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Quantified In Situ Analysis of Initial Atmospheric Corrosion: Surface heterogeneity, galvanic effects and corrosion product distribution on zinc, brass and Galvalume
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The interaction of the surface of a pure metal or an alloy with the surrounding atmosphere occurs in a highly complex interfacial regime. During atmospheric corrosion this interfacial regime involves the metal surface, often covered by a naturally formed oxide layer of a few nanometers thickness; an aqueous adlayer, typically with a thickness of a few to a few tens of nanometers, and the atmosphere from which airborne particles, oxygen, and gaseous pollutants dissolve into the adlayer and influence the atmospheric corrosion process.

This thesis work is mainly concerned with the initial atmospheric corrosion of zinc and brass induced by carboxylic acids (120 parts per billion of formic, acetic, or propionic acid) in laboratory air with 90% relative humidity. This model system has been chosen to mimic indoor corrosion with carboxylic acids as major corrosion stimulators. The study forms part of a broader research program with the ultimate goal to provide a computer model of the early stages of atmospheric corrosion of copper, zinc and copper-zinc alloys, induced by carboxylic acids. Particular emphasis has been given to identify and quantify the corrosion products formed and to determine their lateral distribution over the corroding surface. This has been accomplished through a multi-analytical approach in which two main techniques are infrared reflection absorption spectroscopy (IRAS) which can identify and quantify corrosion products with a relative accuracy of about 10%, and confocal Raman microspectroscopy (CRM) which can identify and resolve corrosion products with a surface lateral resolution of better than one micrometer.

The corrosion products identified on pure zinc are zinc oxide (ZnO) and various forms of Zn-carboxylates. On brass, the main corrosion products identified are a cuprite (Cu2O)-like phase and various forms of Zn-carboxylates. For pure zinc and brass the formation rates of corrosion products in presence of the investigated acids depend, among others, on their deposition velocity and acid strength. The interaction of pure zinc and brass with humidified air containing carboxylic acids follows two spatially separated main pathways: a proton-induced dissolution of metal ions followed by the formation of oxides, and a carboxylate-induced dissolution followed by the deposition of metal carboxylates.

When applying this multi-analytical approach, it has been possible to distinguish between anodically and cathodically active areas for brass, but not for pure zinc. Galvanic effects have been shown to play a significant role during the initial corrosion of brass. 

Further evidence of the selective formation of corrosion products has been found when exploring the more complex heterogeneous surface of Galvalume, a commercial aluminum-zinc alloy coating. This material has been exposed to humidified laboratory air with additions of carbon dioxide (CO2) and sodium chloride (NaCl) and to a marine atmospheric environment. Initiated in the interdendritic zinc-rich areas, a uniform aluminum oxide (Al2O3) layer is formed. This oxide exhibits an inhibiting effect on the subsequent formation of other corrosion products, including aluminum oxyhydroxide (AlOOH), aluminum hydroxide (Al(OH)3), ZnO, zinc hydroxycarbonate and zinc hydroxychloride.

 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2011. , 68 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2011:40
Keyword [en]
Atmospheric corrosion; Zinc; Brass; Galvalume; In Situ; Quantification.
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-34096ISBN: 978-91-7501-012-0OAI: oai:DiVA.org:kth-34096DiVA: diva2:419102
Public defence
2011-06-14, D3, Lindstedtsvägen 5, KTH, Stockholm, 14:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council
Note
QC 20110607Available from: 2011-06-07 Created: 2011-05-25 Last updated: 2011-06-07Bibliographically approved
List of papers
1. Initial Oxidation of Zinc Induced by Humidified Air: A Quantified In Situ Study
Open this publication in new window or tab >>Initial Oxidation of Zinc Induced by Humidified Air: A Quantified In Situ Study
2009 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, Vol. 156, no 3, C81-C86 p.Article in journal (Refereed) Published
Abstract [en]

A multianalytical approach with in situ capability has been used to explore the initial oxidation of zinc in all with 90% relative humidity at 20 degrees C. The only surface species identified were zinc oxide (ZnO) and reversibly adsorbed water. Atomic force microscopy and X-ray diffraction revealed the homogeneous nucleation of ZnO grains the kinetics of ZnO Formation as followed quantitatively by in situ IR reflection-absorption spectroscopy (IRAS) integrated with a quartz crystal microbalance up to an average film thickness of 50 nm after 72 It of exposure. The quantitative results exhibit good agreement with ex situ cathodic reduction and with optical Calculations of IRAS data and provide further evidence of IRAS as all in situ analytical tool with quantification Capability. The ZnO growth followed the logarithmic rate law as predicted by Fehlner and Mott [Oxid. Met., 2, 59 (1970)]

Identifiers
urn:nbn:se:kth:diva-18397 (URN)10.1149/1.3043424 (DOI)000265837900035 ()2-s2.0-59349085533 (ScopusID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2011-06-07Bibliographically approved
2. Initial Atmospheric Corrosion of Zinc Induced by Carboxylic Acids: A Quantitative In Situ Study
Open this publication in new window or tab >>Initial Atmospheric Corrosion of Zinc Induced by Carboxylic Acids: A Quantitative In Situ Study
2009 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, Vol. 156, no 12, C441-C447 p.Article in journal (Refereed) Published
Abstract [en]

The initial atmospheric corrosion of zinc induced by formic acid, acetic acid, and propionic acid has been followed in situ with infrared reflection absorption spectroscopy (IRAS). An optical model was applied to quantify the IRAS data, which enabled the absolute amounts of the two main species detected, ZnO and zinc carboxylate (mainly hydrated or hydroxyl zinc carboxylate), to be derived. The formation rate of zinc carboxylate increases as propionic < acetic < formic acid and is mainly governed by the deposition velocity of each acid into the existing aqueous adlayer. The formation rate of ZnO and the overall corrosion rate of zinc increase in the order formic < acetic < propionic acid and are mainly attributed to the expected pH of the aqueous adlayer. The corrosion rates deduced are at least 1 order of magnitude higher than the experimentally determined field data due to a higher organic acid concentration used herein (120 ppb) and a higher average relative humidity (90%).

