Abstract

RINCON-ORTIZ, Mauricio; RODRIGUEZ, Martín Alejandro  and  CARRANZA, Ricardo Mario. Nitrate Ions’ Influence on the Alloy 22 Corrosion Behavior. Rev. Fac. ing. [online]. 2015, vol.24, n.40, pp.107-116. ISSN 0121-1129.

Alloy 22 (N06022), is a nickel based alloy, with a high content of chromium (∼22%) and molybdenum (∼13%) that belongs to the Ni-Cr-Mo alloys family. Different studies show that the alloy 22 is resistant to generalized and localized (in crevices) corrosion in aqueous solution, with high chloride concentration, and in a wide range of temperatures. Electrochemical techniques such as Electrochemical Impedance Spectroscopy (EIS) and PotentiodynamicGalvanostatic-Potentiodynamic (PD-GS-PD) and non-electrochemical techniques such as the Scanning Electron Microscopy (SEM), were applied to determine the effect of the ionic nitrates and chlorides upon the alloy 22 at 90 ^oC generalized and localized corrosion. The results show that for a critical molar concentration ratio R= [NO₃ ^-]/ [Cl^-] ≥0.2 it is completely eliminated the alloy 22 susceptibility to the crevice corrosion. The corrosion speed rates obtained were about 0.1μm/year at 24 hours of immersion.

Keywords : Alloy 22; Crevice corrosion; Nitrates; Repassivation potential; PD-GS-PD.

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