Combined influence of fluorides and ferric ions on corrosion of titanium and Pd alloyed titanium in 100 g L−1 sulfuric acid solution

Abstract

In hydrometallurgical applications, titanium and its alloys are used as construction material in the most aggressive environments. Under acidic conditions, fluorides are known to be deleterious to titanium, but it is not well known how the presence of small amounts of both fluorides and ferric ions influences the corrosion behaviour of titanium in sulfuric acid solutions. Unalloyed titanium grade 2 (Ti Gr. 2) and palladium alloyed grades, titanium grade 17 (Ti Gr. 17) and titanium grade 7 (Ti Gr. 7), were investigated with electrochemical techniques and immersion tests in 100 g L^?1 sulfuric acid, containing 30 mg L^?1 fluorides and two levels of ferric ions, 0·3 and 3 g L^?1. It was found that the addition of fluorides accelerated the uniform corrosion rate, especially for the unalloyed Ti Gr. 2 in the solution having the lower amount of ferric ions. Palladium alloying was found to have a beneficial effect in reducing the uniform corrosion rate in the presence of small amounts of fluorides.     

Effect of micro-alloying titanium on the dynamic recrystallization behaviour of steels

The effect of titanium addition on the dynamic recrystallization behaviour of steels has been investigated. Constant strain rate tension tests were conducted in vacuum in the temperature range from 925 to 1225°C. Dynamic recrystallization-time-temperature (RTT) curves were developed from the flow curves at ε? = 1 × 10^?2s^?1. The results of the different steels with and without Ti indicate that the onsets of dynamic recrystallization in all the steels are earlier at higher temperatures than at lower temperatures and the addition of titanium may shift the RTT curve of the C–Mn–Si steel towards the right, i.e. retard dynamic recrystallization. The retarding effect of Ti becomes more intensive at temperatures below about 1075°C where a transition of the RTT relationship occurs. Microstructural examinations show that titanium dissolved in austenite can retard the dynamic recrystallization and the precipitation of TiC produces a more intensive retarding effect.     

Effect of titanium on the microstructure and hardness uniformity of non-quenched and tempered prehardened steel for large-section plastic mould

Two non-quenched and tempered (NQT) prehardened plastic mould steels, differing by titanium content, were produced to have good hardness uniformity in large sections (485?×?970 and 465?×?1325?mm²). The effect of titanium on continuous cooling transformation curves, hardness uniformity and microstructure (grain size, phase constituents) were studied. It was found titanium had refined the grain size of NQT steel by the pinning effect of Ti (C, N) at grain boundaries, and titanium also effectively postponed the nucleation of proeutectoid ferrite in intercritical region. Using finite element method, the cooling rate from core to surface along longitude direction of the steels was predicted. The results indicated that the NQT steel with titanium had better process adaptability than that of NQT steel without titanium. Compared with production of NQT steel without titanium, production for NQT steel with titanium can largely save the production cost by shortening the production cycle and reducing the resources.     

Thick Low-Friction nc-MeC/a-C Nanocomposite Coatings on Ti-6Al-4V Alloy: Microstructure and Tribological Properties in Sliding Contact with a Ball

In this paper, we show that duplex surface treatment, combining oxygen diffusion hardening with the subsequent deposition of thick, low-friction nanocomposite nc-MeC/a-C coatings to improve the tribological properties of the Ti-6Al-4V alloy. We have synthesized, in a magnetron sputtering process, the nanocomposite nc-MeC/a-C coatings (where Me denotes W or Ti transition metal) consisting of two dissimilar materials (nanocrystallites of transition metal carbides MeC and an amorphous carbon matrix a-C). The nano and microstructure of the substrate material and coatings were examined with the use of scanning and transmission electron microscopy as well as by X-ray diffractometry. It was found that different carbide nanocrystals of the same transition metal were embedded in an amorphous carbon matrix of both coatings. The HRTEM analysis indicated that the volume fraction of tungsten carbides in the nc-WC/a-C coating was equal to 13 pct, whereas in the nc-TiC/a-C one the volume fraction of the titanium carbides was equal to just 3 pct. The tribological properties, hardness, and scratch resistance of the coatings were investigated as well. The coefficient of friction (COF) of the coatings during dry sliding against 6 mm diameter alumina ball reached very low value, 0.05, in comparison with an oxygen-hardened alloy, whose COF was equal to 0.8. This low-friction effect of the coatings has been attributed to the formation of a self-lubricating film in sliding contact. The coatings exhibited similar failure morphology in the scratch tests. Even though the hardness was rather low, the coatings exhibited a very good wear resistance during sliding friction. The wear rate of the nc-WC/a-C coating was equal to 0.08 × 10^?6 mm³ N^?1 m^?1 and for the nc-TiC/a-C one it was 0.28 × 10^?6 mm³ N^?1 m^?1.     

