A study on the initial corrosion behavior of carbon steel exposed to outdoor wet-dry cyclic condition

• There is a good correlation between outdoor accelerated test and field exposure.
• A transition from corrosion acceleration to deceleration exists in initial stage.
• The corrosion kinetics under both conditions follow empirical equation D = Atn.

The initial corrosion behavior of carbon steel subjected to outdoor wet-dry cyclic exposure and exposure under natural environments have been investigated. The weight loss results indicate a transition from corrosion acceleration to deceleration during the early stage of corrosion of carbon steel under both conditions. The corrosion kinetics under both conditions follow empirical equation D = Atn. Outdoor wet-dry cyclic exposure significantly promoted the initiation but the rate of corrosion was about three times as fast. The morphology of corrosion surfaces and cross-section of rust layer have been examined using SEM and the compositions have been analyzed using XRD and EPMA.