Arc welding painted metal

Bk456

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I've just had my trailer reprinted and now it needs a small welding job, just one of the bars have come off the top horizontal section. Very small job, Ive never actually welded but I think given the job it will be ok. Friend at work has an arc welder I can borrow.

but should I grind back the paint and primer or will I carry on and the welder will bunt through what It needs to.

what can I cover the surrounding farm from to protect fro, splatter as don't want to have to touch up more than I have to after job"
 
Your not going to be be able to weld through paint, and also you need to be able to create a good earth through the same section. So grind back to the steal and and create and nice clear area. Then create a area for a earth ground out of sight. Now depending on the quality of the welder make sure the amps are down and try. Maybe if its not deep penitration maybe try a mig.
 
As stated by @kegnkiwi you need to grind it back clean or the weld will not take properly. Get a good earth on it. Prime and paint it afterwards. Don't cut corners mate or it will not last long.
 
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Cheers guys, we'll I have no option to MIG, very basic job, I thought an arc would suffice but then what do I know.....
 
If you've never welded before, best to practice on something that doesn't matter and gain some experience, it's not as easy as it looks. (This goes for arc, mig or gas). Arc should be OK if the steel is of a reasonable thickness. But it really does need some experience to do a decent job- quite satisfying though once you do get the hang of it.
 
If you've never welded before, best to practice on something that doesn't matter and gain some experience, it's not as easy as it looks. (This goes for arc, mig or gas). Arc should be OK if the steel is of a reasonable thickness. But it really does need some experience to do a decent job- quite satisfying though once you do get the hang of it.
Satisfying??? welding galvanised steel is a must then for you to most definitely try then Mr tron. :puke:
 
Satisfying??? welding galvanised steel is a must then for you to most definitely try then Mr tron. :puke:

I remember burning a shed load of galv bits when I was an apprentice... that smell

Luckily we are not allowed to do it now because of the nasties :)
@Bk456 Where are you? If you are local I can get a professional welder to help.
 
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I'm a metal worker so here's mytupence worth, as suggested clean off the paint make a good contact for the earth under the body somwhere, try to discover what thickness you are welding before you start anything under 3mm thickness will be difficult for a novice using 3.2 welding rods, if like most of the trailors I've seen these days it will be 18 gauge mild steel or lighter thats 1.024mm in new money so pretty thin if so you will need a 2.6mm rod or if you can get smaller all the better.
practice on a bit of scrap the same thickness, when you strike the arc the rod should be no more than the thickness of itself away from what you are welding if you do that and it burns a hole turn down the amps, it's not exact but try holding the rod at 45 degrees to the work you are trying to weld. thats the easiest way to get the hang of it when you get better you can change the angle to direct the heat,
if you are welding 2 different thickness'es say 5mm on the body frame and 2mm on the sides hold 70% of the rod towards the thicker metal and 30% towards the thinner metal you can play with these angles when you get better.
when you are welding slow down it is a lot slower than you think, you will see a small bubble this is the slag whick will come off afterwards but the most important thing you need to watch out for is just behind the slag bubble you will see a molten pool you want it to look like loads of CCCCCCCCCCCCCCCCCCCCCCCCCCCCCC closely together if it's a load of <<<<<<<<<<<<<<< you are either going to fast or are too far away.
if you see the slag lifting away from the weld as you continue welding rejoice, that's what you want, in an ideal world, ie clean non rusted metal thickness/angle of rod correct, you would expect to see the slag lift up in a curve behind you as you weld, if you don't see it don't beat yourself up it will bang off with a hammer if it's stuborn use a hammer and chisel let it cool down wire brush it, see if you can get a bit of Galvafroid paint it's very expensive but really is excellent paint
best of luck
Regards
D
 
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