Research On Key Corrosion Factors And Synergistic Mechanism Of Q345 Steel In South China Sea

With the comprehensive advancement of the country open development and the full implementation of the“13th Five-Year Plan",the marine strategy has continued to mature,and its position and role in the overall national development strategy are becoming more and more important.Investments such as docks,ports,marine platforms,and ships have become the main force in developing the marine economy and building a strong marine nation,and steel products have contributed greatly to these main forces.Most of these steels are used in marine atmospheric environment.Therefore,the steel corrosion problem caused by the marine atmospheric environment has become a hotspot of current research.Corrosion factors such as humidity,temperature,salinity,and light intensity under the marine atmospheric environment have caused a great deal of damage and destruction to the steel.Therefore,the corrosion of steel caused by the marine atmospheric environment has become a hot research topic.In order to study the influence of single corrosion factors and composite factors on the corrosion behavior of Q345 steel in the marine atmospheric environment,indoor accelerated simulation tests were carried out,and weight loss analysis,XRD(X-ray diffraction),SEM(Scanning Electronic Microscopy)and electrical Chemical analysis and other methods are used to analyze corrosion kinetics,rust layer composition,rust layer morphology and corrosion electrochemistry.Using a single key corrosion factor(humidity,temperature,chloride ion mass fraction,light intensity)as the corrosion factor,the corrosion of Q345 steel under the action of a single corrosion factor in the marine atmospheric environment is simulated.The composite corrosion factor(chloride ion mass fraction+humidity,chloride ion mass fraction+temperature,chloride ion mass fraction+light)was used as the corrosion factor to simulate the corrosion of Q345 steel under the action of the composite corrosion factor in the marine atmospheric environment.Corrosion weightlessness results show that under the action of a single corrosion factor in the marine atmospheric environment,Q345 steel has a peak corrosion rate at 1.75%chloride ion mass fraction,indicating that under this condition,Q345 steel has the highest corrosion tendency;The corrosion rate of steel is accelerated;when the illumination range is 70W/m2,the corrosion rate value is the smallest,indicating that under this condition,the corrosion tendency of Q345 steel is low.Under the combined action of a single corrosion factor in the marine atmospheric environment,the corrosion rate of Q345 steel reaches the minimum at 3.5%+75%,and the corrosion resistance of Q345 steel is the best under this condition;the corrosion rate is maximum at 3.5%+35?,indicating Under this condition,the corrosion reaction of the substrate is accelerated;the corrosion rate gradually decreases in the process of 3.5%+65W/m2,and a rust layer with a certain thickness is formed on the surface of the sample.At this time,the rust layer has good protection performance.XRD analysis of the components of the corrosion products showed that the corrosion products on the surface of Q345 steel were mainly ?-FeOOH,Fe3O4,Fe2O3·H2O,?-FeOOH,?-FeOOH when the single corrosion factor acted in the marine atmosphere.Among them,?-FeOOH and ?-FeOOH are reductive,and their production will make the corrosion intensified.Under the combined action of a single corrosion factor in the marine atmospheric environment,the corrosion products produced on the surface of the Q345 steel substrate are the same as those of the single corrosion factor,but the content is different.Due to the presence of Cl-,the continuous occurrence of corrosion is induced,which increases ?-FeOOH,Q345 steel substrate suffered greater corrosion.The SEM results of the rust layer morphology show that:with the increase of chloride ion mass fraction,humidity,temperature,and light intensity,the surface rust area increases,although the rust layer is thick and cracks and holes appear,indicating that the increase of a single corrosion factor makes the rust layer The protection performance becomes weak.The ectrochemical test results show that:in the corrosion test of Q345 steel under the action of a single factor in the simulated marine atmosphere environment,as the corrosion progresses,the change trend of the rust layer's protection performance is first increased and then weakened.In the corrosion test of Q345 steel under the action of composite factors in the simulated marine atmospheric environment,the corrosion of the steel substrate is accelerated due to the presence of Cl-.Under different humidity,when the test conditions are 3.5%+75%,the corrosion potential value and The radius of the capacitive arc is the largest,and the protective performance of the rust layer is the strongest;under different temperatures,the increase in temperature makes the protective trend of the rust layer on the substrate surface increase first,then decrease,and finally increase;when the light intensity increases Due to the presence of Cl-,the radius of the capacitive arc increases first and then decreases,and the protective properties of its rust layer increase first and then decrease.