# Forum Home Renovation Metalwork & Welding  Welding On an ID tag and Rust Underneath.

## abrogard

How to handle welding one flat piece of metal onto another? 
I recently took an ID tag - the number, you know - off a home made trailer. The man who built it stamped the number on a piece of steel, small 'label size' and then welded that onto the trailer. 
Water got between the two and the label and the fame steel got corroded nearly all the way through. 
I am going to have to do the same thing. 
So I make sure both surfaces are painted first.  I don't think he did that.  And then I make sure I weld all around so's there's no way for water to get in. 
The heat is going to burn off any paint near the weld so I have to rely on it  being a water tight weld all around - no tacking at this end and that end.  And could it still corrode?  Is there fractions of moisture in the air or even the steel or even the paint on the steel that can start corrosion later? 
I find it an interesting thought.  For there's large pieces of steel welded onto steel plate all over the world, on bridges and machines and everything.   How many are being eaten away by corrosion inside I wonder? 
Is there a known problem and approved method of tackling the job?

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## m6sports

Why not rivet it on instead of welding

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## abrogard

well rivets come off easy. 
best is stamped into the frame but overpaintings over time means they often get lost.

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## Marc

Get the biggest pop riveter you can find. If air/hydraulic better.
Get a galvanised flat bar, and stamp your numbers on it.
Spray some cold galvanising on the frame where the plate is going to be. 
Clamp the plate in place and drill 4 holes in the 4 corners and through the trailer's frame.
Get the biggest stainless steel pop rivet you can handle with your mega riveter and Bob is your father's brother.
Don't forget to spray some more zinc on your plate when you have finished, particularly the edges.

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## Bros

Bit odd compliance plates are aluminium and are designed to be riveted on the side of the chassis. Go to the rego mob and see if you can get a new plate.

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## Marc

Well ... I didn't want to go there. May be the NT?

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## ringtail

x 2. You must run the transport department compliance plate. You can't just make your own. Plates cost $7 up here and are just riveted. Standard 1/8th or 1/4 rivets are more than fine.

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## Marc

You can rivet the official plate with this though  :Smilie:  Geiger 9/32" Air Hydraulic Riveter Kit GP6304 | Get Tools Direct

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## GDOG

1) Clean both surfaces to be attached with metho.  
2) Apply sikaflex and stick both surfaces together.
3) Grab a beer and watch it dry.   
4) Wait a week and try to remove it.  Impossible without tools.

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## ringtail

Pretty sure the plate requires mechanical fixings

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## GDOG

No doubt rivets are specified for easy removal and replacement.

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## ringtail

Yep

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## PlatypusGardens



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## abrogard

Umm.  No one likes welding but no one says why. Is it because of what I was saying - the welding heat burns off paint and gal and leaves the metal ready to rust? 
For me it is the preferred way of joining things. Zap. Job's done. 
But I don't want to create what I saw on that thing.  Seems to me SHS gal - or ungalvanised but painted even - will get the gal (or paint) burned off with the welding which isn't going to matter much on the exterior where it can be painted over but on the interior of your hs frame there'll be a weak spot. Especially with boat trailers copping so much water.  Any old bolt hole in it could, would, let water in to start eating away from inside and bring you undone one day. 
Never heard of such a thing happening but that doesn't mean much, does it. 
Maybe the sikaflex and the rivets might be the best way. Looks to the law like it is secured and actually (apparently) is secured. 
I think compliance plates are a whole different thing.  Aren't they?  Like ID numbers like your engine number and chassis number are always stamped on the metal.  They might be repeated on the compliance plate but that's not where they "are".

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## Bros

> I think compliance plates are a whole different thing.  Aren't they?  Like ID numbers like your engine number and chassis number are always stamped on the metal.  They might be repeated on the compliance plate but that's not where they "are".

   I'm confused as the only numbers you need are on the compliance plate and they are standard made of aluminium with pre inscribed titles and you have to do the rest and it had to be riveted on. 
 Or are we talking about something else?

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## Bloss

I just arc welded the number directly onto the drawbar i.e.: used the arc to lay down the number & letter. Engraving works too. Compliance plate has to be fixed as per the rego authority requirement. As for the claim "Rivets come off easily" -  Only if they are wrong size, wrong type and/or incorrectly used - they can be drilled out, but if correctly specced (i.e.: steel, SS, ally, bronze etc) and used will last the life of whatever they are attaching to.

