Characterization and corrosion studies of laser-melted carbon steel surfaces

We have observed by conversion electron Mo¨ssbauer spectroscopy CEMS.that the irradiation of carbon steel surfaces with an industrial CO2 laser, under different experimental conditions, brings about the formation of a-Fe2O3, Fe3O4 and Fe1yxO. The larger beam-surface interaction times favour the formation of greater amounts of Fe3q oxides mainly a-Fe2O3.within the depth that can be probed by CEMS f300 nm.. A model based on the numerical solution of the heat-diffusion equation gives evidence that the oxidation processes are mainly dictated by the time at which the metal remains at temperatures higher than the melting point. In addition, the samples have been subjected to wet–dry corrosion cycles in SO2-polluted atmospheres and monitored by CEMS and weight gain. The oxide layer reduces noticeably the corrosion rate of steel against corrosion. This protection is related to the composition of the oxidation layer. q1999 Elsevier Science B.V. All rights reserved