Any suggestions as to how you removed the 'contamination' for want of a better word.
I'd suggest taking a torch and pre-heating the area you are going to weld to 400 F. That should help drive off moisture and contaminates.
Fire... it's been used to solve problems since we started standing upright

Did you try the torch? If you don't have an oxy-acetylene use a hand held propane torch...
Got 'er done,there was still a fair bit of spattering,it ain't pretty but it'll do,you'd need to be a limbo dancing snake to see it anyway plus it's a driver not a show truck!
Once again thanks for all the input guys.