Simultaneous in situ infrared reflection absorption spectroscopy and Kelvin probe measurements during atmospheric corrosion

An experimental setup is described which allows simultaneous in situ measur ements with the Kelvin probe and infrared reflection absorption spectroscop y (IRAS). Variations in the Volta potential were measured during corrosion of zinc surfaces in humid air, and information about the composition and th e growth kinetics of the surface film was obtained by IRAS. The results sho w the Volta potential drops to between 2600 and 2700 mV/SHE after introduct ion of humid air due to activation of the zinc surface. With IRAS the growt h of a surface film containing ZnO and Zn-5(OH)(8)Cl-2.H2O and zinc hydroxy carbonate was followed. With increasing thickness of the surface film the zinc surface is passivated and the Volta potential increases to between -10 0 and -200 mV/SHE after prolonged exposure. The results show that the exper imental setup for simultaneous Kelvin probe and in situ IRAS measurements i s a powerful tool for obtaining information about the changes in corrosion potential associated with the formation and growth of different types of co rrosion products on metal surfaces. (C) 2001 The Electrochemical Society.