Mojtaba Momeni

Comparative study on corrosion behaviour of Nitinol and stainless steel orthodontic wires in simulated saliva solution in presence of fluoride ions.

Localized corrosion and effects of pre-passivation treatment of Nitinol and SS304 orthodontic wires in simulated saliva solution in the presence and absence of fluoride ions were investigated by means of potentiodynamic and potentiostatic polarisations. Results revealed that Nitinol does not show pitting corrosion in saliva solution however, SS304 shows pitting corrosion. Meanwhile fluoride ion has deteriorative effect on pitting corrosion of Nitinol, while its effect on SS304 was marginally constructive. Additionally, the presence of artificial crevice has no effect on corrosion behaviour in the presence of fluoride. Pre-passivation treatment has positive influence on pitting corrosion of both alloys in the presence of F(-) ions.

New High-Resolution Solution for Measuring Degree of Sensitization of Duplex Stainless Steel 2205 Using Double-Loop Electrochemical Potentiodynamic Reactivation Technique

In the present work, a new high-resolution solution for measuring degree of sensitization (DOS) of duplex stainless steel (DSS) 2205 (UNS S31803) by double loop-electrochemical potentiodynamic reactivation (DL-EPR) technique was obtained and the solution parameters were optimizing using the Taguchi method. Sensitized samples in three different conditions were chosen and five solution main factors including acid and two types of depassivator concentrations, scan rate, and surface roughness were considered. To reduce the number of experiments, Taguchi orthogonal array (OA) was used. The resulting optimal condition was to be 0.5 M sulfuric acid (H2SO4), 0.002 M sodium thiosulfate (Na2S2O3), 0.02 M sodium chloride (NaCl), and 120 grid in surface roughness and 30 mV/min scan rate. By introducing the new solution, a DOS value of 78% was obtained in the DSS2205 sample sensitized at 850°C for 40 min. Moreover, topography variations of non-sensitized and sensitized samples measured by atomic force microscopy eluci...

Establishing a New Solution Based on Hydrochloric Acid/Sodium Thiosulfate for Detecting and Measuring Degree of Sensitization of Stainless Steels Using Double-Loop Electrochemical Potentiodynamic Reactivation Method

In this study, a new solution based on hydrochloric acid (HCl) and sodium thiosulfate (Na2S2O3) has been developed for detecting and measuring degree of sensitization (DOS) using the double-loop electrochemical potentiodynamic reactivation (DL-EPR) method. Two types of stainless steels including Type 304 (UNS S30400) and 28Cr-33Ni-39Fe were sensitized at 650°C for 10, 60, and 300 min. The results revealed that the new solution can detect sensitization in stainless steels suitably with higher resolution than previously reported solutions. The optimum acid concentrations were 0.1 M and 0.4 M HCl for Type 304 stainless steel and 28Cr-33Ni-39Fe, respectively. For Type 304 stainless steel, the depassivator concentration was 0.002 M Na2S2O3, while it was 0.001 M for 28Cr-33Ni-39Fe.