How do I stop tools rusting in a shed or garage?

Controlling the humidity rather than oiling the symptoms, and what actually works in an unheated shed.

Difficulty: beginner
Time: 1 hr
Read: 4 min
Safety: caution

Short answer

Rust is a humidity problem, not a wetness problem — steel corrodes above about 50% relative humidity. Control the air with ventilation, a dehumidifier or VCI products, then protect the tools with a light oil or wax. Oiling tools in a damp shed is treating the symptom.

Everyone knows to oil their tools and most sheds are still full of rusty ones, because the oil is the second half of the answer and the air is the first.

Safety

Rust removers are usually acidic — wear gloves and eye protection and ventilate the space. Oily rags can spontaneously combust as the oil oxidises: never leave them screwed up in a bin, but spread them flat to dry or store them in a sealed metal container.

Step by step

Understand the actual cause.Steel rusts when relative humidity is consistently above roughly 50%, which describes most British sheds for most of the year. It does not need to get wet — the moisture in the air is enough.
Measure it.A cheap hygrometer in the shed. It turns guesswork into a number and tells you whether anything you have done has worked.
Deal with condensation first.Cold metal in warm damp air gets wet. Insulating a metal shed or the underside of a roof stops the surface dropping below the dew point, which is what causes the visible dampness.
Ventilate rather than seal.Airbricks, a vent at high and low level, or simply not sealing every gap. A sealed damp shed stays damp; moving air carries moisture out.
Keep tools off the floor and away from walls.Concrete floors wick moisture continuously and outside walls are the coldest surfaces. A gap of a few centimetres makes a measurable difference.
Use VCI products.Vapour corrosion inhibitor paper, bags or emitters release a compound that forms a molecular film on steel. Genuinely effective, cheap, and the best answer for a toolbox or drawer.
Use a dehumidifier or a low-wattage heater if there is power.A small dehumidifier set to 50% transforms a workshop. A tube heater raising the temperature a couple of degrees above ambient also works, by keeping surfaces above the dew point.
Wipe tools down after use.Sweat is salty and acidic and is a common cause of fingerprint-shaped rust patches. A quick wipe with an oily rag after handling is the single most useful habit.
Choose the right protection for the tool.Camellia oil or a light machine oil on hand tools, paste wax on cast iron tables and plane soles — wax does not transfer to the work — and a heavier protectant on anything stored long term.
Keep it off wood contact surfaces.Oil on a plane sole or a saw plate transfers to the timber and shows through the finish. Wax is the answer for anything that touches work.
Deal with existing rust before storing.Light surface rust comes off with fine abrasive and oil, or a rust remover for heavier deposits. Oiling over rust seals moisture in and it carries on underneath.
Store away from anything acidic or damp.Oak and some other timbers are acidic and corrode steel in contact. Cardboard, cloth and foam hold moisture against tools. A drawer liner is better than a rag.
Handle rags safely.Oily rags oxidise and generate heat, and screwed up in a bin they have started fires. Spread them flat to dry or use a sealed metal container.

Tips

A hygrometer and a small dehumidifier do more than any amount of oiling. Get the air below 50% and the rust problem largely disappears.
VCI paper in a toolbox is inexpensive and remarkably effective. Replace it roughly annually.
Wax rather than oil on anything that touches timber, or the oil transfers and shows through the finish.

Common mistakes

Oiling tools without addressing the humidity — The oil film is thin and wears off. In air above 50% humidity the corrosion just resumes, which is why sheds full of oiled tools still rust.
Sealing the shed up to keep damp out — It traps moisture instead. Ventilation lets damp air leave, and without it condensation forms on every cold surface.

If it doesn't work

Fine orange film on everything each spring

Cause: High humidity and condensation over winter — Fix: Ventilate, insulate cold surfaces, and add a dehumidifier or VCI emitters. Remove the rust before it pits.

Fingerprint-shaped rust marks

Cause: Sweat left on the steel — Fix: Wipe tools with an oily rag after handling. Salt from skin is aggressive on steel.

Rust returning through the oil

Cause: Oiled over existing rust — Fix: Remove the rust properly with abrasive or a rust remover, then protect the clean metal.

Rust only where tools touch the bench or a rag

Cause: Material holding moisture, or acidic timber such as oak — Fix: Use plastic or foam-free liners and keep steel out of contact with oak and damp cloth.

Questions people ask

Why do my tools rust in the shed?

Because relative humidity stays above about 50%, which describes most unheated British sheds. Steel does not need to get wet — moisture in the air is enough. Control the air first, then protect the tools.

What is the best thing to stop tools rusting?

Getting the humidity below 50% with ventilation, insulation or a small dehumidifier, plus VCI paper in toolboxes and a light oil or paste wax on the tools themselves.