Converting from Leaded
to Unleaded Electrocoat Primer

The customer wanted it and Thyssen delivered...

By Juergen Heiler
Thyssen Umformtechnik
Bielefeld, Germany

In 1992, Thyssen Umformtechnik installed a batch-type electrocoat line suitable for coating a variety of parts up to 39 ft long. Parts include fabricated sheet parts such as doors or panels for cabs; truck chassis parts up to 39 ft;  subassemblies for cars and trucks; and axle components for cars comprising up to 80 individual parts. The total capital spent on this coating line amounted to around 35 million German marks.

Application process. The coating process is comprised of 13 tanks, 39 by eight by eight ft, with volumes ranging from 300 to 383 cu ft.

A five-unit conveyor system with a useful load of five metric tons carries the workpieces through the installation.

Parts are then baked at a minimum metal temperature of 350F in a 333 ft long oven. Cycle time is seven and a half min, and the complete processing time in the electrocoat line is three and a half hrs. Next to this line, Thyssen installed a separate wastewater treatment plant to treat wastewater generated by the process.

Planning the conversion. When the installation came on line, Thyssen used a black, leaded electrocoat product supplied by BASF (FT82-9636). This two-component system matched the automotive industry's requirements at that time. An order for coating replacement parts resulted in a change of the requirements. For safety and environmental reasons, an unleaded electrocoat product was now required. In cooperation with BASF, plans were made to replace the leaded electrocoat system, with consideration given to the following: