|6. Coating Principles|
Distinction Between Paints and Coatings
Paints are liquids, pastes or powder products, which are applied to a substrate in a specified thickness to protect the substrate against corrosion.
Coating refers to the process of film formation, physically or chemically upon drying of the paint. Coating is a general term denoting a material that is applied to a surface whereas paint indicates a pigmented material, and varnish refers to a clear lacquer.
Functions of Coating
To prevent the substrate against atmospheric or underground or localized corrosion
To maintain appearance and aesthetic values
To decorate the substrate (eg. household appliances)
To provide information (eg. traffic signs, information signs, etc)
Many paintings from ancient times date back to first and second millenium BC. Some examples of early coating materials are given below
Linseed oil has been used since 1100 AD
Milky juice from the bark of the lacquer tree (Rhus rernifera)