Best primer after welding galvanised steel

[surfer4life]

Hi all, ive been searching threads on here but can't find a definitive answer.

I have bought a brand new door for my mercedes vario truck, but i need to extend the bottom of the door as it has had a step fitted when new. I have bought some galvanised steel sheet and will weld that onto the bottom of the mild steel ungalvanised door. What primer do i use to prime the welds and where the galvanised coating has melted away, and also the bare steel of the new door where the weld occured?

I actually bought some zinsser 123 plus as i thought that was what you used to prime galvanised steel before top coating, but now i had read the instructions it says not to use on bare mild steel as flash rusting may occur!!!!! £15 down the drain

I have read varying responses in different threads but none specifically relate to welding galvanised steel.

I also have some rust patches to sort on the body, so would prefer the primer to also be used on the bare metal before priming, or is that asking too much ;-)

 

[norsa]

I suspect most of us pros are wondering why you would want to weld galv into mild but its your choice. Be very careful of the welding fumes, give the whole weld area a good wire brushing immediately and probably prime with epoxy having scuffed up the surface. Pre weld priming is a good idea if you can not get to the weld area post welding. A decent weld through primer will do this but its not a paint preparation primer.
My opinion of course. Others may differ.
Nick

 

[surfer4life]

Because obviously i have been given the wrong advice ;-(

I know someone who panelled the sides and rear of his merc with 1.2mm galvanised steel, and said it was the best to use, i thought that as it was coated and i wouldn't be able to get to the back of the panel once welded it was the best way forward, i take it it isn't?

a decent weld through primer like what? sorry i have no idea about all this stuff, probably why my repairs start to rust after 12 months! Would etchweld do the job?

 

[steve t]

don't know much about paint but I use galvafroid to touch up welds when I have to weld galvanised steel

 

[surfer4life]

Steve, funny you should say that, i was just in my local hardware store and and asked if they had any zinc heavy paint, they produced galvafroid, so i was just trying to do some research on it before buying and you replied ;-)

if anyone else has any experience if galvafroid can they say if i buy this galvafroid, can i use on all the things i have posted above? i.e the rust spots will be grinded to bare metal, then galvafroid, then zinsser 123 galvanised steel primer, then the normal car paint undercoat, then top coat, then laquer? Probably some fibreglass and car body filler in there somewhere after the galvafroid.

 

[norsa]

getting the wrong advice is the reason we have decent sites like this one, so that you can get the right advice from people who have done the job properly, not just read about it somewhere. Galvanised stuff is fantastic if you don't cut it, weld it or want to paint it which is why it was used to panel a van I assume. His 1.2 I would consider 18gge (gauge) which is really chassis grade. I would use 21gge (0.9 1.0mm) mild steel for bodywork. As said, if you cant access the bare steel, post welding then I would coat it with a branded product like U pol weld thru copper primer. Never heard of etch weld. Post welding, I would wire brush and red scotchbrite the area before spraying a coat of activated etch primer, but im old skool. Never be afraid to ask questions, we all had to learn, I, unfortunately had to learn the hard way as there were no forums back when.

 

[zx9]

don't know much about paint but I use galvafroid to touch up welds when I have to weld galvanised steel

Good stuff Galvafroid you can tell it has a lot of zinc in it by the weight I have never painted over it though, I expect it would need some sort of mordent before you paint it just like new galvanised sheet does.

 

[blenkie1]

Welded loads of this on car transporters. Galv decking to mild steel. Galvafroid is the best stuff to use. Very expensive mind. We just primed the mild steel with mio guard I think it was called. It still used to rust mind. We started to use power bolts to fix the sheets down instead.

 

[anjum]

Lechler epoxy primer works on galvanised metal, Needs to be aged or lightly sanded first. See the instruction sheets.

 

[surfer4life]

Thanks guys, Norsa, the guy actually welded galvanised to his van, removed the rear doors and panelled over with galv sheet, the job looks awesome to be fair, but the pics are on facebook so can't link to it.

Where is the best supplier to get mild sheet from then that has zero rust on when it arrives? Ive had bad experiences in the past hence why i wanted to go galv.

Also as far as the rust spots go on the van what is the best to use on the bare metal that will seal it in case it it rains before i can get the fibreglass/filler on? my repairs have to be done outside as i can find anywhere big enough indoors to fit my truck in ;-)

 

[anjum]

Again Lechler epoxy.