Corrosion Resistance Of 2507 Super Duplex Stainless Steel In Ultra-high Temperature Underground Environment

Based on domestic research and application investigation of 2507 duplex stainless steel,this paper uses indoor high temperature and high pressure simulated corrosion test,electrochemical test and physical and chemical performance analysis,and supplemented by modern analysis methods such as SEM,XPS,EDS,etc.The corrosion resistance of stainless steel in ultra-high temperature environment is studied.The results of laboratory weight loss experiments show that in the CO₂ formation water environment,the 2507 duplex stainless steel exhibits excellent uniform corrosion resistance.As the temperature increases,the corrosion rate increases,which are all mild corrosion.At the same time,the 2507 duplex Stainless steel has good SCC resistance to CO₂ formation water.In the formate completion fluid environment,the corrosion rate of 2507 duplex stainless steel is lower at 200?,which is a mild corrosion.When the temperature exceeds 200?,the corrosion rate rises sharply.High,reached the standard of severe corrosion,and the corrosion rate increased with the increase of temperature;in the whole experiment of acid completion,the corrosion resistance of 2507 duplex stainless steel was poor,and the corrosion rate was a very serious corrosion category.As the temperature increases,the corrosion rate changes less.By simulating the 2507 duplex stainless steel in a fresh acid corrosion solution experiment,the fresh acid has the most severe corrosion of 2507 in the whole acidification completion experiment,which exceeds the standard acceptable range.Analysis of the corrosion product composition on the surface of 2507 duplex stainless steel shows that the components of the passivation film of 2507 duplex stainless steel are mainly composed of Cr,Fe,Ni compounds.In the CO₂ formation water environment,the passivation film covers the experimental surface uniformly,and the film layer is thin.The compounds of Cr and Ni enhance the denseness of the passivation film and block the anion in the solution from attacking the base metal;In the formate completion fluid environment,when the temperature is 200?,the passivation film on the sample surface can well protect the base metal.When the temperature is 220?and 240?,the passivation film is loose and porous,and the sample surface occurs.In the whole experiment of acid completion,cracks and voids still appeared on the passivation film on the surface of the sample at four temperatures,and2507 duplex stainless steel still suffered from selective corrosion mainly by ferrite dissolution.Electrochemical tests show that in the CO₂ formation water environment,the anodic polarization curve of 2507 duplex steel has a complete passivation interval.The reaction is controlled by the activation of the anode.As the temperature increases,the passivation interval decreases and the pitting point as the potential decreases,the polarization resistance value decreases,which increases the corrosion rate,and the corrosion resistance of 2507 duplex stainless steel decreases.In an independent fresh acid environment,as the temperature increases,the self-corrosion current increases,and the entire reaction is reacted by the cathode control.Due to the addition of corrosion inhibitors,the EIS spectrum shows inductive and capacitive reactance arcs,and the polarization resistance value decreases with increasing temperature,indicating that the corrosion resistance of the passivation film on the sample surface is reduced.