Article ID: MT-MAW2025001
Structural metallic materials used in hydrogen gas or corrosive environments may suffer from loss of ductility owing to hydrogen atoms (hydrogen embrittlement). To design hydrogen-resistant metallic materials, it is crucial to elucidate the mechanism of hydrogen entry and diffusion. However, visualization of corrosion-induced hydrogen entry and microstructure-dependent hydrogen diffusion requires a highly sensitive hydrogen detection technique with high spatial and temporal resolutions. Hydrogen visualization techniques using polyaniline (PANI), which is a hydrogenochromic sensor, have recently been developed. The PANI layer reacts with atomic state hydrogen in a metal, changing its color from blue to yellow. Thus, the hydrogen distribution in the metal can be analyzed by observing the color distribution of the PANI layer using a digital camera. Owing to the high sensitivity and spatial resolution of hydrogenochromic sensors, corrosion-induced hydrogen entry and microstructure-dependent hydrogen diffusion have been successfully visualized in real time. In this paper, the principles of the sensor and representative application examples are introduced.