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## Bros

> 

    Might be alright for you crab pots but the coloured ones don't last. I suppose you cant expect much else for the $2 shops.

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## abrogard

Yep, I was going to weld numbers right on the chassis and then I had these doubts about burning off the gal. 
Plus my welding isn't too beautiful. 
What I meant by rivets come off easy is that a plate such as a compliance plate is easy ripped off when riveted.  Shove a screwdriver blade down the back and pull.  Who would want to do that?  Thieves.  Boats, boat trailers, trailers are all prime targets for thieves in these parts.  
There's no compliance plate required for home made trailers in south aus or nt that I know of and I've had a few but they need numbers and those numbers get copied onto registration docs if/when they get registered. 
Those are the numbers I'm talking about. 
But that's lost the point anyway. My fault for being anecdotal - i.e. talk too much.  My real question is how to weld two flat plates together without creating a rust hazard.  Especially when one of the plates is a side of a piece of, say, square hollow section?

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## Bros

> But that's lost the point anyway. My fault for being anecdotal - i.e. talk too much.  My real question is how to weld two flat plates together without creating a rust hazard.  Especially when one of the plates is a side of a piece of, say, square hollow section?

  There is only one way and that is to fully seal the welded plate be it by weld material or some other material that will not allow water or air in. Not an easy job for a home welder as you can get pinholes that cant't be seen.

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## abrogard

can you really?  I didn't realise that. would they be too small to see in the bright metal after you've ground your weld back to smooth it out? 
and inside hollow section it'd be hopeless unless you acid bathed the interior to clean it and then cold gal or paint the inside I guess? 
and i think many many hollow section tubes are pierced here and there with screw and bolt holes...  I even saw a boat trailer the transverse piece at the back - about two metres long - didn't have ends on it, was completely open to the air.  and the side pieces welded onto it and a centre piece too.  yep, it was rusted right out.

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## r3nov8or

Weld on 4 small (eg 5mm high) 'posts' for the corners and weld the plate to those. Then you have room to spray cold gal, inspect it, and it can dry out/breathe.

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## abrogard

And then the tag is always 5mm high?  Could work I guess in an out of the way place. Under the body on the side of pipe.  thanks for that. 
Found some interesting stuff about this kind of thing.  I wonder about the 'weld through' stuff this guy mentions: rust between spotwelded seams - Hot Rod Forum : Hotrodders Bulletin Board 
and this one is interesting, you download a pdf. https://www.google.com.au/url?sa=t&r...8B7cZFmF9LG-zw

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## r3nov8or

> And then the tag is always 5mm high?  Could work I guess in an out of the way place. Under the body on the side of pipe.  thanks for that...

   Just one more place to catch some skin on a trailer  :Smilie:

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## Bros

> can you really?  I didn't realise that. would they be too small to see in the bright metal after you've ground your weld back to smooth it out?

  They sure would be to small to see. What I have seen done with welds in high pressure pipe that had a pinhole which showed up in service was to penn the weld which fixed up any small imperfections.

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## abrogard

"penn" a weld?

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## Bros

> "penn" a weld?

  Yep what I said it closes up all the pinholes.

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## r3nov8or

> Yep what I said it closes up all the pinholes.

  Do you mean p*een*ing a weld?

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## Marc

If the tag is hand made and I don't want to know why, All you need is a dremel and engrave the numbers on the chassis. No need for anything else.

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## Uncle Bob

Peening hammer(ing)

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## Bros

> Do you mean p*een*ing a weld?

    What's a misplaced "e" its the thought that counts

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## abrogard

> If the tag is hand made and I don't want to know why, All you need is a dremel and engrave the numbers on the chassis. No need for anything else.

  yup, no need, but a desire - like i said, coats of paint and it gets lost...

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## ringtail

If there is no need for a compliance plate with a home made trailer but you still want / need numbers on the trailer, just go and get a letter/ number punch set from the tool shop a punch the number into the chassis. Done.

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## abrogard

see above

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## Marc

I have the perfect solution. Use your welder to write the numbers Mythbusters' style on the chassis. 
No matter how many coats of paint you will still be able to read the numbers.
Now all is left is get the numbers and play them on next week's lotto.

