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Atomospheric corrosion effects on HNO3 - comparison of laboratory exposed copper, cinc and carbon steel
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.ORCID iD: 0000-0002-9453-1333
2007 (English)In: Atmospheric Environment, ISSN 1352-2310, Vol. 41, no 23, 4888-4896 p.Article in journal (Refereed) Published
Abstract [en]

The effect of HNO3 on the atmospheric corrosion of copper has been investigated at varied temperature (15-35 degrees C) and relative humidity (0-85% RH). Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) confirmed the existence of cuprite and gerhardtite as the two main corrosion products on the exposed copper surface. For determination of the corrosion rate and for estimation of the deposition velocity (V-d) of HNO3 on copper, gravimetry and ion chromatography has been employed. Temperature had a low effect on the corrosion of copper. A minor decrease in the mass gain was observed as the temperature was increased to 35 degrees C, possibly as an effect of lower amount of cuprite due to a thinner adlayer on the metal surface at 35 degrees C. The V-d of HNO3 on copper, however, was unaffected by temperature. The corrosion rate and V-d of HNO3 on copper was the lowest at 0% RH, i. e. dry condition, and increased considerably when changing to 40% RH. A maximum was reached at 65% RH and the mass gain remained constant when the RH was increased to 85% RH. The V-d of HNO3 on copper at >= 65% RH, 25 degrees C and 0.03 cm s(-1) air velocity was as high as 0.15 +/- 0.03 cm s(-1) to be compared with the value obtained for an ideal absorbent, 0.19 +/- 0.02 cm s(-1). At sub-ppm levels of HN03, the corrosion rate of copper decreased after 14 d and the growth of the oxide levelled off after 7 d of exposure

Place, publisher, year, edition, pages
2007. Vol. 41, no 23, 4888-4896 p.
Keyword [en]
nitric acid, materials degradation, deposition velocity, iron, gerhardtite, cuprite, nitrate
National Category
Chemical Sciences
URN: urn:nbn:se:kth:diva-6444DOI: 10.1016/j.atmosenv.2007.02.007ISI: 000247868300010ScopusID: 2-s2.0-34249702872OAI: diva2:11159
Uppdaterad från submitted till published: 20100917 QC 20100917Available from: 2006-11-29 Created: 2006-11-29 Last updated: 2010-09-17Bibliographically approved
In thesis
1. HNO3-Induced Atmospheric Corrosion of Copper, Zinc and Carbon Steel
Open this publication in new window or tab >>HNO3-Induced Atmospheric Corrosion of Copper, Zinc and Carbon Steel
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The role of nitric acid (HNO3) on the atmospheric corrosion of metals has so far received little or no attention. However, the last decades of decreasing sulphur dioxide (SO2) levels and unchanged HNO3 levels in many industrialized countries have resulted in an increased interest in possible HNO3-induced atmospheric corrosion effects. In this study a new method was developed for studying the corrosion effects of HNO3 on metals at well-defined laboratory exposure conditions. The method has enabled studies to be performed on the influence of individual exposure parameters, namely HNO3-concentration, air velocity, temperature and relative humidity, as well as comparisons with newly generated field exposure data.

The corrosion rate and deposition rate of HNO3 on copper was shown to follow a linear increase with HNO3 concentration. The deposition velocity (Vd) of HNO3 increased up to an air velocity of 11.8 cm s-1. Only at a higher air velocity (35.4 cm s-1) the Vd on copper was lower than the Vd on an ideal absorbent, implying the Vd of HNO3 at lower air velocities to be mass-transport limited.

Within the investigated temperature range of 15 to 35 ºC only a minor decrease in the HNO3-induced copper corrosion rate could be observed. The effect of relative humidity (RH) was more evident. Already at 20 % RH a significant corrosion rate could be measured and at 65 % RH the Vd of HNO3 on copper, zinc and carbon steel reached maximum and nearly ideal absorption conditions.

During identical exposure conditions in HNO3-containing atmosphere, the corrosion rate of carbon steel was nearly three times higher than that of copper and zinc. The HNO3-induced corrosion effect of copper, zinc and steel turned out to be significantly higher than that induced by SO2 alone or in combination with either NO2 or O3. This is mainly attributed to the much higher water solubility and reactivity of HNO3 compared to SO2, NO2 and O3. Relative to SO2, zinc exhibits the highest sensitivity to HNO3, followed by copper, and carbon steel with the lowest sensitivity.

Extrapolation of laboratory data to an assumed average outdoor wind velocity of 3.6 m s-1 enabled a good comparison with field data. Despite the fact that ambient SO2 levels are still much higher than HNO3 levels, the results show that HNO3 plays a significant role for the atmospheric corrosion of copper and zinc, but not for carbon steel. The results generated within this doctoral study emphasize the importance of further research on the influence of HNO3 on degradation of other materials, e.g. stone and glass, as well as of other metals.

Place, publisher, year, edition, pages
Stockholm: Kemi, 2006
Nitric acid, deposition velocity, mass transport, air velocity, relative humidity
National Category
Chemical Sciences
urn:nbn:se:kth:diva-4194 (URN)91-7178-483-7 (ISBN)
Public defence
2006-12-08, Sal F3, KTH, Lindstedtsvägen 26, Stockholm, 10:00
Available from: 2006-11-29 Created: 2006-11-29

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