If the shop is not insulated, adding insulation will bring great benefits, not only in reducing rusting, but in comfort..
As already said, temperature changes tend to encourage rusting. Insulation slows the rate of change.
For steel to rust, it needs both moisture and oxygen. A workshop without oxygen is unlikely, (not to mention lethal without breathing apparatus), so minimise the moisture content of the air.
It is taken as read that there is no water ingress to the shop, from leaking windows, walls or roof..
For a start do not use WD40 on the machines, (It is hygroscopic, being Kerosene based, with minimal oil content). Coat exposed surfaces with oil (I used fresh engine oil – NOT used which will contain acids and definitely produce rusting). In an uninsulated, unheated, 5 x 7 ( 1.52M x 2.13M) wooden shed, the oil would be emulsified (grey) but the moisture did not reach the machined surfaces of my Myford, to cause rusting.
The downsides were having to wipe down everything before starting work, and then recoating afterwards..
Do NOT use any form of combustion heater, solid, liquid or gaseous fueled. One of the combustion products is water vapour, and the rest , even the non poisionous parts; do not support life, (yours included).
DO insulate the walls, and ceiling, and if possible the floor. Polystyrene sheets between the verticals on the walls, and the rafters on the ceiling, is an easy way. Ideally, use glassfibre,and overlay with ply.
(Hardboard will eventually warp) The chap who built my shop used 12mm ply "You'll be sure to screw things on there". He was right!. Where else would all the shelves be fixed?
Windows can be insulated, minimally, by fixing polythene sheet over them; sealed to the frame if possible. Acrylic sheet would be more durable, and probably absorb less light.. The ideal would be double glazing, (even triple in a very low temperature region of the world) but only really practical for a new build, or major upgrade.
My shop has no windows (security, plus shelves would be fitted across them anyway), and has 19mm external wooden cladding, on 50mm frames with glassfibre between that and the 12mm ply internal walls.
The pitched roof is 12mm ply fixed each side of 50mm frames with glass fibre insulation between. After eleven years, it now has a one piece 1.6mm EPDM rubber covering in place of the original single layer felt.
The floor is uninsulated 18mm ply sheet, sitting on 200mm x 50mm wooden bearers, which are only open at one end. The small walked on area is covered by 25mm deep plastic mats. The rear wall is sheltered by a 1.8M high wooden fence.
A 60 watt tubular heater under a bench keeps the place suitably warm during the sort of frosts that occur in East Anglia. After a day with it switched on, the steel bench no longer feels cold to the touch.
Moist air is heavier than dry, so there ought to be a vent near floor level, to allow the exit of water vapour. ( We exhale water vapour, and perspire, and so contribute to the problem!) My shop has a small ventilation fan fixed high up, in the rear wall, with an external cowl extended downwards to prevent any rain/snow ingress, to aid air circulation.
When occupied, and it is cold outside, to make it comfortable, there is a thermostatically controlled 2Kw Fan Heater, with the 'stat set to about 18C. Physical activity and heat from the machine motors provide the extra warmth needed. The heater runs for about ten minutes each hour. Externally, the shop is 10 feet 9 inches (3.27M) x 6 feet 9 inches (2.06M) . The height is 8 feet (2.44M) high at the front sloping to 7 feet 6 inches (1.98M) at the rear, to run the water off into the guttering.
In this environment, machined surfaces are left unoiled, and rusting is virtually unknown. The very small areas of very light rust on drill chucks / tools are most likely caused by moisture / acid from my hands, or exposure to the outdoors. Machined surfaces have never rusted.
Matters can be improved in phases; preferably starting with low level heating; then with ventilation, and with improved insulation following on afterwards. The improved insulation will reduce the heating costs.
I hope that some of this will help anyone with rusting problems.
Howard
Edited By Howard Lewis on 24/03/2015 17:39:35