Investigation of atmospheric corrosion layers on historic iron nails by micro‐Raman spectroscopy

Abstract

In this study, some Ottoman low carbon steel nails from a 16th century brick masonry dome of Kiliç Ali Pasha Bath in Istanbul and from a 19th century stone dwelling in Phocaea Izmir were studied for their long term corrosion characteristics. Their corrosion layers were examined with a Senterra Bruker micro‐Raman spectrometer and Tescan Vega model Scanning Electron Microscopy (SEM) with Inca X‐Stream 2 Energy‐Dispersive X‐ray spectroscopy (EDX). Powdered samples scraped from the corrosion layers were studied by X‐ray powder diffraction and Fourier transform infrared spectroscopy. The corrosion layer consisted of two main sub‐layers, namely an ‘inner corrosion layer’ including a ‘reaction front’ and a ‘transformed medium’ which included the depositions from the surrounding media. Peak intensities of X‐ray powder diffraction traces were not proportional to the abundance of oxides and oxyhydroxides in the corrosion layer, most probably because of their partly amorphous and nano‐size nature. Inner corrosion layer and transformed medium layers were studied in detail by micro Raman spectroscopy at 532 nm, 0.2 mW, 200 s. The Protective Ability Index (PAI) of the corrosion layers were expressed as the ratio of isotropic goethite band thickness to the thickness of reaction front composed of other oxides and oxyhydroxides being magnetite, maghemite, hematite, lepidocrocite, distinguished by micro‐Raman which is a unique method for phase identification. PAI was then estimated to be ~6–10 for 16th century nails and ~3 for 19th century nails. Corrosion mechanisms and PAI were concluded to be affected by compositional characteristics of artefacts and their atmospheric conditions. Copyright © 2016 John Wiley & Sons, Ltd.

FTIR spectroscopic semi-quantification of iron phases: A new method to evaluate the protection ability index (PAI) of archaeological artefacts corrosion systems

“…Morevover, Raman spectroscopy is acquiring a steadily increasing importance in studies related to cultural heritage materials due to its versatility and capability of collecting molecular data in a non-intrusive way [18].…”

Vibrational Spectroscopy in Studies of Atmospheric Corrosion

“…Yucel et al, compared the atmospheric corrosion resistance of historic nails made of Ottoman period steels from 16th to 19th centuries and used micro-Raman spectroscopy to identify the composition of the inner and outer layer of the corrosion products [ 95 ]. They found that, a compact geolite layer is formed covering most of the inner corrosion layer resulting in enhanced corrosion protection in the Ottaman steel compared with current low alloy steels, indicating the success of iron metallurgy in that time.…”

Recent advances in linear and non‐linear Raman spectroscopy. Part XI

“…Yucel and co‐workers investigated atmospheric corrosion layers on historic iron nails by micro‐Raman spectroscopy. The Protective Ability Index (PAI) of the corrosion layers was expressed as the ratio of isotropic goethite band thickness to the thickness of the reaction front composed of other oxides and oxyhydroxides being magnetite, maghemite, hematite, lepidocrocite, distinguished by micro‐Raman which is a unique method for phase identification . Zhao et al investigated Chinese jade artefacts stemming from the period 5,000 BC to 771 BC by confocal laser micro‐Raman spectroscopy and other techniques.…”