Study On Effect Of Temperature On Cathodic Protection Of X65 Pipeline Steel And 304 Stainless Steel

In recent years,pipeline steels are widely used in industrial production.Due to the length of pipes,there is certain temperature differences in different sections.Therefore,it is necessary to find out cathodic protection potential and hydrogen evolution potential of X65 steel at different temperatures and make sure the hydrogen evolution reaction does not happen under the potential.With the increase of temperature,the corrosion potential(E_corr)of X65 pipeline steel decreased and corrosion current density(I_corr)of X65 steel increased.As the results of EIS at different cathodic potential,charge transfer resistance R_t increased first and then decreased with the decrease of cathodic potential at different temperatures.And the cathodic protection potential and hydrogen evolution potential negatively shifted with the increased of temperature.The range of cathodic protection of 304 SS is wide.As the results of EIS and polarization curve measurement,the cathodic protection potential of 304SS decreased in the different media with the increase of temperature,which is determined by R_t and C_p.As the results of electrochemical measurement after hydrogen charging,E_corr,E_pit,resistance of solution in pitting holes and charge transfer resistance decreased,amount and size of pits increased with the decrease of cathodic potential,which indicated that hydrogen destroyed the corrosion resistance of 304 SS.As the results of XPS measurement,the concentration of Cr in passive film decreased with the decrease of cathodic potential,which decreased the thickness of passive film.As a consequence,passive film was more likely to be ruptured and corrosion resistance of 304 SS was destroyed with the decrease of cathodic potential.As the results of hydrogen permeation measurement,hydrogen could not diffuse across 304 SS due to its microstructure.By using circulating water channel,temperature gradient of 35⁵5?was provided and the current and potential distribution on surface of wire beam electrode?WBE?was observed.As the results,corrosion potential decreased and current density increased of X65 steel with the increase of temperature.The changes of potential and current on surface of X65 steel became smooth,which indicated that the corrosion of X65 steel reached a stable condition over time.As the results of EIS measurement,corrosion resistance of X65 steel decreased with the increase of temperature.However,due to existence of the corrosion product,rate of charge transfer decreased,which indicated that corrosion rate of X65 steel decreased.