The salt spray (or salt fog) test is a standardized and frequently used corrosion test method, used to check the corrosion resistance of materials and surface coatings. Usually, the materials to be tested are metallic and finished with a surface coating that is intended to provide a degree of corrosion protection to the underlying metal. Salt spray testing is an accelerated corrosion test that produces a corrosive attack on coated samples in order to evaluate the suitability of the coating for use as a protective finish. The appearance of products of corrosion (rust or other oxides) is evaluated after a predetermined period of time.