The dye penetrant method of inspection is a nondestructive test for defects open to the surface. It may be used on such materials as aluminum, magnesium, brass, copper, cast iron, steel, stainless steel, carbides, stellite, certain plastics and ceramics. The essentials of the method are: penetration of the defect by the dye penetrant, removal of the excess penetrant from the surface, development of the indication, and inspection. A deep red indication will mark the defect.
Surfaces should be free of foreign materials and paint. Grease and oils prevent penetration and should be removed by precleaning with cleaner/remover or by solvent degreasing. Scale, sand, dirt, etc., trap penetrant and hinder removal, therefore wire brushing or similar precleaning is necessary. Paint must be removed from areas to be tested.