Spray with ACF 50 prior to storage. When ready to take out of storage simply wash off and dry prior to using again.

It works for my motorcycles and prevents salt corrosion when riding on salt treated roads.

Relatively warm, dry and surface coated. Not much different than machine tools in workshops – of which there are several threads for their protection.

Edited By not done it yet on 26/01/2020 13:24:40

My biggest worry would be freezing, especially small pipes if not the boiler.
Next I would be concerned about soot residue in the tubes, firebox and smokebox. Ash and soot contain sulphur compounds which in damp turn to acid.
Whenever you look at an old machine tool, or lawnmower for that matter that was left in a shed or garage unattended since the owner died there is a film of rust on the top of the handles most noticeably not the bottom. This shows that it has bee subjected to falling dew, just like outside but still possible inside just in a smaller way. Yes dew falls inside your shed by the same mechanism as outside. So after your rust treatment be sure to cover with a cotton sheet or wool blanket using sticks to keep it off surfaces where possible. Don't or plastic or synthetic sheets/blanket. The natural fibres absorb the moisture and return it to the atmosphere when conditions improve.

When you read the machine rust related threads as suggested above you will notice that I always recommend clear Waxoyle or equivalent car uderbody wax diluted with white spirit.

Cover it up and place something like this HEATER under the cover so that it does not touch anything it has a thermostat. Low consumption. I have one in my workshop and not had any problems with rust.

Parked in a corner? 100mm of insulation all round and over, if not some underneath as well. Minimal heating required and some form of desiccation would be an advantage.

That is a bit like my ~12m^2 workshop. Nothing on concrete floor and has a fairly close-fitting, insulated, steel entrance door and some small gaps at floor level. It gets about half a unit of leccy per day most of the time and three quarters when ‘wintry’. A little more if I am working in there. The leccy is for running a desiccant dehumidifier for 2 or 3 hours per night. Ceiling height is 2.2m.

Here's an interesting review in the bike press, which doesn't rate ACF-50 too highly.
Note the methodology though, involving spraying salt water and repeatedly hosing down to simulate riding a bike over winter.

That said, I've been using ACF-50 on Landrover(s) and bikes OK, and it is designed for aviation.

I also like Motorex 645 "Protect and Shine", though I think it's been re-marketed as MotoProtect

The latter goes on nicely as a fine spray and doesn't seem to attract too much dust; when allowed to dry, it's barely noticeable. I've been using that on the bare alloy wheels on the Marlin kit car, and have only polished them properly a couple of times in the last 10 years or so; yes they still look OK, though I tend to avoid using it on salty roads.

Bill

Set on a medium setting. On high it runs continually & costs a fortune in electric.

……

Still get about 1/2 litre a day from the water catch box.

I collect about 1/2 litre for about 8p worth of leccy (3 hours run time). The heat is likely as useful as the humidity reduction. I don’t consider that too much to protect my kit.

Running any dehumidifier continuously, when not required, would be an obvious waste of money.