Initial Corrosion Behavior of Carbon Steel Q235, Pipeline Steel L415, and Pressure Vessel Steel 16MnNi Under High Humidity and High Irradiation Coastal-Industrial Atmosphere in Zhanjiang

The Zhanjiang oil station is located near the sea, and corrosion factors such as Cl-, SO2, humidity, and UV irradiation in the surrounding environment will endanger the service life of the common materials. Carbon steel Q235 is commonly used as an oil tank pressure ring, pipeline steel L415 is used for oil and gas transportation, and pressure vessel steel 16MnNi is commonly used as the outer wall material of an oil tank. These materials are easily corroded when they are directly exposed to the atmosphere, but there have been few studies in recent years on the short-term corrosion behaviour of common metal materials in oil stations in high humidity and high irradiation industrial marine atmosphere environments. In this work, the initial corrosion behaviour of carbon steel Q235, pipeline steel L415, and pressure vessel steel 16MnNi exposed to the real Zhanjiang atmospheric environment for 180 d were studied through weight loss analysis, corrosion product analysis, corrosion morphology observation, and electro-chemical analysis. According to the thickness loss data, carbon steel Q235 had the weakest corrosion resistance of the three materials, whereas pipeline steel L415 had the best corrosion resistance. These common materials were exposed to the same atmospheric environment for the same amount of time, resulting in the same corrosion products in the rust layer, which contained alpha-FeOOH, gamma-FeOOH, and Fe3O4. The difference was that the rust layer of carbon steel Q235 contained a high concentration of beta-FeOOH, which may have facilitated the corrosion process. The concentration of gamma-FeOOH and Fe3O4 varied amongst the three materials. The rust layer of carbon steel Q235 contained more gamma-FeOOH and Fe3O4, followed by pressure vessel steel 16MnNi and pipeline steel L415, which had the least gamma-FeOOH and Fe3O4. Furthermore, carbon steel Q235 had the thinnest rust layer and the greatest thickness loss, whereas pipeline steel L415 and pressure vessel steel 16MnNi had a thicker rust layer and less thickness loss. The results of electrochemical experiments showed that the rust layer of carbon steel Q235 has the weakest ability to protect the matrix, whereas the rust layer of L415 has the best ability to protect the matrix. Additionally, the synergistic effect of Cl-, SO2, and UV irradiation destroyed the protective layer of the rust layer and accelerated the corrosion.