Abstract:The passivation of Ti-2 by Fe(III) and Cu(II) species in acidic chloride solutions was investigated by electrochemical techniques. It was found that the critical concentrations of Fe (III) and Cu(II) species required to induce passivation of Ti-2 increased from 1.0 ± 0 to 6.0 ± 0 mM and from 0.25 ± 0 to 1.15 ± 0.23 mM, respectively, when the temperature was increased from 30 • C to 80 • C. The mechanism associated with the passivation was the acceleration of the cathodic reactions due to the introduction of ox… Show more
“…Passivation of the titanium electrode surface can be linked to the formation of insulating oxide film that prevents corrosion. [59,60] The change of the apparent slope of the polarization curve around 400 mV indicates the beginning of the oxygen evolution; however, the current density did not increase significantly in the studied potential range. The CRs determined by both methods, i.e., by fitting CPP curves to the Butler-Volmer equation (Eq.…”
Recently, an emerging electrodeposition-redox replacement (EDRR) method was demonstrated to provide exceptionally efficient gold recovery from cyanide-free hydrometallurgical solutions. However, the effect of electrode material and its corrosion resistance in this process was overlooked, even though the EDRR process is carried out in extremely corrosive, acidic chloride solution that also contains significant amounts of strong oxidants, i.e., cupric ions. In the current study, nickel alloy C-2000, stainless steels 316L and 654SMO, and grade 2 titanium were for the first time critically evaluated as potential cathode materials for EDRR. The particular emphasis was placed on better understanding of the effect of cathode substrate on the overall efficiency of the gold recovery process. The use of a multiple attribute decision-making method of material selection allowed reaching of a well-founded compromise between the corrosion properties of the electrodes and process efficiency of gold extraction. The 654SMO steel demonstrated outstanding performance among the examined materials, as it enabled gold recovery of 28.1 pct after 3000 EDRR cycles, while its corrosion rate (CR) was only 0.02 mm/year.
“…Passivation of the titanium electrode surface can be linked to the formation of insulating oxide film that prevents corrosion. [59,60] The change of the apparent slope of the polarization curve around 400 mV indicates the beginning of the oxygen evolution; however, the current density did not increase significantly in the studied potential range. The CRs determined by both methods, i.e., by fitting CPP curves to the Butler-Volmer equation (Eq.…”
Recently, an emerging electrodeposition-redox replacement (EDRR) method was demonstrated to provide exceptionally efficient gold recovery from cyanide-free hydrometallurgical solutions. However, the effect of electrode material and its corrosion resistance in this process was overlooked, even though the EDRR process is carried out in extremely corrosive, acidic chloride solution that also contains significant amounts of strong oxidants, i.e., cupric ions. In the current study, nickel alloy C-2000, stainless steels 316L and 654SMO, and grade 2 titanium were for the first time critically evaluated as potential cathode materials for EDRR. The particular emphasis was placed on better understanding of the effect of cathode substrate on the overall efficiency of the gold recovery process. The use of a multiple attribute decision-making method of material selection allowed reaching of a well-founded compromise between the corrosion properties of the electrodes and process efficiency of gold extraction. The 654SMO steel demonstrated outstanding performance among the examined materials, as it enabled gold recovery of 28.1 pct after 3000 EDRR cycles, while its corrosion rate (CR) was only 0.02 mm/year.
“…Fe(III), Cu(II) and O 2 , which are widely present in the leaching conditions, are reported to effectively passivate titanium with a layer of protective TiO 2 /TiO 2 ·H 2 O formed on the surface (reaction ②), which accounts for the excellent corrosion resistance of Ti equipment used in high acidity leaching solutions [18,43]. For the investigated conditions, Fe(III) reduction was believed to be dominant due to its rapid kinetics and high redox potential compared with O 2 and Cu(II) (reaction ③), and this has been reported in previous work [43]. Figure 10 Reaction mechanism proposed for the corrosion of titanium autoclaves covered by solid deposits in a hydrometallurgical leaching condition.…”
Section: Discussionmentioning
confidence: 99%
“…Importantly, passivity is considered to be a dynamic process involving minor breakdown and repair events of the passive film. Either Fe (III), or Cu(II) or O 2 was reported to significantly promote the growth and repair of the passive film of titanium, thus playing an important role in maintaining the stability of the protective passive oxide film and accounting for the high corrosion resistance of titanium in the acidic leaching conditions [43]. Greater mass transfer of Fe(III) to the titanium surface promotes passive film growth and repair and thus inhibits corrosion.…”
Solid minerals are ubiquitous and common deposits on Ti-lined process vessels in the hydrometallurgical industry. This work revealed the effects of inert solid deposits on the corrosion behaviour of Ti-2 in high acidity and highly oxidising leaching solutions. It was found that the deposit-covered Ti-2 had a higher corrosion rate (CR) than bare Ti-2. CR increased with increasing deposit thickness (up to 6 cm) and temperature. Solid deposits mainly affected the corrosion process of Ti by limiting the mass transfer of the oxidising Fe(III) from the bulk solution to the underlying Ti, thus affecting the stability of the protective passive film, and resulting in an accelerated passive CR. High temperatures and solid deposition are both commonly encountered in the hydrometallurgical industry, and their combination may significantly limit the maximum service temperature of Ti-equipment, implying that there is a risk in using Ticomponents under such conditions.
“…Due to the excellent properties of titanium and its alloys, such as high corrosion resistance, high strength to weight ratio, and biocompatibility, they have shown great potential for a wide range of applications, including aerospace, automotive, marine, energy, and medical implant industries 1 – 5 . Their high corrosion resistance is due to forming a thin protective passive layer, a natural passive oxide that provides biocompatibility and strong resistance to pitting corrosion 6 .…”
This study explores the effect of surface re-finishing on the corrosion behavior of electron beam manufactured (EBM) Ti-G5 (Ti-6Al-4V), including the novel application of an electron beam surface remelting (EBSR) technique. Specifically, the relationship between material surface roughness and corrosion resistance was examined. Surface roughness was tested in the as-printed (AP), mechanically polished (MP), and EBSR states and compared to wrought (WR) counterparts. Electrochemical measurements were performed in chloride-containing media. It was observed that surface roughness, rather than differences in the underlying microstructure, played a more significant role in the general corrosion resistance in the environment explored here. While both MP and EBSR methods reduced surface roughness and enhanced corrosion resistance, mechanical polishing has many known limitations. The EBSR process explored herein demonstrated positive preliminary results. The surface roughness (Ra) of the EBM-AP material was considerably reduced by 82%. Additionally, the measured corrosion current density in 0.6 M NaCl for the EBSR sample is 0.05 µA cm−2, five times less than the value obtained for the EBM-AP specimen (0.26 µA cm−2).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
