INVESTIGATION OF CO2 CORROSION PRODUCT SCALEOF N80 OIL TUBE STEEL

摘要

The variation of morphology, structure, mechanical properities of CO2 corrosion productrnscales of N80 oil tube steel was experimented under dynamic high temperature and high pressurernconditions. The results show that corrosion damage primarily happens in the initial stage, subsequently,rncorrosion process is impeded by protective corrosion product scales. Corrosion rate falls down to 1/6rnfrom 48h to 240h. The main component of scales changes from FeCO3 to FeCO3+Fe3C and the scalernthickness increases earlier and decreases later. After 120h, there are plenty of inhomogeneities (flaws,rnpores, etc.) in the scale, whose mechanical parameters are the lowest relatively. Under the interaction ofrnintrinsic growth stresses, extrinsic stresses due to cyclic mechanical loading of flow impacting andrnchemico-mechanic, product scales spall to thin. The fracture strength of product scales is far biggerrnthan the shear strength so shear break happens in the interface scale/matrix when the scale isrnhomongeneous but shear break will preferential happen in the place where inhomogeneties getrntogether.