what does paint primer do

Recommended primers for various substrates

The primer must adhere well to the substrate, offer protection from deterioration or corrosion and provide a good base for the undercoat. To ensure adhesion, the substrate surface must be free of loose or degraded material. Appropriate systems are indicated in Table 15.1. For use on timber, primers may be oils, alkyd resins or acrylic emulsions, frequently with titanium oxide. Aluminium wood primer is recommended for resinous woods and to seal aged creosoted and bitumen-coated surfaces. For the corrosion protection of ferrous metals, primers incorporate zinc-rich com -pounds within oils or alkyd resins. The use of leadbased paints in the UK is subject to the Control of Lead at Work Regulations, 2002. The newly developed low-VOC coatings offer temporary protection against the corrosion of structural steelwork as either pre – fabrication or post-fabrication primers. Alternatively, acrylated rubber paints which form a physical barrier over steel may be used as primers. For non-ferrous metals, zinc phosphate primers are frequently used.The application of primers suitable to ferrous metals may cause increased corrosion on non-ferrous substrates, particularly aluminium. Masonry paints are usually based on alkyd or acrylic resins with titanium oxide; where surfaces are likely to be alkaline, such as new plaster, brickwork or concrete, alkali-resisting primer should be used. Two-component primers are form ulated to give good adhesion on glazed tiles, glass, anodised aluminium, powder-coated steel and stove enamel surfaces.

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