(B) Checking

Identification:

After exposure of the coating to the environment after extended periods of time, small breaks in the coating are formed in a checking pattern.

Description:

In certain environments such as hot and humid, the coating may become hard due to aging and forms a checking pattern on the surface which may be visible to the eye or sometimes microscopic. Fortunately, the checks formed do not penetrate the substrate similar to the situation in chalking. The defect may in certain cases, reach the substrate if the coating is not maintained or if it is catalysed by certain pigments. In those cases, stresses developed would cause the breakdown of the coating and expose the substrate.

Prevention:

• If the damage is confined to the surface only, repair that damaged area. If the defect has reached the substrate, re-apply the coating.

• Select weather resistant binders such as polyurethanes or epoxies.

• Use reinforcing pigments which may help strengthen the film and reduce stresses.

• Make periodical evaluation.