Rusting metal to practice on?

[GeorgeB]

I hope to try out each of MIG, TIG and Arc welding on some scrap metal before I go anywhere near a rusty old panel on my car. I came across this old side plate from a lawnmower. The steel plate is no thicker than car bodywork and might be a realistic panel to practice on. Another bonus is that it's well-rusted, especially on the reverse, just like a typical old car wing or sill panel. I will cut out small sections and weld in some new metal plates: (1) MIG (2) TIG and (3) Arc although probably not in that order. It will be interesting to see how the three patches compare.

QUESTION: for this to be a realistic practice piece, should I de-rust only the front of the panel, as you would certainly do on a car, back to bright steel. Or should I de-rust both sides? On a typical, average car repair are you normally able to get behind the panel which needs a patch, in order to de-rust it?

UPDATE: in reply #3, TIG Paul very helpfully pointed out that my lawn mower plate is "a pressing so apart from the rust the material may not be an ordinary mild steel, and won't give you the experience your looking for." I'm sure he's right, so I won't be using this sample, after all. I will look for some rusty old metal off an old car, instead.

 

[Drains]

You need to de-rust wherever you're welding George. I wouldn't worry about the other side. But if you are going to do anything remotely like proper practice then you will have to do joints, not just put runs onto metal. Do you have a local fabrication company, or even a diy store who can give/sell you some 1mm or so offcuts to practice on?

Rusty lawnmower sideplates are really not the ideal place to start.

 

[Paul.]

I'd sling that in the skip George, Its a pressing so apart from the rust the material may not be an ordinary mild steel, and wont give you the experience your looking for, as Simon says, a local sheet metal shop or fabricator would be the best place to look, or why not look for a car repair shop and see if you can scrounge an old wing or door skin to play with,

 

[aero]

Rust gets included in a weld. Welding 'over'it isn't an option.

If you intend to weld up a car, you'll pretty soon find that you have to remove all the rust if you stand any chance of effecting good welded repairs.

For realist practise try welding some clean steel the same thickness sheet as you will use to make repirs. You will soon see how rust gives bad results when you start to weld rusty steel instead of the clean stuff you practiced with

Good luck with the MMA on that! (can offer some pointers on welding thin sheet with a stick welder)

 

[malcolm]

I'd not start with 1mm offcuts - better trying 0.8mm at best. Car panels are not all that thick. Renaults are often made from 0.6mm so I'd encourage that thickness for any test.

Design of Experiments is a fun topic (actually it's no fun at all and a real pain - but I've done a whole lot of that in the past and might be able to help).

Could you clarify what you are trying to achieve - ie some parameters such as can you spend more than £100 on each welder? And then are you allowed to fiddle around with the welders to improve them? That sort of thing. It's important to base experiments on some criteria such as who is doing the welding, what equipment is allowed in the test, etc. After all that most experiments are perfectly reasonable and many become useful.

Apart from that I'd go for new clean steel. Design of Experiments will be difficult enough without people questioning whether you've welded a different bit with each welder.

 

[GeorgeB]

Many thanks for such helpful posts, so quickly.

SD - I know it's essential to de-rust as far as one possibly can. But from others' experience of renovating cars, how often is it possible to de-rust the reverse side of say a bit of wing or sill panel, where you need to patch in a new section of metal? I know you could sort of wipe a bit of sandpaper and dab on a bit of Kurust 'round the back' of the hole you've cut out, but how often can you go much further than that? My aim is to create 'real world' car conditions with that test panel, and see how I get on.

>You need to de-rust wherever you're welding George.
I could remove every last molecule of rust from that mower panel using electrolysis but I can't do that with a wing or sill in situ on a car, so it wouldn't be a fair comparison, i.e. the test would be too easy from the rust standpoint.

>I wouldn't worry about the other side.
Should I leave most of the rust there, then? Will MIG, TIG and Arc all take a rusty rear panel in their stride?


>But if you are going to do anything remotely
>like proper practice then you will have to
>do joints, not just put runs onto metal.

Yes, that's the whole idea, to cut out a patch and weld back a new patch, with seamed welds all round, like for a car MOT.

