Rust proofing inside hollow tube

[Thrashsmith]

Hello all, I hardly ever get things galvanized, so I'm ruling it out as an option in this circumstance, even though I know it's the best option...
I'm pricing up options for a bespoke wisteria arch that my client wants to paint themselves. One idea I have would require two pieces of 30mm square hollow tube to be rolled to curve.
The cost of getting the parts galved would be crazy because the minimum order charges + return delivery would be more than the cost of the galv itself.
So if I do it in a way where I can cap both ends so it's properly sealed, what can I pour inside the tube to keep it from rusting from the inside out with condensation? Vegetable oil?
Thanks

 

[gaz1]

give the option to the customer advising what will happen per choice then in except only in writing there choice

this saves you from any claim when the unit fails as it does

as seen it from a next door neighbour held back payments claiming unfit for purpose and just leads to small claims court

nowadays its cover your backside otherwise customers will have you over a barrel

 

[colnerov]

Try flooding it with Argon shielding gas, it is inert and heavier than air. Then weld a cap on.

 

[julianf]

A note on hot dipping -

My local plant has all the moq surcharges etc. And even after those, seems to load the pricing massively.

My stuff goes to an agricultural fabricators a stones throw away, and goes in with their stuff. It's all above board, invoiced, vatted etc. Its not a favor to me, but just a service they offer.

My last load was a landrover door frame, a pedal box and a gearbox tunnel. Charge on the whole lot, with the vat, was £35.

Would have been hundreds at the local plant as a walk in.

 

[Onoff]

I built a box section arch circa May 2023 for the pub and it still looks like new. I squirted ACF-50 inside all the sections.

Thread 'Garden Arch'

Apr 2, 2023

I need to make a garden arch, 3 in fact but one immediately. One is to replace an existing curved arch. The other two can be the same. I don't have a ring roller, another "one day" project, I got as far as buying some bearings to make one like @KimB did but to specifically roll this stack of box. So in the meantime this will be a cut and shut job. Some quick CAD:

Doing this outside today so thinking MIG is out. I've a stack of 25x25x2 box and a box of 6013 2.5mm Superon rods been kept dry.

Thinking printed card templates to transfer the angles from the...

• Onoff
• Replies: 62
• forum: Architectural

 

[tigdlo]

If it were me it would galvanised or I would be taking no responsibility for corrosion as the customer wants to paint it themselves, sounds like they want to save money so probably won't be buying the best paint either. As soon as you try to prevent corrosion you are making yourself responsible for it. If the customer wants some kind of guarantee there will be no corrosion they either need to pay for it or take responsibility for it themselves. can you regisign out of solid bar and advise them it will need the coating maintaining to prevent corrosion?

There must be a way of getting galvanising done for sensible money, my local was cheap enough I think it was £0.60 per kg total job was £45 I think.

 

[Screwdriver]

I'd flood it with primer a few times to get 2-3 coats then bung the ends with plastic, err, bungs. They should be easily available for most box sections and are more garden friendly at the very spot where rust wants to develop.

 

[tom2207]

theres always acf50,,, or the likes ,, better than nothing , I find things like that can come back all shapes from galvanising ,, or make it from angle, solid bar , or stainless ,,

 

[Gareth J]

As above, all ours goes via a local fabricator. Last week, I ordered some bits from Brundles but mistakenly ordered one post self colour. Dropped it in with their stuff and should be back next week. I expect it'll cost less than £5.

Regarding your box, with respect to just painted, don't stress about it too much, it's free draining and will take decades to rot from the inside out. You could blow waxoil through it with a lance to give a bit of protection but the outer paint layer is the more important one. I wouldn't try to seal it up, you risk more issues with expansion/contraction dragging in damp air through a pinhole and the following inevitable condensation having nowhere to go than you do leaving drain holes at the lowest bit imo.

Alternatively, you could consider making it from a slightly narrower solid bar. It'll look like it has more permanence (estate style) and probably won't add masses to the materials bill. But maybe it's too tricky to work with.

 

[Redsailor]

If it is capped both ends and therefore airtight It will not rust inside. The small amount of oxygen trapped inside would soon be depleted and there would be no rust. The only drawback to this is if the customer starts drilling large unsealed holes after installation.

 

[bricol]

I cut up a Dutton kit-car chassis - circa mid-80's I would say. I was pleasantly surprised to see little to no corrosion inside - no visible signs of anything sprayed inside to protect it.

However, another one I also cut-up, had had plenty of holes drilled in it by various owners over it's life - so that one was pretty rusty, to the point of failure, inside.

I used some box section for fence posts for my mum 30 plus years ago. I welded a cap on one end, then tipped paint inside it, angling it and rotating it so all faces were covered. Fence was still up two years ago when the house sold.

 

[Agroshield]

So if I do it in a way where I can cap both ends so it's properly sealed, what can I pour inside the tube to keep it from rusting from the inside out...

With any oil, I would be slightly worried about fire/explosion when welding on the second cap.

Perhaps make one of the caps with a female thread then you can do all the welding and afterwards pour in the secret sauce. PTFE tape on the male threaded cap cap.

 

[Onoff]

Yep, still good, as inebriated as I am:

 

[Bornfree]

I would use petrol. That square tube would very quickly turn to round and look far better.