Making a big box how would you do it

[Easywelder]

I’ve possibly got to make a galvanised box approx w3000 x d800 xh600 , with full width hinged lid, To not let water in, will have drain holes in bottom though, and probably doesn’t need a rubber seal round the lid. Oh it will reside on a beach so nice salty conditions. Doesn’t have to be very strong, if moved it would be emptied.

I don’t do a lot of sheet metal work.. Initial thoughts were to use pre galv sheet and bend 3 sheets to form the ‘U’ of the box and join them together, but there would need to be some other metal where the joints are and also additional strengthening or the whole thing would be too flexible, and these would need galvanising as well. I thought that was getting a bit complicated and unsure of galv sheet vs sea water especially any cuts in sheet..

Second thought is build full frame out of angle with something like 25x50 box for the bottom two 3000 lengths to stiffen it up. Seam weld 1mm mild steel to angle which can then be ground back to a nice almost invisible finish to look good. Same with lid angle frame and sheet welded along edge. Hot dip galv then stainless piano hinges, not sure if A4 is available.

Nor going to be cheap, materials alone be £400ish.

Any alternative ideas?

 

[gaz1]

better off with a plastic storage box

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or 3 of these

Black 320L Plastic Storage Box Garden Outdoor Shed Utility Cushion Chest Truck

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the plastic grit boxes have lasted well over 30+ years before they get replaced on the roads for the gritters so plastic should last well enough on the beach

wont be affected by the sea salt but will discolour with the sun

or galvanised angle iron frame using plastic cladding

 

[Blue Chips]

I’ve possibly got to make a galvanised box approx w3000 x d800 xh600 , with full width hinged lid, To not let water in, will have drain holes in bottom though, and probably doesn’t need a rubber seal round the lid. Oh it will reside on a beach so nice salty conditions. Doesn’t have to be very strong, if moved it would be emptied.

Just wondering about the purpose, which could make a difference in materials and methods.
I'm guessing maybe storage for something like a kayak, beach furniture, or?
How important is security?

 

[Bornfree]

Make it from stainless

 

[James1979]

Make it from stainless

That. Or, make a angle frame up, galvanise that then rivet galvanised sheets on with a bead of sika flex under them.

If you try to make the whole thing then dip it, it will twist.

Cold galvanised (Zinga) is always an option

 

[Blue Chips]

That. Or, make a angle frame up, galvanise that then rivet galvanised sheets on with a bead of sika flex under them.

I think that's a pretty good option. @Easywelder said he doesn't work much with sheet metal, and this approach certainly would simplify the sheet metal work (just straight cuts and no bends). It would be imporant to use galvanised sheet with a thick enough zinc coating to stand up to salt water/spray for a long time. I've seen some questionable "galvanised" sheet with pretty thin zinc coating...not much thicker than standard zinc plating...so one needs to get it from a reliable source.

As mentioned, there are also various plastic options, or even wood, depending on how the box will be used.

 

[James1979]

Unless they particularly want the galvanised look, it’s usually best to paint it anyway with a good marine paint. International or Jotun

 

[Blue Chips]

Unless they particularly want the galvanised look, it’s usually best to paint it anyway with a good marine paint. International or Jotun

I've used Rustoleum Galvinoleum primer on galvanised metal in the past for a couple of projects. So far, so good.
https://www.rust-oleum.eu/product/3202-galvinoleum

 

[Easywelder]

It is for oar storage, it wil be lockable but not hi security, it would be in a compound.

I agree hot dip with sheets on could distort, maybe ok as it’s got a frame work.

Riveting sheets on a galvanised frame may be favourite, just concerned any cuts on sheets would rust, but again may be ok as the zinc acts as sacreficial anode?

Plastic/fibreglass would be good, but has to be 3m though….

If galvanised why is best to paint it? Thought painted galv was just for cosmet reasons.

Cold galv spray wouldn’t last 5 mins in marine environment?

 

[James1979]

Cut sheet will be fine if you paint it with Zinga (cold galvanised). It is more than good enough for that environment. It’s what they paint pylons with. It’s approved by Lloyds register for marine use - we have used it at sea with no issues.

Painting the thing is partly for cosmetic reasons but it provides for an extra layer, or three, of protection. Again it’s a marine environment so it needs all the help it can get! Even got dip galvanised will last longer at the sea side if you paint it.

 

[cheb]

Build the box from wood and plywood sheet and the cover it with fibreglass roofing. You might not need the plywood.

 

[MCKDAVID]

Daft question, but does it have to be rectangular, 800mm dia galv spiral wound duct, two end caps, then cut a top hatch to suit. Make up some angle iron frame supports.
3m 800 dia duct would be around 200 quid, so not cheap but quick and easy.

 

[Blue Chips]

Riveting sheets on a galvanised frame may be favourite, just concerned any cuts on sheets would rust, but again may be ok as the zinc acts as sacreficial anode?

Cuts and scratches will receive some protection from the sacrificial action of the surrounding zinc, as long as they aren't too large.

If galvanised why is best to paint it? Thought painted galv was just for cosmet reasons.
Cold galv spray wouldn’t last 5 mins in marine environment?

Extra protection with paint is not really necessary if the metal is properly galvanised, but there's nothing wrong with an added layer of protection. Just make certain that any primer or paint you use is designed to adhere properly to a galvanised surface.

As to high-zinc-content cold galvanising spray, I've found that it works well if it is in direct contact with clean, bare metal. If there is rust or paint between the cold galvanising and the metal substrate, then all bets are off. Note that the cold-galvanising paint that I've used is fairly soft, so it could get worn off of high-wear places like handles, but in most places it should work well on bare metal. And of course, if you use cold galvanising and the paint starts to wear off, it can always be recoated.

I fabricated a set of steel posts to support the 30-foot struts that attach to our floating dock. I cleaned or ground all of the welded areas down to bare metal and sprayed them liberally with cold galvanising paint. That was 8 years ago, and there's not a speck of rust on them (see photos below, w/ American spelling). Granted, it's a fresh water area, but they are right next to the water and exposed to the elements 365 days per year. We take the dock out of the water every winter, but we leave the posts in place all year long.

As another example of cold galvanising applications, I built this stairway about 9 years ago and fabricated the two ends and two bends of the handrail from steel pipe. I ground the welded areas down to bare metal and sprayed them with cold galvanizing paint. The stairway doesn't get a lot of traffic (it's typically just me and my wife going down to the shore), but they have not been re-coated and are still holding up well, with no rust.

I would certainly not rely solely on cold galvanizing paint for your application, but it can be a useful adjunct to other corrosion protections.