Rust is created when water and oxygen combine to attack iron and steel – the ferrous metals. But metal can be protected by putting a barrier of rust-inhibiting metal primer, which contains special ingredients to prevent rust formation, over its surface. At least two coats of finishing paint on top of the primer should keep the enemy at bay.
Some metal items, however, are not suitable for painting, such as garden tools, hinges and latches. Here you should smear the surfaces with oil or grease or use an aerosol to coat the material with a film of water-displacing oil. Oil tends to evaporate quickly outdoors, so items kept or regularly used in the open are best smeared with grease.
Any new metal parts which could be fairly inaccessible after installation should be treated with at least two thick coats of primer and at least one finishing coat of paint. Prominent areas, such as edges which are vulnerable to knocks, should also be given two coats of primer. Pay particular attention to rivets, bolts, nails and screws.
An alternative to rust-inhibiting primer is zinc-chromate paint, which is based on the cold galvanizing process. This paint kills off rust and protects at the same time. It is available in tins or as an aerosol: the latter is useful when treating inaccessible areas, but a brush coat is always preferable since a thicker layer can be applied. Non-painted items should be oiled or greased.
Certain metals can be used outdoors without extra protection. Copper, lead and zinc form a protective film of oxide which prevents corrosion. Anodized aluminium has an artificially thickened oxide coat. GARDEN TOOLS Most gardening equipment is liable to rust; an exception is the stainless steel tool, which never needs protection and is a good long-term investment for anyone prone to leaving things lying around outside. 1 Really heavy coatings of rust can be removed with a wire wheel attachment to an electric drill 2 Go over the cleaned surface with an emery cloth round a wood or cork block 3 Apply a suitable primer to prevent further rust forming on the metal 4 On railings you may find it easier to use a blowtorch and shave-hook rather than a wire brush 5 Petroleum jelly smeared over outdoor equipment will provide a protective coating 6 Guard against corrosion in a metal cold water cistern by suspending a sacrificial anode in the water 7a Drill through the head of a rusted screw holding a batten to the wall 7b With the head removed. lift the batten away from the wall and extract the screw shank with a wrench
Even equipment stored inside tends to suffer unless the storage area is wcatherproofed and insulated. Sheds are particularly vulnerable and it may be better to keep tools in the house or in a dry garage. Small tools can be stored in a special rust-inhibiting paper which is chemically treated to prevent rust action taking place. If you do not want to wrap each tool, line a drawer or cupboard with the paper which has a life of several months.
Before you store gardening tools for the winter remove all mud, grass and any signs of rust. Strip the lawnmower down to reveal all parts that may have collected dirt. When all the metal has been cleaned and treated as necessary, wipe with an oily rag, grease or spray with a water-displacing OIL.
SCREW THREADS Threads of all screws in equipment used outside should be smeared with petroleum jelly to ensure they are always easily withdrawn when necessary.
PAINTWORK Make regular inspections of all painted metal inside and outside the house to check for any breaks in the paint film. Even a pin prick is an invitation to rust, which spreads quickly below the surface and will only show itself when paintwork bubbles or flakes.
COLD WATER CISTERN You must inspect metal cold water cisterns and treat if necessary. An effective rust preventative measure is to suspend a sacrificial anode in the water. This is a piece of magnesium with a higher electrical potential than zinc; the electrolytic action between the zinc on the cistern and the anode will cause the anode to dissolve and protect the galvanizing on the cistern. These anodes, which are available from most builders’ merchants, have a copper wire attached. This is clamped to the cistern, which should first be scraped clean at that point to ensure a perfect electrical contact. The anode is suspended over a timber batten placed across the top of the cistern. Remember to replace the anode before it dissolves completely. Tanks can also be treated with zinc-based cold galvanizing paint.
You must be absolutely scrupulous in treating rust. otherwise it will reappear quickly. Begin by removing any dirt or grease. If there are only small spots of rust, these can BE cleaned up with an emery cloth; for more extensive damage you should use a wire brush. A hand-held brush requires a lot of work and it is easier to use a wire cup brush or wheel held in the chuck of a power tool. Work past the edges of the rusting area because a sound film of paint could be concealing trouble below. To produce a clean, sound surface, finish off with a medium-grade emery cloth.
Brushing with wire will cause flying rust particles: always wear protective spectacles
As soon as you have prepared the surface, prime it to neutralize any particles not visible to the naked eye and to give a protective coating; bare metal can be affected by rust within a couple of days.
GATES AND RAILINGS These contain many curves and crevices where pockets of dust can form that are difficult to reach. These should be attacked with a blowtorch and shave-hook if you cannot get at them with a wire brush.
COLD WATER STORAGE CISTERN If yours has not been fitted with a sacrificial anode and rust develops, you must tackle it immediately before a hole appears; otherwise the consequences could be disastrous. The method of repairing a steel cistern has been covered earlier in the Course.
GUTTERS AND DOWNPIPES Clear, clean and treat any metal pipes or guttering with primer, followed by a normal finishing paint or a bitumen paint, which provides a thick water-resistant coating. Use black bitumen solution for the inside surfaces of the guttering and bitumen enamel for the outside and for downpipes. Small holes can be repaired with epoxy resin filler.
NUTS, BOLTS AND HINGES Where these have rusted you should use penetrating oil or rust-release fluid. Allow 24 hours for the fluid to do its work – especially on hinges which have jammed. You may need to do this a few times before resorting to cruder methods, such as using a saw or cold chisel.
Rust formation increases the size of a ferrous object and this can create quite a problem when screws and bolts jam. Sometimes tightening a bolt or screw will create enough movement to break the rust bond. Heat from a soldering iron applied to the head of a screw sometimes causes enough expansion to break the rust grip. Another solution is to remove the head with a hacksaw or nut splitter and the rest of the fixing with a wrench.
If a screw is countersunk in a batten held to a wall, estimate the size of the screw shank and drill through the centre of the screw head, with a bit of the same diameter, to break off the head. Remove the batten and take out the screw with a wrench.