Preliminary electrochemical testing of some Zr–Ti alloys in 0.9% NaCl solution

The aim of this study is to investigate the corrosion behaviour of three ZrTi alloys (denoted with Zr5Ti, Zr25Ti, and Zr45Ti) in 0.9% NaCl solution. For comparison, cp‐Ti was also investigated. In order to study the localized corrosion resistance and corrosion behavior at open circuit potential versus time, the open circuit potential (E_OC) was recorded, and the cyclic potentiodynamic polarization (CPP) and electrochemical impedance spectroscopy (EIS) were performed. Scanning electron microscopy (SEM) observations were made following the CPP tests. The Zr5Ti alloy was the most susceptible to localized corrosion. The Zr25Ti alloy presents a dangerous breakdown potential but have a sufficiently negative zero corrosion potential that the difference between them is sufficiently to provide a higher localized corrosion resistance in comparison with Zr5Ti. Among ZrTi alloys subjected to investigation, the Zr45Ti alloy had a much larger passive range in the polarization curve and was the most resistant to localized corrosion. For used test conditions, the localized corrosion was not found for the cp‐Ti. The EIS tests show that both investigated ZrTi alloys and cp‐Ti exhibit passivity after 168 h immersion in 0.9% NaCl solution, at open circuit potential.     

Effects of Hf content and immersion time on electrochemical behavior of biomedical Ti-22Nb-xHf alloys in 0.9% NaCl solution

The aim of this study was to investigate the effects of Hf content and immersion time on the electrochemical corrosion behavior of the Ti-22Nb-xHf (x = 0, 2, 4, and 6 at%) alloy samples in 0.9% NaCl solution at 37 °C and neutral pH range, utilizing the potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. From the polarization curves, all these alloys exhibited typical passive behavior, which was indicated by a wide passive region without the breakdown of the passive films and low corrosion current densities. In addition, the values of the corrosion current densities and passive current densities decreased with increase in the Hf content. The EIS results, fitted by R_S(Q_PR_P) model, exhibited capacitive behavior (high corrosion resistance) with phase angles closed to −80° and high impedance values at low and medium frequencies, indicating the formation of a highly stable film on these alloys in the test solution. The resistance of the passive films improved with increase in the Hf content and immersion time. All these observations suggested a more noble electrochemical behavior of the Ti-22Nb-xHf alloys compared to the Ti-Nb binary alloy.     

Evaluating electrochemical behaviour of recrystallized titanium alloys in Ringer's solution

By anodic potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques, the effect of recrystallization on the corrosion and electrochemical behaviour of Ti12Mo and Ti12Mo5Ta alloys was studied. Aerated Ringer's solution was employed as electrolyte solution at 37 °C. The pH was 6.9 and adjusted to 2.5 simulating the disease state. The results show excellent corrosion resistance for recrystallized Ti12Mo and Ti12Mo5Ta alloys, corroborated by high values of polarization resistance and low values of passive current density. Recrystallized structure rendered the Ti12Mo and Ti12Mo5Ta alloys extremely corrosion resistant.     

Corrosion behavior of hydrophobic titanium oxide film pre‐treated in hydrogen peroxide solution

Hydrophobic titanium oxide (TiO₂) film formed on metallic titanium substrate in hydrogen peroxide solution with a subsequent oxidation under air atmosphere. Component, microstructure, and hydrophobicity of the oxide film were characterized by X‐ray diffraction, scanning electron microscope, and water contact angle methods. Corrosion resistance tests were carried out in seawater solution at different heating temperature conditions. Electrochemical impedance spectroscopy techniques and polarization curves were used to study the changes and the corrosion resistance of the TiO₂ film. The results demonstrate that the pre‐treated TiO₂ film heated at 400 °C environment owns small special groove‐shaped structure on its surface, which induce higher hydrophobic capability, larger impedance, and better electrochemical stability than the film that was prepared at other temperatures or the Ti with nature formed oxidation film. It would be an ideal candidate as engineering material in deep seawater environment.     