Spark plasma sintering versus hot pressing – densification,bending strength,microstructure, and tribological properties of Ti5Al2.5Fe alloys

Ti5Al2.5Fe alloys were fabricated by the spark plasma sintering (SPS) and hot pressing (HP) pressure-assisted sintering techniques from pre-alloyed powders with a particle size of about 200?μm. The powders were sintered at 850 °C for two different holding times (5 and 8 min) and heating rates (50 and 150°C?min^?1) at 25?MPa. The maximum relative densities were 99.70 and 98.78% for SPS and HP samples, respectively. All the alloys prepared by the SPS process had significantly higher bending strengths (1825–2074?MPa) than the alloys prepared by the HP process (648–1330?MPa). A decrease in the heating rate from 150 to 50°C min^?1 enhanced the wear resistance of the Ti5Al2.5Fe alloys prepared by both the SPS and HP processes.     

Carburizing of Duplex Stainless Steel (DSS) Under Compression Superplastic Deformation

A new surface carburizing technique which combines superplastic deformation with superplastic carburizing (SPC) is introduced. SPC was conducted on duplex stainless steel under compression mode at a fixed 0.5?height reduction strain rates ranging from 6.25?×?10^?5?to 1?×?10^?3?s^?1?and temperature ranging from 1173?K to 1248?K (900?°C to 975?°C). The results are compared with those from conventional and non-superplastic carburizing. The results show that thick hard carburized layers are formed at a much faster rate compared with the other two processes. A more gradual hardness transition from the surface to the substrate is also obtained. The highest carburized layer thickness and surface hardness are attained under SPC process at 1248?K (975?°C) and 6.25?×?10^?5?s^?1?with a value of (218.3?±?0.5)???m and (1581.0?±?5.0) HV respectively. Other than that, SPC also has the highest scratch resistance.     

Microstructural and mechanical assessment of transient liquid phase bonded commercially pure titanium

Diffusion joining of commercially pure titanium was successfully prepared via transient liquid phase bonding in vacuum environment. The process was carried out using AMS 4772 silver-based filler alloy at 900–1000°C for various holding time under the vacuum of 6?×?10^?7?Torr. Optical and scanning electron microscopy equipped with an EDS analyzer was conducted for microstructural evaluations. Mechanical properties were also investigated by shear test, fractographic assessment and X-ray diffraction analyses. The tendency to achieve isothermally solidified joint increased by increasing bonding time. No sign of athermal solidification was detected of sample bonded at 1000°C for 90?min. Consequently, the bonding condition of a high quality joint was obtained. Elemental analyses revealed that filler alloy’s elements (Ag, Cu) distributed more uniformly in fully isothermal solidified bond, whereas the aggregation of these elements is considerable in athermally solidified bond. Shear test results represented that the highest shear strength attributed to the sample bonded in isothermal solidified condition (bonded at 1000°C for 90?min).     

Thermodynamics and kinetics analyses of ZrB2 formation in molten aluminium alloys

