to weld or to seam-seal...

[Henry James the 47th]

All i know is that rust comes out of the seams earlier than anywhere else, and that if you drill the spot welds apart and look the the join, it is rustiest around the weld zones.

Another factor in this mix is the type of steel. Cars and trucks in the late 1970's were often starting to rust right on the showroom floor and that seems to associate to the composition of the steel used at the time.

 

[crushers]

i agree
the one i am working on is a 1989 BJ75 troopie, replacing the A pillar.
i have it all reworked with a donor panel. when i pulled it apart all the spot welds were in excellent shape but the metal beside them were rotted (in places).
I could seam weld but then the over laps will not be protected at all. I have come across the 606NF from 3M that is specific for this application.

 

[essar5]

The factory primed panels with OEM seam sealer have held up decently for the past 30 years. While the floors were nearly perfect, the outer quarters and rockers were rusted though in several spots. You can see where the wheel well and floor were separated, there is rust below the floor line. The rust starts below the seam seal and even below where the floor contacts the wheel well. I think they did a very good job prepping these surfaces as these seams have held up very well compared to the rest of the body.

 

[Henry James the 47th]

However you are in Washington State - the effects of corrosion are much worse out east, with the heavy road salting. In the picture above, there are places right next to spot welds where corrosion is underway. The progress of that corrosion will be slower where you are, but it still will be happening.

 

[essar5]

However you are in Washington State - the effects of corrosion are much worse out east, with the heavy road salting. In the picture above, there are places right next to spot welds where corrosion is underway. The progress of that corrosion will be slower where you are, but it still will be happening.

I may be in Washington state, but the body panels are from Texas. I think they would corrode way slower if they had stayed put, but the outside body didn't seem to notice as it rusted just like all the others I have seen.

 

[Henry James the 47th]

Yeah, it can be vastly different depending upon where you live and where the truck has spent most of its life.