Cathodic ED Paint Epoxy Electrophoretic Coating
Basic principles and working mechanism
Cathodic epoxy electrophoretic coating (also called cathodic e-coat) is an electrochemical process where epoxy-based resins deposited on a conductive substrate (cathode) form uniform, corrosion-resistant films.
Key reactions:
Electrolysis: Water reduction at the cathode generates OH-ions.
Electrophoresis: Positively charged epoxy-amine particles migrate toward the cathode.
Electrodeposition: Particles coagulate on the substrate, forming an insulating film.
Electroosmosis: Water is squeezed out, enhancing adhesion.
Core components
Component |
Function |
Typical materials |
Epoxyamine resin |
Provide coated skeleton and positive charge |
Epoxy resin + diethylamine modification |
|
Crosslinking agent
|
Forms a three-dimensional network structure during high-temperature curing |
Closed-type isocyanates (e.g., TDI-caprolactam closed compounds) |
Neutralizer |
Endowing resin with water dispersibility |
Formic acid, acetic acid |
Additives |
Enhanced functionality (preservation, leveling, wetting) |
PTFE, silane coupling agent, boron nitride (BN) |
Process flow
Pre-treatment: Degreasing → washing → surface adjustment → phosphating (forming a phosphate layer to enhance adhesion).
Electrophoresis tank: Parameters: voltage 150–400V | time 2–4min | temperature 28–32°C | solid content 18–20%.
Post-rinsing: Ultrafiltration (UF) recirculation system recovers floating paint, with a recovery rate >99%.
Baking and Curing: 160–180°C × 20–30min (deactivates crosslinking agent, completes curing)
Comparison of Coating Types
Property |
Anodic E-coat |
Cathodic Epoxy E-coat |
Corrosion Resistance |
Moderate |
Excellent (1,000+ hr salt spray) |
Metal Dissolution |
Possible (anode oxidation) |
None (cathodic protection) |
Edge Coverage |
Moderate |
Superior |
Environmental Impact |
Low VOC |
Ultra-low VOC (water-based) |
Typical Applications |
Indoor hardware |
Automotive, marine, pipelines |
Application Areas
Automotive Manufacturing: Body panels, wheels, chassis (accounting for 70% of the global e-coat market).
Energy engineering: Oil/gas pipelines, offshore wind turbine towers (paired with cathodic protection systems).
Electronics and appliances: Motor housings, radiators (insulation voltage resistance > 5 kV/mm).
Emerging fields: Hydrogen energy storage and transportation equipment, lithium-ion battery casings (corrosion protection + insulation integration).
Performance advantages
Corrosion protection: When used in combination with cathodic protection systems, it can extend the service life of pipelines in soil/marine environments.
Uniform coverage: Achieves consistent coating thickness (15–30microns) on complex geometries (such as car frames).
Environmental safety: Water-based formulations reduce volatile organic compound (VOC) emissions by more than 90% compared to solvent-based coatings.
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