Materials Technology

Finishing of Materials

Overview - Degradation of Materials

COREThe student will learn about…

“Finishing materials.”

The student will be able to…

• Select suitable finishes for materials, with due regard for environmental factors.

• Show an awareness of the effects of environmental conditions on materials and the importance of suitable finishing techniques.

Finishing of Materials

Wood

Many hardwood species have a natural durability as indeed do some softwoods, e.g. larch or red cedar.

Finishing of Materials

Wood

Wood’s natural durability can be enhanced by applying preservatives;

• Pressure treatment – pre-treated in industrial impregnation plants (preventative)

• Spray, brush or dip application – can be applied with the timber in-situ (curative)

Finishing of Materials

Protecting Wood

• Design features – capping, overhangs, sloping surfaces, stanchions and shoes

• Painting, varnish, etc.

Finishing of Materials

Wood

Wood is usually finished by first planeing then sanding. It may also require a conditioner before either staining or varnishing. A primer and undercoat is usually applied before painting.

Finishing of Materials

Environmental considerations (Painting)

• Irritation from fumes, odours and vapours• Contains hazardous materials such as ammonia,

formaldehyde and volatile organic compounds (VOC)

• Can be harmful to flora and fauna• Can leech into the water table• Is considered a hazardous waste - cans and

leftover paint must be disposed of appropriately

Metals• Some non-ferrous metals are particularly resistant to

corrosion, e.g. Copper

• They form strong oxides on their surfaces (as do aluminium and lead) and these protect the metal from further oxidation. Shown as cladding on the buildings above

and Zinc

Copper Cladding Zinc Cladding

Finishing of Materials

Metals

Protection and Finishing

There are various protection and finishing treatments applied to metals, they include;

• Sacrificial protection• Design features• Anodising of aluminium• Protective coating e.g. paint, plastic, metal• Electro plating

Finishing of Materials

Metals

Anodising of Aluminium

• An electrolytic process that increases the thickness of aluminium's naturally occurring protective oxide film

• Organic acid electrolytes will produce harder films and can incorporate dyes to give the coating an attractive colour

Finishing of Materials

Metals

Protective Coating - Paint

• Paint is widely used particularly to protect steel. It is not effective over time and under certain conditions and must be renewed regularly – often at considerable expense

• The more effective paints contain lead, zinc or aluminium in suspension and part of the protection they provide is sacrificial

Finishing of Materials

Metals

Protective Coating - Plastic

A variety of plastic coatings exist, they include;

• Brush on coating• Electrostatic spraying• Hot dipping in fluidised tank

Finishing of Materials

Metals

Protective Coating - Metal

Metal coatings give the best protection – they include;

• Hot dipping• Powder cementation• Metal spraying• Metal cladding• Electro-plating

Finishing of Materials

Metals

Protective Coating – Electro-plating• Uses the chemical effect of an electric current to provide

a decorative and/or protective metal coating to another metal object

Finishing of Materials