Corrosive Characteristics Of Sediments In Northern South China Sea

Based on two proposed submarine pipeline projects,this paper has carried out a survey of submarine sediment corrosivity in Daya bay and Sanya bay in the Northern South China Sea.It has carried out qualitative analysis and evaluation of the corrosivity of the marine environment in the region,studied the correlation between corrosion factors and their impact on the construction of marine projects,discussed the disastrous factors of marine projects,and provided anti-corrosion measures for the design of submarine pipelines.The data used in this paper were from Daya bay and Sanya bay.A total of 10 seabed surface sediment samples were collected in Daya bay.The characteristics of 9 corrosion factors such as pH,sulfide content,salt content,redox potential?Eh?,organic carbon content,Fe³⁺/Fe²⁺,resistivity,sulfate reducing bacteria?SRB?and sediment type were analyzed,and the redox environment of seabed sediments in the proposed area was divided,and the corrosivity of sediments in the area was evaluated.The results show that the sediments in Daya bay show weak oxidizing environment,and the corrosivity of the sediments is not strong at present.The higher sulfide content is found at station B01 and station B11,with the content of 21.7g/kg and 24.5g/kg respectively,which may be caused by terrigenous materials with higher sulfide content from Ma Bian Zhou Island,E Zhou Island and Xiao E Zhou Island.The corrosivity of sediment is relatively weak,which is consistent with the judgment result of sediment oxidation-reduction environment.A total of 16 surface sediment samples were collected in Sanya bay.The characteristics of 8 environmental factors such as pH,sulfide content,salt content,Eh,organic carbon content,Fe³⁺/Fe²⁺,sulfate reducing bacteria?SRB?and sediment types were analyzed.The redox environment of seabed sediments in the proposed area was divided and the corrosivity of sediments in the area was evaluated.The results show that the sediments in the Sanya bay are generally strong oxidizing and locally weak oxidizing,and the corrosiveness of the sediments is relatively weak.Station S01,Station S02 and Station S03 are located on the beach in the intertidal zone to the east of Xiaoqi Port,with large sediment concentration and coarse particles.Station S14,station S15 and station S16 are located on the coral reef flat in Xi Mao Zhou Island,with large gravel content.Station S09is located in the gravel accumulation body of"Huashidui".The content of gravel and sand is relatively large,so the content of sulfide in the sample is relatively small,exceeding the detection limit of the instrument.Due to sudden changes in seabed topography,the sediment distribution of seabed sediments was affected by seabed hydrodynamic action,resulting in more sulfate reducing bacteria in stations S05 and S11 than in other stations.In general,the corrosivity of this area is relatively weak,which is consistent with the determination result of the oxidizing environment of the deposit.For specific submarine pipeline construction projects in two sea areas,attention should be paid to macro galvanic corrosion and marine attached biological corrosion,and anti-corrosion measures can be combined with heavy anti-corrosion coating and cathodic protection.