Fretting corrosion behaviour of thermally oxidized CP-Ti in Ringer’s solution

The fretting corrosion behaviour of thermally oxidized (at 650 °C for 48 h) commercially pure (CP) titanium in Ringer’s solution was evaluated and reported for the first time in this paper. A cathodic shift in free corrosion potential (FCP) with the onset of fretting occurs very rapidly for untreated CP-Ti whereas it occurs over the entire 18,000 cycles for thermally oxidized (TO) CP-Ti and the extent of cathodic shift in FCP is relatively less for TO CP-Ti. The tribocorrosion performance of TO CP-Ti is better than that of untreated CP-Ti.     

Influence of iodide ions on corrosion of dual‐phase steel in sulfuric acid solution

Potassium iodide was studied for its corrosion inhibition property on the corrosion of dual‐phase steel in 0.5 M sulfuric acid at 25°C by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Scanning electron microscopy was used to characterize the steel surface. The inhibition efficiency increases with the concentration of iodide ions. The thermodynamic parameters K_ads and ΔG⁰_ads are calculated and discussed. The probable inhibitive mechanism is proposed from the viewpoint of adsorption theory.     

Influence of dual‐RRA temper on the exfoliation corrosion and electrochemical behavior of Al–Zn–Mg–Cu alloy

Influence of dual‐retrogression and reaging (dual‐RRA) temper on the exfoliation corrosion (EC) and electrochemical behavior of Al–Zn–Mg–Cu alloy has been investigated by means of transmission electron microscope, energy dispersive X‐ray spectroscopy, tensile test, polarization curve, and EIS. Dual‐RRA temper not only kept the strength similar to retrogression and reaging temper, but also improved EC resistance compared to T76 temper, being attributed to coarser and sparser grain boundary precipitates as well as higher Cu and lower Zn content. Obtained polarization curves and EIS are in good agreement with EC rating sequence.     

Electrochemical corrosion behavior of Al–Si alloy composites reinforced with in situ TiB2 particulate

Understanding the corrosion behavior of TiB_2p‐reinforced aluminum matrix composites is crucial for their development as effective composites. In this work, corrosion characteristics of in situ TiB₂ particulate reinforced Al–Si alloy (A356) composite after T6 treatment are investigated by electrochemical techniques. The electrochemical impedance spectroscopy (EIS) reveals that the protection of nature film for the composites is worse than that for A356 alloy. Polarization experiments testify that the composites are susceptible to corrosion compared with their matrix alloys. Moreover, the corrosion resistance of the composites markedly decreases with increase in the TiB₂ content. The observations of the corrosion morphologies after polarization test show that the corrosion primarily occurs at the interdendritic sites with a large amount of TiB₂ particulates. Corrosion progress continues into the composite inner along the regions of α‐Al dendrite. The poor corrosion resistant properties of the composites are considered primarily due to the galvanic corrosion between noble TiB₂ reinforcements and more active aluminum matrix, as well as the weak protection of the defective nature film on the composite.     

Influence of sintering on the corrosion behavior of a Ti‐6Al‐4V alloy

This work studies the influence of the sintering conditions of a Ti‐6Al‐4V alloy on its corrosion performance. The alloy was vacuum sintered in different conditions of time and temperature. The density and microstructure (designating phase distribution) are evaluated. Corrosion resistance through electrochemical techniques (EIS) in 2 N and 6 N hydrochloric acid solutions, and oxidation resistance at 900, 1000 and 1100°C are appraised, and corrosion is studied by microstructural and X‐ray diffraction.     

Influence of the sulphate reducing bacteria on API‐X70 steel corrosion

The corrosion behaviour of API X70 immersed in a specific medium with a strain of thermophilic sulphate reducing bacteria (SRB) was analysed. Anaerobic corrosion test was carry out for 32 days at 50 °C. During the exposure time, pH, sulphate (SO) and hydrogen sulphide (H₂S) concentration were measured. Corrosion potential, linear polarization resistance and potentiodynamic polarization curve were used in order to get the influence of the SRB in the corrosion phenomenon. Scanning electron microscopy was used to determine corrosion morphology. Results show that the SRB activity influenced the overall corrosion process. The anodic branches in the polarization curves show a passivity feature, whereas, the cathodic branches were not affected. A localized corrosion attack was found.