Mathematical and electro-chemical characterisation of the layer of corrosion products on carbon steel in various environments

The properties of the corrosion products for carbon steel were characterized using the data from 39 corrosion stations in varying environments (urban, rural, marine and marine-industrial) in the province of Las Palmas (The Canary Islands, Spain) using electro-chemical impedance spectroscopy and the gravimetric method via mathematical data modelling. The behaviour of the layer was analysed using a model which established a hyperbolic relation between the quotient of loss of weight (WL) and monthly accumulated weight loss (AM) suffered by the metal test-piece relative to time of exposure. It was found that as the WL/AM increases, the protective capacity of the layer also increases. From the data taken from the 39 stations with respect to degree of corrosivity, it was found that the corrosion products were more protective in urban than in other less aggressive environments at the end of one year's exposure. We also studied the protective capacity via electro-chemistry. The results were compared with the hyperbolic law and were found to concord completely. (C) 2002 Elsevier Science Ltd. All rights reserved.