Environmental conditions in data centers determine the reliability of the IT equipment and operational uptimes. Due to continuous increase in energy usage and a trend towards sustainability, leads many data center operators to lean towards implementing energy efficiency measures. Many of today's data center are operated in a narrow temperature and relative humidity band, however these may change as ASHRAE recently expanded the limits of the temperature and relative humidity. These expansions are triggered by recent interest to implement air side economizer based cooling in data centers. For air side economized data centers besides pollutants that can be introduced unintentionally, the daily variation of temperature and relative humidity could possibly lead to condensation or corrosion. The variation of the corrosion rate due to daily changes of the indoor pollutant concentrations combined with temperature and humidity cycling are presented for a data center. © 2012 IEEE.