The measurement of the resistance of paint film to salt spray conditions is important for the evaluation of anti-corrosive primers and paint systems.

Essentially the apparatus comprises of a plastic box, with a sealed lid to prevent escape of salt spray in which the panels are exposed. Salt mist is generated inside the apparatus by a suitable nebulizer using a standard solution of salt (sodium chlroide) as required by the various specifications, for example 85 3900 and ASTM. The liquid falling on the panel is not recirculated.

The degree of resistance to corrosion is assessed against standard panels and may involve cutting the surface of paint with a sharp blade to the metal surface and measuring the time taken for corrosion to occur for a set distance.