Search

CN-122011903-A - Method for improving surface tension of galvanized NdFeB permanent magnet

CN122011903ACN 122011903 ACN122011903 ACN 122011903ACN-122011903-A

Abstract

The invention belongs to the technical field of permanent magnet materials, and relates to a method for improving surface tension of a galvanized neodymium-iron-boron permanent magnet. The protective agent disclosed by the invention takes the solid epoxy resin emulsion modified by acrylic acid and polyether amine as a core film forming substance, so that an organic film layer with high crosslinking density and high mechanical strength is formed, the corrosion resistance is obviously improved, a glass-like inorganic network rich in Si-O bonds is constructed in the film forming process by nano silica sol, the surface polarity and tension are greatly enhanced, carboxymethyl cellulose has the functions of high hydrophilicity and molecular bridging, silica sol particles are effectively anchored, the uniformity and durability of the film layer are improved, hexamethylenetetramine is taken as a crosslinking accelerator, the film structure compactness is further enhanced, the compound corrosion inhibitor benzotriazole and triethanolamine are synergistic, the former inhibits the oxidation corrosion of a galvanized layer before film forming, and the latter has the functions of pH buffering, corrosion inhibition and auxiliary curing, and the stability and film forming quality of treatment fluid are ensured.

Inventors

  • FANG ZHUFU
  • JIANG JIANFENG
  • WANG SHUANG

Assignees

  • 宁波市镇海福永耀磁材加工有限公司

Dates

Publication Date
20260512
Application Date
20260209

Claims (10)

  1. 1. A method for improving the surface tension of a galvanized neodymium-iron-boron permanent magnet is characterized by comprising the following steps of washing a passivated galvanized neodymium-iron-boron magnet, performing ultrasonic activation treatment, soaking in an aqueous solution containing 0.5-1.5wt% of a protective agent, drying and irradiating with ultraviolet light; The protective agent comprises the following raw materials, by mass, 15-20 parts of an acrylic acid and polyether amine modified solid epoxy resin emulsion with the solid content of 30-50wt%, 20-25 parts of nano silica sol, 1.5-2.5 parts of carboxymethyl cellulose, 1-2 parts of hexamethylenetetramine, 1.5-3.5 parts of corrosion inhibitor, 0.5-1 part of coupling agent and 50-60 parts of water.
  2. 2. A method for increasing the surface tension of a galvanized neodymium iron boron permanent magnet according to claim 1, characterized in that the preparation of the acrylic acid and polyetheramine modified solid epoxy resin emulsion with a solid content of 30-50wt% comprises the following steps: S1, adding epoxy resin into ethylene glycol butyl ether for heating, and then adding polyether amine for gradient heating to obtain polyether amine modified solid epoxy resin; s2, mixing polyether amine modified solid epoxy resin with a polymerization inhibitor, and then adding acrylic acid, ethyl acrylate and a catalyst to perform stirring reaction to obtain acrylic acid and polyether amine modified solid epoxy resin; s3, adding water into the acrylic acid and polyether amine modified solid epoxy resin to emulsify to obtain the acrylic acid and polyether amine modified solid epoxy resin emulsion with the solid content of 30-50wt%.
  3. 3. The method for improving the surface tension of the galvanized neodymium-iron-boron permanent magnet according to claim 2, wherein in the step S1, the mass ratio of the epoxy resin to the ethylene glycol butyl ether to the polyether amine is 100 (20-40): 10-20.
  4. 4. The method for improving the surface tension of the galvanized neodymium iron boron permanent magnet according to claim 2, wherein in the step S2, the mass ratio of the polyether amine modified solid epoxy resin, the polymerization inhibitor, the acrylic acid, the ethyl acrylate and the catalyst is 100 (2-5): (10-20): (10-20): (1-2).
  5. 5. A method for increasing the surface tension of a galvanized neodymium iron boron permanent magnet according to claim 1, characterized in that the nano silica sol has a pH of 6.8-7.2 and a silica content of 25-35wt%, wherein the average particle size of the silica particles is 10-30nm.
  6. 6. The method for improving the surface tension of the galvanized neodymium-iron-boron permanent magnet according to claim 1, wherein the corrosion inhibitor is benzotriazole and triethanolamine in a mass ratio of 1 (1-4).
  7. 7. The method for improving the surface tension of a galvanized neodymium-iron-boron permanent magnet according to claim 1, wherein the coupling agent is at least one of a silane coupling agent and a titanate coupling agent.
  8. 8. The method for improving the surface tension of a galvanized neodymium-iron-boron permanent magnet according to claim 1, wherein the preparation method of the protective agent comprises the following steps: s1, preparing the raw material of claim 1; S2, uniformly mixing water and carboxymethyl cellulose, standing, sequentially adding nano silica sol, hexamethylenetetramine, acrylic acid with solid content of 30-50wt% and polyether amine modified solid epoxy resin emulsion, a coupling agent and a corrosion inhibitor, and uniformly stirring to obtain the protective agent.
  9. 9. The method for improving the surface tension of a galvanized neodymium iron boron permanent magnet according to claim 1, wherein the ultrasonic activation treatment temperature is 20-40 ℃ and the time is 1-5min.
  10. 10. The method for improving the surface tension of a galvanized neodymium-iron-boron permanent magnet according to claim 1, wherein the ultraviolet light has a wavelength of 315-400nm and the irradiation time is 5-10min.

