Corrosion Behavior Of Novel Antibacterial Steel And Its Welded Joints In The Environment With SRB

In oil and gas pipeline transportation,Microbially Influenced Corrosion（MIC）has become one of the factors that cannot be ignored in the pipeline failure.In recent years,with the deepening of research on MIC protection,introducing Cu element to make metal surface have antibacterial ability becomes a new idea of material design which is from the perspective of the material itself.In order to gain an exact insight on the bacterial corrosion behavior and mechanism of the novel antibacterial pipeline steel and its corresponding welded joints,the following research have been carried out as below.Firstly,the corrosion behavior of antibacterial steel in long service was analyzed.The results showed that the novel antibacterial steel could significantly reduce the pitting caused by SRB,and could be better applied to the shale gas field environment.The results of corrosion immersion test also showed that the corrosion behavior of L245 steel might aggravated continuously,whereas the antibacterial steel even had no apparent pitting corrosion in the environment with SRB.Secondly,the corrosion behavior and mechanism of SRB at antibacterial steel welded joints was explored through weight loss experiments,combined with micro-electrochemistry,focused ion beam-scanning electron microscope（FIB-SEM）and other testing methods.The results showed that the corrosion of weld zone of L245 steel was more seriously than the base metal,and pitting corrosion were mostly occurred near the fusion line in the weld zone.No serious pitting corrosion occurred in weld zone and base metal zone of antibacterial steel,showing good resistance to SRB corrosion.The results of bacteria concentration test and SKP showed that the potential of weld zone was higher than the base metal,and SRB was easy to accumulate in the L245 steel weld.The Cu element was found in biofilm and corrosion products of antibacterial steel welded joint,and the number of SRB sessile cells decreased significantly compared with L245 steel.Finally,the corrosion behavior difference and mechanism of SRB on the antibacterial steel welds and L245 steel welds were studied at different cathodic potentials.The results showed that with the cathodic potential from-0.775V_SCE to-0.875V_SCE,the sessile cells of SRB on L245 steel weld increased significantly and the electron transfer process on electrode surface was promoted.The pitting depth and number of antibacterial steel weld showed an rising trend.The Cu element was accumulated in the biofilm and corrosion product layer of antibacterial steel weld.The antibacterial steel weld has fewer bacterial clusters and larger Rct.The antibacterial steel weld could effectively inhibit the corrosion caused by SRB.