when to use weld through primer?

[pukkapunto]

hi all, ive just bought a clarke 90 gas welder to fit some repair arches and sections on my MK1 Fiesta. only small jobs so im hopeing the clarke 90 is up to the job!

i have used migs before at college but i wanted to know when i should be using weld through primer?
all the time on all edges? or just if 2 sheets of bare metal
are put one on top o the other?

any info woud be good thanks
Rick

 

[malcolm]

I've never used weld through primer

Isn't it's purpose to protect metal that might be sitting around before welding rather than to protect seams and things after welding. It would just burn off around the welds like any other primer.

I tend to run with a good seam sealer after welding (for overlapped edges apart from those that will filled and painted) and a waxoyl on the reverse of the panel (or paint and seam sealer if you can get into it).

 

[dstealth]

Weld through primer can be used to protect bare metal that is exposed for a long time until welding commences. You are also then meant to spray it on the matal after you've finished welding because it is enriched with zinc which provides a cathodic protective layer from moisture dirt and rust from other panels etc. Just to give an example, I'm going to be putting a new boot floor panel in my citroen ds soon, and I've sprayed the lip that the boot floor sits on with weld through primer, as it is exposed, bare metal and also because I will be plug welding a new panel (ie. new boot floor) onto it. So that layer of zinc provides a barrier between the two panels, preventing rust.

Hope that helps

Chris.

 

[pukkapunto]

great thanks. i remember panel beaters at my old work spraying it on the newly prepaired edges of roof skins (similar to your boot floor) but i wasnt sure if it was used for everything!
wont need it for my repair arch panels then

thanks
Rick

 

[moler]

Just note on the quality of the product your going to use.

The first stuff that I used was from Bodyline and was great, and at just over £5 a tin reasonable too, the supply dried up as I think Bodyline were bought out so I had to find a subtitute. I found some cheaper on the internet from decorating-direct, it had good corrosion protection but very poor when it came to welding through so much so that I had to reprep the joints.

The only other I know about is the UPOL one, but I haven't used it.

 

[marks-welding]

re:welding through primer

you can only weld through primer, (as far as i know) using a arc welder and using certain types of rod that are designed to work so hot that the stick just blows the paint & rust & crud off before attaching it self.

 

[Shug]

Bilt Hambers etch weld is good stuff. I only use it on metal where its not possible to paint after welding.

 

[novaweld]

The u-pol stuff isnt bad, I was getting nice yellow rings around the plug-welds I did recently with it.

 

[dstealth]

you can only weld through primer, (as far as i know) using a arc welder and using certain types of rod that are designed to work so hot that the stick just blows the paint & rust & crud off before attaching it self.

That's not true. Using a MIG on weld-thru primer is fine. That's why classic car restorers use it.

Chris.