(1) ASTM A179 "Carbon Steel Pollution Cold Drawn Steel Tube": The contact with carbon steel due to scratch and corrosive medium forms a primary battery and electrochemical corrosion.






(2) ASTM A179 cold drawn steel pipe cutting: slag, spatter and other rust-prone materials adhere to the corrosive medium to form electrochemical corrosion of the primary battery.






(3) Heating: The composition and microstructure of the flame heating zone are changed, uneven, and the original medium and electrochemical corrosion of the corrosive medium are formed.






(4) ASTM A179 cold drawn steel pipe welding: physical defects in the welding area (biting, pores, cracks, unfused, unwelded, etc.), chemical defects (coarse grains, grain boundary chrome, segregation, etc.) and corrosive media, forming The primary battery produces electrochemical corrosion.






(5) Materials: Chemical defects (uneven composition, S, P impurities, etc.) and surface physical defects (loose, trachoma, cracks, etc.) of cold drawn steel are favorable for corrosive medium and electrochemical corrosion to form the original medium.






(6) Passivation: Due to the uneven or thin passivation film on the surface of the cold drawn steel pipe, the pickling passivation effect is not good, and electrochemical corrosion is easily formed.