Research On Galvanic Corrosion Behavior Of 110SS Tubing,2830 Tubing And 140V Casing

With the continuous development of high-acid oil and gas wells at home and abroad,more and more materials are widely mixed and used,so galvanic corrosion has become a problem that needs to be considered.Based on the research and application of 2830 nickel-based alloy steel,140V carbon steel and 110SS steel in domestic galvanic corrosion,this paper uses indoor high temperature and high pressure simulation corrosion test and electrochemical test technology,supplemented by SEM,EDS,XRD,etc.Modern analysis methods have studied the galvanic corrosion behavior of three steels in formation water environment after pairwise coupling,and evaluated their electrochemical performance at different temperatures through electrochemical impedance(EIS)technology and polarization curves.Self-corrosion performance,using the mixed potential theory to predict the coupling tendency,coupling potential and current between them.The results of the indoor corrosion weight loss test show that in the high temperature and high pressure CO₂+H₂S formation water environment,2830 nickel-based alloy steel exhibits excellent uniform corrosion resistance under self-corrosion conditions,while 110SS steel and 140V steel have more serious self-corrosion.After 2830-140V steel is coupled,the corrosion of 140V steel is aggravated,and the corrosion rate of 2830 steel is slowed down.This shows that when 2830 and140V form a bimetallic coupling system,140V is used as the anode and the corrosion rate is accelerated.As the cathode,2830 is protected and slows down its own corrosion rate.After 110SS-140V steel is coupled,the corrosion of 140V steel is accelerated,and the corrosion of 110SS steel is reduced.Analysis of the composition of corrosion products on the surface of single-metal 2830 nickel-based alloy steel shows that the passivation film composition of 2830 steel is mainly composed of Cr,Fe,and Ni compounds.In the CO₂+H₂S formation water environment,the passivation film uniformly covers the surface of the sample,and the film layer is thinner.The compound of Cr and Ni enhances the density of the passivation film and prevents the anion in the solution from affecting the base metal.Corrosion:The composition analysis of the surface corrosion products of single metal 140V and 110SS carbon steel shows that FeS,FeS₂,FeCO₃ and Fe₃O₄ are present,and the corrosion product film is loose and porous.After 2830-140V steel is coupled,the corrosion products of nickel-based alloy steel 2830 mainly contain ferrous carbonate and iron sulfide,which are related to the occurrence of galvanic corrosion,and the galvanic corrosion effect is obvious.Electrochemical tests show that in the CO₂+H₂S formation water environment,the anodic polarization curve of 2830 nickel-based alloy steel has a complete passivation interval,and the reaction is controlled by anode activation.As the temperature rises,the passivation interval shrinks.The pitting location decreases,the polarization resistance value decreases,the corrosion rate increases,and the corrosion resistance decreases;as the temperature increases,the self-corrosion current increases and the corrosion rate accelerates for 140V and 110SS carbon steels.The EIS spectrum of 2830 steel shows capacitive reactance arc,and the polarization resistance value decreases with the increase of temperature,indicating that the corrosion resistance of the passivation film on the surface of the sample decreases.The EIS patterns of 140V and 110SS steels are composed of capacitive reactance arcs,and a straight line appears in the low frequency region.When the film forming temperature increases,the density of the passive film of carbon steel becomes worse,and the protective effect of the film on the substrate is weakened.Monitoring the changes of the galvanic potential and galvanic current density of the 2830-140V metal pair,it is found that the two changes more drastically.With the extension of time,the numerical changes of galvanic potential and galvanic current density gradually decrease,and gradually tend to stable.In addition,it can be seen that the greater the temperature,the greater the galvanic current fluctuation,which is related to the more severe the corrosion on the surface of the test piece as the temperature increases.Monitoring the changes of the galvanic couple potential and galvanic current density of110SS-140V,it is found that when the temperature is between 30?and 60?,the temperature increases,the galvanic current increases,and the corrosion accelerates;when the temperature is90?,the two polarities occur Reversal.In any case,under the same temperature conditions,the galvanic corrosion effect of 2830-140V is more obvious than that of 110SS-140V.