Smelter grade aluminium can be used as a source for electrical conductor grade aluminium after the transition metal impurities such as zirconium (Zr), vanadium (V), titanium (Ti) and chromium (Cr) have been removed. Zirconium (Zr), in particular, has a significant effect on the electrical conductivity of aluminium. In practice, the transition metal impurities are removed by adding boron-containing substances into the melt in the casthouse. This step is called boron treatment. The work presented in this paper, which focuses on the thermodynamics and kinetics of Zr removal from molten Al–1?wt-%Zr–0.23?wt-%B alloy, is part of a broader systematic study on the removal of V, Ti, Cr and Zr from Al melt through boron treatment carried out by the authors. The thermodynamic analyses of Zr removal through the formation of ZrB₂ were carried out in the temperature range of 675–900°C using the thermochemical package FactSage. It was predicted that ZrB₂ is stable compared to Al–borides (AlB₁₂, AlB₂) hence would form during boron treatment of molten Al–Zr–B alloys. Al–Zr–B alloys were reacted at 750?±?10°C for 60 minutes, and the change in the chemistry and microstructure were tracked and analysed at particular reaction times. The results showed that the reaction between Zr and AlB₁₂/B was fast as revealed by the formation of boride ring at the early minutes of reaction. The presence of black phase (AlB₁₂), i.e. the original source of B, after holding the melt for 60 minutes advocated that the reaction between Zr and AlB₁₂/B was incomplete, hence still not reached the equilibrium state. The kinetics data suggested a higher reaction rate at the early minutes (2 minutes) of reaction compared to at a later stage (2–60 minutes). Nevertheless, a simple single-stage liquid mass transfer controlled kinetic model can be used to describe the overall process kinetic. The analysis of integrated rate law versus reaction time revealed that the mass transfer coefficient (k_m) of Zr in molten alloy is 9.5?×?10^?4?m?s^?1, which is within a typical range (10^?3 to 10^?4?m?s^?1) observed in other metallurgical solid–liquid reactions. This study suggests that the overall kinetics of reaction was predominantly controlled by the mass transfer of Zr through the liquid aluminium phase.     

The Equilibrium Between Titanium Ions and Titanium Metal in NaCl-KCl Equimolar Molten Salt

The equilibrium between metallic titanium and titanium ions, 3Ti²⁺ ? 2Ti³⁺ + Ti, in NaCl-KCl equimolar molten salt was reevaluated. At a fixed temperature and an initial concentration of titanium chloride, the equilibrium was achieved by adding an excess amount of sponge titanium in assistant with bubbling of argon into the molten salt. The significance of this work is that the accurate concentrations of titanium ions have been obtained based on a reliable approach for taking samples. Furthermore, the equilibrium constant   $ {\text{K}}_{\text{C}} = (x_{{{\text{Ti}}^{{ 3 { + }}} }}^{\text{eql}} )^{3} /(x_{{{\text{Ti}}^{{ 2 { + }}} }}^{\text{eql}} )^{2} $ K C = ( x Ti 3 + eql ) 3 / ( x Ti 2 + eql ) 2 was calculated through the best-fitting method under the consideration of the TiOCl dissolution. Indeed, the final results have disclosed that the stable value of K_C could be achieved based on all modifications.     

Oxide Scales Formed on NiTi and NiPtTi Shape Memory Alloys

Ni-49Ti and Ni-30Pt-50Ti (nominal at. pct) shape memory alloys (SMAs) were isothermally oxidized in air over the temperature range of 773?K to 1173?K (500?°C to 900?°C) for 100?hours. The oxidation kinetics, presented in detail in a companion study, show ~4 times reduction in oxidation rate due to Pt.[1] The microstructure, composition, and phase content of the scales and depletion zones were determined by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). A relatively pure TiO₂ rutile structure was identified as the predominant scale surface feature, typified by a distinct highly striated and faceted crystal morphology, with crystal size proportional to oxidation temperature. The complex layered structure beneath these crystals was characterized by semiquantitative XRD of serial/taper polished sections and SEM/EDS of cross sections for samples oxidized at 973?K (700?°C). In general, graded mixtures of TiO₂, NiTiO₃, NiO, Ni(Ti), or Pt(Ni) metallic dispersoids, and continuous Ni₃Ti or Pt-rich metal depletion zones, were observed from the gas surface to the substrate interior. Overall, substantial depletion of Ti occurred due to the formation of predominantly TiO₂ scales. It is proposed that the Ni-30Pt-50Ti alloy oxidized more slowly than the binary Ni-49Ti alloy by decreasing oxygen and titanium diffusion through the thin Pt-rich layer.     

Formation of Small Blocky Al3Ti Particles via Direct Reaction Between Solid Ti Powders and Liquid Al

The evolution of titanium powders in the pure aluminum melt at a lower temperature was studied in our research. The process involved some titanium powders being added into the pure aluminum melt at 1003?K (730?°C), and then the melt was cast into an ingot after 5 minutes. A reaction layer composed of some loose Al₃Ti particles was formed on the solid Ti surface due to the reactive diffusion between titanium and aluminum. In-situ blocky Al₃Ti particles smaller than 5???m were produced in the aluminum matrix. A reaction-peeling model was suggested to illustrate the formation mechanism of Al₃Ti particles, and a simple approach for fabricating in-situ Al₃Ti/Al-alloy composites was proposed as well.     

