I have a friend who has been an auto body guy for the last 25 years or so. Says the hardly ever weld anymore...at least not things such as patch panels, says they bond everything. He didn't believe in it till he went to some GM seminar on it or something. Says he has been doing it the past 10 years or so without any issues. Just seems to me welding would be quicker and easier but perhaps I'm wrong. Any opinions on this or experience or preferred method?

 

I would ask your friend what he means by Bonding. The only thing I can think of is a bedside replacement on a truck. They are glued, (bonded) on and then spot welded or plug welded. Some body techs I have worked with in the past only wanted to glue the bedsides, but I never allowed it because I have seen them fail. The truck came from the factory welded and glued on, so that is how they should be fixed. Maybe he was talking about replacing a door skin? They are also glued on, altough there are a few welds to make as well on most door skins, so again if he is just glueing them, that is an incorrect repair.

I would ask him to be more specific.

 

Welding vs bonding is all about rust prevention. Welding tab panels destroys the anti-rust or electro galvanized coating in the area welded.
Porsche was one of the 1st automakers to recognize this issue and they required a complex rust proofing process to maintain their warranty. Chemical manufacturers developed the bonding process and was accepted by US Automakers starting in the late '80s. Application of a specialized bonding adhesive is now the preferred method for panel replacement and is accepted by insurance companies and the auto industry.

 

Weld-thru primers, which have been in use for decades in US body shops, restore the anit-rust coating you are talking about. Every US automaker that I have looked up recommends using bonding adhesive and spot welding or mig welding when replacing a panel such as a bedside outer panel, quarter panel, etc... I do not have access to Audi or Porsche recommendations, so it is possible that they recommend bonding only. Even for patch panels, I would never rely on just bonding adhesive.

 

With the improvements made in bonding agents if used in the right manner and in the right application the bonded panels are just as strong if not stronger than welds. The factory's are using more glue and less weld every year and with some of the metal's used bonding is the only option

 

In agreement with most of the others comments here.

At all the shops I've worked at, we do both. Weld and bond. I see the body techs usually bond a panel (bed side,1/4 panel, etc) let it sit over night to fully cure, then do all their welding the next day. Depending on the requirements of the specific job.

 

Bonding is a great advance in body work, but it has its pros and cons just like welding. Bonding takes time to cure,but creates a moisture barrier. Welding is quick but must be under coated or sealed in some way. The shops I have worked in we use both methods. If you can get to all areas of a welded panel or patch after you are done to seal it great . If not, bonding is the way to go and then lay a couple of tack welds for added peace of mind.