Corrosion Mechanism Of La-Ce On X70Pipeline Steel

In this paper, the polarization curves, weight loss measurement methods andscanning electron microscopy and other analytical methods was used. Soaking in0.1mol/L Na2SO4solution experiment studies that the effect of micro addition RareEarth elements on X70pipeline steel corrosion resistance.Different inclusions and pearlite interlamellar spacing on the corrosion behavior ofX70pipeline steel was studied. Rare Earth in different soaking time has different affecton the polarization curve. Soaked in the first cycle, the result of the polarization curveof X70pipeline steel shows corrosion current density is the smallest without addition ofRE. Corrosion current density showed a tendency to increase with the increasing of theaddition of RE. While in the later a few cycles, the polarization curve measurementsshowed that the increase in the amount of X70pipeline steel in0.1mol/L Na2SO4solution in the corrosion current density with RE tends downwards, and when the REamount to0.1%,the corrosion current density is the smallest. This phenomenon occursbecause of the RE has changed the shape and nature of the inclusions, thereby affectingthe corrosion of the electrode potential of the micro-battery.We found that with the increasing in the amount of RE, the pearlite interlamellarspacing tends downwards by measuring the pearlite interlamellar spacing. When the REamount to0.1%, the pearlite interlamellar spacing is the smallest. Contrasting withelectrochemical test results, we found that when the pearlite interlamellar spacingdecreases, the X70pipeline steel corrosion current density decreases.By observing the morphology of the corrosion products, we found that X70pipeline steel without adding RE which soaked in0.1mol/L Na2SO4mainly occursuniform corrosion. While after adding RE, in the beginning stages of corrosion mainlyoccurs regional corrosion. With the inclusion of material was eroded, corrosion type isalso changed from regional corrosion to uniform corrosion. Because of its inclusion waseroded, the composition is more uniform, so the composition micro-batteries is less thanthe without adding RE X70pipeline steel. The corrosion current density is alsodecreases, thus improving the corrosion resistance of X70pipeline steel.