Enameling Technology

Process for online monitoring of component surface quality during coating

The innovative process developed by the project facilitates surface-area spraying of component surfaces with varying test liquids. The resulting wetting patterns are optically recorded and evaluated with the aid of computers. This measurement method facilitates rapid quality testing of large polymer and metal component surfaces. The resulting increased production reliability and reduced scrap rate save energy and material resources. 



Component surfaces intended for adhesive labels, painting or printing need to display good wetting and adhesion properties. Production-related or incidental soiling, even in minimal concentrations, suffices to impair these properties. Such contamination therefore needs to be removed before the coating process by means of pretreatment steps (such as pickling or rinsing with water). Where this is not possible, flaws are identified only in post-process quality assurance subsequent to the coating process. This leads to major economic and ecological losses: the flawed product needs to be disposed of or reworked using additional material and energy. 

The project's aim was thus to develop a monitored process for rapid and large-surface assessment of component wetting properties for subsequent coating processes. Insufficient adhesion and wetting properties can thus be identified earlier and any required corrective measures can be taken in good time. 

The measurement apparatus constructed for the project was implemented in the production processes plastic painting, slide finishing and heat ageing. 



  • The new process facilitates determination of the contact angle of liquids on component surfaces and of the variance of the occurring contact angles.
  • Using the aerosol process, pretreatment processes currently under development (plasma processes, CO2 snow blasting, water-based cleaning and pickling processes) can be more rapidly and more efficiently examined in terms of their effectiveness. This contributes to speeding up their development.
  • The aerosol process records surfaces over a large area and provides statistical mean values.
  • Ultrasound atomiser jets generate the droplets in order to produce as narrow as possible a droplet distribution while maintaining large droplets.
  • To allow detection of the smallest differences in wetting behaviour, a process is used that actively permits soiling of the aerosol droplets on the substrate.
  • Within the range examined, the surface topology of aluminium, stainless steel and PP-EPDM (polypropylene ethylene propylene diene rubber) samples presents no impediment to accuracy for the newly developed measurement procedure.
  • The aerosol process is also suitable for real components with complex three-dimensional structures. The process can also be employed upon vertically positioned test surfaces: the droplets can be produced through lateral spraying of a surface; their adhesion is sufficient to prevent them from running off.

More Project Informations

Project title: Verbundvorhaben: Qualitätssicherung im Prozess: Online-Überwachung der Oberflächengüte von Bauteilen im Kleb- und Lackierprozess

Project number: 01RI05147, 01RI05148, 01RI05149, 01RI05150, 01RI05152

Project period: 2005 - 2008

Project region: Germany (Bavaria, Bremen, North Rhine-Westphalia)

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Quelle: German National Library of Science and Technology Hannover (TIB)