Depending on the type of metal surface you wish to paint, whether interior or exterior, different surfaces require different paint products, pre painting treatments and painting techniques. This ensures the most appropriate treatment for each surface whether inside or outside the home and on all sorts of surfaces. Find out the best paint for the job with this handy article.

Painting Exterior Surfaces

Bricks, masonry and cement render – Usually these surfaces can be coated with two coats of water-based acrylic finish with no sealer required. Sometimes a brown to purple vanadium appears on the surface after painting. This is found within particular bricks. Check that the brickwork is dry. Patch the affected area with an oil-based sealer followed by repainting the bricks or the wall. This will solve the problem.

Concrete tiles – After about 15 to 20 years the coating on concrete tiles can erode. The colour becomes patchy and dull. Before repainting, the surface should be treated to remove moss, mould and lichen. Apply a 3% chlorine bleach solution followed by thorough water rinsing and scrubbing or heater jet cleaning. If the surface is still chalky after this treatment, apply an oil-based pigmented sealer. Finally, apply two coats of exterior water-based acrylic topcoat.

Concrete driveway and patios – All bare concrete surfaces must be acid etched prior to painting. Acid etching is carried out by swabbing liberally with a solution of 1 part hydrochloric acid to 3 parts water. Allow two coats of selected paving paint. Coloured oxide topped concrete may require more than one acid etching to make the surface porous enough for paint adhesion. Check porosity after the concrete has dried by applying a little water. If the concrete is porous enough, the water will be rapidly absorbed. If not, repeat the acid etching. Bubbling and flaking can be caused by moisture rising up through the slab. Unless this can be stopped, over coating with normal house paint may be unsuccessful.

Fibreglass sheeting – Corrugated fibreglass sheeting (and other plastic sheetings) used on pergolas and shade houses can be painted with an exterior water-based acrylic paint. This process will also extend the life of the sheeting. Sheeting should be scrubbed with a steel wool pad and a mild solution of detergent in water, rinsed off and allowed to dry before painting.

Painting Interior Surfaces

Ceramic tiles – Ceramic tiles are difficult to paint satisfactorily, especially highly glazed tiles. On a glassy surface, the paint has no key to stick to. Glazed wall tiles can be painted with an oil-based sealer and enamel with fair results, except in wet areas where the moisture will lift the paint. Painting glazed floor tiles is to be avoided. Foot traffic will easily remove the paint. Unglazed floor tiles can be coated with a slate sealer to keep grease and dirt from penetrating. Don’t use clear polyurethane varnishes as worn areas are difficult to patch.

Craftwood – Craftwood is a form of particle board. It has a wax content which can interfere with the drying of oil-based paints. Undercoat with a water-based sealer/undercoat and then apply oil-based or water-based finishes as appropriate.

Gyprock – Gyprock is a buff coloured plaster ceiling or wall board with a paper facing. Gyprock does not present many problems for painting. For a flat finish, usually two coats of flat plastic paint is sufficient. For a low sheen or semi-gloss finish, use a coat of water based sealer followed by two coats of finish. If peeling has occurred, it will usually be confined to the cornice and about 75mm into the ceiling itself. This is due to the incomplete removal of cornice cement smears prior to the original painting. Should this occur, then scrape back, apply an oil-base sealer, touch up with finish and re-coat the ceiling.

Plasterglass – Plasterglass is a smooth white ceiling board whereas Gyprock has a buff-coloured paper facing. The trowelled joints in Plasterglass ceilings can cause paint adhesion problems if the correct sealer is not used.

Laminex – Laminex, formica or other laminated surfaces can be painted with gloss or semi-gloss enamels. De-grease the surface, sand back to a matt surface and apply two coats of either finish. This is more applicable to cupboard doors rather than benchtops as the enamel is not as hard as the original laminate surface and is likely to scratch. Apply a sealer followed by a coat of flat plastic or flat enamel paint for a two coat finish. For low sheen or semi-gloss finishes, apply a coat of oil-based sealer followed by two coats of finish.

Peeling ceilings –  Peeling ceilings are best treated by wetting thoroughly with a hot detergent/water solution. Areas with poor adhesion will generally blister up and can be scraped off. Allow to dry, patch seal bare areas with an oil-based sealer, fill if necessary with Polyfilla, touch up with top coat and re-coat the ceiling. It is important to find all areas of poor adhesion otherwise further peeling may occur at a later date.

