CN-122007000-A - Preparation process of low-temperature cured high corrosion resistant powder coating for aluminum alloy hub production

Abstract

The invention discloses a preparation process of a low-temperature curing high-corrosion-resistance powder coating for aluminum alloy hub production, which solves the problems of poor adhesive force and insufficient corrosion resistance of the traditional low-temperature powder coating by the combined action of interfacial chemical anchoring and low-stress step curing. The process core comprises the steps of adopting an interface chelating compound curing agent containing beta-diketone structure ligand groups, actively migrating to an interface to form a high-energy coordination bond with an aluminum substrate in a melting and leveling stage, and matching with a micro-nano shielding network constructed by nano aluminum oxide and flaky zinc powder to greatly block penetration of a corrosive medium. Meanwhile, a three-stage step curing program of 60 ℃ wetting, 100 ℃ leveling and 140 ℃ crosslinking is adopted, and the heat deformation amount of the hub is controlled within 0.1mm when the densification of the coating is realized by matching with the heating rate of less than or equal to 5 ℃ per minute. The neutral salt fog resistant time of the coating prepared by the invention exceeds 1200 hours, the adhesive force reaches 0 level, and the dynamic balance performance of the hub is effectively ensured.

Inventors

• ZHANG JIANYU
• WEI DONGFENG
• SONG ZHIPENG
• WU XIUQIANG
• FANG JIKAI
• YAN YAMENG
• ZONG JIANKANG
• XIE BAOPING

Assignees

• 滨州戴森车轮科技有限公司

Dates

Publication Date

20260512

Application Date

20260210

Claims (8)

1. 1. The preparation process of the low-temperature curing high corrosion resistant powder coating for producing the aluminum alloy hub is characterized by comprising the following steps of: S1, surface pretreatment, degreasing, acid etching and water washing are carried out on an aluminum alloy hub base material, and then non-phosphating silanization treatment is carried out, so that a chemical conversion film containing Si-O-Al bonds is formed on the surface of the base material; S2, electrostatic spraying, namely spraying the low-temperature cured powder coating onto the surface of the chemical conversion film through an electrostatic spray gun to form a powder coating; s3, step solidification, namely sending the sprayed hub into a solidification furnace to perform three-stage step heating solidification, and then cooling to room temperature; in S2, the low-temperature curing powder coating comprises, by mass, 50-70 parts of a low-temperature reaction type resin matrix, 10-20 parts of an interface chelating composite curing agent, 10-20 parts of a micro-nano synergistic filler system and 1-3 parts of a leveling agent; The interface chelating composite curing agent is high polymer resin grafted with beta-diketone structure ligand groups, and the ligand groups migrate to the interface of the substrate and form coordination bonds with aluminum ions on the surface of the aluminum alloy in a solidification and melting state; in the step S3, the three-stage step heating curing comprises the first stage of heating to 60+/-5 ℃ at the speed of 2-5 ℃ per minute, preserving heat for 3-6 minutes to enable the resin to wet the substrate, the second stage of heating to 100+/-5 ℃ at the speed of 2-5 ℃ per minute, preserving heat for 3-6 minutes to carry out leveling and exhausting, and the third stage of heating to 140+/-5 ℃ at the speed of 2-5 ℃ per minute, preserving heat for 15-25 minutes to initiate the crosslinking reaction.
2. 2. The process for preparing a low-temperature-cured high corrosion-resistant powder coating for aluminum alloy hub production according to claim 1, which is characterized in that: The micro-nano synergistic filler system consists of nano aluminum oxide with the particle size of 20-40nm and flaky zinc powder with the diameter-thickness ratio of more than or equal to 60:1, wherein the nano aluminum oxide is filled in interlayer gaps of the flaky zinc powder, the proportion of the nano aluminum oxide in the total mass of the coating is 3-5%, and the proportion of the flaky zinc powder in the total mass of the coating is 8-10%.
3. 3. The process for preparing a low-temperature-cured high corrosion-resistant powder coating for aluminum alloy hub production according to claim 1, which is characterized in that: The low-temperature reaction type resin matrix is a mixture of carboxyl-terminated polyester resin and bisphenol A epoxy resin, the glass transition temperature Tg of the mixture is 65-70 ℃, and the acid value of the carboxyl-terminated polyester resin is 30-35 mgKOH/g.
4. 4. The process for preparing a low-temperature-cured high corrosion-resistant powder coating for aluminum alloy hub production according to claim 1, which is characterized in that: the interfacial chelating composite curing agent is prepared by reacting aluminum acetylacetonate with glycidyl methacrylate copolymer in a solvent and removing the solvent.
5. 5. The process for preparing a low-temperature-cured high corrosion-resistant powder coating for aluminum alloy hub production according to claim 1, which is characterized in that: In S1, the treatment liquid adopted in the non-phosphating silanization treatment comprises an epoxy silane coupling agent and fluorozirconic acid, the pH value of the treatment liquid is 4.0-5.0, and the thickness of the chemical conversion film is controlled to be 50-80nm.
6. 6. The process for preparing a low-temperature-cured high corrosion-resistant powder coating for aluminum alloy hub production according to claim 1, which is characterized in that: in S2, aiming at the deep concave part of the joint of the spoke and the rim of the hub, the voltage of the electrostatic spray gun is set to 68-72kV, and the powder output is increased by 5-10% compared with the plane part.
7. 7. The process for preparing a low-temperature-cured high corrosion-resistant powder coating for aluminum alloy hub production according to claim 1, which is characterized in that: in S3, the whole process temperature rising rate of three-section type step temperature rising and curing is strictly controlled to be less than or equal to 5 ℃ per minute, and the thermal deformation of the hub after curing is less than or equal to 0.1mm.
8. 8. An aluminum alloy hub manufactured based on the low-temperature curing high corrosion resistant powder coating preparation process for aluminum alloy hub production according to any one of claims 1-8, which is characterized in that the adhesive force of the powder coating to a base material is 0 level, and the neutral salt spray test time passing the ASTM B117 standard is more than or equal to 1200 hours.

