GB/T 40793-2021 Nonmetallic coatings for sintered neodymium iron boron permanent magnets
1 Scope
This document specifies the coating codes, substrate requirements and pre-painting preparation, technical requirements, test methods, and inspection rules for nonmetallic coatings for sintered neodymium iron boron permanent magnets.
This document is applicable to the protective and decorative coatings on the surface of sintered neodymium iron boron permanent magnets, including phosphating, zirconating and other conversion coatings, as well as coatings applied by electrophoresis, spraying, chemical vapour deposition, etc.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 2423.22-2012 Environmental testing - Part 2: Tests methods - Test N: Change of temperature
GB/T 2423.50 Environmental testing - Part 2: Test methods - Test Cy: Damp heat, steady state, accelerated test primarily intended for components
GB/T 3138 Metallic and other inorganic coatings - Surface treatment, metallic and other inorganic coatings - Vocabulary
GB/T 6739 Paints and varnishes - Determination of film hardness by pencil test
GB/T 6807 Specifications for phosphating treatment of iron and steel parts before painting
GB/T 8264 Glossary of painting terms
GB/T 9286 Paints and varnishes - Cross cut test for films
GB/T 10125 Corrosion tests in artificial atmospheres - Salt spray tests
GB/T 13452.2-2008 Paints and varnishes - Determination of film thickness
GB/T 34491 Coatings for sintered neodymium iron boron permanent magnets
GB/T 39494-2020 Determination for coating adhesion of rare earth permanent magnetic materials for drive motor of new energy vehicle
QB/T 3814 Surface examination method of the metal deposits and conversion coatings for the light industrial products
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 3138, GB/T 8264, and GB/T 34491 apply.
4 Coating codes
4.1 Conversion coating code
The phosphating conversion coating is denoted by PH, and the zirconating conversion coating by ZR.
4.2 Non-conversion coating code
4.2.1 The coating code consists of four parts in sequence: coating symbol, coating color and category, coating thickness, and painting process. An example is given below:
4.2.2 The coating symbol is represented by the letter "T", which may be defaulted if there is no ambiguity; however, it cannot be defaulted when spraying zinc-aluminum, silicon-aluminum, or silicon-titanium coatings.
4.2.3 The coating color and category are represented by code letters. The coating colors include black (Blk) and gray (Gry). The coating color in this part may be defaulted.
4.2.4 The coating thickness is represented by a number, which is an integer value in micrometers (μm). This part may be defaulted.
4.2.5 The painting process is represented by letters. The specific painting processes and their corresponding codes are listed in Table 1.
Table 1 Examples of painting processes and representation codes
Letters Painting process Default state
ED Electrophoresis Can be defaulted
SP Spraying Can be defaulted, except when the coating category is epoxy layer
CVD Chemical vapour deposition Can be defaulted
4.2.6 The coating color and category are connected by a hyphen (-), while both the coating symbol and the coating color-category combination, and the coating thickness and the painting process are connected by a period (.). There is a space between the coating color-category combination and the coating thickness.
4.3 Multilayer composite coating
For multilayer composite coatings, the coating (plating) layers are connected with a "+" sign.
4.4 Examples of coating codes
See Table 2 for the examples.
Foreword I
1 Scope
2 Normative references
3 Terms and definitions
4 Coating codes
5 Substrate requirements and pre-painting preparation
6 Technical requirements
7 Test methods
8 Inspection rules
Annex A (Informative) Conversion coating process guidelines
Annex B (Informative) Electrophoresis process guidelines
Annex C (Informative) Spraying process guidelines
Annex D (Informative) Process guidelines for CVD-applied Parylene
Annex E (Informative) Time for high-corrosion-resistant coatings to show corrosion
