Weathering steel is a type of high-strength, low-alloy steel that contains copper, phosphorus, chromium, and nickel. This steel is designed to form a stable rust-like oxide layer that protects the steel from corrosion. The corrosion resistance of weathering steel is due to the formation of a tightly adhering, protective rust layer that develops over time through exposure to the atmosphere. However, in harsh environments, such as those with exposure to acid rainwater or UV radiation, the corrosion behavior of the steel may be affected. This paper will investigate the corrosion behavior of A588 Grade B weathering steel plate under the combined effects of UV radiation and acid rainwater spray.
Experimental Procedure:
The experimental procedure involved exposing the A588 Grade B weathering steel plate to UV radiation and acid rainwater spray for a period of three weeks. The weathering steel plate was first cleaned with distilled water and then allowed to dry. A spray bottle containing acid rainwater (pH 4.3) was used to spray the weathering steel plate at a frequency of four times per day for three weeks. The weathering steel plate was also exposed to UV radiation at a wavelength of 254 nm for three weeks using a UV radiation lamp.
The corrosion behavior of the weathering steel plate was evaluated using potentiodynamic polarization tests and electrochemical impedance spectroscopy. The potentiodynamic polarization tests were conducted using a three-electrode electrochemical cell consisting of a saturated calomel electrode (SCE) as the reference electrode, a platinum electrode as the counter electrode, and the weathering steel plate as the working electrode. The weathering steel plate was immersed in a 3.5 wt% NaCl solution to simulate a corrosive environment. The corrosion potential (Ecorr) and corrosion current density (icorr) were measured using a potentiostat/galvanostat. The electrochemical impedance spectroscopy tests were conducted using an autolab potentiostat/galvanostat and an impedance analyzer. The weathering steel plate was immersed in a 0.1 M NaCl solution for the impedance tests.
Results:
The results of the potentiodynamic polarization tests showed that the corrosion behavior of the weathering steel plate was significantly affected by the combined effects of UV radiation and acid rainwater spray. The Ecorr of the weathering steel plate under the combined effects was more negative than that of the weathering steel plate without exposure to UV radiation or acid rainwater spray. This indicated that the corrosion rate of the weathering steel plate increased under the combined effects. The icorr of the weathering steel plate under the combined effects was also higher than that of the weathering steel plate without exposure to UV radiation or acid rainwater spray. This indicated that the corrosion rate of the weathering steel plate increased under the combined effects.
The results of the electrochemical impedance spectroscopy tests showed that the corrosion behavior of the weathering steel plate under the combined effects of UV radiation and acid rainwater spray was also affected. The impedance spectra of the weathering steel plate under the combined effects exhibited a semicircle in the high-frequency range and a linear region in the low-frequency range. The presence of a semicircle in the impedance spectra indicated that a passive film had formed on the surface of the weathering steel plate. However, the diameter of the semicircle was smaller under the combined effects than that of the weathering steel plate without exposure to UV radiation or acid rainwater spray. This indicated that the passive film on the weathering steel plate was less stable under the combined effects.
Conclusion:
In summary, the corrosion behavior of A588 Grade B weathering steel plate was significantly affected by the combined effects of UV radiation and acid rainwater spray. The electrochemical tests showed that the corrosion rate of the weathering steel plate increased under the combined effects, which was due to the decrease in stability of the passive film on the surface of the steel. The results of this study provide important information for understanding the corrosion behavior of weathering steel in harsh environments and can be used to develop strategies for protecting weathering steel from corrosion.
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