Neodymium iron boron rare earth permanent magnet surface anti-corrosion coating and preparation method thereof

Abstract

The invention belongs to the technical field of surface treatment and particularly relates to a neodymium iron boron rare earth permanent magnet surface anti-corrosion coating and a preparation method thereof. The neodymium iron boron rare earth permanent magnet surface anti-corrosion coating is composed of a bottom coating and a top coating, the thickness of the bottom coating is in a range from 10mum to 25mum, the chemical components of the bottom coating comprise 55% to 65% of one or two types of metals of zinc and aluminum, 0% to 5% of one or a plurality of types of metals of nickel, chromium, molybdenum, neodymium, praseodymium, cobalt and titanium and 34% to 40% of neutral resins, the thickness of the top coating is in a range from 5mum to 15mum, and the chemical components of the top coating comprise 55% to 65% of one or a plurality of types of metals of zinc, aluminum, titanium, molybdenum, nickel, cobalt and chromium and 35% to 45% of phenolic resins or acrylic resins. The preparation method includes that firstly the surface of a permanent magnet is preprocessed, a centrifugal immersion tossing is utilized to prepare the bottom coating, and a rolling spraying process is utilized to prepare the top coating. The neodymium iron boron rare earth permanent magnet surface anti-corrosion coating and the preparation method thereof have the advantages that by means of double layers of coatings, the corrosion resistance is high, the surface binding force is high, the usage temperature is higher than 200 DEG C, the magnetic property of the neodymium iron boron rare earth permanent magnet is improved, the service life is prolonged, and the service environment is widened.

Description

technical field [0001] The invention belongs to the technical field of surface treatment, and in particular relates to an anti-corrosion coating on the surface of an NdFeB rare earth permanent magnet and a preparation method thereof. Background technique [0002] NdFeB rare earth permanent magnets are used more and more for their excellent magnetic properties, and are widely used in automobile motors, elevator motors, energy-saving motors, medical nuclear magnetic resonance imaging, computer hard drives, mobile phone vibration motors, audio , Hybrid car motors and wind turbines. [0003] However, neodymium in NdFeB permanent magnets is a rare earth element with strong chemical activity. Its standard equilibrium potential is -2.431V. It is easily oxidized in air and has poor corrosion resistance. Medium-rich B phase, Nd-rich phase, Nd 2 Fe 14 The electrochemical potentials of the B phases are different, and the electrode potentials of the Nd-rich phase and the B-rich phase...

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Problems solved by technology

[0003] However, neodymium in NdFeB permanent magnets is a rare earth element with strong chemical activity. Its standard equilibrium potential is -2.431V. It is easily oxidized in air and has poor corrosion resistance. Medium-rich B phase, Nd-rich phase, Nd 2 Fe 14 The electrochemical potentials of the B phases are different, and the electrode potentials of the Nd-rich phase and the B-rich phase are lower than those of the matrix Nd 2 Fe 14 Phase B, forming an electrochemical micro-battery in a hot and humid environment, the Nd-rich phase and the B-rich phase are corroded first, thereby reducing the performance of the magnet

[0004] Therefore, to apply NdFeB rare earth permanent magnets to the industrial production field, it is generally necessary to carry out surface coating treatment first. At present, the surface coating methods widely used are: electro-galvanizing, electro-nickel plating, electroless nickel plating, electro-nickel-copper plating Nickel and electrophoresis, etc., the solution system of the surface coating of the NdFeB rare earth permanent magnet prepared by the above method is an acidic or alkaline environment, which is easy to form microscopic erosion, thereby affecting the bonding force between the coating and the NdFeB substrate, and electroplating The lower density of the layer will affect the corrosion resistance of the coating, which is affecting its application in the fields of motors, electronics, etc.

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