Magfine Corporation is the best magnet company with 25 years in business
High-density color coating to improve anti-rust performance Rust prevention and insulating properties can be dramatically improved by coating the surface of magnets with an air-tight resin. Not only is the surface protected but also the mechanical strength is improved. Also, designability can be enhanced through the use of pigments. Three types of coatings are most commonly used in surface treatment: epoxy resin, polyimide resin, and nylon. By adding fluoride, a coating similar to Teflon made by Dupont can be achieved.
Epoxy resin Epoxy resin is used as a raw material in industrial products used in environments where corrosion resistance is required. Epoxy resin mixed with a hardening agent demonstrates good adhesive strength and hardens when heated. Epoxy resin is a type of thermosetting resin and further includes excellent properties such as toughness, heat resistance, electrical insulation, and corrosion resistance. Recently, a single component adhesive, in which the epoxy resin and the hardening agent do not need to be mixed just before use, has been developed and is widely used.
Polyimide resin Polyimide resin is a plastic with the highest level of heat resistance among the thermosetting resins, and demonstrates superior values for mechanical strength, scientific properties and chemical characteristics since it has a strong molecular structure. Polyimide resin is commonly used in the field of semiconductors since it can be coated in very thin amounts. It is used widely in many industries such as in coated products, electrical insulating materials, electronic components, and automotive parts due to its excellent properties.
| Coating | MF304 (Epoxy resin) | MF305 (Polyimide resin) | Measuring methods |
| Colors | All colors except pure white | Black, green, brown, etc. | Visual |
| Film thickness | 20 to 200 μm recommended | Recommended film thickness 20 to 40 μm (5 to 200 μm possible) | Micrometer |
| Working temp. range | -30 to 200°C (250°C×1H)-30 to 200°C (250°C×1H) | -30 to 300°C (400°C for momentary use)-30 to 300°C (400°C for momentary use) | |
| Hardness | Tensile hardness (pencil method) 6H | Tensile hardness (pencil method) 6H | JIS K 5600-5-4 |
| Adhesiveness | After coating stainless steel plate to 20 μm and heating at 250°C. Crosscut test: Class 0 | After coating stainless steel plate to 20 μm and heating at 250°C. Crosscut test: Class 0 | JIS K 5600-5-6 |
| Impact resistance value | Deadweight 500 g/1 mm SUS plate 35 μm coating thickness. No abnormality 30 cm | Deadweight 500 g/1 mm SUS plate 35 μm coating thickness. No abnormality 50 cm | JIS K 5600-5-3 |
| Water absorbency | 0.05% | 0.05% | conforming to JIS K 6911 |
| Dielectric breakdown voltage | AC1.7 KV or higher / coating thickness 30 μm | AC1.5 KV or higher / coating thickness 30 μm | Sandwiched between 15 x 20 copper electrodes Tester: Kikisui T0S5050 |
| Permittivity | 4.1(10KHz), 4.0(100KHz), 308(1MHz) | 6.7(10KHz),6.6(100KHz),6.5(1MHz) | conforming to ASTM D-150 |
| Dielectric tangent | 0.013(10KHz),0.025(100KHz),0.032(1MHz | 0.005(10KHz),0.012(100KHz),0.025(1MHz) | conforming to ASTM D-150 |
| Volume resistivity | 3.2×10^16 Ω-cm | 5.6×10^15 Ω-cm | conforming to IEC 93 |
| Autolysis | Conforming to UL94 V-0 (10 to 50µm) | Conforming to UL94 V-0 (10 to 50µm) | conforming to IEC 94 |
| Corrosion resistance | SST method Sample (NdFeB 36.2×32×2.7t) Flat area film thickness 25μm: 500 hrs or more |
SST method Sample (NdFeB 36.2×322×2.7t) Flat area film thickness 25μm: 400 hrs or more |
conforming to JIS Z2371 |
| Moisture resistance | 49℃×98%：500 hrs or more 5% salt water： 500hrs or more (sample: NdFeB coated to 25 μm and thermosetted) |
49℃×98%：500 hrs or more 5% salt water： 500hrs or more (sample: NdFeB coated to 25 μm and thermosetted) |
In-house testing |
| Chemical resistance | RT×168hrs, 25μm Hydrochloric acid: 35% solution: no change, MEK: 100%: no change Xylene: 100%: no change Methylene chloride: 100%: no change Sodium chloride (saturated solution): no change |
