Welding and rust prevention - zinc paint?

[FastKat]

When you are welding two pieces of steel together, is there anything you should prep the steel with to prevent rust? I thought I remembered someone using "zinc paint" but I could be wrong. Is that frequently used? What does it do?

There is an obvious answer to this question... you can paint whatever you welded together. However, sometimes, after you start welding, you lose access to the back of your work and can't get any paint back there. That is the situation I am looking at, and want to try to find a way to keep the work from rusting from the inside out.

Thanks, -Dave

 

[Wackerjr]

You are looking for Weld thru primer..... I prefer the 3m brand seems to have the best zinc content.... and NEVER forget to shake the **** out of it, and clear the tip will plug up quick....

 

[zmotorsports]

If there is limited access to the parts such as inner panels of sheetmetal then I use a Weld Thru primer as mentioned above. 3M does make a good one. It is mainly zinc which bonds to the metal. Shake the can VERY well prior to spraying. I also store the can upside down because of it being such a high solids aerosol. This prevents it from settling at the bottle of the can and clogging the pickup tube.

If you have access to the parts such as heavier steel on a bumper or some other component that is not inaccessible after installation, I prefer to not spray anything on prior to welding. I will coat after welding/fabrication has been completed. Mike.

 

[asp]

I've used the Rustoleum weld through primer. It's about $8/can. Was a real PITA to weld to/through... I have to do more of the same stuff in the near future and I will not be using it.

 

[FastKat]

Thanks for the info guys!

 

[e-tek]

In addition to the Zinc weld - throughs, you can condition any metal for welding and to prevent rust with a phosphoric acid soloution. The one I use, Metal Ready (no affiliation!) has both Phosphoric Acid (turns rust inert) AND Zinc Oxide. When doing rust work, I ALWAYS use both, in addition to coating the metal with an anti-rust treatment or paint AFTER the welding.

 

[twarren]

In addition to the Zinc weld - throughs, you can condition any metal for welding and to prevent rust with a phosphoric acid soloution. The one I use, Metal Ready (no affiliation!) has both Phosphoric Acid (turns rust inert) AND Zinc Oxide. When doing rust work, I ALWAYS use both, in addition to coating the metal with an anti-rust treatment or paint AFTER the welding.

E-Tek, what form does the Metal Ready and Zink Oxide come in, spray or brush, and where in Canada do you buy it?

Warren...................

 

[Keep]

Also look at Galvanizing paint, same make up as weld through primer, half the price.

 

[atari]

I have used eastwood automotives weld through primer with good results. I welded full length subframe connectors under my mustang and never painted over it. Still looks the same as they did 2.5 years ago, and I drive it in the salt.

 

[bitbycarbug]

My welding teacher told us not to ever weld on the weld through primer. We could use it to get at inaccessible areas but clean the area where we were going to lay our welds(told us the only thing we should be welding is clean metal). My autobody teacher told us to weld right on it.

It does weld like **** and have seen techs weld on it while others won't. Any input as to which is the right answer( if there is one) is greatly appreciated.