MULTI TREATMENTS :
Combining successive treatments to improve mechanical and surface properties
Multi treatments, also known as multi systems, multi coatings, duplex or two-layer coating systems, combine several complementary finishing technologies to deliver enhanced corrosion protection, long-term durability, and improved aesthetics.
At Electropoli, we master a complete range of multi coating services — integrating plating, painting, and e-coating processes — for steel, aluminum, and cast-iron components.
Operation – Description of the process
A multi coating system involves applying a first metallic or conversion coating — such as zinc plating, zinc-nickel plating, phosphating, or aluminum passivation — followed by an organic topcoat like e-coat, powder coating, or liquid paint.
This dual-layer protection system acts synergistically:
- The base metallic layer provides sacrificial corrosion protection,
- The organic layer ensures barrier protection, aesthetic finish, and additional mechanical resistance.
Range of Multi Treatments
Electropoli offers a broad portfolio of multi coating systems and combined surface finishing processes:
- Zinc plating + E-coat
- Zinc-nickel plating + E-coat
- E-coat + Powder coating / E-coat + Liquid painting
- E-coat + stone-chips coating
- Aluminum passivation + Painting
- Ni + Zn alloy undercoat
- Zn + Painting + Tampo printing
- E-coat + liquid painting
Why choose Our
Multi Treatments
Offers maximum protection and exceptional durability, even in the harshest conditions.
Looking for a specific service
For your multi treatments, our technical teams can design tailor-made multi-treatment services adapted to your performance and compliance needs.
Access our customized multi-treatment solutions.
Need technical support
Are you developing a new component, validating specifications, or facing a technical challenge?
Our multi-treatment experts are at your disposal to study your needs and create the right surface treatment solution.
OUR OTHER TREATMENTS
Painting
Aluminum passivation
Multi treatments
Finishing
FAQ
What are the primary benefits of using a duplex coating system (e.g., zinc plating + e-coat, or e-coat + powder coating) compared to a single layer coating for long-term corrosion protection on steel components?
A duplex coating system combines two complementary protection mechanisms to improve long-term corrosion resistance on steel components.
The metallic layer (such as zinc or zinc-nickel) provides sacrificial protection, while the organic layer (E-coat or powder coating) acts as a durable barrier against moisture and corrosive agents. This synergy delays corrosion initiation and limits its propagation in case of coating damage.
Compared to a single-layer coating, duplex systems offer increased durability, extended service life and improved reliability in aggressive or outdoor environments. The optimal system is defined according to exposure conditions and performance requirements.
Which duplex treatment combination do you recommend for components exposed to highly corrosive environments or requiring extreme durability, such as automotive underbody parts or outdoor industrial equipment?
For highly corrosive environments, duplex systems combining a metallic coating and an organic layer offer the best long-term performance.
Zinc or zinc-nickel + E-coat (cataphoresis) combinations are commonly used for automotive underbodies, thanks to the combination of sacrificial protection and a homogeneous barrier. For outdoor industrial equipment, E-coat + powder coating systems may also be preferred in order to improve mechanical strength and durability during prolonged exposure.
The final choice depends on the level of exposure, the geometry of the parts and the applicable specifications.
How does the application of a duplex system, for example zinc-nickel plating followed by an e-coat (KTL) treatment, enhance the mechanical properties or abrasion resistance of the final finish, in addition to corrosion protection?
A duplex system enhances overall durability by combining complementary functions rather than by relying on a single coating.
The zinc-nickel layer provides sacrificial corrosion protection and a robust metallic base, while the E-coat adds a uniform organic layer that improves surface toughness, adhesion and resistance to mechanical damage. This top layer helps limit abrasion, chipping and coating damage during handling or service.
While corrosion protection remains the primary benefit, the duplex system also improves the robustness and reliability of the finish under mechanical stress, especially in demanding industrial or automotive environments.
What considerations are there for interlayer adhesion between the different layers in a duplex coating system (e.g., between a metallic plating and a subsequent paint layer), and how do you ensure the integrity of the combined system?
Interlayer adhesion is a critical factor in the performance of a duplex coating system. It depends mainly on surface preparation, compatibility between layers and controlled process parameters.
Before applying the organic layer, the metallic coating surface is properly prepared and activated to ensure optimal adhesion. Pretreatment steps, curing conditions and coating parameters are carefully controlled to ensure strong bonding between layers.
The integrity of the duplex system is validated through process monitoring and adhesion testing, ensuring long-term durability and reliable performance in service.
Are there specific industry standards or performance testing methods (e.g., extended salt spray testing, cyclic corrosion testing) that your duplex treatments are designed to meet, particularly for sectors like automotive or heavy machinery?
Yes. Our duplex coating systems are designed to meet common industry standards and customer specifications, particularly in the automotive and heavy machinery sectors.
Their performance is typically validated through corrosion testing such as extended salt spray tests and cyclic corrosion tests, in accordance with applicable standards or OEM requirements. The exact testing scope and performance targets depend on the application and are defined in line with customer specifications.
