Effect of Flowing Seawater on Corrosion Characteristics of Passivation Film on TA2 Pure-Ti Pipes
TA2 pure-Ti is a new generation of marine pipeline material,and the flowing seawater in-duced failure of its passivation film can deteriorate the durability of TA2 pure-Ti pipes.Hence the effect of flowing seawater on the corrosion behavior of TA2 pure-Ti being subjected to different surface treatments is of great significance for evaluating the service performance of TA2 pure-Ti pipes.Herein,the corrosion behavior of two surface treated TA2 pure-Ti rings in flowing seawater was comparatively studied in a home-made seawater pipeline integrated simulation set by means of measurements such as dynamic po-tential polarization,electrochemical impedance,and Mott Schottky analysis,as well as characterization of corrosion morphology and corrosion products.The results showed when the seawater flow rate below 5 m/s,the change in seawater flow rate had a relatively small impact on the corrosion resistance of the pas-sive film on the surface of TA2 pure-Ti.When the potential rises,the passive film on the surface of TA2 showed a transient dissolution in flowing seawater,but it would soon be re-passivated,which did not have a significant impact on the corrosion resistance of the substrate material.Compared to the surface passivation treated ones,the polished TA2 exhibit limited diffusion characteristics of cathodic polarization in flowing seawater.This is mainly due to the presence of a passivation film on the surface of the passiv-ated TA2,which consumes less oxygen than the surface polished ones that have not yet formed a passiv-ation film.The depolarization of the polished TA2,which was controlled by oxygen mass transfer rate de-velops slowly,resulting in a limit current density that does not vary with the potential.The passivation films on the TA2,after being subjected to two surface treatments only exhibit n-type semiconductor char-acteristics in seawater,and after polarization testing,the material surface is flat without significant local corrosion.
TA2 pure-Tiseawater pipelineerosion-corrosionelectrochemistrypassivation film
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