Atmospheric corrosion effects of HNO3- : Influence of concentration and air velocity on laboratory-exposed copper

Abstract A recently developed experimental set-up has been used to explore the atmospheric corrosion effects of nitric acid (HNO 3 ) on copper, in particular the influence of concentration and air velocity. Characterization and quantification of the corrosion products on exposed samples were performed with Fourier transform infrared (FT-IR) microspectrocscopy, ion chromatography, X-ray diffraction (XRD), micro-balance and microscopy. At low air velocity (0.03 cm s −1 ) HNO 3 deposition and weight gain of copper increased linearly with concentration up to 400 μg m −3 or 156 ppb. The influence of air velocity on corrosion of copper was tested within the range of 0.03–35.4 cm s −1 . Although the air velocity in this study was significantly lower than typical outdoor wind values, a high HNO 3 concentration of the air velocity of 35.4 cm s −1 resulted in a relatively high deposition velocity ( V d ) of 0.9 cm s −1 on the metal surface and 1.2 cm s −1 on an ideal absorbent, which would imply a limiting deposition velocity on the copper surface ( V d,surf ) of 3.6 cm s −1 . Results obtained in this study emphasize the importance for future research on the corrosion effects of HNO 3 on materials as very little has so far been done in this field.