Effects Of Aging Treatment On Corrosion Resistance Of Cu-bearing Stainless Steels

Cu-bearing stainless steel made by adding some copper to traditional stainless steels is an innovative class of structural/functional material.Its excellent and lasting antibacterial performance is mainly attributed to the precipitation of Cu-rich phases formed during proper solution and aging process.However,aging normally leads to the reduction of corrosion resistance,which restricts the practical application of Cu-bearing stainless steel to some extent.Therefore,in order to solve this problem and promote the application of Cu-bearing stainless steel,it is really important to clarify the relative corrosion mechanism.In this work,the stainless steels and Cu-bearing stainless steels were aged at various temperature for different time to investigate the effects of aging and Cu precipitation on the corrosion resistance of Cu-bearing stainless steels.The double loop electrochemical potentiokinetic reactivation(DL-EPR),potentialdynamic polarization and potentiostatic polarization were employed to analyse corrosion resistances;The TEM and 3D APT were used to observe and analyse precipitation;and the optical microscope and CLSM were used to observe surface morphology.The experimental results showed that the sensitization of Cu-bearing 304L stainless steel most likely occurred at 735? and required 1.4 h to achieve.Aged at 700? for 10 h,the pitting potential of Cu-bearing 304L stainless steel drops from 230 mV to 160 mV,and the intergranular and pitting corrosion resistance decreased with extension of aging time.Under the same heat treatment condition,Cu-bearing stainless steels showed lower intergranular and pitting corrosion resistance than traditional stainless steels.The precipitation of the Cu-rich phase during aging was the main cause that induced the intergranular and pitting corrosion resistance of Cu-bearing stainless steel.Carbides were not found in the Cu-bearing stainless steel.Meanwhile,due to the quick nucleation of Cu-rich phase,Cu-bearing stainless steels required less time to achieve intergranular sensitization than stainless steels(aged at 700?,Cu-bearing 304 stainless steel requires 2h to achieve intergranular sensitization while 304 stainless steel requires 10h)and showed wider temperature range of intergranular sensitization.However,the sensitization rate of Cu-bearing stainless steel gradually decreased after some time because of the slow growth of Cu-rich phase.