Projects

Metal surfaces with organophilic structures for reproducible and long-life bonded joints

Laser pre-processing (diagram of an implemented pre-processing and coating process)
© Fraunhofer IWS Dresden

Laser pre-processing (diagram of an implemented pre-processing and coating process)

Task

Aluminum materials and other metals with an anodic oxide outer film, need anticorrosive and inhibiting oxide layers of sufficient thickness and density. In addition to the chemical oxidation processes, selective and ecological alternative methods have to be developed for industry. For this purpose, thermal oxidation was produced by laser beam.

Solution

Polymer spry application (diagram of an implemented pre-processing and coating process)
© Fraunhofer IWS Dresden

Polymer spry application (diagram of an implemented pre-processing and coating process)

To obtain aluminum surfaces for reproducible and long-life bonded joints, commercially available aluminum sheets were processed with a solid state laser, and the emergent aluminum oxide layer was coated with polyamines as reactive polymers. As a result, uncontrolled adsorption of organic substances from the environment was repressed, on the one hand. On the other hand, at the surface, primary amino groups were fixed as reactive functional units that can chemically react with components in the adhesives within the subsequent bonding process.

Results

Drying (diagram of an implemented pre-processing and coating process)
© Fraunhofer IWS Dresden

Drying (diagram of an implemented pre-processing and coating process)

The present research results demonstrate that the combination of laser processing and polyvinyl amine coating represents a simple and efficient pre-processing method resulting in higher strength bonded joints made of aluminum alloys with magnesium content. The bonding of the pre-processed joining parts can, as a result of this combination of pre-processing variants, be performed in a time-shifted manner. Thus, pre-processing of joints is feasible separate from the actual joining process, for instance at the site of the supplier, without any loss of strength.