Process for coating workpieces, in particular vehicle bodies

Abstract

When coating workpieces, in particular vehicle bodies, the following coating layers are applied in succession and in a manner known per se: a primer layer in an electrophoretic dip coating process, a functional layer, an aqueous base coating layer and a clear coating layer. In order to configure this process in an environmentally compatible manner, in particular in order to avoid solvent emissions and coating sludge, the functional coating layer is also applied by an electrophoretic dip coating process and the clear coating layer is applied as a powder coating by electrostatic spraying, which coating is subsequently stoved. In this manner, it is possible to bring about an overall reduction in solvent emissions to approximately one sixth of the previous value of known processes and in coating sludge formation to approximately one third of the previous value.

1 . A process for coating workpieces, in particular vehicle bodies, comprising the following process steps: 
 a) pre-treatment of the workpiece surface;    b) application of a primer layer upon the workpiece surface in an electrophoretic dip coating process;    c) application of a functional coating layer upon the primer layer in an electrophoretic dip coating process;    d) application of an aqueous base coating layer upon the functional coating layer; and    e) application of a clear coating layer by spray application of a clear powder coating upon the aqueous base coating;    wherein further steps of at least one of rinsing and drying may be optionally applied between process steps b), c), d) and e.    
     
     
         2 . The process according to  claim 1 , wherein in step b), a coating material is used which possesses elevated electrical conductivity for performance of process step c).  
     
     
         3 . The process according to  claim 1 , wherein differently coloured functional coating layers may alternatively be applied in process step c).  
     
     
         4 . A process according to  claim 1 , wherein the step of pre-treatment comprises a step of cleaning the workpiece.