Paints are mixture of pigments and binders which are in a liquid state. The construction industry is a major user of different types of paints. Here we take a look at the most common types used, what they are made from and their specific applications.
Paints form a solid film when applied on a surface. The aim of this film is to protect the surface, regardless of what it is from aggressors such as corrosion, weathering and chemical degradation. This protection extends the life of the timber, metal or concrete structure it is applied to. Paints also improve and enhance the aesthetic appearances of the surface.
Classification of Paints and their Applications
All paints are not suitable for all conditions. For different conditions, different types of paints may be useful.
There are many different types of paints which are used in the construction industry: aluminum paints; asbestos paints; anti-corrosive paints; bituminous paints; cement based paints; synthetic rubber paints; silicate paints; graphite paints; plastic paints; cellulose paints; enamel paints; emulsion paints and oil paints.
Not all of these paints are commonly used in the local market, however it is interesting to know the origins of these paints.
Aluminium paints are made by mixing finely ground aluminium with spirit or oil varnishes. Spirit varnish makes the drying period shorter and oil varnish imparts slow drying facility. It is mainly used for painting wood works, metallic surfaces etc. It is waterproof, offers resistance against electricity, corrosion and weathering.
Asbestos paint is a special purpose paint which is made of fibrous asbestos. It is used for covering leakage in metal roofs, for patch works, for protecting surfaces from acid gases and steam. Rusting of pouts, flashings, gutters etc. can also be prevented using asbestos paint coating.
Bituminous paints are made by dissolving tar or asphalt in petroleum or white spirit. They provide black appearance to the surface. This type of paint is mainly used for metal structures in under water conditions, iron pipes carrying water. Bituminous paints have good alkali resistant property.
Cement based paints contain cement as the base material. These paints contain cement, accelerator, pigment and other additives. They are available in powder form. By mixing water to this powder and stirred to the required consistency the paint is obtained. It is waterproof and can be applied to internal or external surfaces.
Silicate paints are basically a mixture of silica and resinous substances. Silica gives good adhesion to the paint which will form hard surface after drying. It enables the surface it is applied to, to resist extreme heat. This type of paint never reacts chemically with the metals and is therefore useful in hot conditions and for metal structures.
Graphite paint is made of graphite which is black in colour. Commonly used for painting underground structures like mines and iron structures.
Plastic paints have plastic as the base. Plastic paints dry very quickly, provides better appearance and have high covering power. They are used for coating walls, slabs and decks.
Cellulose paint is a special type of oil paint made from celluloid sheets, nitrogen-cotton, amyl acetate and photographic films. In the case of normal oil paints, the paint layer is hardened by oxidation but in this case layer is hardened by the evaporation of solvent. This paint provides a smooth finish and is not affected by smoke, water, acids etc. it is very expensive and only used for painting aircrafts and motor cars.
Enamel paints are widely available and are used for painting doors, windows, stairs and decks. The main constituents of enamel paints are metallic oxide, petroleum spirit, oil and resinous matter. Enamel paint dries very slowly but after drying it forms very hard, impervious and smooth layer, which is not affected by acids, alkalis, gas fumes or water.
Emulsion paints have good alkali resistant properties, which is achieved by using polyvinyl lactate, styrene or alkyd resin. It dries very quickly and it can be washed with water because of its film forming constituent is emulsified in water instead of solvent. Ideal for all masonry work.
Oil paints normal paints contain a base and vehicle. General base constituents used for making oil paints are white lead, zinc white, lithopone, red lead and titanium oxide. General vehicles used in oil paints are linseed oil and tug oil. Along with base and vehicle, driers and colour pigments are also used. The driers used may be litharge, red lead, zinc sulphate and manganese sulphate. These paints are very economical and are easy to apply. Used on walls, doors, windows and metal structures. Not ideal for humid weather conditions.
For more information on the local paint industry, raw materials and additives contact Chemgrit Coatings on www.chemgrit.co.za or marilyn@chemgritsa.co.za .
[SOURCE: www.theconstructor.org]