In the normal processing of aluminum forgings, a caustic etch operation is employed for the dual purpose of cleaningThe process of removing scale, oxides, or lubricant—acquired during heating for forging or heat treating—from the surface of the forging. (See also Blasting, Pickling, Tumbling.) parts and emphasizing defects to facilitate visual inspection. Immersion of parts for too long or use of too concentrated a solution will produce a rough, slightly pitted surface.