The scanning photoelectrochemical microscopy of diffusing hydrogen into metals

A new photoelectrochemical (PEC) technique is reported to image in real time the hydrogen diffusion into a metal in situ and continuously by means of a scanning laser spot. When a metal such as iron, stainless steel or nickel covered by a passive film is loaded with hydrogen and illuminated, the photoresponse of the passive film (the electrode is anodically polarized in an alkaline solution) is improved owing to the hydrogen photooxidation. This photoresponse is proportional to the hydrogen concentration in the metal. Scanning the metal surface by a laser spot in real time a well-detailed image is obtained of the diffusing hydrogen into the metal at a microscopic level. The present report describes the scanning photoelectrochemical microscopy (SPEM) of hydrogen diffution into an AISI 304 stainless steel foil. © 1995 Elsevier Science Ltd.