rust

[TBD]

what can be put on metal before you do a lap weld so it want rust between the two raw pieces of metal?

[lotechman]

What you need to do is seal weld the joint. If oxygen cannot get between the faces of the joint then you will not get rust.
If you cannot seal weld the joint then use a good quality weatherproof caulk and run a bead of caulking where you have not welded.

[TBD]

I was thinking of putting high temp 1200 paint 1st then run a bead of silcone before I paint

[Rojodiablo]

Originally Posted by TBD

I was thinking of putting high temp 1200 paint 1st then run a bead of silcone before I paint

The paint will likely burn in there, at least part of it. The fumes could be nasty. I'd say at least clean the area where you weld to be sure there is no paint to burn through. It makes for a better weld.

[lotechman]

Paint between is a waste of effort. Seal weld is the proper approach. Silicone based caulks often do not take paint well. You would be better off with a paint compatible caulking. Also some caulking does not stand up to strong sunlight. All these things have to be taken into consideration.

[zapster]

Originally Posted by TBD

what can be put on metal before you do a lap weld so it want rust between the two raw pieces of metal?

canning wax..rub it on..(i know its steel)

and you can weld over it (with proper cleaning..wipe it down with a rag and some acetone) and weld away..
it wont hurt anything..it acts like a sealer...

i use it on aluminum all the time while grinding/sanding
but its been awhile since i actually did any of this i know...


my tig will be up soon enough...i hope

...zap!

[Sandy]

There are a lot of different little things a guy can do ahead of welding to make yourself feel better. But, if you weld it, really weld it, you're gonna burn at least some of it off around the HAZ. So I guess that brings up the point of whether a partial layer of protection is of any great advantage.

I'm with lotech. If not sealed there will still be water intrusion, and air, and it's going to rust right at the worst location, right at the weld line. The best way to seal up steel is with steel. If welding it closed is extreme overwelding or is going to weaken it then put your efforts into sealing it up some other way.

[bodyman]

weld thru primer. You can get it at an autobody supply. Wurth brand is about the best out there. 3m is lousy. Upol also makes a good weld thru primer-with copper in it....