Why is a special primer required for asbestos cement?

Because asbestos cement is highly alkaline, which can chemically react with and destroy ordinary oil-based paints (a process called saponification).

How should an old asbestos cement surface be prepped?

It must be gently cleaned of dirt, grease, moss, and efflorescence, washed with water, and allowed to dry completely. Avoid abrasive dry cleaning to prevent inhaling toxic asbestos dust.

Can cement paints be applied to asbestos cement?

Yes, cement paints are often suitable as they are compatible with the alkaline nature of the asbestos cement surface, but the surface must be properly wetted before application.

IS 3140

: 1965

Code of practice for painting asbestos cement building products

CurrentRareCode of PracticeArchitectural · Building Construction Practices incl. Painting, Varnishing

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This code of practice covers the recommended methods and precautions for painting asbestos cement building products. It emphasizes the need for alkali-resistant primers due to the high alkalinity of asbestos cement surfaces.

Code of practice for painting asbestos cement building products

Quick Reference Values

Recommended primer typeAlkali-resistant primer

Surface condition before paintingCompletely dry and free of efflorescence

Practical Notes

Asbestos cement surfaces are highly alkaline and porous, requiring alkali-resistant primers to prevent saponification (breakdown) of ordinary oil-based paints.

Due to severe health risks associated with asbestos fibers, aggressive dry sanding or power wire-brushing should be strictly avoided during surface preparation.

Ensure the surface is completely dry before application to prevent moisture entrapment and subsequent blistering or flaking of the paint layer.