of 300-500 meshes, and then the obtained spherical Al-Mg-Ce alloy powder, zinc stearate and φ2mm stainless steel balls are added to a ball mill, and vacuum is first evacuated and then an inert gas is introduced. A cooling liquid is introduced into the interlayer of the ball mill to control the temperature not to exceed 50°C during the ball milling process, and the ball mill is started. The ball milling time is 10-15 hours, and the ball mill speed is maintained at 30-50rpm, so that the spherical Al-Mg-Ce alloy powder is ball-milled into flaky alloy powder, and the flaky Al-Mg-Ce alloy powder is prepared after screening.

[0032] In the second stage, a powder coating containing flaky rare earth aluminum-magnesium alloy powder is prepared.

[0033] First, epoxy resin E-12, novolac epoxy resin GT7255, phenolic epoxy curing agent PSG-01, dimethylimidazole, toughening agent PVB, mica powder, GLP588, 701, benzoin, and 1 / 2 of flaky Al-Mg-Ce alloy powder were put into a flip mixing tank and mixed at a low speed for 30 minutes.

[0034] Then, a twin-screw extruder is used for melt extrusion, and a tablet press is used for sheeting. The front temperature of the extruder is controlled at 110°C ± 5°C, the rear temperature is controlled at 80°C ± 5°C, the main engine speed is controlled at 40Hz-50Hz, and the tablet press thickness is controlled at 0.5-1.5mm.

[0035] Next, the ACM grader mill is used to grind the powder to control the D50 particle size to be between 20 μm and 30 μm.

[0036] Finally, the powder coating obtained by grinding ACM and the remaining flaky Al-Mg-Ce alloy powder are put into a binding machine for mixing and binding, and then cooled and sieved to obtain the powder coating containing flaky rare earth aluminum-magnesium alloy powder.

[0037] Embodiment 2

[0038] Formula of powder coating containing flaky rare earth aluminum-magnesium alloy powder: E-1245g, GT72555g, PSG-0112g, dimethylimidazole 0.5g, PVB 3g, mica powder 5g, flaky rare earth aluminum-magnesium alloy powder 16g, GLP5881g, 7011g, benzoin 0.5g.

[0039] Among them, the formula of flaky rare earth aluminum-magnesium alloy powder is: 0.1g cerium, 3g magnesium, and 96.9g aluminum.

[0040] The preparation method is the same as that of Example 1, except that 2 / 3 of the flaky Al-Mg-Ce alloy powder is mixed, extruded and ground, and the remaining 1 / 3 of the flaky Al-Mg-Ce alloy powder is added by an external mixing and binding method.

[0041] The preparation method of rare earth aluminum-magnesium alloy powder coating is the same as that of Example 1.

[0042] Embodiment 3

[0043] Formula of powder coating containing flaky rare earth aluminum-magnesium alloy powder: GT725555g, PSG-0113g, dimethylimidazole 1g, PVB 3g, mica powder 3g, flaky rare earth aluminum-magnesium alloy powder 20g, GLP5881g, 7011g, benzoin 0.5g.

[0044] Among them, the formula of flaky rare earth aluminum-magnesium alloy powder is: 0.5g cerium, 5g magnesium, and 94.5g aluminum.

[0045] The preparation method of rare earth aluminum-magnesium alloy powder coating is the same as that of Example 1.

[0046] Comparative Example 1

[0047] Formula of powder coating containing flaky zinc powder: E-1250g, GT72555g, PSG-0113g, dimethylimidazole 0.8g, PVB 3g, mica powder 5g, flaky zinc powder D20014g, GLP5881g, 7011g, benzoin 1g.

[0048] Preparation method: Put epoxy resin E-12, novolac epoxy resin GT7255, phenolic epoxy curing agent PSG-01, dimethylimidazole, toughening agent PVB, mica powder, GLP588, 701, benzoin, and flaky zinc powder into a flip mixing tank and mix at low speed for 30 minutes.

[0049] Then, a twin-screw extruder is used for melt extrusion, and a tablet press is used for sheeting. The front temperature of the extruder is controlled at 110°C ± 5°C, the rear temperature is controlled at 80°C ± 5°C, the main engine speed is controlled at 40Hz to 50Hz, and the tablet press thickness is controlled at 0.5 to 1.5mm. Then, an ACM grading mill is used for powder grinding, and the D50 particle size is controlled at 20μm to 30μm to obtain a powder coating containing flaky zinc powder.

[0050] Comparative Example 2

[0051] Formula of powder coating containing flaky aluminum powder: E-1250g, GT72555g, PSG-0113g, dimethylimidazole 0.8g, PVB 3g, mica powder 5g, flaky aluminum powder CYH-214g, GLP5881g, 7011g, benzoin 1g.

[0052] The preparation method is the same as that of Comparative Example 1, except that the flaky zinc powder is replaced by flaky aluminum powder.

[0053] Comparative Example 3

[0054] Formula of powder coating containing flaky rare earth aluminum-magnesium alloy powder: GT725555g, PSG-0113g, dimethylimidazole 1g, PVB 3g, mica powder 3g, flaky rare earth aluminum-magnesium alloy powder 20g, GLP5881g, 7011g, benzoin 0.5g.

[0055] Among them, the formula of flaky rare earth aluminum-magnesium alloy powder is: 0.5g cerium, 5g magnesium, and 94.5g aluminum.

[0056] The preparation method is different from that of Example 3 in that: in the second stage, when preparing a powder coating containing flaky rare earth aluminum-magnesium alloy powder, epoxy resin E-12, phenolic epoxy resin GT7255, phenolic epoxy curing agent PSG-01, dimethylimidazole, toughening agent PVB, mica powder, GLP588, 701, benzoin, and all flaky Al-Mg-Ce alloy powders are put into a flip mixing tank and mixed at a low speed for 30 minutes.

