Surface Treatments & Finishes
Why Apply a Surface Finish?
A raw material straight from the workshop is rarely ready for the consumer. Surface treatments and finishes serve two purposes: they protect the material from damage (corrosion, moisture, UV degradation, wear) and they enhance its appearance (colour, texture, gloss). You need to know specific finishes for each material category and to explain why each one is chosen.
Surface finishes have two key purposes: functional protection (preventing corrosion, rot, UV damage, moisture absorption) and aesthetic enhancement (improving colour, texture, gloss and visual appeal).
Papers & Boards
Printing is the primary finish for papers and boards — it adds colour, text and graphics. Embossing creates a raised pattern by pressing the material between shaped dies, giving a tactile quality used on greetings cards and luxury packaging. UV varnishing applies a glossy, scratch-resistant coating cured by ultraviolet light — often used on magazine covers and product boxes to make colours more vibrant and the surface more durable.
Timber-Based Materials
Painting covers the natural grain and provides a coloured, protective layer. Oil-based and water-based paints both seal the surface against moisture. Varnishing provides a transparent or tinted protective coat that shows the natural grain — polyurethane varnish is hard-wearing and water-resistant, making it ideal for tabletops and floors. Tanalising is a pressure treatment that forces preservative chemicals deep into the timber, protecting it against rot and insect attack. Tanalised timber is widely used for fencing, decking and garden furniture.
Metal-Based Materials
Metals are particularly vulnerable to corrosion (e.g. rust on steel, tarnishing on copper). Several finishes address this:
Dip coating: The metal component is heated and dipped into a tank of polymer powder or liquid plastic, which melts and forms a smooth, coloured coating. Used on tool handles, dish racks and playground equipment.
Powder coating: Dry polymer powder is sprayed onto the metal surface using an electrostatic charge, then baked in an oven to form a tough, even finish. It is more durable than paint and available in many colours. Used on bicycle frames, car wheels and metal furniture.
Galvanising: The metal is coated with a layer of zinc by hot-dip galvanising (dipping into molten zinc) or electro-galvanising. The zinc acts as a sacrificial layer — it corrodes before the steel underneath. Used on gates, crash barriers and roofing sheets.
Anodising: An electrochemical process that thickens the natural oxide layer on aluminium, making it harder and more resistant to corrosion. The porous surface can absorb dyes, allowing a range of colours. Used on aluminium window frames, phone cases and kitchen utensils.
Polymers
Polymers often need less finishing than metals or timber because they do not corrode or rot. However, finishes can still improve appearance and durability. Polishing (buffing with fine abrasive) creates a high-gloss finish on acrylic. Printing adds graphics to polymer surfaces — pad printing transfers ink from a silicone pad onto curved shapes (e.g. logos on bottle caps). Vinyl decals are adhesive graphics applied to polymer casings (phone cases, laptop covers, product branding).
Textile-Based Materials
Textiles are finished to add colour, pattern or functional properties. Printing applies colour designs to fabric using screen printing, digital printing or block printing. Dyeing saturates the entire fabric with colour — it can be done at the fibre, yarn or fabric stage. Stain protection (e.g. Scotchgard) applies a chemical coating that causes liquids to bead on the surface rather than soak in, protecting upholstery and outdoor clothing.
In the exam, you should be able to name at least one specific finish per material category and explain both its protective and aesthetic benefits.
Electronic & Mechanical Systems
PCB lacquering applies a protective conformal coating to printed circuit boards, shielding components from moisture, dust and chemical contamination. Lubrication reduces friction between moving parts in mechanical systems, preventing wear and overheating. Both are functional finishes with no aesthetic purpose.
The choice of finish depends on: the material category, the product's environment (indoor vs outdoor, wet vs dry), the desired appearance, cost, and whether the finish needs to be food-safe. Outdoor products need UV and weather resistance. Food-contact products need non-toxic, food-grade coatings. High-traffic surfaces need scratch and abrasion resistance.