Introduction to Brake Pad Powder Coating and Operating Procedures
I. Introduction to Brake Pad Powder Coating
1. Purpose
- Anti-corrosion and rust prevention: Isolate moisture and oxygen to extend service life.
- High-temperature resistance: Withstand heat generated by friction during braking (coating typically requires ≥200°C tolerance).
- Enhanced adhesion: Optimize surface roughness to ensure strong bonding between friction materials and metal backplates.
- Aesthetic improvement: Provide uniform coating to meet branding or color requirements.
2. Applicable Materials
- Powder coatings: Commonly epoxy-polyester hybrid systems or formulations with high-temperature-resistant fillers (e.g., ceramics, graphite).
- Substrate: Brake pad metal backplates (cast iron, aluminum alloy, etc.).
II. Process Principles and Workflow
Process Principle
Utilize corona discharge to adsorb powder coatings onto workpiece surfaces. High-temperature baking melts, levels, and cures the powder to form a durable coating.
Workflow
1. Pre-treatment
- Degreasing and derusting: Remove oil, rust, and impurities via ultrasonic cleaning or sandblasting.
- Phosphating treatment: Form a gray phosphating film on the surface to enhance rust resistance and coating adhesion.
2. Electrostatic Spraying
- Equipment setup: Configure electrostatic generators, powder supply systems, spray guns, and recovery devices to maintain powder suspension.
- Spraying operation: Use a high-voltage electrostatic field to evenly adsorb powder onto the workpiece surface. Specialized high-performance electrostatic sprayers are required for complex areas.
3. High-temperature Curing
Transfer coated workpieces into a curing oven, heat to 185–230°C, and maintain for 15–30 minutes to melt, level, and cure the powder.
4. Post-treatment
- Surface finishing: Perform slotting, chamfering, or drilling on the coating to improve mechanical strength.
- Anti-rust treatment: Apply sandblasting or drying to non-contact surfaces to prevent corrosion.
- Decorative treatment: Achieve special effects (e.g., wood grain, crack patterns) via gloss coating or transfer printing.
Operating Procedures
1. Wear personal protective equipment (PPE).
2. Turn on the main power switch. Activate heating and preheat the oven for 30 minutes. During preheating, adjust fluidizing air to 0.5 kg/cm² to pre-fluidize powder in the hopper. Clean the recovery fan filter, filter chamber, and dust bags (enable reverse blowing for at least one cycle; clean daily before operation). Start the dust collection system.
3. Adjust fluidizing air to 0.25 kg/cm² and observe if powder flows uniformly upward. During operation, set fluidizing air to 0.1 kg/cm² (powder should roll visibly in the hopper). Activate left/right spray guns, set electrostatic voltage to 1–3 kV, adjust atomization pressure to ~0.5 kg/cm², and powder supply pressure to 1–2 kg/cm². Spray test samples and measure coating thickness to meet specifications. Ensure all temperature gauges reach required values.
4. Start the conveyor and adjust speed (ensure uniform coating thickness). Use an air gun to remove surface contaminants and dust from products. Clean residual powder from the conveyor with a brush and place products at the oven's inlet.
5. Activate cooling and conveyor systems. Process products through heating, curing, and cooling stages. Ensure no products remain on the conveyor when stopped.
Through the above procedures, brake pad powder coating achieves efficient surface treatment, meeting demands for wear resistance, corrosion protection, and aesthetics.
