Epoxy-coated laminated magnets for new energy vehicles

Black Coated Laminated Magnets & Stacked Magnetic Steel — Black Epoxy Laminated NdFeB / SmCo for High-Frequency Motors, Robot Joints, EV Traction, and UAVs

Black epoxy insulation + eddy-current lamination in one custom magnetic assembly — corrosion-resistant, salt-spray-rated, Halbach-ready

FAIZEAL black coated laminated magnets are precision-engineered magnetic assemblies built by stacking ultra-thin, electrically insulated layers of sintered NdFeB or SmCo, and applying a high-performance black epoxy coating as the final surface layer. The lamination process cuts eddy-current losses by 60-90% and reduces temperature rise by 30-50% in high-frequency motor operation. The black epoxy coating, applied at 15-30 um per pass, delivers >100 MOhm surface insulation resistance, 500-1,000 hour neutral salt spray rating, strong chemical resistance to motor coolants and lubricants, and a low-gloss optical finish that integrates cleanly into assembled motor housings.

For new-energy vehicle traction motors, humanoid robot joint motors, UAV propulsion motors, high-speed CNC spindles, and precision industrial automation, black coated laminated magnets are the default building block where the magnet must deliver both low electrical loss and long-term corrosion protection. Every FAIZEAL assembly is 100% custom — material grade, lamination thickness, insulation chemistry, geometry, surface treatment, and magnetization pattern are all specified to your design. Send a CAD or STEP file, your operating environment (temperature, humidity, salt / chemical exposure), and a target flux and loss budget. FAIZEAL returns a manufacturable lamination and coating proposal, an FEA-based loss estimate, and a prototype plan.

Why black epoxy laminated magnets are the new default for high-frequency motors

A solid sintered NdFeB or SmCo magnet is electrically conductive. In an alternating magnetic field, time-varying flux drives eddy currents in the magnet body, and those currents dissipate as I-squared-R heat. The loss scales with the square of the magnet thickness, so a 5 mm solid magnet can show 20-50 times the eddy loss of a 0.35 mm laminated stack under the same field. At PWM fundamental frequencies of 5-20 kHz — typical of modern SiC drives — this is the difference between a motor that runs cool and a magnet that creeps past its thermal limit, demagnetizes, and fails the warranty.

Lamination solves the loss. A black epoxy coating solves the survivability. The magnet runs in a real motor: exposed to coolant vapor, gearbox oil mist, road salt, marine atmosphere, and humidity. Bare sintered NdFeB has a porous, multi-phase surface (Nd-rich grain boundary phase, B-rich phase) that is electrochemically active and corrodes quickly if not sealed. A 15-30 um black epoxy coating seals the surface, raises surface insulation resistance above 100 MOhm, and provides the chemical and abrasion resistance the motor needs to last.

Key benefits for the motor design engineer

· Black epoxy insulation and anti-corrosion. 15-30 um black epoxy spray coating delivers >100 MOhm surface insulation resistance, 500-1,000 h neutral salt spray rating, strong chemical resistance to motor coolants, lubricants, and cleaning agents, and abrasion resistance suitable for mechanically assembled rotor stacks.

· Low eddy current loss and cooler operation. Custom lamination thickness (0.10-2.00 mm) and inter-layer insulation (epoxy, polyimide, parylene-C, ceramic-filled) reduce eddy current loss by 60-90% and temperature rise by 30-50% versus a solid magnet of the same shape, in the same drive and cooling conditions.

· Full geometric flexibility. Sector / fan-shape, tile / arc-shape, rectangular block, square, and complex irregular geometries for Halbach arrays and motor pole pieces are all in-house. Typical planar dimensions 10x10 mm to 200x200 mm and stack heights 3 mm to 60 mm. Custom sizes outside the standard envelope are evaluated on request.

· Multiple material options. Sintered NdFeB (N35 to N52; H / SH / UH / EH / AH grades for elevated temperature) and SmCo 1:5 or Sm2Co17 for high-temperature and corrosion-edge applications. The material is selected to give sufficient Hcj margin against the worst-case working point at maximum operating temperature and reverse field.

· Halbach array magnetic circuit support. Lamination is the ideal building block for Halbach arrays, where each pole pitch is split into 3-8 segments with rotated magnetization directions. The laminated construction controls eddy loss in every individual segment, preserves Halbach single-face flux concentration (+25-40% versus radial-magnet), and reduces cogging force by 50-80%.

