SPEC5CT-1999 API (API Instiute), the American Petroleum Institute (American) is prepared and published by the American Petroleum Institute (Petreleum). Where: the casing: from the ground into the hole, as the lining of the shaft lining, the tube through the connection between the tube. The main materials are J55, N80, P110, etc., as well as C90, T95, etc.. Its low grade (N80, J55) can be welded steel pipe. Tubing: a tube that is inserted into the casing until the oil layer is inserted into the casing. Its role then pumping unit to the oil in the oil pipeline to the ground. The main materials for the J55, N80, P110, and C90, the corrosion of hydrogen sulfide, the American Petroleum Institute to prepare and publish in the world.