Surface Finishes. For woods metals and plastics

Transcription

1 Surface Finishes For woods metals and plastics

2 Reasons for Surface Finishes Some kind of surface finish is always necessary for the following reasons Resistance to decay (Stopping the material from rotting / rusting / perishing (UV Light)) Resistance to wear (Preventing scratches / breakage) Resistance to absorption (Water resistance / Chemical resistance environment) Also the Aesthetic considerations of a surface finish are an important factor (To make the material look or feel (or even smell!) better)

3 Surface finishes for Wood Wood always requires a surface finish to prevent it from drying out, to prevent it from absorbing water from spills or the environment and to protect it from stains and scratches Wood finishes can be for Exterior and Interior use Polishes (Interior) - provide a durable and aesthetically pleasing finish for furniture but are not always waterproof Polyurethane Varnish/ Yacht Varnish. Waterproof, gloss finish which enhances the natural grain. Can peel over time Lacquers (Interior/Exterior) - can provide a high gloss protective coating to ensure water resistance Oils (Interior/Exterior) - seal in the moisture of the wood and enhance the natural finish of the wood (bring out the grain) Linseed Oil, Danish Oil, Olive Oil for food use Chemical preservation (Exterior) is where wood is treated with chemicals to prevent it from rotting when used outdoors (Pressure Impregnation) Paint (usually exterior) Can provide protection from weather, chemicals, wear and tear as well as changing the appearance and colour but it covers the natural finish of the wood. Cellulose Paint, Oil based gloss paint NEED A PRIMER

4 Surface finishes for Metal Metals (except precious metals) almost always require a surface finish. Mainly to prevent oxidisation Ferrous metals (Steels and Iron) rust when exposed to moisture but non ferrous metals like Aluminium, Brass and Copper also oxidise when exposed to the atmosphere. Therefore they must be protected from the air by a surface finish Steel is often electroplated with zinc (Galvanised) or Chromium which is an effective way of preventing rust but the two differ greatly in cost and appearance Plastic coating is a way of preventing rust and wear to any metal. It also changes the aesthetics of a metal (colour, warmth to the touch) However it is only suitable for smaller items Cellulose Paint provide effective protection from oxidisation but can flake off after time and if applied poorly. NEEDS A PRIMER Anodising is a surface finish for aluminium only which protects it from abrasion and corrosion. It involved passing electricity through acid to produce a hard oxide surface.. This can be dyed to any colour required. Cellulose Lacquer can be applied to decorative non-ferrous metals like brass to prevent oxidisation Stainless Steel is the exception in that it does not need a separate surface finish. Instead the surface can simply be polished to a high shine. (Stainless steel is an alloy of iron, carbon and chromium)

5 Surface finishes for Plastics Plastics rarely need a separate surface finish as the vast range of types and properties of plastics enable suitable plastics to be chosen for their properties i.e. Chemical resistance, resistance to sunlight etc Therefore the surface finish of plastics is usually as a result of the moulding or forming process e.g. High shine, textured Plastics properties can also be amended for aesthetic reasons (colour, texture) or formed in to shaped finishes (knurling or patterns)

6 Selection of surface finishes Aesthetic: Colour, touch, texture, smell Function: the purpose of the finish Durability: How long the finish will last Ease of preparation and Application: Time considerations, Primer, number of coats, cost, specialist equipment etc

7 Applying surface finishes Brush Spray Dip