Effect Of Hydrogen On The Electrochemical Corrosion Performance Of Super Duplex Stainless Steel

As the third-generation super duplex stainless steel,S32750 SDSS has excellent corrosion resistance and good mechanical properties,and is often used in harsh service environments such as petroleum,petrochemical,and marine.S32750 SDSS often faces the influence of hydrogen when used in these environments,which has an adverse effect on corrosion performance.In this paper,S32750 SDSS was charged with hydrogen by electrochemical methods,and the surface roughness and aging effects were studied by the open circuit potential curve,potentiodynamic polarization curve,electrochemical impedance spectroscopy measurement,MottSchottky curve test and other electrochemical methods.The parameters such as cooling method,holding temperature and holding time after hydrogen charging affect the corrosion behavior of S32750 SDSS in simulated seawater,and the following conclusions are obtained:(1)As the surface roughness of the S32750 SDSS hydrogen-charged specimen increases from 0.054 ?m to 0.254 ?m,the scratches on the surface of the specimen become deeper and deeper,and the surface area for hydrogen adsorption becomes larger and larger,and more hydrogen enters the specimen.The increase of hydrogen leads to an increase in the defect concentration in the passivation film,which promotes the reaction between the passivation film and the solution interface,reduces the integrity and stability of the passivation film,reduces the corrosion resistance of the passivation film,and increases the pitting sensitivity.Big.Metallographic observation also confirmed this.(2)The cooling method of aging treatment and the dual action of hydrogen affect the corrosion resistance of S32750 SDSS.When water cooling,air cooling and furnace cooling are used respectively,its corrosion resistance also shows a downward trend.This is mainly because the three methods lead to different residence time of S32750 SDSS in the high temperature sensitive area.The residence time of water cooling is the shortest,the precipitation is the least,and the precipitation is the most during furnace cooling,and the location of the precipitation is easy to form pitting nucleation.In some places,coupled with the role of hydrogen,the stability of the passivation film is reduced,and the defects of the passivation film increase,and it is easily eroded and broken down by ions,resulting in a decrease in corrosion resistance.(3)The hydrogen in the material can be reduced by heating,which affects the corrosion performance.When the temperature is 200-400 ?,300 ? shows the best corrosion resistance;when the S32750 SDSS is kept at 300 ? for 0.5-2h,the open circuit potential of S32750 SDSS in simulated seawater is from-0.320 V Change to-0.260 V and finally reach-0.190 V,and the capacitive arc diameter also shows an increasing trend.The longer the holding time,the better the recovery effect of the material's corrosion resistance.This is mainly because the hydrogen content gradually decreases with time..