This study aims to determine the rate of corrosion of a condensing unit. Condensing unit is the main component of a split air conditioner which is installed outside a building (outdoor) and is always exposed to the elements as well humidity. Such conditions make the condensing unit vulnerable to corrosion. Further, the corrosion affects the performance of the air conditioner. Temperature and humidity (air velocity, hot and cold temperature) greatly affect the corrosion rate. This is an experimental study and data was based on observation and analysed using the formula corrosion rate. The results indicate that FeFe2O4 and FeO compounds affect corrosion rate. Specifically, the rate of corrosion on the metal plate of condensing units is 0.054 millimetres per year (mpy) at an ambient temperature of 30°C and 85% humidity.