Mechanistic Investigation on the Effect of Molybdate on the Critical Pitting Temperature of 2205 Duplex Stainless Steel

Abstract

In this research, a mechanistic approach was used to investigate the effect of molybdate ion on the critical pitting temperature (CPT) of 2205 duplex stainless steel. Firstly, the CPT of 2205 DSS was measured using potentiodynamic and potentiostatic polarization. It was found that with addition of 0.0005, 0.005 and 0.05 M Na 2 MoO 4 to 0.5 M NaCl solution, the CPT increases approximately 4, 9, and 14°C, respectively. Using the lead-in pencil electrode technique, the mechanism by which molybdate ion influences the CPT was interpreted using the CPT model proposed by Salinas-Bravo and Newman. The results showed that molybdate has a negligible effect on the pit solution chemistry, resulting in a slight change in the diffusion-limited current density. However, it reduces the rate of alloy dissolution within the simulated pit solution, which was found as a reduced maximum current density.

Effect of Molybdate on the Stability of Pit Growth in Duplex Stainless Steel 2205

“…As shown, molybdate causes a decrease in i diss,max , suggesting that the presence of molybdate in the pit-like solution prevents metal from dissolving as reported previously. 26 In order to investigate the active dissolution behavior of the 2205 DSS pencil electrode in a real pit electrolyte, the lead-in-pencil electrode experiment was performed in 0.5 M NaCl and 0.5 M NaCl + 0.05 M Na 2 MoO 4 solutions. Figure 10a 20 mA.cm −2 lower than in its absence.…”

“…Molybdate can also reduce the number and size of the metastable pits. 22,25 In a previous paper, 26 raising the CPT of the 2205 DSS in the presence of molybdate ions has been reported which was attributed to the decline in i diss,max in pit solution. This work, it is aimed to investigate the role of molybdate ion in the pit growth stage on the E pit using the new model of Frankel et al 6…”

Influence of Rust Inhibitors on the Microstructure of a Steel Passive Film in Chloride Concrete

“…Anodic rust inhibitors include nitrite, chromate, and molybdate [14]. They prevent steel bar corrosion by improving the passive film and reducing the contact between the steel bar and oxygen [15,16]. Unfortunately, the anodic rust inhibitor causes the pitting corrosion of the steel bar to accelerate corrosion within a certain concentration range.…”

Enhancing the Stability of Passive Film on 304 SS by Chemical Modification in Alkaline Phosphate–Molybdate Solutions

“…Mo-or P-containing passive films are beneficial to passivity, leading to an increased corrosion potential [22][23][24]. Phosphate and molybdate have been considered to be beneficial passivators for carbon steel, aluminum alloy, and zinc [25,26]. However, passivation in molybdate-only solution has resulted in a film with cracks [27].…”