A new mathematical model for the estimation of atmospheric corrosion rates that satisfactorily describes the behaviour of carbon steel F111 in a fragmented subtropical region has been developed. It is a semi-empirical equation that includes a set of qualitative coefficients established from collections at short exposures (typically one year), in addition to environmental parameters, namely duration of exposure, time of wetness, and deposition rate for chloride ions and sulphur dioxide. The validity of the proposed model has been tested by comparing the estimates obtained using this equation with the experimental data collected from 35 outdoor test sites during 3 years. Satisfactory estimates of the corrosion rates matching the majority of the experimental observations for longer exposures were obtained
