On the Corrosion Mechanism of Borided X12CrNiMoV12-3 Steel Immersed in a Neutral Aqueous Solution Containing Chloride and Sulfate Ions

The corrosion behavior of borided X12CrNiMoV12-3 steel immersed during 5 days in a 0.1 M NaCl + 0.04 M Na₂SO₄ aqueous solution was obtained. The boride layer (FeB/Fe₂B) formed on the surface of the material was developed using the powder-pack boriding process at 1223 K during 6 hours of exposure. Some corrosion electrochemical parameters such as the polarization resistance, the current density, the anodic and cathodic Tafel slopes were determined by means of the potentiodynamic polarization technique, in which the corrosion resistance values of the borided stainless steel were compared with those estimated for the non-borided X12CrNiMoV12-3 steel (reference material).The corrosion behavior of the borided X12CrNiMoV12-3 steel was associated with the development of B₂S₃ and Fe₂O₃ on the surface of the boride layer as well as for the presence of texture fibers such as {020}//ND and {021}//ND (estimated from crystallographic texture analysis), which drastically reduced the corrosion resistance values of the boride layer exposed to the aqueous solution. Finally, the electrochemical reactions produced during the immersion of the borided X12CrNiMoV12-3 steel in the neutral chloride-sulfate aqueous solution were proposed.