Effect Of MnS And Al₂O₃ Inclusions On Corrosion Induced In Steel

Corrosion resistance is an important indicator to measure the properties of the steel,especially oil and gas pipelines,marine engineering steel need higher corrosion resistance.The non-metallic inclusion in steel is an important factor to influence the corrosion property of steel.It is very important to clarify the relationship between the properties of non-metallic inclusions and the corrosion initiation.In this paper,the effects of typical MnS and Al₂O₃ inclusions on the corrosion initiation of steel were studied,and new ways were provided for improving the corrosion resistance and inclusion control of steel.The experiments included the non-metallic inclusions were controlled by the tubular heating resistance furnace,the characteristics of the inclusions and the morphology of the corrosion were observed by optical microscope and scanning electron microscope,the corrosion potential of steel was studied by electrochemical polarization curve and electrochemical impedance spectroscopy.The results show that: 1)Corrosion is induced at the interface between MnS inclusions and matrix,once the inclusions appear on the surface of the matrix,the steel matrix will be destroyed seriously.2)The inclusions that are small size or buried shallowly in the steel matrix will dissolve or fall from the matrix in the process of corrosion,thus reducing the damage to the steel matrix;MnS and Al₂O₃ inclusions distributed in clusters are more likely to induce corrosion than those distributed alone and have a large degree of damage to the steel matrix.3)In situ corrosion process,the MnS inclusions are more soluble than the Al₂O₃ inclusions at 15 s.And the dissolved matters of MnS inclusions are more aggressive and have greater damage to the steel matrix.