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TGA-FTIR study of the vapours released by volatile corrosion inhibitor model systems
Thesis (PhD)--University of Pretoria, 2013.
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| Format: | Thesis |
| Language: | Eng |
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University of Pretoria
2014
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| _version_ | 1867613537143095296 |
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| access_status_str | Open Access |
| author2 | Focke, Walter Wilhelm |
| author_browse | Focke, Walter Wilhelm |
| author_facet | Focke, Walter Wilhelm |
| collection | Thesis |
| dc_rights_str_mv | © 2013 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Thesis (PhD)--University of Pretoria, 2013. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/32945 |
| institution | University of Pretoria (South Africa) |
| language | Eng |
| last_indexed | 2026-06-10T12:37:43.241Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2014 |
| publishDateRange | 2014 |
| publishDateSort | 2014 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/32945 TGA-FTIR study of the vapours released by volatile corrosion inhibitor model systems Focke, Walter Wilhelm Vuorinen, Eino Nhlapo, N.S. (Nontete Suzan) Amines Carboxylic acids VCIs Atmospheric corrosion Evaporation Vapour pressure Gas permeability Corrosion efficiency TGA-FTIR UCTD Thesis (PhD)--University of Pretoria, 2013. Proprietary mixtures of amines and carboxylic acids are used as volatile corrosion inhibitors (VCIs) for the protection of steel and iron components against atmospheric corrosion during storage and transportation. Interactions between amines and carboxylic acids have been comprehensively reported in the literature. However, little is known about the nature of the vapours these mixtures emit. The present study focused on the development of the evolved gas analysis method which will help in the characterisation of the vapours released by VCIs. In the method, the evaporation of various amine-carboxylic acid binary mixtures was monitored by thermogravimetric analysis (TGA). The nature and the composition of the released vapours was followed by Fourier transform infrared (FTIR) spectroscopy. Mixtures consisting of triethylamine (TEA) and acetic acid were studied as a model compound using TGA-FTIR at 50 °C to validate the TGA-FTIR method. As vaporisation progressed, the composition of the remaining liquid and the emitted vapour converged to a fixed amine content of ca. 27 mol %. This is just above the composition expected for the 1:3 amine: carboxylic acid complex. Mixtures close to this composition also featured the lowest volatility. TGA-FTIR proved to be a convenient method for studying the evaporation of TEA-acetic acid mixtures, and the nature and composition of the released vapours. Amine addition leads to the dissociation of carboxylic acid dimers in favour salt formation. The formation of an ion pair between the amine and carboxylic acid was confirmed by the FTIR spectra of the liquid phase. The resulting amine-carboxylic acid mixtures showed a slow mass loss rate on TGA when compared with the pure amines and pure carboxylic acids. This indicated that the mixtures have low volatility, hence low vapour pressure compared with the pure components. The low vapour pressure of the mixtures was confirmed by the calculated gas permeability values. These values were much higher for the pure amines and the pure carboxylic acids. However, they dropped significantly on amine addition. The strong amine-carboxylic acid interaction is responsible for the suppressed volatility of the mixtures. No interaction is observed between amine and carboxylic acid molecules in the vapour phase at 230 °C. The method developed was applied to characterise the model compounds simulating the amine-carboxylic acid-based volatile corrosion inhibitors. These model systems contained the primary, secondary and tertiary amines (hexylamine, morpholine and triethylamine), as well as carboxylic acids with different chain lengths (acetic, propanoic, hexanoic and octanoic). These systems are usually employed as equimolar mixtures to protect ferrous metals against atmospheric corrosion. The key finding of the study was that the vapours released by such equimolar mixtures initially contain almost exclusively free amine. After prolonged vaporisation, a steady-state “azeotrope”-like composition is approached. It contains excess acid and features impaired corrosion-inhibition efficiencies according to the Skinner test. In part, this behaviour can be attributed to the mismatch between the volatilities of the amine and carboxylic acid constituents. gm2013 Chemical Engineering unrestricted 2014-01-09T11:12:54Z 2014-01-09T11:12:54Z 2013-09-04 2013 Thesis Nhlapo, N.S. 2013, TGA-FTIR study of the vapours released by volatile corrosion inhibitor model systems, PhD thesis, University of Pretoria, viewed yymmdd <http://hdl.handle.net/2263/32945> D13/9/1048/gm http://hdl.handle.net/2263/32945 Eng © 2013 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf University of Pretoria |
| spellingShingle | Amines Carboxylic acids VCIs Atmospheric corrosion Evaporation Vapour pressure Gas permeability Corrosion efficiency TGA-FTIR UCTD TGA-FTIR study of the vapours released by volatile corrosion inhibitor model systems |
| title | TGA-FTIR study of the vapours released by volatile corrosion inhibitor model systems |
| title_full | TGA-FTIR study of the vapours released by volatile corrosion inhibitor model systems |
| title_fullStr | TGA-FTIR study of the vapours released by volatile corrosion inhibitor model systems |
| title_full_unstemmed | TGA-FTIR study of the vapours released by volatile corrosion inhibitor model systems |
| title_short | TGA-FTIR study of the vapours released by volatile corrosion inhibitor model systems |
| title_sort | tga ftir study of the vapours released by volatile corrosion inhibitor model systems |
| topic | Amines Carboxylic acids VCIs Atmospheric corrosion Evaporation Vapour pressure Gas permeability Corrosion efficiency TGA-FTIR UCTD |
| url | http://hdl.handle.net/2263/32945 |