Summary: Cathodic electrocoat (e-coat) is the body's corrosion base: waterborne resin deposits uniformly under an electric field, and 'throwing power' carries film into cavities and seams for whole-body protection.
Mechanism
Throwing power depends on voltage, bath conductivity/solids, temperature and time; cavities rely on field distribution, so part orientation and gaps must be controlled.
Key data
- Film thickness is usually about 18-25 µm, coating inner and outer surfaces evenly.
- Bath temperature and pH are tightly controlled for deposition and appearance.
- After baking it cures to high chip resistance and good topcoat adhesion.
Parameter vs result
| Variable | Effect |
|---|---|
| High voltage | Thicker film, but water marks/roughness |
| Low throwing power | Thin cavities, inner rust |
Defects & fixes
- Thin cavity walls: low throwing power — adjust voltage/time/orientation.
- Water marks/roughness: over-voltage or slow rinse — control voltage and UF rinse.
- Particles: bath filtration/cleanliness — strengthen circulation filter.
FAQ
Why e-coat for bodies?
Conductive aqueous deposition coats complex geometry and cavities evenly; the top heavy-duty primer.
Cathodic vs anodic?
Bodies use cathodic e-coat; film has better alkaline/corrosion resistance protecting steel.
What if throwing power is low?
Seams/cavities are too thin and rust early; raise parameters or add supplementary spray.
Ref: automotive body cathodic electrocoat process notes (public).
Kexin New Materials (Guangdong) Co., Ltd. · 2026-09-18