Introduction of Durable Surface Conditioner Before E-Coat

Toyota Motor Corporation has been developing technologies for reductions on the environmental load. This paper reports the following as a part of technological development for the painting process.

Prior to the application of the E-coat, vehicle bodies are pretreated with zinc phosphates. This is applied to ensure good adhesion and corrosion resistance of the E-coat film. To obtain an excellent pretreatment film, surface conditioning with titanium colloid is generally applied before pretreatment. Since colloid flocculation control was difficult in the case of a conventional titanium colloid-type surface conditioner, the surface conditioner had to be renewed at approximately two-month intervals. The liquid life, however, increased remarkably as a result of adopting fine zinc-type surface conditioners and adding an organic protective surface layer. The water supply/discharge amount was decreased significantly compared with previous amounts. This was due to the reduction of the amount required for maintaining the surface conditioning effect, thanks to the lengthened pot life.