Microwave Heating, Isothermal Sintering, and Mechanical Properties of Powder Metallurgy Titanium and Titanium Alloys

This article presents a detailed assessment of microwave (MW) heating, isothermal sintering, and the resulting tensile properties of commercially pure Ti (CP-Ti), Ti-6Al-4V, and Ti-10V-2Fe-3Al (wt pct), by comparison with those fabricated by conventional vacuum sintering. The potential of MW sintering for titanium fabrication is evaluated accordingly. Pure MW radiation is capable of heating titanium powder to ≥1573 K (1300 °C), but the heating response is erratic and difficult to reproduce. In contrast, the use of SiC MW susceptors ensures rapid, consistent, and controllable MW heating of titanium powder. MW sintering can consolidate CP-Ti and Ti alloys compacted from ?100 mesh hydride-dehydride (HDH) Ti powder to ~95.0 pct theoretical density (TD) at 1573 K (1300 °C), but no accelerated isothermal sintering has been observed over conventional practice. Significant interstitial contamination occurred from the Al₂O₃-SiC insulation–susceptor package, despite the high vacuum used (≤4.0 × 10^?3 Pa). This leads to erratic mechanical properties including poor tensile ductility. The use of Ti sponge as impurity (O, N, C, and Si) absorbers can effectively eliminate this problem and ensure good-to-excellent tensile properties for MW-sintered CP-Ti, Ti-10V-2Fe-3Al, and Ti-6Al-4V. The mechanisms behind various observations are discussed. The prime benefit of MW sintering of Ti powder is rapid heating. MW sintering of Ti powder is suitable for the fabrication of small titanium parts or titanium preforms for subsequent thermomechanical processing.     

Implantation of HA into Superplastic Ti-6Al-4V: Kinetics and Mechanical Behaviors of Implanted Layer

An implanted layer is produced by implantation of hydroxyapatite (HA) into superplastic Ti-6Al-4V. X-ray diffraction (XRD) analysis indicates that the surface of the implanted layer is composed of HA and Ti-6Al-4V, and line-scanning analysis confirms a mutual elemental diffusion of HA and Ti-6Al-4V. According to the scanning electron microscope (SEM) images, by increasing the implantation temperature, the thickness of the implanted layer increases. The bonding strength between implanted layer and titanium substrate is examined by conducting a friction wear test. Higher surface removal of an implanted layer is observed when as-received Ti-6A1-4V was used in the implantation process, which is an indication of higher bonding strength between implanted layer and superplastic Ti-6A1-4V. The effect of implanted layer thickness on the wear resistance is also investigated. The reduction in thickness of the implanted layer is more evident in thicker implanted layers. The results suggest that the adhesion between the implanted layer and titanium substrate is stronger than the cohesion within the implanted layer.     

Solubility of oxygen in Fe–Co melts containing titanium

Solutions of oxygen in Fe–Co melts containing titanium are subjected to thermodynamic analysis. The first step is to determine the equilibrium reaction constants of titanium and oxygen, the activity coefficients at infinite dilution, and the interaction parameters in melts of different composition at 1873 K. With increase in cobalt content, the equilibrium reaction constants of titanium and oxygen decline from iron (logK(FeO · TiO₂) =–7.194; logK(TiO₂) =–6.125; logK(Ti₃O₅) =–16.793; logK(Ti₂O₃) =–10.224) to cobalt (logK(CoO · TiO₂) =–8.580; logK(TiO₅) =–7.625; logK(Ti₃O₅) =–20.073; logK(Ti₂O₃) =–12.005). The titanium concentrations at the equilibrium points between the oxide phases (Fe, Co)O · TiO₂, TiO₂, Ti₃O₅, and Ti₂O₃ are determined. The titanium content at the equilibrium point (Fe, Co)O · TiO₂ ? TiO₂ decreases from 1.0 × 10^–4% Ti in iron to 1.9 × 10^–6% Ti in cobalt. The titanium content at the equilibrium point TiO₂?Ti₃O₅ increases from 0.0011% Ti in iron to 0.0095% Ti in cobalt. The titanium content at the equilibrium point Ti₃O₅ ? Ti₂O₃ decreases from 0.181%Ti in iron to 1.570% Ti in cobalt. The solubility of oxygen in the given melts is calculated as a function of the cobalt and titanium content. The deoxidizing ability of titanium decline with increase in Co content to 20% and then rise at higher Co content. In iron and its alloys with 20% and 40% Co, the deoxidizing ability of titanium are practically the same. The solubility curves of oxygen in iron-cobalt melts containing titanium pass through a minimum, whose position shifts to lower Ti content with increase in the Co content. Further addition of titanium increases the oxygen content in the melt. With higher Co content in the melt, the oxygen content in the melt increases more sharply beyond the minimum, as further titanium is added.     