>Do you have a local fabrication company, or
>even a diy store who can give/sell you some
>1mm or so offcuts to practice on?

I have plenty of 1mm and 0.7mm metal already but the rust seems to add a real-world challange, just like I face on the car. 1mm new steel seems too easy when I face something like 0.7mm sheet (as new on the car) less at least 0.1mm rust erosion all over = 0.6mm to weld.


Paul

>It's a pressing so apart from the rust the
>material may not be an ordinary mild steel

Good advice, thanks. I wondered how they did the edges, so if it's a fudamentally different type of metal to car bodywork, then you're right - it will be a waste of time. Yes, perhaps I should go to a car scrap yard or body shop and ask for a rusty old wing. I specifically want a rusty old panel to practice on, so it's closer to what I face on the car.


Aero

>Rust gets included in a weld.
>Welding 'over'it isn't an option.

How do you mean by 'included', please? Do you mean it's an undesirable contaminant? I just thought that on many car repairs it might be inevitable, just for the rear of a panel where you can't always get much access. I wanted to see how each of MIG, TIG and Arc dealt with that.


>For realist practise try welding
>some clean steel the same thickness
>sheet as you will use to make repirs

Stage 1 practice will be with clean steel but I thought I should then move on to some practice on rusting steel for it to be like the real world on an old car.

>You will soon see how rust gives bad
>results when you start to weld rusty
steel instead of the clean stuff you
>practiced with

I know you're right but I fear it might be inevitable on the car. Or do you need to remove a whole wing or sill to ensure you get rid of ALL the rust before welding a car?

>Good luck with the MMA on that! (can offer
> some pointers on welding thin sheet
>with a stick welder)

Great. Do please help on the current thread about welding 0.8mm steel, under the arc welding section of the forum.


Malc

>I'd not start with 1mm offcuts - better trying
>0.8mm at best. Car panels are not all that thick.

That's my thinking too. My 'new metal' practice is on 0.7mm or 0.8mm steel. I know I'll be down to 0.5mm or 0.6mm by the time much rust erosion is taken into account on a car.


>Renaults are often made from 0.6mm

Do you mean 0.6mm from the factory, less any rust making it even thinner?!


>Could you clarify what you are trying to achieve

Yes, I'm trying to develop the ability to do seam welds to MOT standards, to repair some rusty holes on my car, or to be ready for when any appear. That's almost my sole objective as far as welding thin steel sheet is concerned.


>some parameters such as can you spend more than
>£100 on each welder?


I already have (low cost) MIG, TIG and Arc welders. The only one I've used so far is the arc welder. The hobby side of it - the experiment - is simply the challange of seeing how far I can get with the arc, before I move on to MIG and TIG.

>And then are you allowed to fiddle around with the
>welders to improve them? That sort of thing.

Yes, that's what I want to do, just for fun, as a challenge.

Thanks again.

 

[Omniata]

"Oxalic acid" is a good thing to use for de-rusting after you've done a good job with a wire brush.
It complexes the Iron salts and strips them and isn't that agressive so tends to leave the clean metal alone.

A quick wash with some very dilute caustic will remove any trace acid and you should be down to clean metal. Thoroughly anti bacterial combination with oxalic acid too, but then again were not going for the "sterile" market with a door panel hehe...
Caustic will strip any residual paint too...

Another thorough rinse and your done...

Regards,

Jim.

 

[Drains]

Blimey George! Some reply.

1)Ok - de-rusting. Forget electrolysis. Use a grinder and a flap disc/ fibre disc and backing pad. Edit - I like Omniata's Oxalic acid suggestion - i've only ever used it on wood.

2)The other side - if you're not putting weld on it, it's not a problem (until later, when the rust keeps eating away at the panel - get the Kurust etc in there)

3)Try to avoid butt joints if you can't clean or if the steel will end up too thin after cleaning - use a joggler to offset the panelling.

4)Mig will handle a bit of rust - the odd pit here or there. So will arc. So will tig TBH, but it's far from ideal, and more difficult.

5) You have to cut out rot and replace with new steel. It's the law. (say that with a silly french accent though)

6) You won't get anything done by asking questions. Although it may help avoid a few mistakes.

