How to rust-proof a weld on the inside? - PeachParts Mercedes-Benz Forum

sanchezc · #1 03-03-2009, 02:57 AM

I have wondered about this for a while... Say that you need to weld a portion of an enclosed volume, i.e. whose interior is not accessible from the outside, e.g. the quarter panel:

Is it possible to properly rust-proof the weld on the inside?

rocky raccoon · #2 03-03-2009, 06:09 AM

Zeibart drills holes into the voids for the rustproofing wand then inserts a plastic plug. The holes are of course in a non visible area.

babymog · #3 03-03-2009, 10:03 AM

Zeibart around here is known as the rust creator, voids warranties and nobody I know would ever use it or any more drill&tar rustproofer.

Properly rustproof? Probably not. There will be no way to clean the slag and get into clean metal to protect. Any voids in the metal or slag will tend to accumulate and hold moisture and/or air.

The best thing I could suggest if you can't get to it is to try and spray some kind of penetrant into it such as a tenacious oil. If you are able to displace any air with oil, which will tend to repel moisture, it will help. Maybe a second coat with something more viscous to keep the oil from running away.

A friend used to make his own slurry from kerosene and some kind of tar, and spray it with a yard-sprayer, then leave the car over cardboard in the sun for a day. Seemed to work, really stunk and dripped, kind of the Ziebard/Tuff-Coat formula, be careful in these cases to not fill body drains.

LUVMBDiesels · #4 03-03-2009, 10:23 AM

Spray the weld area with U-Pol weld-through primer before welding it in place.

It is expensive, but cheaper than fixing the area a second time.

Oracle12345 · #5 03-03-2009, 10:35 AM

you can only weld bare metals together so really theres nothing rust proof when you weld. Ive seen enough MBs where they start rusting at the spot welds.

bgkast · #6 03-03-2009, 02:53 PM

I spray "spray Galv" into any overlapping areas before I weld. Do not spray it within 1/4" or so of where your seam will be.

PanzerSD · #7 03-03-2009, 06:39 PM

Fluid-Film. after the parts are welded and painted and all that, spray some in the wheel wells and rockers and what not and it creeps (through capillary action) up down underneath anything it can find. I'd seen work that was done on a trans am quarter panel that was rust proofed with fluid film. when we wrecked the car, the metal between the two surfaces still had MY felp pen marks on the inside of the panel after 15 years of Canadian winters and salt!.

Dee8go · #8 03-16-2009, 10:46 AM

I'm having difficulty picturing that. I may need to weld some new quarter panel sections into my SEC to fix rust. I was wondering how you would rust proof that myself. What's the alternative? I know Chad likes to use pop rivets and JB Weld. That would make rust proofing easier, I would think, but don't know how it would look for a repair like that.