In low‐alloy steels under accelerated atmospheric corrosion conditions the type of weathering, particularly the ratio of the time of wetness to the drying time, has a greater influence on the corrosion behavior than does the composition of the alloys. Electrochemical measurements show that the rust protection is not only due to the formation of compact macroscopic protective layers, but also to passivation effects. Passivation occurs for a prolonged period only at favorable accelerated weathering conditions. We propose a model for the interpretation of the corrosion behavior of low‐alloy steels.