Watch a video of the high throwing power e-coat in Mazda's production line
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Mazda has already completed the introduction of its world-first "Three Layer Wet Paint System" to all of its plants in Japan. The Mazda Three Layer method combines the primer, base and clear coats into one painting process, significantly reducing the burden on the environment. With the Three Layer Wet Paint System and the new e-coating process, Mazda is aiming to be greener in its manufacturing processes and also improve the rust protection quality of its vehicles. By employing these two technologies, Mazda's painting process has advanced to a new level of eco-friendliness.
The electrodeposited base coat, or e-coat, is so called because electricity is used to apply the paint. The process involves vehicle bodies being immersed in a paint tank, with an electric current passing through the steel parts causing the paint to adhere to the metal surfaces. Using an electric charge facilitates an excellent paint-to-metal bond, and is generally used to help prevent corrosion on all body surfaces. However, with conventional paints, discrepancies in paint film thickness can result between the inner and outer body surfaces because of the variation in electric current. The current tends to be weaker on the inner surfaces, so the paint film is thin and provides less protection from rust. Conversely, electric current flows easily through the outer surfaces, producing an excessively thick layer of paint. To prevent this, a method of equalizing the inside and outside paint film thickness is necessary. Minimizing the discrepancies in film thickness also leads to a reduction of the total amount of paint needed. Less paint means decreased volatile organic compound (VOC) emissions, and the reduced energy consumption will result in lower carbon dioxide (CO2) emissions from the painting line.
The new eco-friendly e-coat has been developed to ensure an even distribution of paint film inside and outside the vehicle body and thereby:
- - reduces the environmental impact from VOC and CO2 emissions by reducing the amount of paint used.
- - improves rust protection.
- - promotes environmental friendliness and further reduces VOC emissions by lowering the concentration of solvent in the e-coat paint.
(1) Ensuring a uniform paint film
The resins in conventional paints are highly viscous (thick), which means gaps remain between the resin molecules through which electrons can flow. Therefore, several layers of molecules are needed to stop the flow of electricity. This is why an excessive amount of paint adheres to the outer surfaces, which have a relatively high electric charge. Mazda's newly-developed e-coat contains low viscosity (thin) resin. The molecules can therefore move together with smaller gaps and more easily stem the flow of electricity. This high electrical resistance results in a thinner layer of electrodeposited paint, even on the outer surfaces where the electric charge is strongest. Consequently, the volume of paint needed for Mazda's e-coat is substantially reduced.
(2) Improvement of the paint film's rust protection properties
The newly developed e-coat has modified solvent characteristics that raise the paint's electrical resistance. This means the electric current flows to the inner surfaces more easily, so less electricity is needed for painting. It also means the film thickness is uniform even on the inner surfaces and the e-coat therefore ensures enhanced protection from rust.
(3) Reduction of solvent content in the e-coat
By ensuring a more appropriate film thickness on the outer surfaces, the new e-coat reduces the total volume of paint needed. The new low-solvent paint also has a decreased concentration of VOCs. Both factors result in the volume of VOC emissions from the paint line being cut in half. Additionally, the reduced volume of paint means that CO2 emissions from Mazda's painting lines are also significantly lower.