Description

Method for improving surface tension of galvanized NdFeB permanent magnet Technical Field The invention belongs to the technical field of permanent magnet materials, and relates to a method for improving surface tension of a galvanized neodymium-iron-boron permanent magnet. Background The sintered NdFeB magnet is a permanent magnet material with the highest magnetic energy product at present, is known as 'magnetic king' by virtue of the excellent comprehensive magnetic performance, and is widely applied to the fields with extremely high requirements on hard magnetic materials, such as maglev trains, high-performance motors, electroacoustic equipment (such as speakers and headphones), wind power generation, new energy automobile driving systems, various precise instruments and the like. However, despite its excellent magnetic properties, neodymium-iron-boron magnets face a significantly shorter plate in practical use—poor corrosion resistance. Because the main components of the alloy contain rare earth element neodymium and active metal iron, oxidation and corrosion are extremely easy to occur in a humid or salt-containing environment, thereby seriously affecting the service life and the performance stability. Thus, the industry typically requires protective treatments of its surfaces, common protective means including electroplated metal layers (e.g., zinc, nickel, copper, etc.) and organic or inorganic coatings. Among them, electrogalvanizing is widely used because of its low cost, mature process and certain antiseptic effect. However, this surface treatment method, while improving corrosion resistance, presents a new challenge in that in many application scenarios, the neodymium-iron-boron magnet needs to be assembled with other components by gluing, for example, in an acoustic unit or a micro-motor, which makes clear demands on wettability and adhesion performance of the magnet surface, and the surface tension needs to be above 36 mN/m to ensure that the glue can be sufficiently spread and form a firm adhesion. However, the galvanized magnet is typically further passivated to further enhance its corrosion resistance. The passivation process forms a dense but smooth passivation film on the surface, which, while improving corrosion resistance, significantly reduces the surface energy. Experiments show that the surface tension of the passivated magnet is often lower than 36 mN/m in a dry state, and the surface tension also continuously decreases along with the storage time, so that the subsequent bonding process fails or the bonding strength is insufficient. The contradiction highlights the importance of balancing the corrosion resistance and the adhesion performance in the surface treatment process of the NdFeB magnet, and also becomes one of the key technical problems to be solved in the current material engineering and surface science fields. Chinese patent application document (CN 119252636A) discloses a neodymium-iron-boron magnet containing a sealing film, a preparation method and application thereof, wherein the galvanized and passivated neodymium-iron-boron magnet is treated by a sealing agent, salt spray resistance test is improved after treatment, and the surface tension of the magnet is improved and stable and improved due to the fact that a plurality of nonpolar groups are contained in a protective film, so that guarantee cannot be provided for adhesion during magnet assembly. Disclosure of Invention Aiming at the defects in the prior art, the invention aims to provide a method for improving the surface tension of the galvanized NdFeB permanent magnet, so that the NdFeB permanent magnet has high and stable surface tension and good salt fog resistance. One object of the present invention can be achieved by the following technical solutions: The method for improving the surface tension of the galvanized neodymium-iron-boron permanent magnet comprises the following steps of washing the passivated galvanized neodymium-iron-boron permanent magnet, performing ultrasonic activation treatment, soaking in an aqueous solution containing 0.5-1.5wt% of protective agent, drying and irradiating with ultraviolet light; The protective agent comprises the following raw materials, by mass, 15-20 parts of an acrylic acid and polyether amine modified solid epoxy resin emulsion with the solid content of 30-50wt%, 20-25 parts of nano silica sol, 1.5-2.5 parts of carboxymethyl cellulose, 1-2 parts of hexamethylenetetramine, 1.5-3.5 parts of corrosion inhibitor, 0.5-1 part of coupling agent and 50-60 parts of water. According to the invention, a layer of functional protective film with high surface tension, excellent adhesive force, good corrosion resistance and long-term stability is constructed on the surface of the galvanized neodymium iron boron permanent magnet through the multi-component synergistic effect, the acrylic acid and polyether amine modified solid epoxy resin emulsion with the solid content of 30-50 wt