E-coating is a process that has been used since the 1970s for the corrosion protection of metal parts and the production of smooth, durable and protective finishes.
Unfortunately, too little is known and the process is under-utilized in today’s industry. The following summary therefore intends to explain the general principle and exposes the major advantages of e-coating.
The e-coating process is best described as a crossover between plating and painting to protect metal from outside influences. A metallic workpiece is immersed in a water-based solution containing a paint emulsion. An electric voltage is applied to the workpiece causing the paint emulsion to cover the surface.
The workpiece can be painted both inside and outside, wherever the liquid is able to reach the metal surface. The coating thickness is controlled by the applied voltage. At the end the E-coat is cured by heat and the curing time and temperature is determined by the E-coat chemistry; epoxy, acrylic, etc.
E-coating gives a smooth, even and lasting finish to metal products but despite its advantages, it is not as well-known as other finishing processes.
The e-coat is an emulsion of organic resins and de-ionized water, which is in a stable condition. This e-coat solution is also comprised of some solvent and some ionic components.
When a D.C. voltage is applied across two immersed electrodes, the passage of current is accompanied by electrolysis of water. This results in oxygen gas being liberated at the anode (positive electrode) and hydrogen gas being liberated at the cathode (negative electrode). The liberation of these gases disturbs the hydrogen ion equilibrium in the water immediately surrounding the electrodes. This causes a corresponding pH change and in turn de-stabilizes the paint components of the solution and they coagulate onto the appropriate electrode.
The workpiece is the anode (positively charged). It attracts the negatively charged paint particles in the paint emulsion. But small amounts of metal ions migrate from the workpiece into the paint film, so the metal ions contaminate the coating.
This process causes degraded corrosion resistance and durability, but allows a lower cure temperature.
The workpiece is the cathode (negatively charged). It attracts the positively charged paint particles. The negatively charged polarity of the workpiece greatly reduces the amount of iron entering the cured paint film, enhancing the corrosion resistance and durability and reducing the contamination in the baths. The best way and our way to e-coat!
1. Pickling - Our Pickling and de-rusting operation is capable of stripping rust, dirt, grime and scale from workpieces that have been exposed to outside influences returning their finish to a point that is able to be electro-coated.
2. & 3. Cleaning & Pressure washer -We clean the workpiece in a special bath and with a pressure washer to prepare it for the phosphating process.
4. Phosphating -The workpiece is dipped into phosphoric acid to create a surface protecting phosphoric layer.
5. Cleaning -We clean the workpiece once again from acid leftovers.
6. E-coating dip tank -The workpiece gets into the e-coating bath. The paint emulsion covers the workpiece and creates the protective e-coat layer.
7. & 8. Cleaning & Pressure washer-We clean the workpiece once again from paint emulsion leftovers.
9. Baking -The workpiece gets baked to harden the e-coat layer. This guarantees the optimal protection for our products.
E-coating became popular in the 1970s when many companies adopted the process to quickly apply an even base coat to their products.
One industry where it caught on was the automotive industry. Today, e-coating is used in many other fields like household appliances, agricultural machinery and street furniture. Many automobile companies still use E-coating to apply a weather resistant base coat to their body panels.
For the best finish, we recommend applying a powder coat on top of an E-coated base coat. The E-coating provides protection and the powder coating gives a stylish finish, as you can see on our pipe bollard.
So why should you choose E-coating over the more traditional options such as hot-dip galvanizing?
E-coating is much cheaper and more cost-effective than hot-dip galvanizing and offers a smoother finish with less chance of defects. Furthermore, E-coating offers a uniform coating with an equal layer across the length of a product; whereas hot-dip galvanizing might not have the needed uniform thickness.
If you want to learn more about e-coating or about our production, feel free to contact us!
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