Study On Corrosion Behavior Of Marine High Strength Steel In NaCl Solution

With the development of marine resources to the deep sea and polar regions,the development and use of marine engineering steel is becoming more and more important,and the performance requirements of marine structural steel also need to be improved.At present,high strength,easy welding and corrosion resistance are the main performance indexes of steel used in marine engineering structures.Compared with foreign countries,the development of marine resources in China is relatively late,and the research and development of marine steel is relatively backward compared with foreign countries.E690 steel is a new type of high-strength low-alloy steel independently developed in China,which is widely used in marine engineering structures because of its high strength and excellent comprehensive properties.However,the marine environment is extremely complex and harsh,and the E690 steel structures in service,such as offshore platforms,ships,anchor chains and so on,are prone to corrosion,hydrogen embrittlement,friction and wear under the action of corrosive media,cathodic protection,waves and other conditions,which will cause huge safety risks and economic losses.However,the hydrogen charging corrosion,friction and wear corrosion behavior and failure mechanism of E690 high strength low alloy steel in marine environment have not been studied.Therefore,it is of great theoretical and practical significance to study the failure behavior and failure mechanism of E690 high strength low alloy steel in seawater environment,which lays a stable foundation for the following protection work.In this thesis,simulation experiments are carried out in the laboratory,in which 3.5 wt.%Na Cl solution is used to simulate the actual marine environment.Firstly,the immersion corrosion of different periods and the electrochemical corrosion behavior in seawater environment at different temperatures were studied,and then the electrochemical corrosion behavior of E690 steel after hydrogen charging with different current density was studied by using electrochemical workstation.The friction and wear corrosion behavior of E690 steel in air and solution was further studied.The specific work is as follows.(1)Study on immersion corrosion of E690 steel.The weight loss of E690 steel immersed in simulated marine solution is measured at first,and the macroscopic morphology of the surface is analyzed.The corrosion rate of E690 steel after soaking in simulated marine solution for different periods is obtained.(2)Study on electrochemical corrosion of E690 steel under different temperature solution.Using electrochemical workstation device,the corrosion behavior of E690 steel under simulated ocean conditions was studied by self-corrosion potential,polarization curve and electrochemical impedance spectroscopy.The surface morphology of samples after corrosion in different temperature solutions was scanned and analyzed.At the same time,the corrosion products produced after corrosion were detected and analyzed.The corrosion mechanism of E690 steel under different temperature solutions was discussed.(3)Study on electrochemical corrosion of E690 steel under different hydrogen current density.The electrochemical corrosion experiments were carried out on E690 steel samples by electrochemical workstation,and then on the samples with different current densities.The effect of pre-hydrogenation on the corrosion behavior of E690 steel samples under simulated marine conditions was studied.and the surface morphology,corrosion layer structure and corrosion product composition of all samples after corrosion are analyzed in depth to reveal the corrosion mechanism of E690 steel samples after pre-hydrogenation.(4)Study on friction and wear corrosion behavior of E690 steel in air and solution.By controlling the load variables,the friction wear corrosion behavior of E690 steel samples in air and solution is studied.tribological properties of E690 steel samples under different conditions were investigated by friction coefficient and wear rate.At the same time,the morphology characteristics of the wear surface of E690 steel samples were deeply analyzed,and the element content of the wear products was semi-quantitatively analyzed to reveal the wear mechanism of the samples under different conditions.