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.