Atmospheric corrosion monitoring (ACM) sensors were employed to study the initial atmospheric corrosion,of carbon steels over a one-month period in six outdoor dynamic atmospheric environments in China.Based on the ～250,000 corrosion data sets collected,the environmental impacts of relative humidity,temperature and rainfall on the initial corrosion behavior of carbon steels were investigated.The results showed that rainfall was the strongest environmental factor influencing the initial atmospheric corrosion rate.Relative humidity significantly influenced the corrosion of carbon steels in low-precipitation environments and non-rainfall period.