Phosphating process for phosphating layer on neodymium-iron-boron surface

A NdFeB technology, applied in the field of phosphating process, can solve the problems of low porosity, corrosion resistance and insufficient corrosion resistance of phosphating film layer, so as to achieve low porosity, avoid magnetic performance decline, and process stability controllable effect

Inactive Publication Date: 2018-12-28
FOSHAN UNIVERSITY
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  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] In view of the defects existing in the existing NdFeB surface phosphating process and the problem of insufficient corrosion resistance of the existing phosphating film layer, the purpose of the present invention is to provide a phosphating process for the phosphating layer on the NdFeB surface, Preparation of a new type of phosphating layer with low porosity, good corrosion resistance, and large-scale production and its corresponding phosphating process

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  • Phosphating process for phosphating layer on neodymium-iron-boron surface

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Embodiment 1

[0026] In this implementation case, the composition of the phosphating solution is: magnesium oxide 4g / L, phosphoric acid 28mL / L, sodium borate 4g / L, and NaOH is used to adjust the pH of the phosphating solution to 4.8.

[0027] After derusting and cleaning the NdFeB substrate, the cathode direct current electrodeposition method is used to prepare the surface phosphating film layer, and the cathode current density is 4A / dm 2 , the temperature of the phosphating solution is 80°C, and the phosphating time is 0.5 hours. After phosphating, wash and dry. The film weight after phosphating is about 12g / m 2 , the color is off-white. its microscopic appearance figure 1 , the grain size is uniform, and there are no pores between the grains. The copper sulfate spot test (QB / T3824-1999) time of the prepared phosphating film layer is more than 120 seconds, and the antirust effect is more than 13 months.

Embodiment 2

[0029] In this implementation case, the composition of the phosphating solution is: magnesium oxide 3g / L, zinc dihydrogen phosphate 2g / L, triphosphoric acid 2mL / L, sodium borate 8g / L, glycine 0.2g / L, dodecylbenzenesulfonate Sodium acid 2g / L, sodium citrate 15g / L. And adjust the pH of the phosphating solution to 4.5 with NaOH.

[0030] After derusting and cleaning the NdFeB substrate, the surface phosphating film layer is prepared by cathodic direct current electrodeposition, and the cathodic current density is 3A / dm 2 , the temperature of the phosphating solution is 65°C, and the phosphating time is 1 hour. After phosphating, wash and dry. The film weight after phosphating is about 19.7g / m 2 , the color is off-white. its microscopic appearance figure 2 , the grain size is uniform, and there are no pores between the grains. The copper sulfate spot test (QB / T3824-1999) time of the prepared phosphating film layer is longer than 150 seconds, and the antirust effect is longe...

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Abstract

The invention discloses a phosphating process for a phosphating layer on a neodymium-iron-boron surface. The process comprises the following steps of 1) preparing a phosphating solution: firstly adding a magnesium salt and a zinc salt into the solution, then dropwise adding phosphoric acid, after the phosphating solution is clarified, sequentially adding a buffering agent, a complexing agent, a surfactant and a phosphating accelerator, and finally adjusting a pH value of the phosphating solution by the phosphoric acid and sodium hydroxide; and 2) putting the phosphating solution into an electrolytic cell, and treating the phosphating solution on the surface of a neodymium-iron-boron matrix in an electrolytic phosphating mode. According to the process, the phosphating solution is treated onthe surface of the neodymium-iron-boron matrix in the electrolytic phosphating mode, so that the magnetic performance reduction due to the corrosion of the matrix can be avoided; and meanwhile, due to the adoption of the electrolytic phosphating method, the phosphating accelerator such as nitrite or the like does not need to be added into the phosphating solution, so that the environment is not polluted and disrupted.

Description

technical field [0001] The invention belongs to the field of surface treatment, and in particular relates to a phosphating process for a phosphating layer on the surface of neodymium-iron-boron. Background technique [0002] Sintered NdFeB has excellent comprehensive magnetic properties, and has been widely used in high-end equipment manufacturing, new energy vehicles, high-performance medical equipment and other fields, accounting for more than 80% of the market for rare earth permanent magnet materials. Corrosion will cause the magnetic properties of NdFeB to decline and powder failure, so corrosion has always been one of the main challenges faced by the NdFeB industry. Phosphating is a commonly used surface treatment method in the NdFeB industry. The phosphating layers currently used in industrial production include surface zinc-based phosphating film, iron-based phosphating film, manganese-based phosphating film and their composite phosphating film layers. [0003] How...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C25D11/36C25D7/00
CPCC25D7/001C25D11/36
Inventor 周琼宇陈东初
Owner FOSHAN UNIVERSITY
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