Corrosion Characteristics Of Zn-based Composite Coatings Under The Condition Of Sulfate-reducing Bacteria

The microbial corrosion of metallic materials can cause serious economic losses,and in some cases even bring environmental pollution and safety problems.Therefore,solving the problem of metal corrosion is a very meaningful work.In microbial corrosion,sulfate-reducing bacteria(SRB)is one of the most important bacteria causing metal corrosion.The research on sulfate-reducing bacteria is also a hot issue,especially in oilfield drilling,oil and gas storage and transportation,etc.The corrosion caused by the reducing bacteria is particularly serious.At present,corrosion inhibitor,cathodic protection,coating,electrodeposition technology and other technologies are widely used in the field of anti-corrosion.Based on the predecessors,the Zn-based composite coating was prepared by electrodeposition technology,and its sulfate was studied.Corrosion characteristics of reducing bacteria conditions.In this paper,two different zinc-based composite coatings were prepared by electroplating method in the sulfate plating system.The corrosion characteristics of Zn-based composite coatings under sulfate-reducing bacteria conditions were studied by electrochemical impedance spectroscopy(EIS),open circuit potential(OCP)method and scanning electron microscope(SEM).The effect of Zn-based composite coatings on the growth of sulfate-reducing bacteria was also studied.The results show that:(1)Under the condition of sulfate reducing bacteria,the corrosion rate of Zn-TiO2 coating was 0.011 mm/a,and the corrosion rate of 20#carbon steel was 0.03 1mm/a,indicating that Zn-TiO2 coating can effectively inhibit the corrosion of carbon steel by sulfate-reducing bacteria.The results of electrochemical experiments showed that SRB and its metabolite film can reduce the corrosion of 20#carbon steel in a certain period of time.However,some tiny peeling of the corrosion product film will aggravate the corrosion of 20#carbon steel,while Zn-TiO2 coating can prevented the adhesion of SRB and its metabolite film due to the presence of plating.It can be seen from the SRB count that the SRB content of the plating group was less than the carbon steel group,indicating that the Zn-TiO2 coating can inhibited the growth of SRB.(2)Nano-Ag particles were added into the sulfate plating solution system,and the Zn-Ni-Ag coating was successfully prepared by the galvanostatic method.Studies have shown that the plating efficiency of this plating process was related to its current density only,regardless of the plating time and other conditions.The addition of nano-Ag particles changes the original crystal formation,and the nano-Ag particles are embedded on the surface of the plating layer by extrusion or the like.The corrosion of Zn-Ni-Ag ternary composite coating under SRB condition was further studied by static coupon test and electrochemical experiment.The corrosion rate of Zn-Ni-Ag ternary composite coating was less than that of 20#carbon steel.The SRB count shows that the number of SRB bacteria in the ZnNi-Ag ternary composite coating system was less than that of the 20#carbon steel system,indicating that the existence of Zn-Ni-Ag ternary composite coating can inhibit the growth of SRB bacteria to a certain extent.