Several types of surface treatments have been evaluated for their ability to inhibit the corrosion of archaeological iron. These are, octadecyltrimethoxysilane (ODTMS), CH3(CH2)17Si(OCH3)3, IH, 1H,2H,2H-henicosafluorododecyltrimethoxysilane (HFTMS), CioF2iH4Si(OCH3)3, decylamine (DCA), C10H21NH2, octadecylamine (ODA), C18H37NH2, and isopropyl-triisostearoyltitanate (TTS), CH3.CH.CH3OTi(0C0.C17H35)3. These molecules bind to corrosion product surfaces, forming hydrophobic layers. Evaluation of treatments has been carried out using accelerated corrosion tests at elevated temperature and humidity. Assessments have also been made using electrochemical monitoring, water adsorption isotherms, Fourier transform infra-red spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS) and floatation tests. A method of producing corroded iron coupons containing the chlorine containing corrosion products akaganeite, found on archaeological iron, has been devised. TTS was found to be the most effective treatment of those investigated. Amine treatments gave some inhibition, but were not as effective as TTS. Floatation tests showed that amines are easily hydrolysed and detached from iron oxyhydroxide surfaces and they therefore are not as effective as corrosion inhibitors. An anomaly was found in the behaviour of HFTMS which contrary to expectation actually accelerated the rate of corrosion. This has been attributed to 'pin' holes in the inhibitor coating which allows the formation of differential aeration cells, and thus accelerates corrosion. The success of the TTS treatment is attributed to the fact that each molecule contains three Cig hydrocarbon chains, providing a more densely packed hydrophobic surface. Further long term testing of the TTS treatment on archaeological iron is recommended. Several forms of polyaniline were synthesised and tested as corrosion inhibitors for archaeological iron. These were found not to be effective inhibitors for corroded iron, although they have been found to be effective on clean iron surfaces. This may be because they work as anodic inhibitors and therefore need to be in contact with the metal surface.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:399749 |
| Date | January 1999 |
| Creators | Brazil, Rachel Bronja |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/10063676/ |
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