Study Q345 Steel Corrosion In Simulated Atmospheric Aerosols Environment

With the rapid development of modern construction, as the fundamental structure materials, steels play an important role in the fields such as transportation, buildings, aerospace, marine resource exploitation and etc. In fact, there is a big demand for steel in these fields. Therefore, the problem of steel corrosion while it is exposed to atmospheric environment has attracted considerable attention. Atmospheric environment pollution has been much more serious nowadays, and the frequent fog haze weather has caused the damage and destruction for the steel structures. There is a close relationship between the formation of fog haze and aerosol pollutants. As a consequence, the corrosion process and behavior of steel in atmospheric aerosol environment has already drawn a great attention. In order to investigate the influence of corrosion behavior of Q345 steel in atmospheric aerosol environment, we have performed an indoor accelerated corrosion simulation test. At the same time, weight-loss method, X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical techniques were utilized to characterize and analyze the relationship between corrosion dynamics and the structure, composition and stability of rust layers.In this paper, NaCl and HCl were chosen as the corrosive medium to simulate the atmospheric corrosion process of Q345 steel under acid marine aerosol environment. NaCl and NaHSO3 were selected as the corrosive medium to simulate the corrosion process of Q345 steel under marine and industrial atmospheric aerosol environment. (NH4)2SO4 was used as the corrosive medium to simulate the corrosion process of Q345 steel under ammonium salt aerosol environment.The fitting results of mass loss showed that the rust layers have no protective ability in acid marine aerosol environment and ammonium salt aerosol environment, and the protective ability of rust layers which were formed in marine and industrial atmospheric aerosol environment was not obvious.The results about composition of corrosion products showed that corrosion products on the surface of Q345 steel contained reducing substances such as y-FeOOH and β-FeOOH in the early stage of experiment, these substances were unfavorable to the protective ability of rust layers, a-FeOOH was found in the corrosion products in the later stage of experiment, a-FeOOH was benefit to the stability of rust layers.Through the SEM results we knew that the rust layers were thin and loose at first, the density of rust layers was increased in the later stage of steel corrosion. The protective ability of rust layers was increased so that it could protect the substrate from invasion of the corrosive medium.The electrochemical analysis results showed that the variation trend of stability of rust layers exhibited weaker first, and then enhanced in the accelerated corrosion test of Q345 steel under acid marine aerosol environment and ammonium salt aerosol environment. The rust layers could restrain the dissolution of steel to some extent under marine and industrial atmospheric aerosol environment. The protective ability of rust layers enhanced in the later stage in three atmospheric aerosol environment, this phenomenon illustrated that rust layers contained substance of electrochemical stability.