Quantitative measurement of cast metal relics by pulsed thermal imaging

Corrosion in cast metal relics has always been a concern for the conservation and restoration of ancient culture relics. In recent years, there is an increased interest in the determination of the corrosion/rust thickness and the substrate thickness of bronze and iron cultural relics. The solution of this problem is of great significance in the evaluation of the corrosion status, rust cleaning, and the restoration and conservation of metal cultural relics. This paper presents a new method for the measurement of the rust thickness and the substrate thickness of a replica cast-iron Buddha head by one-sided pulsed thermal imaging. In this method, the rust thickness and the substrate thickness of cast-iron Buddha head were determined simultaneously by a non-linear fitting of a theoretical solution with experimental values. The finite flash duration effect and the finite substrate thickness effect on the rust thickness measurement are analysed and discussed. Besides the new method, the conventional Flash method for single-layer materials was also used to estimate the wall thickness. The measurement results show that this new method has great potential and capability in the quantitative measurement of ancient iron and bronze cultural relics.