No corrosion allowance is required for such parts not in contact with the inside fluid as the outside surface of shell, skirt, support lugs and so on, except for anchor bolts.
对于不同内部介质接触的部件，如外表面、防护罩及支承凸缘等不需腐蚀余度，地脚螺栓除外。
2
Destruction of cement sheath outside casing is one of the causes for channeling and corrosion.
套管外水泥环的破坏是导致管外串槽、套管外腐蚀的原因之一。
3
By using this method consisting of directional edge detection, directional mathematical morphological method and mimesis watering corrosion method, a better close outside boundary was obtained.