Finishing techniques

Paints:

Advantages	Disadvantages
Stops rusting/corrosion Aesthetically pleasing Range of colours Saves time/money	Chips/flakes away Environmently unfriendly

Uses: Bridges, metal work, brick work

Varnishes:

Advantages	Disadvantages
Protects from dirt/sunlight/water Enhances look of wood Easy to apply Can't see brush strokes	Can be dull colour Bubbles can ruin finished look Some varnishes are bad for the environment (brushes cleaned result in varnish into water system)

Uses: Hardwoods and sodtwoods

Sealant:

Advantages	Disadvantages
Waterproof finish Thermal/acoustical insulation Electrical insulation Used for simple smoothing/filling	Does not have great strength

Uses: Pipe threads, aquariums, roofs, hydraulic systems

Preservatives:

Advantages	Disadvantages
Improves lifespan of timber Reduce biological corrosion Improves aesthetics of wood	Toxic More effective if used to pressure treat wood

Uses: Wood products exposed to water and corrosion

Anodising:

How it works:

1. Used to add a coating to aluminium
2. An electric current is passed through an acidic electrolyte
3. The metal being protected (anode) then builds a layer of aluminium oxide

Advantages	Disadvantages
Can be done in a range of colours Very durable finish Hard finish/scratch resistant Thin finish - doesn't block holes in product Heat resistant finish	Joining/machining can't be done after anodising Expensive

Uses: Window frames, bike frames

Electro-plating:

How it works:

1. A cheap metal is coated onto a metal to protect it
2. An electric current is passed through an acidic electrolyte
3. The metal being protected (anode) then builds a layer of metal oxide

Advantages	Disadvantages
Corrosion resistant Easy to do Improves mechanical properties Improves aesthetics appeal Cost effective Durable finish	Time consuming Toxic fumes released Non-unifrom finish

Uses: Spoons, taps, shower heads

Powder coating:

How it works:

1. The metal is heated to 230 degrees
2. The metal is then dipped into polymer powder
3. The polymer coating is then allowed to cool

Advantages	Disadvantages
Range of colour finishes Non-toxic Evenly coated finish More protective than paint Better for environment that paint	Harder to do than paint Uses energy/needs energy for heating powder (unlike paint)

Uses: Cars, wheel arches, sports equipment

Oil coating:

Advantages	Disadvantages
Replaces oils in wood lost as timber dries out Hard wearing Protective finish	Multiple layers needed to be applied Time consuming Labour intensive

Uses: Teak oil used on woods to give better protection

Galvanisation:

How it works:

1. The metal is dipped into molten zinc
2. The zinc acts as a sacrifical anode to protect metal underneath

Advantages	Disadvantages
Prevents rusting/corrosion Simple process Quick process that can be done on a mass production scale	Zinc layer can be chipped away over time Not a very aesthetic finish

Uses: Bridges, pipes, metal brackets

Cathodic protection (Impressed current and sacrifical anode):

How it works (Impressed current):

1. Metal is connected to electric power supply which is connected to a cathode
2. The cathode rusts over time whilst the anode (metal being protected) remains intact

How it works (Sacrifical anode):

1. A metal which is more reactive is connected to the metal being protected
2. The more reactive metal (sacrifical anode) rusts over time whilst the metal being protected remains intact

Advantages	Disadvantages
Proetcts structures that are buried in dirt/water Greatly increases lifespan of metal being protected Cost efficent to run	Hard to install Complex to upkeep Uses energy/needs connection for impressed current Expensive to install

Uses: Pipelines, ships, cars

Laminating:

How it works:

• Coating the paper with liquid/film to protect it

Advantages	Disadvantages
Aesthetic/high quality look Rigid/strengthens paper Low cost Hard to tear/rip	Paper hard to access/write on

Uses: Posters, pictures, song music

Varnishing:

How it works:

• Clear, non-pigmented ink used on pre-coated papers

Advantages	Disadvantages
Enhances the colour of paper Protects against dirt/fingerprints	Long dry time Slows down overall completion time - slower production rate Sticks to other surfaces/pages if not fully dried

Uses: Brochures, magazines

Hot foil blocking:

How it works:

1. A foil sheet is place between the paper and the die
2. The die is then pressed onto the foil and heated to allow the foil to join to the paper
3. The die is then removed and the foil cools

Advantages	Disadvantages
Enhances/adds value to paper Improved aesthetics Range of colours/foils etc	If heated for too long the foil can bubble and melt If heated not long enough the foil will not stick Difficulty in reproducing tints and halftones

Uses: Passports, gold foil decorations, wedding invite cards

Embossing:

How it works:

1. The paper is placed between the two formers
2. The formers then close around the paper to form the shape
3. Formers can be heated/cold

Advantages	Disadvantages
High quality finish Sophisticated appearance	Expensive

Uses: Toblerone card packaging, birthday cards

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