绿色杀菌缓蚀剂对不同粗糙度碳钢的腐蚀行为影响研究

Effect of Green Bactericidal Corrosion Inhibitor on Corrosion Behavior of Carbon Steel with Different Surface Roughness

目的揭示绿色杀菌缓蚀剂对不同粗糙度碳钢表面SRB+IOB生物膜的杀菌缓蚀行为与规律的影响。方法本文采用失重实验、表面分析、电化学测试等手段,探究20#碳钢在不同粗糙度(240#、600#、1200#)下,添加绿色杀菌缓蚀剂对混合菌的杀菌行为和对碳钢的缓蚀效果的影响,阐明D-酪氨酸分解抑制生物膜的作用机理。结果试样表面的腐蚀产物层厚度、点蚀坑大小与深度随表面粗糙度的降低、杀菌缓蚀剂的添加,而减小。在不添加杀菌缓蚀剂情况下,碳钢随表面粗糙度从240#降到1200#,其年腐蚀深度由0.186 mm/a降到了0.157 mm/a,下降幅度达15.6%。自腐蚀电流密度icorr由20.5 mA/cm^(2)降到了6.93 mA/cm^(2),下降幅度高达66.2%。其中,在240#表面粗糙度下,碳钢年腐蚀深度由不添加杀菌缓蚀剂的0.186 mm/a降到了添加杀菌缓蚀剂的0.116 mm/a,下降幅度达37.6%。icorr由20.5 mA/cm^(2)降到了11.8 mA/cm^(2),下降幅度达42.4%。结论随表面粗糙度降低,碳钢表面趋于光滑,应力集中减小,碳钢表面很难聚集混合菌里的硫化物、矿化物,以及腐蚀性阴离子,H+很难与阴离子结合形成酸性环境,不易产生氧浓差电池,减缓了均匀腐蚀向局部腐蚀的转变,降低了点蚀发生概率。而D-酪氨酸的加入可将生物膜中的细菌由固着态转变为浮游态,同时破坏了细菌细胞结构、蛋白质、氧浓差环境,进而增强了杀菌缓蚀效果。

At present,as microbial corrosion has gradually become an important form of pipeline material destruction,and some traditional chemical methods to mitigate corrosion will bring various negative effects such as environmental pollution.From the angle of green environmental protection,a new green bactericidal corrosion inhibitor of our research group was selected,and the effect of the green bactericidal corrosion inhibitor on the corrosion process of carbon steel in the sulfate-reducing bacteria(SRB)and iron-oxidizing bacteria(IOB)mixed bacteria on the different surface roughness was studied to reveal the effect of the green bactericidal corrosion inhibitor on the bactericidal corrosion inhibition behavior and law of SRB+IOB biofilms on carbon steel surfaces with different roughness.Weight loss experiments,surface analysis and electrochemical tests were conducted to investigate the bactericidal behaviour and the corrosion inhibition effect on 20#carbon steel at different roughness(240#,600#and 1200#)with the addition of green bactericidal corrosion inhibitor on mixed bacteria,as well as the mechanism of action of D-tyrosine to decompose and inhibit biofilms.The thickness of the corrosion product layer,the size and depth of pitting pits on the surface of the 20#steel sample decreased with the decrease of surface roughness and the addition of bactericidal inhibitor.In the case of no added bactericidal corrosion inhibitor,with the surface roughness decreasing from 240#to 1200#,the annual corrosion depth of carbon steel was reduced from 0.186 mm/a to 0.157 mm/a by 15.6%,and the self-corrosion current density icorr was reduced from 20.5×10^(-6) A/cm^(2) to 6.93×10^(-6) A/cm^(2) by 66.2%;For 240#surface roughness,the annual corrosion depth of carbon steel was reduced from 0.186 mm/a without bactericide to 0.116 mm/a with bactericide by 37.6%;the icorr was reduced from 20.5×10^(-6) A/cm^(2) to 11.8×10^(-6) A/cm^(2) by 42.4%.On the one hand,the rougher the surface of carbon steel,the deeper the surface groove will be,which is easy to produce stress concentration,and cause local defects in the oxide film on the metal surface.The defective part is used as the anode,and the surrounding part is used as the cathode,resulting in occluded cells,gradually forming pitting nuclei,causing surface damage.However,with the reduction of surface roughness,the carbon steel surface tends to be smoother,the stress concentration is reduced.It is difficult for the carbon steel surface to gather sulfide,mineralized substances and corrosive anions in mixed bacteria.H+is difficult to combine with anions to form an acidic environment,thus not likely to generate oxygen concentration difference cell,slow down the transformation from uniform corrosion to local corrosion,and reduce the probability of pitting corrosion.On the other hand,aerobic IOB bacteria can utilize O2 to oxidize Fe2+to Fe3+in water and form an oxide film on the surface of the sample,with Fe2+as carrier,O2 as terminal receptor,which will accelerate the reaction with iron.At the same time,the oxide film blocks the O2 in the solution,and provides anaerobic space for SRB anaerobic bacteria,so that SRB reduces SO42-to HS-.Fe2+and S2-can combine to produce FeS,which is more likely to aggravate corrosion;However,the addition of D-tyrosine can effectively decompose and inhibit biofilm,make bacteria change from fixed state to floating state,reduce the generation of EPS,reduce the complexation of Fe2+,and reduce the synergy of IOB and SRB;At the same time,the green bactericidal and corrosion inhibitor also changes the cell structure in the cell membrane,destroys the bacterial cell membrane,cell wall,and cell protein,and also destroys the oxygen concentration environment,thus enhances the bactericidal and corrosion inhibition effect.