Advisory note:- Seam welding to MOT standard is not difficult, and bitumen-based paints hide a multitude of sins. You will be accomplishing this by removing steel too thin to weld with 0.6mm wire on a mig, with argoshield style gas, and replacing it with other, new metal, and fixing it in place, then painting it with thick black stuff. You don't have to show off to the MOT man, you just want it so that when he hits it with a hammer or stabs it with a screwdriver, he doesn't make holes, and bits don't drop off.

Now, George, you have a stable of welders. Go out and ride them!!!!!!

 

[Iain Westland]

find a car panel sales shop, most large towns will have one and they will sell 20 guage sheets of steel.

you can only weld to decent metal (nissans are the worse for me, fag paper thin) so make sure you clean it right off and get a really good earth.

all the mot stations around here want is that the 'hole' is completely covered and the new metal seem welded.

find out where the local taxis get their body work done, theres always spare nakered panels there to take away and practice with.

hi ho silver

Iain

 

[GeorgeB]

Great responses, thank you.

Jim - I guess the main component of 'Kurust' might be Oxalic acid or something similar. Any idea where one can buy Oxalic acid?

Simon - Electrolysis remains my preferred rust-removal method but only where it's practical! Rust removal on the visible surface is not my concern, really. I can deal with that, back to bright steel. It's how one removes rust behind a panel, when there's no easy access - that strikes me as the challenge, to facilitate a good welded joint. I guess you just do the best you can, and remove as much rust as possible from the back of an almost inaccessible panel. I like your idea of using a joggler - whatever that is. Does it fold metal back and double up the panel thickness, or anything like that? I must find out. I know I have to cut out rotten metal and replace with new steel - that's what I want to practice. But even the 'good' steel which is left will have been thinned by gradual rust erosion, all over, for years/decades. This metal can be so thin (a) I wonder about the safety of any old car and (b) it can't be easy to weld by any method.

Iain - perhaps I need to practice on scrap Nissan body panels! Anything afterwards should be easier, if they are so thin. Thank you for the body shop tip for getting old panels.

 

[Splatfest]

I like your idea of using a joggler - whatever that is. Does it fold metal back and double up the panel thickness, or anything like that? I must find out.

Its one of these it just puts a step into the panel (about 10mm ish,and about the depth of the metal thickness) so you can overlay the new metal creating an overlap.The head of the joggler swivels 180 deg and the other side is a hole punch.With this make the holes in the new panel so you can plug weld to the old "stepped" panel.The seam is then seam welded, cleaned up with a flap disc and skimmed with filler for an invisible repair,if that makes sense.

Re cleaning the back of a panel.As Mr Drains says youre not putting weld on it,so it doesnt matter,however you don't want any further rust to develop so it needs some protection after you've done welding.Thing is you're limited by what access you have to it.

Plenty of room-wire brush attachment/Kurust/paint

No room- Errr not much option really except maybe drill a hole and squirt gallons of waxoyl in

The way to learn is for your 17 yr old daughter to turn up with a rusty old banger of a car and say "Look what I've bought dad" This is what happened to me and although I've been welding (amateur shed/garage based stuff) for quite a while I'd never welded car bodywork before but I managed to change both sills after having repaired the inner sills and got it thru the MOT.The MOT man commented on it being repaired to a good standard which is down to the advice found here,having a look at how others tackled similar jobs and some practice.Read through Malcs tutorials,they're excellent,especially the "welding thin metal" one.Then having read those have a read at some of the restoration threads on the Turbosport forum for inspiration as to what can be "saved".No amount of reading though is substitute for getting in the garage and having a go.

 

[GeorgeB]

Splatfest - many thanks for helping me understand what the joggler tool does, when I couldn't really work it out from Frost's description, which I'd previously found. So, if I understand correctly, it puts a lip just in the outer (original) panel work - if you're patching a hole and you then put a flat piece of new metal on top?

Will the joggler work on both circles and squares (holes) of, say, 3" across?

If you did a simple butt weld on a hole 7.5cm across (about 3"), the patch would be almost exactly the same size. But after putting a lip all around the circumference/edge of the hole, the new panel would need to be larger by about 2x10mm across. Is that right?

