Corrosion Behaviors Of Copper In The Marine Atmospheric Environments

Due to their excellent performance,copper and its alloys are widely applied in the marine engineering,electrical,mechanical manufacturing,transportation,and national defense fields.Copper has strong corrosion resistance in nature environment,but is susceptible to corrode in environments with high relative humidity and corrosive media.However,copper is prone to more serious corrosion in the marine environments.Under the combined action of oxygen,water,corrosive medium,sunlight and other factors,a series of complicated physical and chemical reactions will occur.The resulting corrosion and destruction will greatly shorten the service life of many devices,e-ven lead to the scrapping of instruments,resulting in huge economic losses.At the same time,it may also cause serious pollution to the marine environment and affect the development of new technologies.Therefore,it is of great practical significance to study the corrosion process and mechanism of copper in the marine atmosphere.The corrosion behavior of copper under various factors,such as NaCl deposition,temperature,relative humidity and ultraviolet radiation were analyzed in a simulation system to investigate the corrosion mechanism in the marine atmospheric environment.The corrosion weight gain and loss,microscope,SEM,XRD and electrochemical technique are used to analyze the corrosion rate,surface morphology,structural characteristics and corrosion potential of the sample separately.The influence of the surface state,marine atmospheric environmental factors on the corrosion behavior,and the corrosion mechanism were studied in this thesis.The key issues are summarized as follows:Copper samples with various degree of roughness(Ra ranging in 0.06～0.32 μm)are acquired by using the different size of water proof abrasive papers and polishing compound to explore the effect of surface condition on the corrosion behavior of the sample:it was found that along with the surface roughness increases,copper corrosion is more serious,and put forward the formula of weight loss per unit area and the sample surface roughness;By adjusting the temperature and relative humidity in the corrosion test chamber to explore the influencing degree of the two factors,the corrosion in the atmospheric environment of South China Sea is also simulated:void and micro-cracks appear during the electrochemical corrosion process.The new products grow above the defects,which indict that micro-cracks provide channels for ion transport.The corrosion weight loss increased and the corrosion rate reduced gradually with the etching time;The combined influence of ultraviolet illumination and NaC1 deposition,temperature,relative humidity on corrosion mechanism of copper,and the wavelength and intensity on corrosion behavior were studied.It shows that copper is most susceptible to UV light with the wavelength of 185nm and 254nm.The corrosion potentials of copper samples illuminated by UV light with the different wavelengths are different:the sample illuminated with 185nm is the highest,and that with 254nm is the lowest.The corrosion rate of copper samples after UV irradiation at wavelengths of 254nm with different intensity show that with the increase of intensity,the extent of corrosion was aggravated.