Corrosion Behavior Of Ti Research Articles

Ｔｉ‐Ｍｏ系焼結合金の腐食挙動について

The corrosion behavior of Ti-(0-40)mass%Mo alloys prepared through P/M technology was studied by corrosion test and electrochemical measurements. The corrosion rate of sintered Ti-Mo alloys in 35% HCl solution decreased remarkably with increasing molybdenum content. The corrosion rate of Ti-40mass%Mo alloy, for example, exhibited 5*10-3 [mm/year], which was 104 times lower than that of pure titanium. On the other hand, the corrosion rate in 3%NaCl solution wasn't affected by molybdenum content in alloys and was less than 10-3 [mm/Year].Potentiodynamic polarization curves in 35%HCl solution showed that increasing molybdenum content caused the open circuit potential (corrosion potential) to be noble and the anodic current density to be low. It was thought that the presence of spontaneously passivated film in which molybdenum was enriched by preferential dissolution of titanium suppressed the anodic reaction and improved their corrosion resistance. On the other hand, potentiodynamic polarization curves in 3%NaCl solution revealed that increasing molybdenum content caused the open circuit potential to be base and the anodic current density to be high because molybdenum dissolved actively.

In-Situ Corrosion Studies on Cast Steel High-Level Waste Containers Plated with Titanium/Nickel-Alloys

ABSTRACTPrevious corrosion studies have shown that the passive alloys Ti 99.8-Pd and Hastelloy C4 are the most promising corrosion protection materials for long-term resistant carbon-steel containers for the disposal of heat-generating wastes in rock salt formations. Consequently, these materials are subject to more detailed investigations. The influence of selected container manufacturing characteristics (sealing technique, application mode of the corrosion protecting layer on the steel) on the corrosion behaviour of Ti 99.8-Pd and Hastelloy C4was studied using in-situ experiments. The corrosion resistance of the materials was examined both in NaCI brine and MgCl2-rich brine, which might enter into an HLW borehole under certain disposal conditions. Four electron-beam welded cast-steel tubes plated with corrosion protection layers made of Ti 99.8-Pd and Hastelloy C4, respectively, were stored for 18 months in 2-m deep heated boreholes in the Asse salt mine. The annular gap between the tubes and the borehole wall was filled with saturated NaCl-brine or Qbrine (MgCl2-rich). The vertical temperature profile in the boreholes ranged from 90°C to 200°CIn the cast-steel tube with a corrosion protection of Ti 99.8-Pd, no indication of corrosion was observed on the EB-welds or on the explosion plated material in both brines. The cast-steel tube with a corrosion protection of Hastelloy C4 also was found to be resistant to any kind of corrosion in the NaCl-brine. In the MgCl2-rich brine, however, small pitting corrosion of 15 pm was observed after 1.5 years on the passive surface layer that was formed.On the basis of these results, Ti 99.8-Pd continues to be considered as a promising corrosion protection material for long-lived HLW containers.

XPS and UPS studies of gas‐phase oxidation, electrochemistry and corrosion behaviour of Ti and Ti5Ta

AbstractOwing to its high corrosion resistance, Ti is used as a containment material for processes in hot nitric acid. The corrosion stability of Ti can be improved still further by alloying with 5% Ta. The oxidation behaviour of Ti and Ti5Ta and the composition and stability of their oxide layers are compared by means of XPS, UPS, electrochemical measurements and corrosion test. Thin oxide layers of up to 2 nm have been formed by gas‐phase oxidation. Three regions can be observed due to chemisorption, oxide formation and oxide growth. The average composition of the oxide layer after an oxygen exposure of 1000 L is Ti2O3, with a layer thickness of 1.8 nm. The change of Ti oxidation states during oxidation shows that the metal/oxide interface is a mixed oxide of TiO, Ti2O3 and TiO2, while TiO2 is formed at the oxide/vacuum interface. The change of work function during oxidation is similar for Ti and Ti5Ta.Thicker oxide layers have been built electrochemically, with no differences in capacity measurements between Ti and Ti5Ta, indicating similar electronic properties. No significant Ta enrichment in 1 N H2SO4 and 1 N HNO3 is found up to 10 V. Preferential dissolution of Ti in corrosion tests in hot HNO3 leads to Ta enrichments by factors of >10, which explains the improved corrosion stability of the alloy. The surface is covered by a barrier oxide of ∼10 nm and a porous outer layer with a thickness of >50 nm.

Corrosion Behavior of Ti and Zr in Dissolution Process for Spent Nuclear Fuel Reprocessing

KEYWORDS: corrosioncorrosion resistancecorrosion potentialpolarization curvetitaniumzirconiumdissolver solutionrutheniumreprocessing

Corrosion behavior of Ti and Zr in dissolution process for spent nuclear fuel reprocessing.

Corrosion behavior of Ti and Zr in dissolution process for spent nuclear fuel reprocessing.

A study of the behaviour of titanium in acidic solution. Part 1 — Anodic behaviour and behaviour in “ababdoned” conditions

AbstractDespite numerous investigations into the corrosion behaviour of Ti and its alloys there are numerous discrepancies in literature with respect to the type of the tetravalent ion formed during the dissolution of titanium in aerated acid solutions; the same applies to the thermodynamical data concerning a possible redox reaction between titanium ions having different valencies.It is for this reason that the authors make an attempt at showing the importance of the formation of tetravalent titanium ions during the spontaneous passivation of titanium in acidic solutions. In this context they start by studying the anodic behaviour of titanium, in order to work out a basis for the evaluation of specimens of different origin. The studies are carried out in aerated and deoxygenated sulfuric acid, with and without external polarization. The anodic behaviour is then interpreted in terms of the mixed potential theory.

Factors Controlling the Corrosion Behavior of Titanium and Titanium-Nickel Alloys in Saline Solutions

Abstract The corrosion behavior of Ti in boiling acidic chloride solutions has been evaluated with regard to the nickel ion content of the corroding environment and the detailed crystallographic st...

Stress Corrosion Cracking and Corrosion Behavior of Ti and Ti-Al Alloys in Methanol Iodine Solutions

Abstract Studies have been made of the corrosion characteristics and susceptibility to stress-corrosion cracking of pure titanium and Ti-Al binary alloys in methanol-iodine solutions. The results indicate that two distinct stress-corrosion mechanisms may be operative, depending on the composition of the solid. In pure titanium and a Ti-2.09 w/o Al alloy failures were found to be intergranular, while in the higher alloys (>5 w/o Al) only the initial part of the crack was intergranular, the part adjacent to the final ductile fracture being largely transgranular. In all the materials examined, the intergranular stress-corrosion process could be inhibited by cathodic polarization or the introduction of water in the methanol-iodine solution. On the basis of these and other observations, it is suggested that this process represents stress-accelerated intergranular corrosion involving dissolution of metal at a crack tip. The transgranular crack propagation stage observed in the higher alloys has the characteristics of mechanical failure, and its occurrence appears to be related to a reduced propensity for cross-slip.