[0057] Then, a twin-screw extruder is used for melt extrusion, and a tablet press is used for sheeting. The front temperature of the extruder is controlled at 110°C ± 5°C, the rear temperature is controlled at 80°C ± 5°C, the main engine speed is controlled at 40Hz to 50Hz, and the tablet press thickness is controlled at 0.5 to 1.5mm. Then, an ACM graded mill is used for grinding, and the D50 particle size is controlled at 20μm to 30μm.

[0058] The powder coatings obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were respectively prepared by electrostatic spraying and baking curing to prepare samples, and their physical and mechanical properties and anti-corrosion properties were tested. The results are shown in Table 1.

[0059]

[0060] It can be seen from the test results in Table 1 that with the increase of the content of flaky rare earth aluminum-magnesium alloy powder, the salt spray resistance is significantly improved, but the external mixing and binding process causes the flaky rare earth alloy powder to partially float on the coating surface during baking and curing, and the physical and mechanical properties are slightly reduced. By comparison, it can be seen that the corrosion resistance of the coating of the present invention is significantly better than that of the flaky zinc powder coating and the flaky aluminum powder coating, and is also better than the powder coating produced by the pure internal extrusion process.

[0061] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A rare earth aluminum-magnesium alloy powder coating, characterized in that: The composition includes the following components by mass: 50-55 parts of epoxy resin, 10-13 parts of epoxy curing agent, 0.3-0.8 parts of dimethylimidazole, 2-3 parts of toughening agent, 3-5 parts of mica powder, 2-3 parts of auxiliary agent and 14-20 parts of flaky rare earth aluminum-magnesium alloy powder.

2. The rare earth aluminum-magnesium alloy powder coating according to claim 1, characterized in that: The flaky rare earth aluminum-magnesium alloy powder is composed of 0.01% to 0.5% of cerium or lanthanum rare earth elements, 2% to 5% of magnesium, and the rest of aluminum.

3. The rare earth aluminum-magnesium alloy powder coating according to claim 2, characterized in that: The epoxy resin is one of bisphenol A epoxy resin and novolac epoxy resin or a mixture of the two.

4. The rare earth aluminum-magnesium alloy powder coating according to claim 3, characterized in that: The epoxy curing agent is a phenolic epoxy curing agent.

5. The rare earth aluminum-magnesium alloy powder coating according to claim 4, characterized in that: The auxiliary agents described are leveling agent, brightener and degassing agent.

6. A method for preparing a rare earth aluminum-magnesium alloy powder coating, characterized in that: The steps include: S1. Preparation of flaky rare earth aluminum-magnesium alloy powder S101, first preheating the smelting furnace to 400-450°C, and evenly coating the inner wall of the furnace with a layer of KCl-NaCl molten salt covering agent, after the KCl-NaCl molten salt is completely melted, weighed aluminum ingots and a formulated amount of rare earth aluminum master alloy are sequentially put into the smelting furnace, followed by heating and smelting, and controlling the smelting temperature at 870°C; S102, after the magnesium ingot is completely melted, the magnesium ingot is put into the furnace, and the magnesium ingot is quickly pressed into the bottom of the furnace for melting. After the magnesium ingot is completely melted, the compressed air is used for slag removal, and the slag removal refining agent is pressed into the bottom of the melt for refining treatment. The refining process is controlled within about 10 to 15 minutes until the surface of the melt presents a bright mirror surface; S103, after refining, stir for about 15 minutes, then stand for about 30 minutes to clean the slag, and take samples to analyze the alloy components. After passing the test, put them into a holding furnace and control the temperature at 760°C, and then cast them into rare earth aluminum-magnesium alloy bars; S104, then put the rare earth aluminum-magnesium alloy rod into a vacuum atomization powder making device to atomize into 300-500 mesh spherical rare earth aluminum-magnesium alloy powder, then add the obtained spherical rare earth aluminum-magnesium alloy powder, grinding aid and ball milling medium into a ball mill for ball milling, the ball milling medium is a stainless steel ball or a zirconium oxide ball with a diameter of 0.8-2 mm, before ball milling, vacuum must be drawn and then an inert gas is introduced, a cooling liquid is introduced into the interlayer of the ball mill to control the temperature during the ball milling process not to exceed 50° C., the ball milling time is 10-15 hours, and the ball mill speed is maintained at 30-50 rpm, so that the spherical rare earth aluminum-magnesium alloy powder is ball-milled into flaky alloy powder, and after screening treatment, the flaky rare earth aluminum-magnesium alloy powder is prepared; S2. Preparation of powder coating containing flaky rare earth aluminum-magnesium alloy powder S201, firstly put epoxy resin, epoxy curing agent, dimethyl imidazole, toughening agent, mica powder, additives and 1 / 2 to 2 / 3 of flaky rare earth aluminum-magnesium alloy powder into a flip-type mixing tank and mix at a low speed for 30 minutes. S202, then use a twin-screw extruder to melt extrude, and a tablet press to roll the tablets. The front temperature of the extruder is controlled at 110°C ± 5°C, the rear temperature is controlled at 80°C ± 5°C, the main engine speed is controlled at 40Hz to 50Hz, and the tablet press thickness is controlled at 0.5 to 1.5mm. Then use an ACM grading mill to grind the powder and control the D50 particle size to 20μm to 30μm. S203, finally putting the powder coating obtained by grinding ACM and the remaining flaky rare earth aluminum-magnesium alloy powder into a binding machine for mixing and binding, and then cooling and sieving to obtain the powder coating containing flaky rare earth aluminum-magnesium alloy powder.

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