Iron and steel rust when they get damp, and the metal is gradually eaten away. Rust is formed by chemical action between the metal, oxygen in the air and water made into a weak acid by dirt and dust. Iron and steel will not rust if you keep them protected from the combined effects of air and water, so most preventative measures involve doing just that.
Preventing Rust
Paint iron or steel in need of decoration as soon as possible. First remove grease with white spirit and allow the metal to dry. Then paint with a metal primer, followed by a gloss paint. This will exclude air and water.
Repaint even small scratches in paint work before rust can form.
During winter, when roads are being salted, wash the underside of your car as often as possible – particularly the sills and wings – because chemicals such as salt accelerate rusting.
Protect metal that cannot be painted, such as hand tools, with a thin film of oil or greases. Or use one of the moisture displacing oils available as aerosol sprays. Thin coatings soon evaporate, so renew them regularly.
Use silica gel crystals to keep small cupboards dry (they have little or no effect in large spaces). The crystals absorb moisture from the air and need drying off time in an oven from time to time to keep them effective.
Many tools and appliances are now made from materials that will not rust – such as stainless steel or aluminum alloy – or have chrome or other coatings
that discourage rust. When you buy tools, check the labels about the materials used; it can save problems in the future.
Curing Rust
Deal with any rust formation, however slight, as soon as possible. Minor attacks may need only a rub with fine emery cloth.
For serious rusting, use a wire-brush (either a hand held brush or one fitted in a power drill) to remove all loose scale from the rusted area. Protect your eyes with safety goggles while you do it.
Once loose scale has been removed, treat the area with a proprietary rust neutralizing fluid that converts any remaining rust into a harmless black coating which can be over painted with an undercoat of necessary and finished with gloss paint.
Alternatively, use cold-galvanizing paint or zinc-rich paint. These not only neutralize any remaining rust, and provide a silvery priming coat, but also inhibit further rusting. Once dry, the coating can be over painted with any good exterior gloss paint.
Another alternative is to use a rust inhibiting enamel paint. Remove all loose rust, then paint the enamel straight onto the bare metal. No primer or undercoat is necessary. Work fairly fast, as the paint dries faster than standard paint, especially in warm weather.
When treating rusted areas on painted metal work, be sure to strip off the paint until you come to bright metal. If you leave any hidden rust untreated it will quickly spread and push up the paint in blisters.
Where rust has caused staining of a surface such as ceiling plaster (after water damage for example) paint the stained area with aluminum primer sealer. This isolates the stain fro any new paint or paper.
Repairing Hollow and Holes
Where rust has eaten into the metal, first remove all loose and flaking rust. Fill up a hollow with an epoxy based repair filler paste. The paste inhibits any further rusting, so no priming paint is needed.
Back a small hole with glass-fiber matting, if necessary, or for a larger hole use expanded zinc alloy mesh.
Stick it in place with a little repair paste, then build up the surface with the filler keyed to the mesh.
Build the filler a little higher than the surrounding metal. When it has hardened, smooth it level with wet and dry abrasive paper, used wet, before cleaning and painting the area.
