Evaluation of Corrosion Resistance of Steel Materials By Hyperspectral Analysis of Corrosion Products

Abstract

Direct visual inspection at short range and hammering test every five years are obligatory for inspection and evaluation of bridges in Japan. However, simple and quantitative inspection techniques are required due to issues such as a shortage of bridge inspectors and a lack of inspection cost. We focused on the spectrum analysis by a hyperspectral camera as a new tool to evaluate corrosion resistance. The purpose of this study is to investigate the feasibility of evaluating the corrosion resistance of steel materials by hyperspectral analysis of corrosion products.α-FeOOH, β-FeOOH, γ-FeOOH and Fe3O4 were used as the samples of standard iron corrosion products. These corrosion products were set on the sample holder, and the spectra were taken by a hyperspectral camera using halogen lamps as a source of irradiation light. The average spectrum obtained at almost the center of the sample was analyzed.The reflection spectra were observed at 595 nm and 770 nm for α-FeOOH, 745 nm for β-FeOOH, and 790 nm for γ-FeOOH, respectively, and Fe3O4 showed a low reflection spectrum. This means that different corrosion products can be identified from the reflection spectrum. In addition, the spectrum analysis was conducted for the corrosion products formed on the sample exposed in coastal area for six months. The peaks in the spectrum were correspondent with them observed in the spectra of the standard iron corrosion products. The spectrum analysis by a hyperspectral camera can be powerful tool to evaluate the corrosion performance of steel materials.