Driers are one of the major components of paint. Driers also know as plasticizers, are chemically added to the paint as they act as catalysts. The main function of a drier is to accelerate the drying of vehicle (linseed oil) in the paint and in consequence paint film becomes hard. Paint film gets hardened as drier absorbs oxygen from the air & transfer it to the vehicle.
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Driers are basically available in two types of forms in its physical state which is solid & liquid. Driers may either be available in the form of soluble or paste driers in the market. Both of the driers are compounds of cobalt, lead, manganese, etc. dissolved in linseed oil or some other volatile liquid. Red lead, Litharge, and sulphate of manganese mostly used as driers. Red lead is less effective than the litharge and litharge is the most commonly used drier.
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Red lead is the best for a primary coat over steel and metal work; it produces an extremely hard and tough film, almost impervious to air and moisture adheres firmly to the metal and is extremely effective in protecting steel from corrosion.
The quantity of driers added in the paint is limited to 8%. If uses in excessive amount especially in the finishing coat, it have tendency to destroy the elasticity of the paint and causes a flaking defect in the paint.
The following precautions should be taken while adding driers in paint:
- A drier should not be added in the paint until the paint is about to be used.
- More than one drier is not allowed in a mixture of paint.
- The driers should not be used with pigments that dry rapidly and well.