| Stainless steel plays an important role in the construction of national economic.When stainless steel is used in harsh(high salt,acid environment)environment,it is easy to occur pitting,and the occurrence of pitting directly affects the service life of stainless steel products.It is great significance for maintenance and safely warming of large stainless steel structures to carry out monitoring and research on pitting process of stainless steel.The atmospheric pitting monitoring device of 304 stainless steel was designed,analysing the electrochemical noise data collected from the indoor acceleration simulation experiment and the outdoor exposure experiment of 304 stainless steel,combining the electrochemical impedance spectroscopy,potentiodynamic polarization and morphology analysis,the research and application of monitoring the atmospheric pitting behavior of 304 stainless steel were explored.The main results of the paper research were as follow:The noise data of 304 stainless steel in simulative oceanic atmosphere and oceanic-industrial atmosphere were monitored in real time by the self-made monitoring system,and the pitting behavior of 304 stainless steel in the above environment was studied by analyzing the noise data.The results show that the pitting process of 304 stainless steel in the above environment can be divided into three stages: passivation stage,metastable pitting stage and steady pitting stage.In the passivation stage,the electrochemical potential noise and the electrochemical current noise show a small amount of synchronous-homdromous fluctuations,the corrosion events’ frequency is high and the average electric quantity is low.In the metastable pitting stage,the electrochemical current noise and electrochemical potential noise exhibited exponential increase and adrupt decay simultaneously,the corrosion events’ frequency decrease and the average electric quantity increases.In stable pitting stage,electrochemical current noise exhibited exponential increase and abrupt decay,corresponding to the pulse in electrochemical potential noise which characterized by exponential decay following by abrupt recovery.Meanwhile,the lifetimes of fluctuations of electrochemical current noise and electrochemical potential noise were longer.The corrosion events’ frequency is low and the average electric rise significantly,and some small and flat pitting spots could be found from the SEM micrographs.The potentiodynamic polarization and electrochemical impedance spectrum can verify the nucleation of stable pitting.The results obtained by the two methods are consistent with each others,which proves that the monitoring system can continuously monitors the pitting behaviors of 304 stainless steels in simulative oceanic atmosphere and oceanic-industrial atmosphere and judges the occurrence of stable pitting.The noise data of 304 stainless steel in tropical oceanic atmosphere were monitored in real time by the self-made monitoring system,and the pitting behavior of 304 stainless steel in the above environment was studied by analyzing the noise data.The results show that the pitting behavior of 304 stainless steel in the tropical oceanic atmosphere can be divided into three stages: passivation stage,metastable pitting stage and steady pitting stage.The result of indoor accelerated simulation experiment and outdoor exposure experiment are consistent with each others,which proves that the self-made monitoring system has realized the continuous monitoring of 304 stainless steel in the outdoor atmosphere,and the monitoring results accurately reflect the noise fluctuation caused by pitting corrosion. |
PDF Full Text Request