EFFECT OF CARBON STEEL INHOMOGENEITY AND ANIONS IN SOILS ON CORROSION
碳钢的不均匀性和土壤中阴离子对腐蚀的影响

Corrosion behavior of carbon steel buried in soils after 20 years was studied by means of SEM,EDAX and metallographic techniques.The observations revealed that the inclu-sions in steel,welded joints and heat-treated region of the steel tube specimens resulted in pitting corrosion. It is evident that,therefore,localized and penetrated corrosion is caused chiefly by the inhomogeneity of carbon steel itself.In addition,the existence of a lots of SO2-and Cl-elements in corrosion pit indicates that anion contents in surrounding soil is an important factor for local-ized corrosion.CaCO3 deposited on the surface of buried specimens will protect the specimens from further corrosion.