Characterization and In Vitro Corrosion Investigations of Thermal Sprayed Hydroxyapatite and Hydroxyapatite-Titania Coatings on Ti Alloy

In the current investigation, hydroxyapatite (HA) powder was mixed with titania (TiO₂) in 50:50?wt?pct for depositing composite coatings on a Ti-alloy substrate using a thermal-spray coating technique. The coatings were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDS) analyses. The corrosion behavior of the coatings was studied by electrochemical corrosion testing in simulated human body fluid. After the corrosion testing, the samples were analyzed by XRD and SEM/EDS analyses. HA and TiO₂ (rutile) were the main phases observed in the developed coatings. Bulk HA coating was amorphous; however, the addition of TiO₂ effectively improved the crystallinity of HA in HA-TiO₂ coating. The SEM analysis confirmed the formation of a well-formed HA-TiO₂ composite coating. HA coating exhibited higher bond strength (67.8?MPa) compared with HA-TiO₂ composite coating (37.6?MPa). The electrochemical study showed a significant improvement in the corrosion resistance of the Ti alloy after the deposition of the coatings.     

Painted steel mounted dye sensitised solar cells: titanium metallisation using magnetron sputtering

Abstract

Dye sensitised solar cells (DSCs) have been assembled directly onto a prepainted construction steel substrate. This has been achieved by chemically isolating the underlying substrate through the application of a high temperature resistant organic polymer rendered conducting by applying a 1·2?μm collection electrode of magnetron sputtered titanium. The resultant DSCs achieved 2·9% energy conversion efficiency under one sun illumination compared to 3·2% for identical cells manufactured on 1?mm thick Ti coupons. The slight reduction in efficiency reflects the increasing resistance of the substrate 1·2?μm Ti layer, which results from microcracking during the titania sintering step.     

Unidirectionally solidified Ti−TiB and Ti−Ti5Si3 eutectic composites

Induction melting and electron beam melting techniques were employed in the production of unidirectionally solidified eutectic composites of Ti-1.7 wt pct B and Ti-8.5 wt pct Si. The grown eutectics were reinforced by 7.7 volume pct of TiB fibers and 31 volume pct of Ti₅Si₃ fibers respectively. Controlled dendritic solidification of a hypereutectic composition of Ti-12 wt pct Si was also accomplished. Tensile, compressive, creep, and stress rupture specimens were cut from the eutectic composites and tested with reinforcing fibers parallel to the load axis. Ti?TiB eutectic was found to have less than the critical volume fraction of fibers necessary for reinforcement, while Ti?Ti₅Si₃ composite attained a compressive yield strength of 275,000 psi and a compressive Young's modulus of 30×10⁸ psi after heat treatment. The 500 and 4000 hr stress rupture properties of Ti?Si eutectic were superior to commercial titanium alloys at 1000° and 1200°F. The minimum creep rate of Ti?Ti₅Si₃ eutectic composite was lower than all other titanium alloys at 1000°F. Tensile, compressive, and creep properties of the Ti-8.5 wt pct Si eutectic are discussed in terms of the current theories of composite behavior.     

Kinetics of Alkaline Decomposition and Cyaniding of Argentian Rubidium Jarosite in NaOH Medium

