Portable Raman study on the conservation state of four CorTen steel‐based sculptures by Eduardo Chillida impacted by urban atmospheres

Abstract

Weathering steel, and particularly CorTen steel, is a very used material for modern artworks exhibited outdoors. One of the characteristic that makes this material so attractive to artists is the property to develop a protective rust layer composed by iron oxides which preserves its metallic core from atmospheric corrosion. This study was conducted to evaluate the conservation state of four CorTen sculptures by Eduardo Chillida, located in different places of Bilbao city (north of Spain) and affected by different factors (environmental among others) by using Raman spectroscopy. Measurements were performed in situ with a handheld Raman spectrometer mounted on a tripod with x–y–z axes motorization at the micron level. The most common oxyhydroxides detected were lepidocrocite (γ‐FeO(OH)), goethite (α‐FeO(OH)), hematite ( ‐Fe2O3) and magnetite (Fe3O4), being goethite the most stable phase. All the iron oxyhydroxides were identified in all of the studied sculptures but their relative amounts were different for each sculpture. The consequences of the marine aerosols exposure in the steel surface were also studied, detecting limonite (FeO(OH)·nH2O) and akaganeite (β‐FeO(OH)). The results confirmed that the evolution of the rust layer present on the analyzed weathering steels is different, depending both on the exposure and the particular type of the steel. Copyright © 2012 John Wiley & Sons, Ltd.

Bioimpact on weathering steel surfaces: Oxalates formation and the elucidation of their origin

“…This compound detected on the Plow sample could be related to the high concentration of SO 2 in Bilbao atmosphere. In previous works carried out using a 785 nm laser (Aramendia et al, 2012(Aramendia et al, , 2013(Aramendia et al, , 2014a, no signal from biological markers was detected. For some organics, especially the ones with long carbon unsaturated chains, the use of a green excitation often induces some resonance effects which enhance the Raman scattering allowing its detection even with some fluorescence or low amounts of compounds.…”

“…Severe consequences of this leaching process include the material loss, visual alteration of the surface, environmental problems if heavy metals are leached, etc. In addition, the presence of silicates can retard the normal evolution of the weathering steel protective corrosion layer (Aramendia et al, 2012). In the case of weathering steel used in Cultural Heritage there is no consensus about the main factors in the acceleration of decay.…”

Mobile Spectroscopic Instrumentation in Archaeometry Research

“…They applied mobile Raman spectroscopy and similar mathematical models to monitor cleaning and consolidation processes of art objects. 39,40 The same group also used Raman spectroscopy to investigate wall paintings and mortars in Marcus Lucretius' house in Pompei. 41 A select number of papers were published demonstrating the possibilities of mobile Raman spectroscopy for gemstone analysis.…”

Raman Spectroscopy of cultural heritage Materials: Overview of Applications and New Frontiers in Instrumentation, Sampling Modalities, and Data Processing

“…In many of these studies, the availability of compact portable Raman instruments is extremely valuable for in situ studies where several areas can be monitored and mapped in expanded time-and length-scales [11,195,235].…”