This tool looks worth buying. Thank you everyone for pointing it out.

 

[Omniata]

You can pick up loads of Oxalic acid off eBay lol... Reasonably priced too...

Word of warning with it though, don't get it on your skin or eat it or its salts, it's only a mild poison but safety pays huge dividends...

That's how our government successfully poisoned a large proportion of the population during one of the great wars by getting the people to eat Rhubarb leaves which are high in sodium oxalate. Essentially what you'll be making if it mixes with caustic...

 

[aero]

Oxalic acid is I believe used to correct the Ph of swimming pools. It is also sold as Deox-c by bilt hamber. A google search of deox c will bring it up.

This is much better the jenolite or kurust as it removes the rust, where as the latter just convert it. Chemical treatment is never really used though on sheet.

However as has been mentioned an grinder or flap wheel make a good enough job. I used to have a friend who was a sheet metal worker. He always cleaned both sides or car panels. Often you can olny get to a small area of the rear of the panel, but he'd still clean the metal to leave it bright both sides of the weld.

Going out and doing the job is way more useful then sitting on here writing reams about how to do it

 

[ben8vgte]

there's only one way to learn how weld up rusty cars and that with one, get an old mot failed fiesta for £20 patch it up and sell it on should make just enogh for some welding wire and tea bag. You'll quicky learn to get a clean weld after you've burnt yourself all over for a couple days. I only ever use a flap disk to clean up before welding as paint wont stick to chemicals and if your underneth the last thing you want is acid dripping in your eye's.

 

[Splatfest]

Splatfest - many thanks for helping me understand what the joggler tool does, when I couldn't really work it out from Frost's description, which I'd previously found. So, if I understand correctly, it puts a lip just in the outer (original) panel work - if you're patching a hole and you then put a flat piece of new metal on top?

Yep thats about it.Although there is nothing to stop you joggling (is that a real word ) the patch and punching holes in the edge of the original panel

Will the joggler work on both circles and squares (holes) of, say, 3" across?

Hmm never tried it on a circle but I would imagine it would look a bit of a dogs breakfast on that tight a radius.Yes to the squares.The limit is getting the head of the joggler in,thats when you switch to joggling the patch instead of the panel.(Provided of course you can put the patch in place from the rear.)

If you did a simple butt weld on a hole 7.5cm across (about 3"), the patch would be almost exactly the same size. But after putting a lip all around the circumference/edge of the hole, the new panel would need to be larger by about 2x10mm across. Is that right?

No its the opposite,the patch is slightly smaller as you have a radius where the joggled panel "steps down" so to speak.See crappy pic below

 

[GeorgeB]

I was going to throw away my rusty old lawnmower panel (see photos in post #1) but, before I did, I thought I'd have a crack at arc welding it, just to see what happened. As mentioned above, I hope to try out each of MIG, TIG and Arc welding on some rusty scrap metal before I go anywhere near a rusty old panel on my car. This is very thin pressed steel.

I welded on to a patially prepared top and a zero-prepared rust-ridden reverse side. Here's the top of the arc weld, just like might be the sill of an old car.

and here's the reverse side straight on to rust. It looks OK. The rust appears to have been blasted out of the way.

I'm packing away all my arc welding gear now because, for my limited needs, I think I've just about 'cracked it' on both thick and thin metal. The next time it will come out is when I need to use it on something. I will now turn my attention to learning MIG welding, with a special interest in gasless.

 

[Wozzaaah]

Are those blow-holes either end of the welds George?
We look forward to your gasless exploits, good luck .

 

[GeorgeB]

Are those blow-holes either end of the welds George?

Yes, but I was still pleased because there's a good few inches in between. I think it demonstrates how challenging it is trying to weld any thin, rusting metal, regardless of the type of gear used. I hope I could fill the holes in quite easily on a real job and/or limit each weld run to 3 or 4 inches, to help prevent heat build up. One of the holes was at the start, which is always a bit difficult. The idea of using a run-on panel seems useful but I didn't do that here.

 

[Benji]

Very impressive George! Did you join two pieces of metal together or just run a bead on the surface of a single piece, if that is the case, do you feel that there will be much call for this when you come to repairing your car?
cheers, Benji