A multianalytical approach with in situ capability has been used to explore the initial oxidation of zinc in all with 90% relative humidity at 20 degrees C. The only surface species identified were zinc oxide (ZnO) and reversibly adsorbed water. Atomic force microscopy and X-ray diffraction revealed the homogeneous nucleation of ZnO grains the kinetics of ZnO Formation as followed quantitatively by in situ IR reflection-absorption spectroscopy (IRAS) integrated with a quartz crystal microbalance up to an average film thickness of 50 nm after 72 It of exposure. The quantitative results exhibit good agreement with ex situ cathodic reduction and with optical Calculations of IRAS data and provide further evidence of IRAS as all in situ analytical tool with quantification Capability. The ZnO growth followed the logarithmic rate law as predicted by Fehlner and Mott [Oxid. Met., 2, 59 (1970)] (C) 2008 The Electrochemical Society. [DOI: 10.1149/13043424] All rights reserved.