What is the context?

E-coating or electrocoating or electropainting or electrophoretic lacquering is basically an electrophoretic process by which a paint layer is deposited on a substrate. However, unlike electroplating, electrocoating layers are composed of low-conductive paint.

This process is widely used for industrial applications, mainly in the automotive industry, due to its excellent corrosion protection properties, low cost and self-leveling effect. E-coatings are mainly used for applying the primar paint layer on a substrate, although it might also be used for the finishing paint layer. Typical layer thickness values to be obtained are in the order of 20 micron.

E-coating is one of the last engineering areas where computer simulations are not commonly used, and mainly Automotive OEMs are looking for solutions in this domain.

E-coating related engineering has to be completed preferably before the first prototype is build. Today, this is done based on experience. Being able to not only identify problem areas but also demonstrate the effect of proposed design changes enables corrosion engineers to drastically reduce the lead time and to work with similar tools as their colleagues working on crash, durability, NVH,…

What are the issues?

Electrocoating issues are as well product as process oriented:

E-coatings are known for their leveled thickness distribution, due to the highly resistive properties of the electrocoated paint layer, thereby directing the electrical current to surface areas that have not yet received full paint coverage.

A key factor for this self-limiting effect is the process time. Often the process is not allowed to reach equilibrium, turning the process time into a critical parameter in a compromise between productivity and paint layer thickness distribution. A typical automotive paint process time takes a few minutes.
The local current density on the substrate is also a critical parameter, not only with respect to the final coating thickness but with respect to the layer quality as well. Defects as ‘mushrooms’ and burning spots are due to elevated current density values, while layer thickness values below specifications in recessed areas are related to the occurrence of very low current density values.

What value do we bring?

Elsyca’s Advanced Engineering Services team uses its CAD integrated e-coating simulation technology to compute the distribution of electrical properties (potential, current density, paint layer thickness) over the substrate to be painted.
With this technology, we are able to:

• Simulate the ‘moving body’ trajectory in real time throughout the e-coating tank, including:
• entry/exit angle,
• CAD of part (racks containing dozens of parts, as well as large scale parts with complex geometry as car bodies (body-in-white) can be simulated);
• part load on the rack (if multiple parts e-coated on the same rack)
• Impose the adequate voltage programs for each group of tank anodes;
• Identify problem areas with paint layer thickness values below spec’s e.g. surface areas inside reinforcement pillars
• Identify gas traps and paint ‘drag over’ with the dipping module
• Investigate the full body (BIW) as well as detailed zooms
• Take into account bath characteristics (conductivity, paint resistance, etc.) and different base materials in one structure 

Elsyca’s electrocoating simulation technology is a powerful tool both for e-coating shops and OEM’s either to quote, plan or troubleshoot projects and to rule out layer quality and thickness problems in an early stage of the design cycle, thereby strongly reducing prototype costs and avoiding warranty issues.
Also it enables answering to the green coating need: Selecting a new paint bath is a tedious process: you only know how the bath behaves till you try it… unless Elsyca’s simulation technology is used, in combination with an upfront laboratory determination of paint bath characteristics (for more info on paint bath characterisation, read more here). It will clearly predict how the new paint bath will work in your existing infrastructure with your current and future part or car programs. This allows you to make the right choice based on objective criteria.