Corrosion behaviour of steels after laser surface melting

Laser surface melting (LSM) were carried out in three types of stainless steels - austenitic, martensitic and ferritic - in order to improve pitting corrosion resistance. After the LSM, most of the steels present a shift in the pitting potential to more noble values, a longer passivity stage and lower passive current density than the substrate. These improvements are achieved by means of a modified surface layer, more homogeneous with a fine cellular dendritic structure free of large precipitates. Nevertheless, the corrosion resistance depends critically on the laser processing parameters, particularly for the cases of ferritic and martensitic stainless steels. Therefore, care must be taken in the choice of the laser-processing parameters that leads to optimal properties in each material. (C) 2000 Elsevier Science Ltd. All rights reserved.