How do we apply E-coating on Flexpipe parts and what is E-coating?

What is cathodic electrocoating?

The electrocoating process (E-Coating) is best described as a cross between plating and painting. It is a process where a metal part is immersed in a water-based solution containing emulsion with 10% to 20% paint, epoxy, or other components and 80% to 90% water. An electric voltage is applied to attract the particles suspended in the deionized liquid solution and deposit them onto the surface of the substrate.

The electrode positioning continues until the desired level of coating thickness is achieved, which can be regulated by increasing or decreasing the voltage level. The coated substrate is then cured in an oven to promote crosslinking.

If this process seems familiar to you, it’s maybe because you know it under another name, such as electrocoating, electropainting, electrophoretic, E-Coat Painting, ED Paint, or EPD coating.

How is E-Coating applied?

There are five main steps to the cathodic electrocoating process. However, for this post, we have broken the following steps into smaller ones to give you more information. Here, then, are the five main stages and all the sub-steps involved in the process.

1 – Pre-treatment

Loading metal joint

Each metal joint is manually hung to an overhead conveyor.

Hot water washing

Initial washing to prepare the part for degreasing.

Degreasing

Three stages of degreasing – pre-degreasing, main degreasing, and triple washing to remove dirt and oil.

Phosphating

Zinc phosphate is sprayed on the part as a base coating to prepare the surface for
e-coating.

Pure washing

Two stages of washing: water rinse and demineralized water rinse.

2 – Electrocoat Bath

A cathodic voltage of 210-220 V is applied to the part, causing the paint emulsion to condense onto the piece. Note that the thickness of paint put on the joints is 15um (+/- 5um).

3 – Post Rinses

Rinsing

As the part exits the bath, paint solids cling to the surface and must be rinsed off to maintain efficiency and aesthetics.

UF pure washing

Pure wash from color filtering devices with ultrafilter (UF) membranes.

4 – Bake-cure-dry oven

Baking

Parts enter an oven for 20 minutes at 350˚F to crosslink the polymers, allowing the coating to flow out and become smooth and continuous.

5 – Post-treatment

Cooldown

Before unloading parts, cold air is sprayed to cool down parts hanging on the overhead conveyor.

Unloading metal joint

While unloading from the conveyor, each joint is visually inspected before packing.

Advantages of electro-coating

Although it is almost impossible to change the color of a part after an E-Coating process, this method has multiple visual and technical quality advantages such as:

1. Provides uniform coating density across the entire component, regardless of the complexity of the product;
2. The best option for coating parts that contain hard-to-reach areas. No missed spots;
3. Excellent aesthetic appearance;
4. High corrosion resistance, usually more than 1000 hours of salt spray resistance;
5. Greater ease of regulating the thickness level, including thin application.