Best way to prep front fenders?

[tocobill]

Going to be putting the front fenders back together here soon after my rsr flares are welded on. Fenders are in two pieces as of right now. All the gaps are set from fitting. Had alot of rust repairs in and around the inner fender cowl area and lower drainage area ... typical stuff. Its kinda a hard place to get paint to for rust protection. What is the best method of rust/paint prep before spot welding the two pieces of the fender back together? Ive heard Rust Shield by SEM is a good product. Can it withstand the spot welding heat? Thanks guys.

[962porsche]

there are a number of ways .
in my shop we tend to brush weld primer on the areas were the welds will be and then spray a coat of rust shield over the inner part of the rest of the panel were the heat of the weld will not cook the rust shield off . we just red pad the inner side of the panel then grind the pinch weld area down to bare metal . brush some weld primer on the bare area about a inch to a inch and a half over the pinch weld are then spray or brush the coat of rust shield over the rest of the back side of the panel .

[tocobill]

962 .. Thanks! I had a hunch that might be the way to do it. Am actually going to be using a spot welder so might keep the heat down more then say using a mig welder. Do you use SEM weldable primer or does any weldable primer work? So as long as I brush the weldable primer about an 1 1/2 inch from the fender fold where the inner cowl slips in I can paint the rest with Rust Shield. Is it worth hitting the primer with some cold zinc compound afterwards or does the primer do the trick the first time around? Thanks!

[962porsche]

yes we tend to only use resistance welders our selfs and it does not heat the metal the same way a mig and plug welding does .
we tend to use a hell of a lot of SEM products there weld primer also but any weld primer will do .

if the chassis is a bare chassis with no parts left on it we will go back over the hole inside and underside of the chassis once we are finished with all the welding on and cleaning up of the new panels and spray the hole thing with rust shield flat black and there hardener mixed 8 to 1 this will match the OE look of the chassis . this way if there is any bare metal at all left that you may have missed coating when your installing the new panels you will hit it then when your spraying the chassis for it final time .