View Full Version : Protecting rear of welded piece?
03-22-2007, 09:10 PM
I am new to body repair. I am going to cut out and mig weld in a new piece of sheet metal to a Ford P/U cab. After the new piece is installed,how do you protect the back from rusting? If I finish it prior to installing won't the heat from the weld damage the protective coating on the rear? I am not to concerned about looks since the truck is 17 years old. I just want to keep the rust from expanding.
03-22-2007, 10:08 PM
Far and away, the best weld-thru primer I've used is that made by U-POL, second would be by Standox (and in my experiences Autotech and 3M made for poorer weld quality than plain old cold galvanizing spray).
Picklex is also a great product to use to prep prior to welding, but still calls for some sort of topcoating afterwards.
It's a debate...what does the heat of welding due to the coating...well, the theory is the resins are in fact not totally cooked off, the weld-thru coatings are basically a suspension high in zinc...it's what's out there, and I believe that in terms of what a quality product is designed to do, a good weld-thru primer does offer protection and isn't burned off...but do yourself a favor and spend the extra $ on U-POL becuase it's far better than the others in terms of making the weld process go smoothly (just be sure to not overapply it, and let it flash dry before welding).
Afterwards, it's a matter of access...if you get hold of a "flexible wand" you can use any host of a number of suitable products to schmutz something in there (perhaps a well placed / drilled access hole, later covered up w/ a plastic plug in the cab). You could shoot some epoxy, some thinned ZeroRust, and even enhance the protection by getting some "cavity wax" (like WaxOil) in there to seal the metal from the moisture. (if you REALLY have access, then getting some seam sealer over the edges would be great, but that's not always feasible).
Some areas are just prone to rot...the key is knowing where the moisture is getting in in the first place, and then ensuring their is adequte and proper drainage that's not plugged up, and air circulation to dry out any moisture that does find a way in.
If I can get to the inside seam I ALWAYS apply a good urethane seam sealer like Fusor 800 or 803. It's fairly inexpensive for the protection it offers and it won't crack later like other products and it's paintable. Great stuff!
Fusor Sealer Link (http://autobodystore.net/Merchant2/merchant.mvc?Screen=PROD&Product_Code=FUSSS&Category_Code=JASS)
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