6533b7d6fe1ef96bd12659e4

RESEARCH PRODUCT

Photocurrent spectroscopy of thin passive films

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Publisher Summary This chapter reviews theoretical background on the photoelectrochemistry of metal and semiconductor electrodes on which photocurrent spectroscopy (PCS) relies, by focusing particularly on new features that are typical of the photoelectrochemical behavior of thin passive films and usually absent in the behavior of bulk crystalline semiconductors. The chapter also highlights the advantages of PCS in getting in situ information on the structure of the metal-passive-film-electrolyte systems and shows a more recent quantitative use of this technique in characterizing the composition of passive films. The formation of a protective film on a metallic surface is a key step in establishing passivity, with strong reduction of the corrosion rate of the underlying metal. In many cases of practical importance, passivity of metals is attained in the presence of very thin oxide films whose physicochemical properties play an important role in determining the nature of possible chemical reactions occurring at the interface between the passive metal and the environment. For these reasons, the physicochemical characterization of passive films and corrosion layers is a preliminary task for a deeper understanding of the corrosion behavior of metals and alloys. In many cases, the identification of the passive films on metal and alloys requires the use of different in situ and ex situ techniques to get information on the chemical composition, morphology, and crystalline or disordered nature of the passivating layers.