RT×168hrs, 25μm Hydrochloric acid: 35% solution: no change, MEK: 100%: no change Xylene: 100%: no change Methylene chloride: 100%: no change Sodium chloride (saturated solution): no change |
In-house testing |
The above 2 resin types are used in Hi-DEN coatings
Nylon is a type of polyamide synthetic fiber. There are many types of nylon and we use Nylon 11 made in France. Nylon 11 is a non-toxic material that is environmentally friendly and conforms to food hygiene laws, and so is used widely in food processing machinery and healthcare equipment. Nylon demonstrates excellent low temperature impact resistance and the mechanical strength of products can be increased greatly by using this coating.
| Food hygiene | Conforms to food hygiene laws. Can be cleaned using ethanol |
| Weatherability | Resistant to ultraviolet rays and does not degrade easily when used out of doors. |
| Heat resistance | Excellent heat resistance for continuous use up to 130 C. |
| Wearability | Low coefficient of attrition, excellent corrosion and wear resistance |
| Impact resistance | Difficult to peel off even when struck |
| Salt water resistance | High corrosion resistance even in sea water |
| Insulating properties | Can withstand up to 30 kv/mm with a film thickness of 0.4 mm. |
| Decorativeness | 20 colors available。 |
Coatings are used in many products that we use everyday. The technology of coating has been around for a long time but there are still some issues that remain to be addressed. The following are the typical issues involved with the coating process. An ideal coating is one that overcomes these issues, is technically easy to use and also addresses environmental concerns. At Magfine, we develop coatings that tackle these issues and we manufacture coating devices.
1) Rust The resin in normal coatings is dissolved in a solvent, and the solvent evaporates by passing through gaps in the resin at the molecular level. The paths that the solvent evaporates through is caused by cracks due to drying. Rust is caused by water molecules seeping through these uneven cracks that cannot be seen by the naked eye.
2) Surface tension Coating pointed portions is technically very difficult. Acute angles and the tips of needles are not easily coated due to the movement of liquids because of the surface tension. This problem can be solved with coatings not containing solvents to reduce the surface tension.
3) Environmental problems Environmental issues have become more of a concern in the last few years, and the solvents used in coatings represent one factor in environmental pollution.
The multilayer coating method is a coating method that achieves high density and no pinholes due to the repeated drying and application of coating that is similar to Japanese lacquerware. While the pinholes may reach all the way to the base material in a cross-section of a normal coating, a cross-section of a film applied through the Hi-DEN coating shows that the pinholes do not extend all the way to the base material thus improving insulation properties and rust prevention effects.
The same level of film thickness can be applied at the edge portions and the flat portions of the base material. All portions, even detailed portions such as the insides of holes can be coated. Edge coating is perfect for applications where loads on edges are applied such as EMC cores etc.
Plating and coating have the similar objective of creating a film on a surface. However, the main difference is that since plating consists of a metallic film, plating does not provide electrical insulation. While plating can be used in high temperatures since it is metallic, coating is made from resin and so begins to melt at 100 °C to 200 °C depending on the type of resin. Also plating has the advantage of being thinner and can be applied to less than one-tenth the thickness of coating. But plating and coating also share an unexpected similarity - poor quality platings and coatings both suffer from poor adhesiveness with the base material and tend to peel off easily. Poor quality cannot be seen easily, but inferior products are soon found out when put into use.
