Corrosion trend on Q450 weathering steel deposited with Na2SO4, NaCl under ultraviolet light illumination

Abstract

A contrastive study about ultraviolet light (UV) illumination on Na2SO4, NaCl induced Q450 weathering steel was qualitatively and quantitatively studied. The corrosion rate was calculated from mass losses and the order was as following, coupons deposited with Na2SO4 under UV illumination (238.18 μA·cm−2) > with NaCl under UV illumination (213.77 μA·cm−2) > with NaCl under Dark condition (71.98 μA·cm−2) > with Na2SO4 under Dark condition (43.26 μA·cm−2). The influence of UV illumination on metal corrosion followed this sequence: Na2SO4 > NaCl, and which was on account of corrosion products film on metal depositing Na2SO4 with a larger carrier density on metal depositing Na2SO4 with a larger carrier density (9.32×1020 cm−3) and stronger electric conductivity ability than NaCl (8.93×1020 cm−3). Electrochemical impedance spectroscopy studies revealed charge transfer resistance Rct value, suggesting that smaller resistances gained on the rusted samples due to UV illumination, and an accelerated corrosion effect on rusted sample was also obtained under UV illumination. The improved corrosion performance by UV illumination was due to corrosion products of semiconductor property and photovoltaic effect.