Today most chassis sheets are zinc galvanized for corrosion resistance. Different joints of the sheets are Plasma Brazed using low melting copper-silicon alloys.
Plasma Brazing of an engine bonnet
In this application the edges of the engine bonnet are folded and glued. To make sure that in case of an accident the mechanical properties of the joints fit for the purpose, the notch is additionally spotted. If the heat input during the spotting is too high there will be distortion on the top side wich is not acceptable.
The second picture on the right side shows the spotted area. The black soot are the residues of the burned glue which can be removed easily.
On the first picture on the right side the top side of the bonnet section can be seen. There are no distortions nor a melted respectively vaporized zinc surface visible.
Generally, Plasma Brazing is a suitable process for manually repairing of laser- & MIG-brazed or welded, galvanized frame parts in the assemby line. The low heat input and the easy handling enable very good results with no distortion of the sheet or destruction of the zinc coating.