Description

Preparation process of low-temperature cured high corrosion resistant powder coating for aluminum alloy hub production Technical Field The invention relates to the technical field of metal surface coating, in particular to a preparation process of a low-temperature curing high corrosion-resistant powder coating for aluminum alloy hub production. Background Aluminum alloy hubs have become a dominant configuration in modern automotive manufacturing due to their light weight and aesthetics. A356.2 and the like aluminum-silicon-magnesium alloy materials need to be subjected to T6 heat treatment to obtain the best mechanical property, and the time-effect temperature is usually between 155 ℃ and 170 ℃. The existing aluminum alloy hub powder coating process mainly has two technical bottlenecks, firstly, the traditional powder coating needs to be solidified for more than 20 minutes at 180-200 ℃, the temperature exceeds the ageing temperature of the aluminum alloy, so that a strengthening phase (Mg 2 Si) coarsens, the yield strength is reduced, and more seriously, the residual internal stress in the casting and machining processes is released at high temperature, so that the hub undergoes micro plastic deformation (usually more than 0.5 mm), the roundness and dynamic balance performance of the hub are seriously affected, and the rework rate of a production line is high. Second, in order to solve the problem of thermal deformation, attempts have been made in the industry to use low temperature cured powders below 150 ℃. However, the decrease in curing temperature directly leads to a decrease in the rate of the resin crosslinking reaction, and the coating is insufficient in compactness. Meanwhile, an oxide film naturally formed on the surface of the aluminum alloy has strong chemical inertia, and the viscosity of a resin melt at low temperature is high, so that micropores of a base material are difficult to sufficiently wet, and the coating is attached mainly by weak Van der Waals force. In a salt fog or damp-heat environment, water molecules are very easy to replace physical adsorption points of the coating and the substrate, so that the coating is foamed and falls off. The neutral salt fog resistant life of the low-temperature powder coating currently sold in the market is generally only 500-800 hours, and the severe standard of more than 1200 hours proposed by a high-end host factory is difficult to meet. Therefore, developing a preparation process which can realize rapid solidification at the temperature of less than or equal to 140 ℃ to control deformation and can also realize high corrosion resistance by constructing super-strong interface binding force through a chemical mechanism is a technical problem which is urgently needed to be solved in the field. Disclosure of Invention The invention provides a preparation process of a low-temperature curing high-corrosion-resistance powder coating for aluminum alloy hub production, which aims to overcome the defects of poor coating adhesion, insufficient corrosion resistance and large thermal deformation of a hub in a low-temperature curing process in the prior art. A preparation process of a low-temperature curing high corrosion resistant powder coating for aluminum alloy hub production comprises the following steps: s1, surface pretreatment. Degreasing, acid etching and washing an aluminum alloy hub base material, and then performing non-phosphating silanization treatment to form a chemical conversion film containing Si-O-Al bonds on the surface of the base material; S2, electrostatic spraying. Spraying the low-temperature solidified powder coating on the surface of the chemical conversion film through an electrostatic spray gun to form a powder coating; S3, step solidification, namely sending the sprayed hub into a solidification furnace to perform three-stage step heating solidification, and then cooling to room temperature. Further, in order to better realize the invention, in S2, the low-temperature curing powder coating comprises 50-70 parts of a low-temperature reaction type resin matrix, 10-20 parts of an interface chelating composite curing agent, 10-20 parts of a micro-nano synergistic filler system and 1-3 parts of a leveling agent, wherein the interface chelating composite curing agent is macromolecular resin grafted with beta-diketone structure coordination groups, the coordination groups migrate to the interface of a substrate and form coordination bonds with aluminum ions on the surface of an aluminum alloy in a curing molten state, and in S3, the three-stage step heating curing comprises the first stage of heating to 60+/-5 ℃ at a rate of 2-5 ℃ per minute, the heat preservation for 3-6 minutes to enable the resin to wet the substrate, the second stage of heating to 100+/-5 ℃ at a rate of 2-5 ℃ per minute, the heat preservation for 3-6 minutes, the leveling and the air exhaust, and the third stage of heating to 140+/-5 ℃ at a rate of 2-5 ℃ per minute, a