Due to the nature of cast iron galvanizing, it is recommended that any cast iron pieces be sandblasted before processing to achieve the best possible finish. Cast iron often contains scrap iron, and as a result, the chemistry of the metal is unpredictable. Also, casting residues embedded in the pores of the metal are not cleaned during chemical cleaning, and can result in uneven galvanizing and bare spots. It is best to choose the least porus cast iron possible. Sandblasting helps to remove impurities from the cast iron surface, giving it a more consistent finish.