Identifiers
urn:nbn:se:kth:diva-18901 (URN)10.1149/1.3240878 (DOI)000271218900034 ()2-s2.0-70350733417 (ScopusID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2011-06-07Bibliographically approved
3. Initial Oxidation of Brass Induced by Humidified Air
Open this publication in new window or tab >>Initial Oxidation of Brass Induced by Humidified Air
2011 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 258, no 3, 1235-1241 p.Article in journal (Refereed) Published
Abstract [en]

Complementary surface and near-surface analytical techniques have been used to explore a brass (Cu-20Zn) surface before, during, and after exposure in air at 90% relative humidity. Volta potential variations along the unexposed surface are attributed to variations in surface composition and resulted in an accelerated localized growth of ZnO and a retarded more uniform growth of an amorphous Cu2O-like oxide. After 3 days the duplex oxide has a total mass of 1.3 μg/cm2, with improved corrosion protective properties compared to the oxides grown on pure Cu or Zn. A schematic model for the duplex oxide growth on brass is presented.

Place, publisher, year, edition, pages
Elsevier, 2011
Keyword
Atmospheric corrosion, Cu-Zn, Humid air, Surface analysis, Cu2O, ZnO
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-34115 (URN)10.1016/j.apsusc.2011.09.080 (DOI)000296725000040 ()2-s2.0-80455122757 (ScopusID)
Note
Updated from submitted to published. QC 20120119Available from: 2011-05-31 Created: 2011-05-25 Last updated: 2012-01-19Bibliographically approved
4. Multi-Analysis of Initial Atmospheric Corrosion of Brass Induced by Carboxylic Acids
Open this publication in new window or tab >>Multi-Analysis of Initial Atmospheric Corrosion of Brass Induced by Carboxylic Acids
2011 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, Vol. 158, no 6, C172-C177 p.Article in journal (Refereed) Published
Abstract [en]

The initial atmospheric corrosion of a brass (Cu-20Zn) alloy induced by carboxylic (formic, acetic, and propionic) acids has been investigated through surface or near-surface analytical techniques. The main reaction products identified were Zn-carboxylate and a Cu2O-like layer. Their formation kinetics reveal the galvanic effects due to Volta potential variations along the surface, which result in corrosion cells with central anodic formation of zinc-carboxylate and peripheral cathodic formation of Cu2O. The corrosion cell size increases as propionic < acetic < formic acid, reflecting the dependence on ionic conductivity of the aqueous adlayer.

Keyword
PROBE FORCE MICROSCOPY, MOLECULAR STRUCTURAL INFORMATION, SUM-FREQUENCY SPECTROSCOPY, QUANTITATIVE IN-SITU, ACETIC-ACID, ZINC, COPPER, INTERFACES, HUMIDITY, COBALT
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-33710 (URN)10.1149/1.3577600 (DOI)000289854700047 ()2-s2.0-79955536502 (ScopusID)
Funder
Swedish Research Council
Note
QC 20110525Available from: 2011-05-20 Created: 2011-05-16 Last updated: 2011-06-07Bibliographically approved
5. Evolution of corrosion products and metal release from Galvalume coatings on steel during short and long-term atmospheric exposures
Open this publication in new window or tab >>Evolution of corrosion products and metal release from Galvalume coatings on steel during short and long-term atmospheric exposures
2012 (English)In: Materials Chemistry and Physics, ISSN 0254-0584, Vol. 133, no 1, 419-428 p.Article in journal (Refereed) Published
Abstract [en]

Non-treated Galvalume (55% Al, 43.4% Zn and 1.6% Si by weight) coatings have been studied through a combination of surface, near surface and bulk analysis after exposure at marine conditions, and for comparison also in an urban test site and in successively more complex short-term laboratory exposures. Slightly polished Galvalume surfaces exhibit dendritic aluminum-rich areas with higher Volta potential compared with interdendritic zinc-rich areas. These effects were not observed on bare as-received surfaces due to the overall presence of aluminum oxide. As a result, preferential corrosion occurred initially in interdendritic areas. The zinc release rate followed the same time-dependence as the surface coverage of zinc-containing phases at the marine exposure condition with zinc predominantly released compared to aluminum. Short term laboratory exposures generated the same main phases as formed at marine conditions. This confirms that the evolution of corrosion products and time dependence of zinc release rates can be explained by the uniform formation of less soluble Al2O3, AlOOH and Al(OH)(3) compared to observed zinc-containing phases, e.g. ZnO, zinc hydroxycarbonate and zinc hydroxychloride. The same underlying mechanism is believed to operate also during exposure of Galvalume in the urban site studied.

Keyword
Galvalume coating, Atmospheric corrosion, Runoff, Corrosion product evolution
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-34118 (URN)10.1016/j.matchemphys.2012.01.054 (DOI)000302032300064 ()2-s2.0-84857786407 (ScopusID)
Funder
Knut and Alice Wallenberg Foundation
Note
QC 20120424Available from: 2011-05-31 Created: 2011-05-25 Last updated: 2012-04-24Bibliographically approved

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