Fouling Organism Attachment Behavior and Corrosion Mechanism of Titanium Alloy in the Sea
Titanium and its alloy are widely used in marine engineering equipment,and the marine environment is an extremely complicated natural environment.The complex marine environment has caused many severe tests of titanium alloy materials.Among them,biological attachment corrosion is one of the difficult problems that need to be solved.Therefore,this article has selected TC4 titanium alloys for research on biological adhesion and corrosion behavior,so as to provide a scientific basis for pollution-loss biological prevention and material corrosion protection.The polished TC4 titanium alloy samples were encapsulated with threaded joints and epoxy resin,and then put into the real sea of Tiaoshun Island in Zhanjiang,Guangdong.The research team observed the attachment and growth behavior of fouling organisms in different test cycles by soaking and hanging samples.The corrosion morphology of TC4 titanium alloy in different test periods was observed by ultra-depth-of-field microscope,and the influence of fouling organism attachment on the corrosion behavior of TC4 titanium alloy was analyzed by polarization curve and electrochemical impedance spectroscopy(EIS).The composition of corrosion products was analyzed by XRD,and the mechanism of biological adhesion corrosion of TC4 titanium alloy was explored.Results showed that TC4 titanium alloy had good biocompatibility in marine environments.Among them,macrofouling organism gave priority to barnacles,and the number of which was as high as 4.5 pcs/cm2.The proportion of barnacles to sample area changed in a"∫"shape.There was no obvious corrosion pit where was no barnacle attachment position or the gap between barnacles and barnacles on the surface of sample,but the barnacle attachment position had corrosion pit,which formed ulcer pit with time.The succession of fouling organism changed the efficiency of dissolved oxygen transfer to the surface of titanium alloy,and at the same time caused the inhomogeneity of the surface medium properties of titanium alloy,thus affecting the formation and regeneration of passive films.The electrochemical impedance and polarization results showed that the corrosion potential,corrosion current and capacitive reactance arc radius fluctuated.Fouling organisms such as barnacles were unevenly attached to form a"closed retention layer",which lead to oxygen-rich areas and oxygen-poor areas,forming an oxygen concentration difference battery.The reduction reaction occurred in the oxygen-rich region and the oxidation reaction occurred in the oxygen-poor region,thus promoting corrosion.A passive film containing TiO2 and Al2O3 was formed on the surface of TC4 titanium Al2O3,and CaCO3 mainly came from calcareous shell fouling organisms.In conclusion,barnacles are the dominant species for marcofouling organisms in this sea area.The corrosion mechanism of barnacles in different growth stages is different.The calcareous shell and dense barnacle glue of living barnacles with complete structure can effectively isolate the external corrosion medium to inhibit corrosion,while the dead barnacles promote corrosion because of the incomplete shell structure and the decomposition of organisms.The adhesion of fouling organisms makes the surface of TC4 titanium alloy undergo complex physicochemical,biochemical and electrochemical processes,which leads to local corrosion of the sample in marine environment,and the corrosion rate is nonlinear.
万方数据
维普
