Study of the Effects of Cu/Cu-Zn Alloy Components Adjacent to Wood in Historic Architecture: Surface Performance Changes by Artificial Wood Degradation

Abstract

Here, we investigated the wood-whitening phenomenon adjacent to metal components that are commonly observed in Japanese historic architectures. The higher detection of Cu/Zn elements and fine particles of copper/zinc oxalate hydrate in whitened wood has been verified in a previous field investigation. In order to explore the related cause of this phenomenon, this study established model experiments to evaluate some surface performance changes of wood plate samples with impregnated Cu(II)/Zn(II) contents under artificial degradation. The evaluation included the following: (1) the state of metal oxalates in the wood tissue; (2) the mechanical performance of the resistance to the external forces; and (3) the colour change of the wood surface. As the result, the accumulation of metal oxalates and their growth in particle sizes were confirmed in samples containing metal, in particular those with a higher Cu(II) content, regardless of wood species. Meanwhile, this metal-involved degradation could introduce the risk of embrittlement of wood ahead of the occurrence of visible whitening discolouration.