Corrosion of small carbonaceous steel in soil taken from Baku subway ground has been examined. There were determined metal mass loss and corroded surface depending on duration of test, on basis of which corrosion rate, depth of local affections – corrosion penetration, ratio of polished surface to corroded one, have been calculated. It has been established that experiensed test of soil is ²corrosion-active ground² furthering the formation of oxides of iron, calcium, silicon what is confirmed by the data of roentgenographic diffractograms.