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When it comes to MIG brazing, there are some common mistakes that are easily avoidable and can have a huge effect on the durability of the repair joint.
The first common mistake that people make is selecting MIG brazing in areas that do not have any OEM supporting documentation. This may not sound like a big mistake, but keep in mind that MIG brazing is not fusing metal, it's only adhering two metals with silicon bronze. Because MIG brazing is not a fusion process, it often requires a larger surface area on the backside than when plug welding using traditional GMA welding. This is because there needs to be room for enough filler metal to give the weld its strength. This is the reason that double holes or slot welds are typically required instead of a plug weld. You should also only be using MIG brazing in areas where approved by an OEM or with a specific repair procedure.
The next mistake that technicians tend to make is, making MIG brazed open butt welds the same way as GMA welds. There is a tendency to turn up the heat and try to get the MIG brazed seam to look like a GMA weld. This not only defeats the purpose of using a welding wire that melts at a lower temperature, it also will not make a strong joint when capillary action is not achieved.
The moral of the story is, everything you may have learned about GMA welding doesn't necessarily apply to MIG brazing. It is a different process and has specific techniques, machine setup, and panel preparation that must be learned and followed to achieve a complete, safe, and quality repair.
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