This study investigates the oxidative dissolution of Fe monosulfide (FeS) as a function of sample pretreatment. The dissolution rates of FeS (troilite) either untreated or pretreated with water (FeS#1) or 1 M HC1 (FeS#2) were determined at 25 degrees C and initial pH 2.0 in aerated solutions. Fourier Transform Infrared Spectroscopy and Differential Scanning Calorimetry analyses show that, compared to the initial sample (FeS#0), pretreated FeS samples contain an excess of sulfur and ferric oxyhydroxides which form external amorphous layers. For FeS#1, the external layer is rich in ferric oxyhydroxides. A diminution of dissolved amount of FeS#2 and FeS#1 compared to FeS#0 occurs after only 3 h of reaction. This dissolution inhibition was also confirmed by electro-chemical measurements (potentiodynamic polarization measurements and Electrochemical Impedance Spectroscopy). (C) 2015 Elsevier B.V. All rights reserved.