In situ infrared reflection absorption spectroscopy studies of confined zinc surfaces exposed under periodic wet-dry conditions

An experimental setup for in situ infrared reflection absorption spectrosco py (IRAS) studies of atmospheric corrosion of confined metal surfaces is de scribed. Information about the drying process of confined metal surfaces an d the chemical composition and growth rate of the corrosion products in the confinement was obtained during exposure to periodic wet-dry conditions. T he drying process and the formation of corrosion products during periodic w et-dry conditions with different CO2 concentrations was studied. The decrea se of the water bands from the water on the zinc surface was followed and t he drying time of the confinement was approximately 6-8 h. The formation of corrosion products during the drying period was followed with in situ IRAS . The corrosion product formed under these conditions was mainly composed o f ZnO with a smaller amount of Zn-5(OH)(8)Cl-2 . H2O with <5 ppm CO2 concen tration in the air. When the CO2 concentration was <greater than or equal t o>350 ppm, Zn-5(OH)(6)(CO3)(2) and Zn-5(OH)(8)Cl-2 . H2O were the dominant species in the corrosion product. With increasing CO2 concentration the amo unt of chloride precipitated as Zn-5(OH)(8)Cl-2 . H2O increased. This can b e explained by the neutralization of the surface electrolyte by CO2 resulti ng in the precipitation of insoluble Zn-5(OH)(8)Cl-2 . H2O and Zn-5(OH)(6)( CO3)(2). (C) 2001 The Electrochemical Society. All rights reserved.