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## abrogard

see #18

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## Bros

If you insist on welding most trailers have a triangular piece of steel for the coupling attachment. Weld the plate on to the back of this which will be butted up and as it proberbly is only a piece of 6mm plate welding on this will not destroy the galv on the chassis rail. Make sure it is above the chassis rail so any water that gets under it will escape.

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## Marc

> see #18

   Mate, I am not sure what answer you want. You either weld the numbers on, weld the plate on, stamp the numbers on, engrave the numbers on, rivet the plate on, screw the plate on. There are not many more combination of this very basic job.
If you weld the plate all around, even if you don't do a nice job, you can seal the weld with paint. However would be thieves can grind your plate off easy. Numbers punched or engraved on the chassis are harder to conceal. You concern that paint will cover the numbers is noted but paint will also conceal the numbers on the plate. Furthermore how many times in your lifetime will you paint the trailer? 
Two pieces of metal welded against each other will not rust if oxygen can't get to the steel in question. The same reason painted steel does not rust if the paint is not damaged.

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## PlatypusGardens

> Mate, I am not sure what answer you want. You either weld the numbers on, weld the plate on, stamp the numbers on, engrave the numbers on, rivet the plate on, screw the plate on. There are not many more combination of this very basic job.

   :2thumbsup:

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## abrogard

> 

  Yeah, you don't get the question. It is not about how many ways to do a job. See post #1. 
We addressed it pretty well, see posts #18 - #24. 
Most of the other posts were addressing associated questions concerning such as riveting. 
Myself I don't mind people bringing in associated and tangential issues to a discussion, even just having a chat, doesn't worry me. 
But if it exasperates you in any way - and I can well understand certain temperaments would be exasperated by what they'd see as time wasting perhaps - then might I suggest it may be better to turn your attention to a different thread perhaps better suited to your temperament and perhaps more in need of your expertise? 
We were actually getting along quite well. 
In fact we were just about finished.  See posts #18 - #24

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## PlatypusGardens

> Yeah, you don't get the question. It is not about how many ways to do a job. See post #1. 
> We addressed it pretty well, see posts #18 - #24. 
> Most of the other posts were addressing associated questions concerning such as riveting. 
> Myself I don't mind people bringing in associated and tangential issues to a discussion, even just having a chat, doesn't worry me. 
> But if it exasperates you in any way - and I can well understand certain temperaments would be exasperated by what they'd see as time wasting perhaps - then might I suggest it may be better to turn your attention to a different thread perhaps better suited to your temperament and perhaps more in need of your expertise? 
> We were actually getting along quite well. 
> In fact we were just about finished.  See posts #18 - #24

  I'm exasperated?  :Unsure:   
Yes, you did (eventually) make yourself clear (in post #18) _"My real question is how to weld two flat plates together without creating a rust hazard. Especially when one of the plates is a side of a piece of, say, square hollow section?"_ 
Perhaps the thread title was a bit misleading?   :Wink:  
Marc's post, which I quoted and gave two thumbs up, has merit and I liked it.
No skin off my back, nor does it have anything to do with temperament. 
All is well.   :Smilie:   
*shuffles off to the shed to do some welding*

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## ringtail

FFS, get a proper plate from the transport department and rivet the f##ker on there a be done with it.

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## Marc

> FFS, get a proper plate from the transport department and rivet the f##ker on there a be done with it.

  You could tig weld the official aluminium plate all around to a bigger thicker aluminium plate and then bolt the aluminium plate to the chassis with through bolts and then weld the nut end of the bolt to the chassis. Paint may be necessary on the aluminium plate to avoid galvanic corrosion ...  :Smilie:

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## m6sports

After 42 posts I hope a decision was made 
if not just sell the trailer and buy on with a plate already attached it seems like it's too difficult of a choice  :Smilie:

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## ringtail

> You could tig weld the official aluminium plate all around to a bigger thicker aluminium plate and then bolt the aluminium plate to the chassis with through bolts and then weld the nut end of the bot to the chassis. Paint may be necessary on the aluminium plate to avoid galvanic corrosion ...

   :2thumbsup:  :2thumbsup:

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