The alkaline decomposition of Argentian rubidium jarosite in NaOH media is characterized by an induction period and a progressive conversion period in which the sulfate and rubidium ions pass to the solution, leaving an amorphous iron hydroxide residue. The process is chemically controlled and the order of reaction with respect to hydroxide concentration in the range of 1.75 and 20.4?mol OH^? m^?3 is 0.94, while activation energy in the range of temperatures of 298?K to 328?K (25?°C to 55?°C) is 91.3?kJ mol^?1. Cyaniding of Argentian rubidium jarosite in NaOH media presents a reaction order of 0 with respect to NaCN concentration (in the range of 5 to 41?mol m^?3) and an order of reaction of 0.62 with respect to hydroxide concentration, in the range of 1.1 and 30?mol [OH^?] m^?3. In this case, the cyaniding process can be described, as in other jarosites, as the following two-step process: (1) a step (slow) of alkaline decomposition that controls the overall process followed by (2) a fast step of silver complexation. The activation energy during cyaniding in the range of temperatures of 298?K to 333?K (25?°C to 60?°C) is 43.5?kJ mol^?1, which is characteristic of a process controlled by chemical reaction. These results are quite similar to that observed for several synthetic jarosites and that precipitated in a zinc hydrometallurgical plant (Industrial Minera México, San Luis Potosi).     

TiB whisker coating on titanium surfaces by solid-state diffusion: Synthesis,microstructure, and mechanical properties

The study demonstrates the feasibility of synthesizing TiB whiskers on titanium (Ti) surfaces by solid-state diffusion to form a hard and wear-resistant coating. The microstructural and mechanical properties of the TiB coating layer have also been investigated. The TiB coating was formed by the solid-state diffusion of boron (B) from a powder mixture containing amorphous boron, Na₂CO₃ powder, and charcoal (activated) powder. The diffusion process was carried out at various temperatures ranging from 800 °C to 1000 °C for various periods of time ranging from 1 to 24 hours. The amount of Na₂CO₃ in the mixture was also varied. It has been found that pristine and extremely fine TiB whiskers form on the surfaces of titanium, with the whiskers growing more or less normal to the surface. A maximum coating thickness of about 218 μm was observed for the pack diffusion conditions at 850 °C for 24 hours with 15 pct Na₂CO₃. The kinetics of TiB formation was found to follow the growth rates in bulk composites. The X-ray diffraction (XRD) patterns of the coatings revealed the dominant TiB peaks with a very few TiB₂ peaks, with small intensity at higher temperature and time. The surface hardness of the coated layer increased to a Vickers hardness of about 550 kgf/mm² due to the presence of TiB whiskers in the coating. It is shown that pack diffusion of boron in the solid state is a simple and very effective means of generating hard and wear-resistant coatings on titanium.     

Ti/TiO2/Ni2+ interface: unexpected protection of Ti by Ni2+ cations in hot sulphuric acid

Abstract

The processing of nickel ores involves: high temperatures (>100°C), high [H₂SO₄] and high [Cl^?]. Despite the severity of this service, pure titanium can be used because it presents very low corrosion rates. Looking for the fundamental causes of this behaviour, it was found that the potential of the couple Ti⁴⁺/Ti³⁺ shifted to more negative potentials than the couple Ni²⁺/Ni in these conditions. Thus, Ni²⁺ was reduced to Ni metal, oxidising Ti³⁺ to Ti⁴⁺. This increased the concentration of Ti⁴⁺ which was critical for the formation of the protective TiO₂ layer. In turn, the TiO₂ passivated the active titanium dissolution. Also, the deposited Ni catalysed the cathodic kinetics, producing a mixed potential in the passive region for titanium. This process involves Ti/TiO₂/Ni²⁺ and Ti/Ni²⁺ interface systems, and Ti/Ni²⁺ behaviour is somewhat like a titanium–nickel alloy.

Le traitement des minerais de nickel implique des températures élevées (>100°C) et une concentration élevée de [H₂SO₄] et de [Cl^?]. En dépit de la sévérité de ces conditions, on peut utiliser le titane pur parce que celui-ci présente de très faibles taux de corrosion. Examinant les raisons fondamentales de ce comportement, on a trouvé que le potentiel du couple Ti⁴⁺/Ti³⁺ se déplaçait vers des potentiels plus négatifs que celui du couple Ni²⁺/Ni sous ces conditions. Ainsi, le Ni²⁺ était réduit en métal Ni, oxydant le Ti³⁺ en Ti⁴⁺. Ceci augmentait la concentration de Ti⁴⁺, qui est critique pour la formation de la couche protectrice de TiO₂. À son tour, le TiO₂ rend passive la dissolution active du titane. Également, le Ni déposé catalyse la cinétique cathodique, produisant un potentiel mixte dans la région passive du titane. Ce procédé implique les systèmes de l’interface Ti/TiO₂/Ni²⁺ et Ti/Ni²⁺et le comportement du Ti/Ni²⁺ est plus ou moins comme un alliage de titane-nickel.