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Atmospheric corrosion of zinc by organic constituents II. Reaction routes for zinc-acetate formation
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.ORCID iD: 0000-0002-9453-1333
2006 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, Vol. 153, no 12, B542-B546 p.Article in journal (Refereed) Published
Abstract [en]

The acetic acid and acetaldehyde-induced atmospheric corrosion of a zinc surface was investigated by in situ infrared reflection-absorption spectroscopy. Independent of the relative humidity, both corrosive gases yielded zinc oxide and zinc acetate as reaction products. However, faster kinetics for the acetate formation was observed for acetic acid, which was attributed to an acetate-induced zinc dissolution mechanism as the rate determining step, and a more complicated reaction path for acetaldehyde to form the zinc-acetate surface species. Additionally, the rate varied significantly with the relative humidity, and an enhanced corrosion rate was observed under more humid conditions, when the water adlayer that always covers a metal surface is thicker. Scanning electron microscopy revealed the formation of radial growth of corrosion products in the case of acetic acid and filiform corrosion for acetaldehyde. By X-ray diffraction of the powderlike corrosion products, solely zinc oxide was detected. This implies a minute production of zinc acetate in comparison to zinc oxide, or a noncrystalline phase of the acetate. Reaction paths for acetic acid and acetaldehyde were proposed.

Place, publisher, year, edition, pages
2006. Vol. 153, no 12, B542-B546 p.
Keyword [en]
Acetic acid, Atmospheric humidity, Dissolution, Reaction kinetics, Surface reactions, Zinc
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-24288DOI: 10.1149/1.2360740ISI: 000241757400032ScopusID: 2-s2.0-33750810816OAI: diva2:346276
QC 20100831Available from: 2010-08-31 Created: 2010-08-31 Last updated: 2010-10-29Bibliographically approved
In thesis
1. Vibrational Sum Frequency and Infrared Reflection/Absorption Spectroscopy Studies of the Air/Liquid and Liquid/Metal Interfaces
Open this publication in new window or tab >>Vibrational Sum Frequency and Infrared Reflection/Absorption Spectroscopy Studies of the Air/Liquid and Liquid/Metal Interfaces
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Atmospheric corrosion, the most common form of metal corrosion, occurs within the interfacial region between a solid, and the surrounding atmosphere. In fact three phases and two interfaces are involved: the gas, a thin liquid layer, a solid, the gas/liquid and the liquid/solid interfaces. In this thesis, the vapor/liquid and liquid/metal interfaces have been studied by the in-situ techniques vibrational sum frequency spectroscopy (VSFS), and infrared reflection/absorption spectroscopy (IRAS). The main focus has been on characterization of the corrosive organic molecules formic acid, acetic acid, and acetaldehyde, at the two interfaces. Additionally, the headgroup of sodium dodecyl sulfate (SDS) has been examined at the air/water interface.

VSFS is an inherently surface sensitive laser spectroscopy technique, which provides vibrational spectra solely of the molecules residing at the surface of for example a liquid, despite the vast excess of the same molecules in the bulk. To obtain a comprehensive molecular picture of the organic compounds at the air/liquid interface, studies have been undertaken in several spectral regions, targeting the CH, C=O, C-O, OH, and SO3 stretching vibrations. Furthermore, the surrounding water molecules have been investigated in order to study hydration phenomena. Acetaldehyde has been determined to partly form a gem-diol (CH3CH(OH)2) at the air/water interface, whereas acetic acid forms various hydrogen-bonded species, with hydrated monomers at low concentrations and centrosymmetric cyclic dimers at high concentrations. Formic acid was found to form a different complex at very high concentrations, in addition to the species observed at low concentrations. Performing experiments with different polarizations of the laser beams has enabled the determination of the orientation of the interfacial molecules. The methyl group of acetic acid was concluded to be oriented close to the surface normal throughout the concentration range, whereas the tilt angle of the CH group of formic acid was determined to be ~35°. The SDS studies revealed that the headgroup orientation is constant in a wide range of concentrations, and also in the presence of sodium chloride.

IRAS has provided information regarding the composition and kinetics of the corrosion products formed upon exposure of a zinc oxide surface to the organic compounds. The importance of the water adlayer on metal surfaces has been confirmed by the faster kinetics observed at higher relative humidities. Exposure to formic acid resulted in the formation of zinc formate, whereas both acetic acid and acetaldehyde formed zinc acetate upon reaction with the zinc oxide surface. However, the kinetics were faster for acetic acid than acetaldehyde, which was explained in terms of an acetate-induced zinc dissolution process and a more complicated reaction path involved in the acetaldehyde case to form the zinc acetate surface species. Scanning electron microscopy indicated the formation of radially growing reaction products for acetic acid and filiform corrosion for acetaldehyde.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. vi, 57 p.
Corrosion science, laser spectroscopy, nonlinear optics
National Category
Materials Engineering
urn:nbn:se:kth:diva-455 (URN)91-7178-156-0 (ISBN)
Public defence
2005-10-28, M3, Brinellvägen 64, KTH, 10:00
QC 20101029Available from: 2005-10-20 Created: 2005-10-20 Last updated: 2011-03-18Bibliographically approved

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