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Atmospheric corrosion of zinc by organic constituents - III. An infrared reflection-absorption spectroscopy study of the influence of formic acid
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, B547-B550 p.Article in journal (Refereed) Published
Abstract [en]

The initial corrosion of a zinc surface exposed to formic acid at various relative humidities has been investigated by in situ infrared reflection-absorption spectroscopy. The major corrosion product observed was zinc formate, as evidenced in particular by the two strong carboxylate stretching vibrations. The importance of the thickness of the water adlayer always covering a metal surface was confirmed by the more rapid corrosion process monitored at higher relative humidities. Nonetheless, significant corrosion rates were observed even at low (25%) relative humidities. The corrosion rate at a given humidity was observed to initially be very fast, followed by slower kinetics at longer exposure times. This indicates a protective ability of the corrosion products formed compared to the initially more reactive fresh zinc surface.

Place, publisher, year, edition, pages
2006. Vol. 153, no 12, B547-B550 p.
Keyword [en]
Atmospheric humidity, Corrosion protection, Molecular vibrations, Organic acids, Reaction kinetics, Surface reactions, Zinc
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-24286DOI: 10.1149/1.2360741ISI: 000241757400033ScopusID: 2-s2.0-33750820117OAI: diva2:346258
QC 20100831. Tidigare titel: Atmospheric corrosion of zinc by organic constituents: 3. An IRAS study of the influence of formic acidAvailable 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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