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Surface phosphorization-passivation method for metal coating of sintered NdFeB magnet

A metal coating and surface phosphating technology, which is applied in the field of magnetic material surface protection and corrosion-resistant coatings, can solve the problems of environmental pollution and poor corrosion resistance of traditional passivation processes, and achieve good environmental adaptability and long-term corrosion The effect of protection

Inactive Publication Date: 2019-11-29
HEFEI UNIV OF TECH +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0005] Aiming at the problems of poor corrosion resistance of metal coatings on the surface of sintered NdFeB magnets and serious environmental pollution

Method used

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  • Surface phosphorization-passivation method for metal coating of sintered NdFeB magnet
  • Surface phosphorization-passivation method for metal coating of sintered NdFeB magnet

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0025] (1) After cleaning the NdFeB matrix with a nitric acid solution with a concentration of 3% for 30 seconds, ultrasonically use absolute ethanol for 2 minutes;

[0026] (2) Put the acidified NdFeB substrate into the furnace and vacuumize it, and use the argon ions generated in the vacuum chamber to bombard the substrate for 30 minutes; magnetron sputter the NdFeB substrate after ion cleaning for 20 minutes, and conduct vacuum evaporation after cooling down 20min, prepare Al coating on the surface of sintered NdFeB, the thickness of Al coating is about 20μm;

[0027] (2) Place the metal-coated NdFeB magnet and sodium hypophosphite in the burning boat in the tube furnace successively, feed Ar gas as the carrier gas, the flow rate is 100 sccm, the heating temperature is 300 ℃, and the holding time is 2h, slow cooling with the furnace to complete the surface phosphating and passivation of the metal coating.

[0028] The comparative example is an Al coating on the surface of ...

Embodiment 2

[0031] The preparation method of this example is the same as Example 1, except that the heating temperature in step (2) is 250°C.

[0032] After testing, according to the Al coating after phosphating and passivation in Example 2, the corrosion potential in the electrochemical corrosion test is -1.10V, and the self-corrosion current density is 60 μA cm -2 , The salt spray test time is 120h.

Embodiment 3

[0034] The preparation method of this example is the same as Example 1, except that the heating temperature in step (2) is 270°C.

[0035] After testing, according to the Al coating after phosphating and passivation in Example 3, the corrosion potential in the electrochemical corrosion test is -0.83V, and the self-corrosion current density is 4.225μA·cm -2 , The salt spray test time is 120h, and its comprehensive corrosion resistance performance is obviously better than that of the comparative example.

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Abstract

The invention discloses a surface phosphorization-passivation method for a metal coating of a sintered NdFeB magnet. The surface phosphorization-passivation method is aimed at the metal Al coating onthe surface of the sintered NdFeB magnet; through a high-temperature gas-phase method, the surface phosphorization-passivation of the metal coating is achieved by adopting sodium hypophosphite as a Psource; and accordingly, the corrosion resistance of the coating can be improved. Compared with a conventional hexavalent Cr and trivalent Cr liquid-phase passivation method, the surface phosphorization-passivation method has the advantages that the environmental adaptability is higher; the discharge of sewage containing heavy metal ions is avoided; and a dense and uniform phosphorized-passivatedfilm can be formed on the surface of the metal coating, thereby providing the longer-acting corrosion protection effect for the sintered NdFeB magnet.

Description

technical field [0001] The invention belongs to the field of magnetic material surface protection and corrosion-resistant coatings, and in particular relates to a method for surface phosphating and passivation of sintered NdFeB magnet metal coatings. Background technique [0002] NdFeB permanent magnet materials are widely used in high-tech fields such as aviation, aerospace, maglev trains, and magnetic medical technology due to their high magnetic properties and high cost performance. The proven reserves of rare earth resources in my country account for about 80% of the world's total reserves, which puts them in a favorable position in the competition in the field of rare earth permanent magnets. However, the sintered NdFeB magnet prepared by powder metallurgy has a three-phase structure (mainly including: main phase, Nd-rich phase and B-rich phase), and the potential difference between each phase is relatively large, especially the electrochemistry of the Nd-rich phase. I...

Claims

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Application Information

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IPC IPC(8): C23C14/58C23C14/35C23C14/16C23C14/24C23C14/02
CPCC23C14/022C23C14/165C23C14/24C23C14/35C23C14/5846
Inventor 徐光青陈婧刘晴张鹏杰吕珺李炳山汪冬梅孙威刘辉张威峰吴玉程
Owner HEFEI UNIV OF TECH
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