Tracing correlations of corrosion products and microclimate data on outdoor bronze monuments by Principal Component Analysis

Although the corrosion of outdoor bronzes has been extensively studied for the last decades, there is no quantitative correlation of corrosion products to microclimatic factors. The present work aims to demonstrate how Principal Component Analysis (PCA) can serve this purpose. Thirty corrosion product samples were collected from the bronze monument of Theodoros Kolokotronis (Nafplio, Greece) and analysed using X-Ray Diffractometry (XRD). The quantitative XRD data together with data on surface orientation and exposure to rain or wind were treated by PCA and three distinct groups were found. Each group includes samples of similar composition and microclimate characteristics showing that PCA may give useful information on corrosion mechanisms.

[1]  A. Moropoulou,et al.  Correlation between stone weathering and environmental factors in marine atmosphere , 1995 .

[2]  Daniel de la Fuente,et al.  Morphological study of 16-year patinas formed on copper in a wide range of atmospheric exposures , 2008 .

[3]  R. Cattell.  The Scree Test For The Number Of Factors. , 1966, Multivariate behavioral research.

[4]  L. Selwyn,et al.  Outdoor bronze statues: analysis of metal and surface samples , 1996 .

[5]  Mike Baxter,et al.  Exploratory Multivariate Analysis in Archaeology , 1994 .

[6]  Christofer Leygraf,et al.  The evolution of outdoor copper patina , 2002 .

[7]  J. Tidblad,et al.  The Classification System of ISO 9223 Standard and the Dose–Response Functions Assessing the Corrosivity of Outdoor Atmospheres , 2004 .

[8]  H. Takenouti,et al.  Composition and electrochemical properties of natural patinas of outdoor bronze monuments , 2007 .

[9]  R. Reyment,et al.  Statistics and Data Analysis in Geology. , 1988 .

[10]  Antonia Moropoulou,et al.  Principal Component Analysis in monument conservation: Three application examples , 2009 .

[11]  L. Robbiola,et al.  Morphology and mechanisms of formation of natural patinas on archaeological Cu–Sn alloys , 1998 .

[12]  D. Bish,et al.  Quantitative phase analysis using the Rietveld method , 1988 .

[13]  Andrew Lins,et al.  Outdoor bronzes: some basic metallurgical considerations , 1985 .

[14]  L. Robbiola,et al.  New model of outdoor bronze corrosion and its implications for conservation , 1993 .

[15]  Masamitsu Watanabe,et al.  Surface Observation and Depth Profiling Analysis Studies of Corrosion Products on Copper Exposed Outdoors , 2003 .

[16]  R. Livingston.  Influence of the environment on the patina of the Statue of Liberty , 1991 .

[17]  A. Atrens,et al.  Atmospheric corrosion of copper and the colour, structure and composition of natural patinas on copper , 2006 .

[18]  Th. Skoulikidis,et al.  Mechanism of Sulphation by Atmospheric SO2 of the Limestones and Marbles of the Ancient Monuments and Statues: II. Hypothesis concerning the rate determining step in the process of sulphation, and its experimental confirmation , 1981 .

[19]  F. Corvo,et al.  Influence of the corrosion products of copper on its atmospheric corrosion kinetics in tropical climate , 2004 .

[20]  H. Kaiser.  The Application of Electronic Computers to Factor Analysis , 1960 .

[21]  Michael F. Lynch,et al.  Sculptural Monuments in an Outdoor Environment , 1987 .