· High motor efficiency and continuous power density. Lower magnet loss means less waste heat, smaller heat sinks, and higher continuous power density. In high-frequency applications, laminated magnets routinely add 1-3 percentage points to overall motor efficiency, enough to be the difference between a design that passes efficiency class and one that does not.

· Tight tolerance, OEM-ready. Lamination layer parallelism +/- 0.02 mm, stack height tolerance +/- 0.05 mm (down to +/- 0.02 mm for precision grade), surface flatness 0.03 mm, surface roughness Ra 0.4-0.8 um. Black epoxy coating adds a controlled 15-30 um layer per pass without affecting the critical magnetic air-gap face, which is masked during coating and re-ground to spec after coating if required.

· Long service life in harsh environments. The combination of lamination insulation and black epoxy coating gives the magnet the chemical, thermal, and electrical resilience to run in automotive underbody, marine, food-processing, and outdoor wind environments. SmCo versions rated to +350 deg C continuous; Ni-Cu-Ni plated NdFeB versions pass 1000 h salt spray; black epoxy topcoats extend the protection further.

Coating performance and technical specification matrix

The tables below summarize the standard production envelope. Combinations outside these ranges are evaluated on request.

Material grade selection

Geometry / shape selection

Frequently asked questions (B2B engineer FAQ)

Q1. How does the black epoxy coating thickness affect the magnet tolerance and air-gap?

A. The black epoxy coating is a controlled 15-30 um per layer applied by spray. For magnets where the working face is also the coated face, the coating is applied first to the non-working faces and the working face is masked, or the working face is ground to spec after coating. In either case the air-gap tolerance is held to +/- 0.02 mm, the same as a bare magnet. For OEM designs where the working face is not coated, we can also pre-grind the working face and then mask it during the coating cycle to keep it absolutely clean. The black epoxy does not affect magnetic performance — it is non-magnetic and adds essentially no thickness on the rotor-stator air-gap side.

Q2. What is the maximum operating temperature for the black epoxy coating, and what happens at the limit?

A. The standard black epoxy coating is rated to 155 deg C continuous service. Above that, the coating softens and loses dielectric strength. For higher-temperature motors (UH/EH/AH NdFeB at 180-220 deg C, or SmCo at 300-350 deg C) we substitute a high-temperature epoxy or a different topcoat (ceramic-filled, Parylene-C, or no topcoat with Ni-Cu-Ni plating as the primary corrosion layer). Always tell FAIZEAL your maximum operating temperature, and we will specify the coating accordingly.

Q3. What is the typical sample delivery time for a custom black coated laminated magnet?

A. Sample lead time is typically 2-4 weeks for a single-sector or single-block sample and 4-6 weeks for a full Halbach ring or curved track. Lead time depends on the grade, geometry, lamination count, and whether a custom magnetizing fixture is needed. For urgent prototype programs, FAIZEAL can hold a 1-2 week slot for expedited samples. Production lead time is 4-8 weeks after sample sign-off.

Q4. Can the black epoxy coating be applied over a Ni-Cu-Ni plated magnet?

A. Yes. The typical build is Ni-Cu-Ni plating (15-25 um) on all surfaces for primary corrosion protection, then a black epoxy topcoat (15-30 um) on selected surfaces for additional insulation, color, and chemical resistance. This build is common in EV traction and industrial servo where the magnet must pass 1000 h salt spray, run in coolant vapor, and present a clean low-gloss appearance in the assembled motor. The two layers together give 30-55 um total coating with the best available balance of corrosion, insulation, and surface appearance.

Call to action

Order now to upgrade your high-frequency motor with black coated laminated magnets built to your exact geometry, material, coating, and performance target. For new designs, send your CAD or STEP file, target operating temperature, fundamental switching frequency, magnet grade preference, operating environment (humidity, salt, chemical exposure), and any loss or thermal budget. FAIZEAL will return a manufacturability review, a recommended lamination thickness, inter-layer insulation chemistry, and black epoxy coating spec, an FEA-based loss estimate, and a quotation. Engineering consultation, prototype samples, and OEM/ODM production are available for qualified projects. Contact FAIZEAL for custom black coated laminated magnets, black epoxy laminated magnets, and Halbach array magnetic assemblies.