These include sheet, strip, tube, wire, wrought Shapes and castings. When the product is thin and of a high surface finish, scratches, gougings, tears, etc., may ruin the product to the extent of the damaged area. Seawater and fresh water produce stains, and seawater may give rise to corrosion. So long as the stains are superficial the product can be used, but if rough and pitted the material may be rejected. Manufacturing difficulties such as scabbiness, roughness or folds ("pinches") can be readily identified, as these cannot be produced by rough handling or by corrosion in transit. Cracks, particularly in tubes or pressings, may generally be attributed to mild corrosive conditions in transit in conjunction with the omission of a stress relieving heat treatment after manufacture.
Surface defects, apart from corrosion pits, scratches and dents, can usually be attributed to faulty manufacture. Scabbiness is caused by the metal splashing when it is poured into the mold and cooling in droplets on the side. An oxide film is formed around these droplets which prevents them mixing with the rest of the metal in the ingot. Roughness is caused by the ingot sticking to the mold, causing a tearing of the surface on removal. Folds ("pinches") are caused in casting with too low a pouring rate allowing a series of oxide films to be formed. All these defects originate in a faulty ingot and the faults remain because of the inability of oxidized surfaces to weld together.
Superficial staining or slight corrosion may be removed by the use of mild abrasives and provided the product is not made to accurate dimensions, scratches, etc., may be polished out with an abrasive. Ammonia solutions with, or without, mild abrasives may be used for cleaning by wiping provided the operation is controlled and the surface is washed thoroughly afterwards. There is the possibility that stressed brass may crack when brought into contact with ammonia. Sheets intended for utensil manufacture have a smooth finish. While scratches, gouging, tears, etc. may ruin the sheets for this purpose to the extent of the damaged area, the undamaged part of the sheets can be used for cutting segments of a suitable size from which utensils may also be made.
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