The Study Of Corrosion Behavior Of Carbon Steel In Different Environment Applied By Wire Beam Microelectrode

Wire beam electrode(WBE)technology,as a kind of technique which combined the conventional electrochemical method and probe technique.The working area of each small electrode on the surface of the WBE is less than 3.14 mm2,which is different from the traditional electrode(working area is more than 100 mm2).Therefore,it was also defined as wire beam microelectrode.Due to it has the advantages such as fast detection rate,accurate data and high resolution,wire beam electrode has become an important technical method to reveal the local corrosion behavior of metal materials and surface coatings.However,the complex preparation process,strict requirements on quality of metal substrate and low yield limited the application of wire beam electrode technology in other fields to a large extentIn this paper,a new type of component gradient-distributed wire beam electrode is designed and prepared based on wire beam electrode technology.The corrosion characteristics and behaviours of carbon steel in different corrosion conditions were studied by wire beam electrode combined with conventional electrochemical method,micro-zone electrochemical technology,micro-morphology characterization and theoretical calculation,etc.It is expected to master the corrosion behavior of carbon steel in the different corrosion conditions and further expand the detection and application scope of metal materials.The main contents and conclusions include1.The local corrosion behaviors of Q235,45 and T9 carbon steel immersed in 3.5wt.%NaCl solution at 25? were studied by using single and component gradient-distributed carbon steel wire beam electrode.The results showed that the local corrosion strength of three kinds of carbon steel ranked as 45>Q235>T9;The average anode current o of T9 carbon steel on the composition gradient distributed wire beam electrode is 10 times higher than the average current on the surface of T9 single component wire beam electrode,and the surface of T9 carbon steel in the component gradient-distributed WBE was corroded seriously.The SEM images supports the experimental phenomenon and proved tha the WBE technology can characterize the corrosion behavior and characteristics of three kinds of carbon steel in 3.5wt.%NaCl solution accurately at room temperature2.The crevice corrosion behaviors of three kinds of carbon steel were studied by single component WBE.In the semi-covered crevice structure,the sensitivity of the three kinds of carbon steels to crevice corrosion ranked as:Q235>45>T9;while in the full-covered crevice structure,the sensitivity order ranked as:T9>45>Q2353.The corrosion behaviors of three kinds of carbon steel immersed in 3.5wt.%NaCl solution at different temperatures(25?,40?,60? and 80?)was measured by component gradient-distributed WBE.When the temperature increased to 60?,the surface of T9 carbon steel appeared large amount of anode current points,where was considered as the main corroded area,while the surface of 45 carbon steel and Q235 carbon steel maintained as cathode current.After 8 hours,the location of 45 carbon steel became the new anode current area,while the anode currents on the surface of T9 carbon steel disappeared.When the temperature is further increased to 80?,the anode current area changed and transfered continuously.The general rule as followed:the surface of T9,45 and Q235 carbon steel generates anode currents alternately.The surface of T9 carbon steel is the position which is still corroded seriously.Macroscopic corrosion morphology and SEM images were consistent with electrochemical results of wire beam electrode.In conclusion,WBE technique can record the "polarity reversal"of carbon steel in 3.5wt.%NaCl solution system accurately4.Four kinds of silane films were prepared on the surface of Q235 carbon steel WBE,the corrosion behavior of Q235 carbon steel protected by different silane films was studied based on WBE technology.The results of WBE technology showed that the average current on the surface of four kinds of silane film respectively are 1.66×10-6 A,6.02×10-7 A,2.48×10-7 A,2.31×10-6 A.Elelctrochemical impedance spectroscopy revealed that the charge transfer resistances respectively are 1980 ?,2130 ?,4768?,1732 ?.Dynamic potential polarization curve displayed that coroosion potential respectively are-0.442 V,-0.386 V,-0.2 17 V,-0.474 V and corrosion current density are 2.36×10-6A·cm-2,8.77×10-7A·cm-2,1.74×10-7A·cm-2,5.67×10-6A·cm-2.It can be seen that the WBE technology is consistent with the results of EIS and Tafel curve,the third silane film with the best corrosion resistance can be accurately screened out Meanwhile,the microscopic morphology atlas can also prove the test results of the WBE technique and other electrochemical methods appropriately.5.The measuring system of thin liquid film with different concentration of chloride ion(0.5wt.%NaCl?1wt.%NaCl?3.5wt.%NaCI and 5wt.%NaCl)were constructed,which was based on the array electrode technology and the principle of double electrode electrocouple.The galvanic pair of Q235 carbon steel and H62 brass were tested in this condition,it was found that the average current density of Q235 carbon steel reached the maximum value of 3.17×10-5 A·cm-2 in 3.5wt.%NaCl thin liquid film system,the galvanic corrosion effect y=14.74.Corrosion Master module predicted that the galvanic couple of Q235 carbon steel-H62 brass was most serious corroded in the 3.5wt.%NaCl thin liquid film environment.The maximum corrosion current value could reach to 3.62×10-5 A.The theoretical calculation was consistent with the electrochemical experiments.Amorphous Cell module in Materials Studio software is used to construct the liquid film model with different concentration of chloride ion.It was found that the virtual part of the dielectric constant increased with the concentration of chloride ion improved in the liquid film,which means that the thin liquid film's ability to retain and transfer charge is gradually enhanced,and the degree of metal corrosion became more serious.Therefore,the simulation analysis provided by the theoretical calculation was consistent with the array electrode test results.