Texture coatings – Acrylic texture coatings are used for their decorative effect or to cover up uneven or cracked surfaces. They may contain fine or coarse aggregate or be unfilled. The textures range from a smooth rippled finish through sand-type finish to a bold rough finish. The finish also depends on the type of roller used. Because they produce a thick heavy film, the surface to which they are applied must be sound, otherwise loss of adhesion may occur. Because the spreading rate of texture coatings is only 2 sq. metres or less, they are relatively expensive coatings. The coarser the texture, the greater the dirt pickup especially on exterior surfaces.

Coolrooms – Coolrooms running at temperatures down to 4°c are common in restaurants, hotels, hospitals and wholesalers. They may be built with bricks, masonry or Colourbond/foam sandwich panels. If repainting is required, then the temperature of the interior surface must be allowed to come up to at least 10°c otherwise the paint will not dry properly. Any mould or mildew should be treated with chlorine bleach before painting. Water-base acrylic gloss paints can be used. These will not taint food. At least 24 hours curing time should be allowed before returning the coolroom to service.

Preparation and Painting

Aluminium –  Scrub bare aluminium with turpentine and a steel wool pad. Rinse with clean water and dry off. Paint as soon as possible with water-based acrylic paint or prime with water-based galvanised iron primer if an enamel top coat is to be applied. Anodised aluminium window frames can be cleaned down with water and detergent and repainted with water-based acrylic finishes.

Brass –  Sand and prime with re-oxide metal primer or polish with Brasso. Wipe with methylated spirits to remove residues of the Brasso. To maintain polished brass protect by spraying with a clear spray pack.

Colorbond – Colorbond is pre-painted galvanised or zincalume steel sheeting. It is carefully factory-coated for long life. If Colorbond is damaged in transit or during erection you should touch up. Special Colorbond touch up spray packs are available. For the painting of surfaces adjacent to Colorbond, use Colorbond Trim Colour. This is a water-based acrylic matched exactly to the Colorbond colours. For repainting of weathered Colorbond, wash down to remove any chalkiness, then apply low sheen exterior paint.

Copper – Sand back and prime with red oxide metal primer. Polished copper can be treated as for polished brass.

Galvanised iron – Galvanised iron is steel sheeting with a surface layer of zinc. The zinc coating prevents the steel from rusting. Painting galvanised iron can cause problems if the wrong primer or no primer is used.The zinc can attack oil-based paints causing them to flake from the surface. The usual primer for domestic galvanised surfaces is a water-based acrylic galvanised primer. This can be top coated with either oil-based or water-based paints

Gutters – Gutters and downpipes are usually made from zincalume or galvanised steel. Both can be treated in the same way. New gutters should be scrubbed with a steel wool pad and a suitable cleaning agent or detergent, rinsed with water and allowed to dry. Apply one coat of acrylic galvanised primer. If within 5km of the sea, apply with two top coats of gloss enamel. Otherwise either enamel or water-based acrylic is suitable.

Rusty steel – Rusty steel is probably one of the hardest surfaces to treat properly in a domestic situation. Ideally all the rust should be removed by abrasive blast cleaning or acid pickling. If this cannot be done then scraping, chipping or wire brushing are the only methods available. Apply either a phosphoric acid pre-treatment, such as deoxidine or rust remover, or a tannic acid rust converter, such as Fertan. Then apply an oil-based metal primer. The paint coating must exclude as much water, oxygen and salts as possible. The thicker the oil-base coating the better. A minimum system would be a metal primer and two coats of oil-based finish.

Zincalume – Zincalume is similar to galvanised iron except that the coating is a zinc-aluminium alloy instead of pure zinc. This has a lower corrosion rate and so zincalume has a longer life before rusting occurs. Paint the same method as discussed in galvanised iron above.

How Long Will It Take?

In one hour you are likely to cover about 7 square metres of an ordinary surface, or about 5 square metres of bare wood or plaster. You will probably be able to paint that 4m x 5m room with one coat in five to six hours. If you apply two coats, you must allow time for the first coat to dry. Allow four hours for water based paint and overnight for oil based paint (check the label on the can). You can safely reckon on two or three days to paint a room and clean up afterwards.

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