| With the development of offshore oil and gas,offshore wind power and other marine resource,a lot of offshore equipment needs not only huge amounts of corrosion resistant structure materials,but also highly reliable electrical control system.With the development of electronic equipment towards miniaturization and integration,printed circuit boards(PCBs)not only bear complex electrical,mechanical and thermal loads,but also are subjected to alternating temperature and humidity,polluted gas(CO2?SO2?H2S?NOX?O3)and solid particles(NaCl?PM2.5?PM10).Once the package is damaged and corrosive gas penetrates,it is easy to form an absorbed thin electrolyte film to cause corrosion of materials,reducing the reliability of electronic equipment.In this dissertation,focusing on corrosion of electronic copper in marine atmosphere,firstly,electrochemical impedance spectra(EIS),quartz crystal microbalance(QCM),and thin film resistance(TER)monitoring technologies are used to study the condensation and evaporation process of thin electrolyte layer(TEL),atmospheric corrosion kinetics of copper,and inhibition mechanism of vapor corrosion inhibitors(VCIs);secondly,a new superhydrophobic ultra-thin coating was developed for corrosion protection of PCBs;finally,self-developed electrical resistance monitor was applied for online measuring corrosivity of service environment of electronic materials.The main results are summarized as follows:Comb-like EIS sensors are used to study the deliquescence and drying process of sodium chloride(NaCl)on Cu surface in a climatic chamber,which was situ monitored by digital microscope and Attenuated Total Reflection Fourier Infrared Spectroscopy simultaneously.The results show that at 25?,when relative humidity is below 60%,NaCl particles are not deliquescent and copper corrosion is slight(0.02 ?m/a);when relative humidity is between 60%?76%,salt particles pre-deliquesce and corrosion rate slightly increases;when relative humidity is higher than 76%,salt particles deliquesce completely with formation of a large number of microdroplets,and corrosion rate rises sharply(>20?m/a).During drying process,TEL on copper surface changes from continuous to discontinuous until precipitation of NaCl particles.Accordingly,a model for calculating the TEL thickness based on conductivity of TEL is proposed,which solves the measurement problem of TEL thickness.In addition,the sensor could sensitively monitor the condensation phenomenon during high-low temperature alternating process.TER sensors are used to investigate the medium/long-term atmospheric corrosion of copper and inhibition performance of 2-phenyl imidazoline(2-PI).The corrosion rate of copper increases evidently with relative humidity,temperature and NaCl loading density,but decreases as a power function with prolonged test.At low NaCl loading density(?40?g/cm2),2-PI presents increasing inhibition efficiency with elevated temperature,mainly owing to that elevated temperature enhances the vapor pressure of 2-PI and its concentration on Cu surface;however,under high NaCl loading density,corrosion inhibition performance of 2-PI is significantly reduced,possibly due to that the defective corrosion product layer formed at high relative humidity has loose and porous property,retarding the diffusion of 2-PI on Cu matrix,which seriously restricts its corrosion inhibition performance.In comparison with fresh copper surface,inhibition performance of 2-PI is impaired significantly on corroded copper surface.In view of higher sensitivity of QCM than TER sensors,the effect of NaCl on copper initial atmospheric corrosion is further researched by QCM.It is found that in comparision with clean copper-coated crystal quartz,corrosion rate of contaminated copper-coated crystal quartz increases by about two orders of magnitude,mainly due to that NaCl deliquescence forms a thicker liquid film,resulting in accelerated copper corrosion.QCM and EIS results show that inhibition performance of 2-PI on chloride-induced initial atmospheric corrosion of copper enhances with an increase of temperature.However,on corroded copper,the adsorption amount of 2-PI is much higher than on clean copper,which is possibly due to that the rough corrosion products layer absorbs and entraps a large number of 2-PI molecules through capillary condensation mechanism.To avoid mass gain caused by copper corrosion,a dry deoxygenated argon atmosphere is selected for studying pure adsorption behavior of 2-PI on copper,finding that it obeys a simple pseudo first-order model for lack of corrosion products.Through sol-gel method and subsequent curving process,a fluorinated silica-based superhydrophobic coating is prepared on PCBs,which exhibits a high contact angle of 158°and low sliding angle of 3°.The weathering resistance tests verify that the superhydrophobic coating not only has good waterproof and self-cleaning capacity,but also shows certain protection ability even under ultraviolet irritation or in acid/base solution.Further electrochemical tests indicate that superhydrophobic coating on PCB-Cu and PCB-Sn specimens exhibits excellent corrosion resistance in 1 wt%NaCl aqueous solution with 99.6%and 98.7%inhibition efficiency respectively.In addition,compared to conventional conformal coatings(>100 ?m),the superhydrophobic coating(?2 ?m)is extremely thin,beneficial to heat dissipation of underlying electrical components.The superhydrophobic coating is expected to replace conformal coatings for improving the weathering resistance of PCBs.The above sensors are tested for atmospheric corrosion monitoring in the field,and results show that copper corrosion rate measured by electrical resistance monitor has a strong correlation with weight loss data of copper coupons.Finally,the electrical resistance corrosion monitor realizes the engineering application in the air clip of the main cable of Humen Second Bridge and the electrical control system of offshore booster station,for corrosivity monitoring of service environment and fault early warning of electrical components in the marine atmosphere. |
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