Cathodic electrodeposition coating — widely known as CED coating or e-coat — is the most uniform, corrosion-resistant and environmentally friendly industrial primer process available to Indian OEMs today. Every modern automotive body coming off a production line passes through a CED dip tank; the reason is simple — no other process deposits a consistent film on complex, recessed and hidden surfaces with such reliability. This guide covers how CED works, why it outperforms alternatives, and when to specify it for your components.
What is CED coating?
CED coating is an immersion process in which a cleaned, phosphated metal part is submerged in a water-based paint bath containing positively charged (cationic) paint particles. An electric current is applied between the part (acting as cathode, hence "cathodic") and opposing anodes, attracting the paint particles to every surface of the component — including internal cavities, welded seams and blind corners that spray processes can never reach uniformly.
Once the desired film thickness (typically 18-25 microns) is reached, the part is rinsed and baked at 170-180°C to cure the cross-linked film. The outcome is a smooth, hard, extraordinarily uniform primer coat with 1000+ hours salt-spray performance — ready either for topcoat or as a standalone functional finish.
How the CED process works
- Pre-treatment — degreasing, rinse, zinc (or tricationic) phosphate, rinse, passivation, DI rinse.
- CED dip — part submerged in water-based cationic e-coat bath for 2-3 minutes under DC voltage.
- Post-rinse (UF rinse) — ultrafiltrate recovered and recycled back into the bath (99%+ material utilisation).
- Bake cure — 170-180°C for 20-30 minutes depending on substrate mass.
The water-based formulation contains less than 2% VOCs and generates near-zero hazardous waste — a meaningful compliance advantage for OEMs working to ISO 14001 environmental standards.
Why automotive OEMs prefer CED
- Uniform coverage on complex geometries — the process coats every inch, including interior cavities, welded joints and recessed features.
- Superior corrosion resistance — 1000+ hours salt spray is typical; critical for automotive body-in-white and underbody applications.
- High material utilisation — ultrafiltrate recovery pushes efficiency above 99%.
- Consistent film thickness — self-limiting deposition eliminates over- and under-coating.
- Water-based, low VOC — environmentally superior to solvent-based primers.
- Excellent adhesion — ideal basecoat for subsequent powder or liquid topcoats.
CED vs powder coating — when to specify which
CED is a primer-grade process delivering thin (18-25 μm), uniform, corrosion-resistant films. Powder coating is a topcoat-grade process delivering thicker (60-300 μm), decorative, chip-resistant films. Many automotive parts use CED as primer followed by powder or liquid topcoat — getting the best of both.
Choose CED when:
- Part geometry has cavities, recesses or complex welded joints.
- Maximum corrosion resistance on a thin film is the priority.
- You need a primer layer for subsequent topcoating.
- Environmental/VOC compliance is paramount.
Typical CED coating applications
- Automotive body-in-white — primer layer across car, truck and two-wheeler bodies.
- Chassis components — suspension arms, brackets, subframes.
- Fasteners & hardware — automotive-grade bolts, nuts, washers requiring uniform coverage.
- White goods — washing machine drums, oven frames, refrigerator shelving.
- Industrial hardware — valves, pumps, motor housings with cast cavities.
Specifications & testing
Standard CED film thickness: 18-25 microns. Colour: typically black (most common), grey or primer-compatible shades. Hardness: H-2H on pencil test. Salt spray: 500-1000+ hours depending on substrate and topcoat. Every batch is validated in our in-house lab — see the quality & testing guide for method details.