Paint / coating questions for mild steel tank ice bath

[mightymig]

Hello!

Hoping some of the painting / coating gurus on here could help me with deciding what to do with the inside of a mild steel tank im considering for use as an ice bath.

- Will be around a 1000-1200 litre cylinder 3mm thick.
- Temperature of water will be 3-4 centigrade 24/7x365.
- Not using chlorine or other chemicals to treat the water (will be filtered and changed monthly)
- Outside of tank will be wrapped with closed cell insulation

Considering multiple options:

1) Epoxy primer (Lechler) + Epoxy Pond Liner
2) Epoxy primer (Lechler) + Fibreglass(?) / Gelcoat
3) Some form of liner?

If anyone has experience or advice when coating the inside of a water tank with super low temperatures it would be much appreciated. I want it to be durable for a long time and not have to **** about with things peeling or bubbling etc.

Cheers

 

[brightspark]

why not a grp lining

 

[hotponyshoes]

Why not just make it out of stainless and be done with it?

 

[mightymig]

Why not just make it out of stainless and be done with it?

I got given two massive pressure vessels and they're free hence thinking about using them...

 

[mightymig]

why not a grp lining

Definitely an option, its a cylinder with a hemispherical buttom and I would like it to be one piece without any seams hence thinking about coatings

 

[mightymig]

why not a grp lining

Wonder how well it would last at close to sub zero immersion?

 

[knighty]

how are you going to cool it?

I'm assuming pumping through a water chiller? or s chiller coil in the bottom of it? if so there's those fittings/ports to think about - makes a pond liner etc. a bit more tricky

I think you'll have to add something to the water to keep it fresh... salt would be an easy choice.... it'll lower the freezing point too so no freezing up around however you're cooling it either

 

[mightymig]

I have a 5kw cooling capacity refrigerated chiller with integrated pump - currently thinking through the fittings + ports, because its a pressure vessel it does have a fitting on the bottom already but as you say it then requires protection itself. Could potentially weld the fittings I want on, then coat the inside of them in whatever I use. Exterior threads could be left alone and dealt with as required.

Front runner for coatings right now is polyaspartic, and this one appears to have some form of 'food grade' rating and I think id get 2 coats out of it.

Just wondering if I should prime the tank first with Lechler because of the high zinc content - but then kind of defeats the point of polyaspartic as its apparently more flexible / resistant to movement with heat changes e.g. if I drain the tank and it suddenly gets a lot warmer.

The polyaspartic one also seems very chemical resistant so if I did end up adding chlorine, hydrogen peroxide or ozone then it may hold up much better. Its also specifically mentioned for use in cold chilled rooms etc which gives me more confidence.

Freezing wise to protect the condenser I was thinking about an inline heater for the winter with something like an inkbird to control the two replacing the PID on the chiller.

 

[hotponyshoes]

If your not going to drink it I'd expect Tap water to be fine for a month at anything under 5⁰.

Pub beer coolers only get drained once a year (and that's only if they are on a service contract) as long as they keep running/cool it normally comes out looking/smelling clean enough

 

[mightymig]

Yep general consensus seems to be keep the water moving by exchanging the tank about 3-5 times per hour, or use a bubbler. A 20 micron cheap filter also helps a lot as does showering off before hand. If you still have issues you can add UV lights, ozone, chemicals etc but it will be fine.

Just more concerned about lining the tank for rust prevention, and then whatever I line it with not falling off in a year

 

[Ross365]

Zinc phosphate primer https://www.palatinepaints.co.uk/product/carboxide-metal-primer/
Top coat from same company

 

[Erie Fred]

I got given two massive pressure vessels and they're free hence thinking about using them...

Is this something like an opposite to a hot tub ?

 

[Smallfry]

Wonder how well it would last at close to sub zero immersion?

It does OK on boats. Maybe speak to a resin supplier for advice.

I spilt some GRP resin on the road outside my mums house while "repairing" my first car while in my teens, and its still there, at least 47 years ago.

 

[mightymig]

Zinc phosphate primer https://www.palatinepaints.co.uk/product/carboxide-metal-primer/
Top coat from same company

Any reason to suggest this compared to lechler epoxy primer with zinc? Cheers