The influence mechanism of Fe³⁺ on corrosion behavior of Ti6Al4V in sulfuric acid solutions

Abstract

The corrosion behavior of titanium alloy Ti6Al4V in 44.6 wt% sulfuric acid solutions, was studied via potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), Mott–Schottky and X‐ray photoelectron spectroscopy (XPS) techniques. The results indicated that the Fe3+ played an important role in the passivation and stability of the passive film formed on Ti6Al4V. When the concentration of Fe3+ reached to 0.001 M, the hydrogen evolution reaction (cathodic process) was remarkably influenced, the anode process of the corrosion reaction changed from active state to passivation state, and it showed an enormous increase of the impedance values (Rc) with the capacitive arc varying from two to one. XPS results showed that as the concentration of Fe3+ increased, there were less intermediate valence oxides Ti2O3 and more stable valence oxides TiO2. Fe3+ made more intermediate valence titanium ions or instability titanium oxides transformed into stable valence oxides, which enhanced the stability of the passive film.

Effect of Cr on Corrosion Behavior of Laser Cladding Ni-Cr-Mo Alloy Coatings in Sulfuric Acid Dew Point Corrosion Environment

“…All three specimens exhibit typical passivation behavior along with the active region, active-passive transition region, passive region and transpassive region, which is similar to that reported by other researchers for Ni-Cr-Mo alloys in sulfuric acid solutions [23,40,43,50]. The existence of active-passive transition and locating of stable OCP at an active region of each specimen indicate the spontaneous active behavior of studied Ni-Cr-Mo alloy coatings [12,[60][61][62]. The corrosion potential of Cr18 and Cr26 locates at a similar value, which is slightly higher than that of Cr22.…”

Electrochemical Behavior and Passive Film Properties of Hastelloy C22 Alloy, Laser-Cladding C22 Coating, and Ti–6Al–4V Alloy in Sulfuric Acid Dew-Point Corrosion Environment

“…The depressed capacitive arc and the broad peak of the phase angle imply that the predominantly capacitive behavior of the compact passive film combines with the reaction products absorbing on the surface. This result is different from the time constant measured by Mogoda in sulfuric acid with a lower concentration [42], but is similar to the results reported by other studies of titanium under more aggressive conditions [16,17,55,56]. It could be attributed to the larger amount of absorption reaction products resulting from a more concentrated sulfuric acid.…”

“…It could be attributed to the larger amount of absorption reaction products resulting from a more concentrated sulfuric acid. The sharp reductions in the capacitive arc, impedance modulus, and the phase angles as the temperature increases to 70 • C indicate the significant thinning or localized disruption of the passive film [16,50,51,54,56]. As the applied potential increased, the diameter of the capacitive arc and impedance modulus at 50 and 70 • C basically remained unchanged as the applied potential increased, while those at 60 • C slightly increased.…”

The bifunctional role played by thiocyanate anions on the active dissolution and the passive film of titanium in hydrochloric acid

“…This equivalent circuit fits the EIS data perfectly, as seen for the solid lines in Figure 9(a,c). Wang and co-authors [47], who researched Ti alloys in H 2 SO 4 at high concentrations, suggested a similar equivalent circuit fitting approach. Table 7 shows the proper results for R s , CPE dl , R ct , CPE f , R f , and Z W .…”