Portions of the frame are galvanized. Take time and prep well, otherwise your welds will suck.Cut 6.5" off the front frame rails and am building a winch bumper on the front of the wife's JLUR. While welding some plate to the frame near the core support last night, apparently a molten ball of spatter from the GMAW (Mig) was thrown at the bottom portion of the aluminum radiator and blew a pin hole in it.
I've welded practically on top of several different makes and models' radiators and never had the issue. So, either I just won the lottery on this or the aluminum just isn't as robust as those other vehicles. Regardless, just a warning...the radiator seems to be pretty thin. The molten ball went through a tiny gap that I probably couldn't have prevented even with a welding blanket since I would have had to have moved the blanket to weld the area I was trying to get to. That...or TIG it.
Also, I wonder if the problem with the porous beads we've seen is not from the welding process but from the quality (or lack thereof ) of the base material the frames are made of. It seems to vary when welding. Some sections laid down really nice beads while the ones next to the core support didn't weld worth a darn. All of them were cleaned down to bare metal before welding. I'm suspecting that this is some sort of pot metal or bad alloy mix....at least for ER70S-6.