Study On Failure Behavior Of Organic Coatings In Deep Sea Pressure-Fluid Simulation Environment

China's national policy proposes "toward the deep ocean and the ocean".The deep ocean is an important area for national economic and military development.At present,deep submerged equipment and other devices and equipment in service in the deep sea environment suffer severe corrosion,which significantly restricts the development of the deep sea area.The problem of metal corrosion and protection in the deep sea environment needs to be solved urgently.Organic coatings are one of the most commonly used methods of protecting metallic materials.Although the application of organic coatings can delay metal corrosion,organic coatings will inevitably experience various forms of failure during service.Organic protective coatings currently in service in deep sea environments have fast failures,short lifespans,and outstanding problems.Previous research revealed that the hydrostatic pressure and alternating pressure in the deep sea accelerate the failure of organic coatings.However,in the actual service environment,the deep sea is a dynamic fluid environment and the flow rate is a key environmental factor that cannot be ignored.The research on the failure mechanism of coatings has not been reported.Based on this background,this article will use deep sea dynamic simulation equipment to take epoxy varnish and epoxy glass flake organic coatings as research objects,and use characterization methods to further study the service behavior of two coating materials to reveal the failure mechanism of organic coatings in deep sea pressure-fluid environment.The dissertation starts with the research on the failure mechanism of epoxy varnish coatings under deep sea pressure-fluid environment(6 MPa,3 m/s),using electrochemical impedance spectroscopy in-situ monitoring technology(EIS),free film water absorption test,drawing The characterization methods such as mechanical and mechanical performance tests systematically studied the failure process of coatings and the laws of changes in performance with service time,and then cooperated with differential scanning calorimetry(DSC),scanning electron microscopy(SEM)and energy spectrometer(EDS),laser test methods such as confocal microscope(CLSM)and Fourier transform infrared spectroscopy(FTIR)explore the coating failure mechanism.The results show that the impedance value of epoxy varnish coating/metal system has a rapid decrease under the deep sea pressure-fluid environment with service time;the water absorption of epoxy varnish coatings has risen sharply in the deep sea pressure-fluid environment,and a large amount of water has accumulated at the coating/metal interface in a short time,causing the coating to blister;thereby reducing the coating adhesion rapidly,causing coating failure.Deep sea pressure-fluid environment accelerates the water transport process,the fluid motion enlarges the coating defects,causes the coating to crack and continuously cross-link into a network,and the surface coating part is peeled off in the later period of service.The depth is about 2.896?m.Epoxy varnish coatings have no change in the form of chemical bonds throughout the service life,mainly due to changes in physical properties,and the tensile strength and glass transition temperature of the coatings have been significantly reduced.Secondly,the paper studies the service process of organic epoxy coatings on glass flakes under deep sea pressure-fluid environment(6 MPa,3 m/s).The results show that after the filler is added,the barrier effect of the organic coating increases,but the deep sea pressure-fluid environment still accelerates the water transport process in the coating,which causes the coating resistance Rc to decrease rapidly and the coating capacitance Cc to continuously increase.The coating/metal system still causes blisters in the form of blisters during service,which leads to coating failure.Compared with the immersion in atmospheric pressure,the water absorption rate of the coating significantly increased after 240 hours of service in the deep sea pressure-fluid environment,and the tensile strength and glass transition temperature decreased more.The failure mechanism of the coating is that the deep sea fluid environment destroys the bonding between the filler and the base material,which makes the coating experience the process of bulging,partial shedding,crack initiation and finally the complete failure.The chemical structure of the coating did not change throughout the failure process.