Mobile welding equipment is used in many different environments. Consequently, their casings are protected against corrosion by a base coating and then finished with a decorative top coating. However, the complete curing of both coatings involves considerable cost – and until now considerable time. A gas catalytic oven from Heraeus is now significantly helping to allow the anti-corrosion coating on the mild steel casings of the welders to be dried in half the previous time. This also saves operating costs.
This innovative solution has been developed by Miller Electric Mfg LLC, a leading manufacturer of arc welding equipment, with the coating supplier TCI Powder Coatings and Heraeus. The heart of the new system is a gas catalytic infrared oven , which removes the requirement for a full cure of the Zinc primer. The final top coat can be applied whilst the primer has reached the gel stage in the Gas Catalytic IR oven. The final top coat can then be applied, before coated parts pass through a convection oven for final cure. This process actually improves the bond between the primer and the top coat, yet shortens the total cure time, improves the quality and saves energy.
Optimisation thanks to good co-operation
Miller Electric Mfg LLC is always looking for continuous improvement in the development of its mobile welding machines and this includes optimization of its coating plant. Previously this was a two-stage thermal curing process which components passed through twice, first to apply and fully cure the primer, a process that is then repeated for the top-coat. The Miller Electric engineers sat down with IR specialists from Heraeus Noblelight and the powder supplier TCI Powder Coatings to examine the opportunities offered by gas catalytic infrared. These investigations revealed that a totally innovative solution could eliminate the separate curing process during base coating required by the existing system.
Process Optimisation: A gas catalytic oven eliminates one curing process
The components which require coating with the zinc-rich base powder, using a conventional oven, undergo a two-stage process, where the powder is applied, melted, gelled and cured. In the new infrared oven the full cure of the zinc rich primer, is eliminated. Instead, the decorative coating is now applied when the Zinc primer is still in the gel state. The components, with the base coating at the gel stage and the newly applied top coat are then passed into a convection oven, where both the primer and the top coat are completely cured.
The gas catalytic infrared oven acts as a booster in the process. Infrared radiation gels the powder faster than hot air. In addition, rapid gelling reduces powder „blow-off“ and dust contamination.The use of the gas catalytic infrared oven not only reduces the overall cycle time by 50% but also improves the bond between the primer and top coat, thus improving overall corrosion resistance of the parts when in service.