Passive Film Research Articles

The effect of B and Sb on the corrosion behavior of T6-treated Al–Si–Mg alloys

The influence of B and Sb on the microstructure and corrosion behavior of T6-treated Al–Si–Mg alloys has been specifically studied. It is found that the addition of 0.03 wt% B to Al–Si–Mg alloys results in the lowest corrosion rate (0.02451 mm/y) when immersed in 3.5 wt% NaCl solution for 3 days. This improvement can be attributed to the transformation of coarse dendritic α-Al grains into refined equiaxed grains, which is beneficial for the formation of uniform and compact passive film. In contrast, the Al–Si–Mg alloy with addition of 0.2 wt% Sb shows the highest corrosion rate (0.05795 mm/y), which can be attributed to two reasons. First, the addition of Sb contributes to the transformation of rod-like eutectic Si particles into a spherical morphology, increasing the number of micro-galvanic corrosion sites and thus accelerating the corrosion process. Second, the generated Mg3Sb2 phase, being more noble than the eutectic Si phase, strengthens the micro-galvanic corrosion.

Cryogenic etching of positively tapered silicon pillars with controllable profiles

Fabrication of high aspect ratio silicon nanopillars is challenging for various applications. A cryogenic silicon etching process using SF6 and O2 plasma is investigated to create silicon nanopillars with 10 μm height and tens of nanometers apex. In the process, fluorine radicals react with silicon atoms, releasing volatile SiFx byproducts and then oxygen atoms interact with SiFx and deposit a SiOxFy film acting as an inhibitor. By adjusting the O2 concentration and the forward radio frequency power, this process modifies the formation of the SiOxFy passivation film and adjusts the bombardment of ions onto the inhibitor, resulting in the desired positive taper angles of silicon pillars. Two etching steps, with higher and lower O2 concentrations, are consecutively combined to create a sharp apex and a wide base. The results demonstrate the high etching rate and controllability of cryogenic etching to obtain high aspect ratio silicon pillars with desired profiles.

Corrosion behavior of two Cu‐based shape memory alloys in NaCl solution: An electrochemical study

AbstractThe corrosion behavior of two different Cu–Al–Mn–Ni alloys, pseudoelastic and pseudoplastic, was studied in a 0.6 M sodium chloride aqueous solution by monitoring the open circuit potential for 100 h and characterizing the resulting corrosion products. Electrochemical impedance spectroscopy analysis detected three processes related to the electrochemical double layer, a passive film and a diffusive contribution associated with the dissolution/precipitation of corrosion products. Potentiodynamic scans revealed a cathodically controlled corrosion mechanism and the presence of active–passive behavior at anodic potentials for both alloys studied. Polarization of the samples at selected potentials in the anodic branch allowed the investigation of the reactions involved, highlighting an improved corrosion resistance of the pseudoelastic alloy. The corrosion rates of the pseudoelastic and pseudoplastic alloys, after 100 h of immersion, were determined to be 0.007 and 0.011 mmpy, respectively. The post‐experiment characterization was carried out by means of scanning electron microscopy, micro‐Raman spectroscopy and X‐ray diffraction, supporting the electrochemical results.

Effect of hydrogen on the pitting corrosion behavior of Incoloy 825

PurposeIn this paper, the authors aim to study the effect of hydrogen on the pitting corrosion behavior of Incoloy 825, a commonly used material for heat exchanger tubes in hydrogenated heat exchangers.Design/methodology/approachThe pitting initiation and propagation behaviors were investigated by electrochemical and chemical immersion experiments and observed and analyzed by scanning electron microscope and energy dispersive spectrometer methods.FindingsThe results show that hydrogen significantly affects the electrochemical behavior of Incoloy 825; the self-corrosion potential decreased from −197 mV before hydrogen charging to −263 mV, −270 mV and −657 mV after hydrogen charging, and the corrosion current density increased from 0.049 µA/cm2 before hydrogen charging to 2.490 µA/cm2, 2.560 µA/cm2 and 2.780 µA/cm2 after hydrogen charging. The pitting susceptibility of the material increases.Originality/valueHydrogen is enriched on the precipitate, and the pitting corrosion also initiates at that location. The synergistic effect of hydrogen and precipitate destroys the passive film on the metal surface and promotes pitting initiation.

Effect of Iron Content on the Pitting Corrosion Behavior of Laser-Cladded Ni-Cr-Mo Alloy Coating in a Simulated Seawater Environment

In order to study the effect of iron content on the pitting corrosion behavior of a Ni-Cr-Mo alloy coating in a simulated seawater environment, a Ni-Cr-Mo-xFe (x = 0, 5, 10, 15, 20, 25) alloy coating was prepared through laser cladding technology. These coatings primarily consist of a γ-Ni solid solution phase, with observable iron segregation in the interdendritic regions when the iron content reaches 25 wt%. After 42 days of salt spray corrosion, it was found that pitting began to appear on the surface when the iron content in the coating increased to 10 wt%. The results of electrochemical behavior revealed that the coatings with iron contents in a range of 10–25 wt% exhibited metastable pitting characteristics, and the impedance modulus decreased with the increase in iron content. Pitting corrosion occurs due to selective corrosion of the dendritic regions. When the iron content exceeds 10 wt%, the accumulation of iron in the outer layer of the passivation film would lead to an excess of cationic vacancies, and the stability of the passive film is then reduced. This study provides a reference for the control of the iron content in a Ni-Cr-Mo alloy coating when applied in marine environments.

Design and characterization of (TiZr)95-xHfxMo5 multi-principal element alloys with excellent properties for biomedical applications

Developing new bio-metallic materials with improved performance has attracted intensive research focus over the last decades. In the present work, a new series of (TiZr)95-xHfxMo5 (x = 0, 10, 15, 20, 25, 31.67) multi-principal elements alloys (MPEAs) have been designed for potential implant materials. The mechanical properties, deformation characteristics, tribological properties, corrosion resistance, and in vitro biocompatibility of the MPEAs were characterized. All the TiZrHfMo alloys possess a high yield strength (913–––1083 MPa) and tensile strength (931–––1118 MPa) and a large microhardness (296–––333 Hv). The addition of Hf into the alloys induced severe lattice distortion, which increased the solid-solution strengthening effect. It also resulted in a finer grain size and led to excellent wear resistance. Meanwhile, the results showed that the dislocation glide mode transformed from planar slip to cross-slip and the transformation became apparent with the decrease of Hf. Also, the MPEAs showed a good corrosion resistance compared to CP-Ti, which was credited to the superior passivation films. The in vitro biocompatibility experiments displayed that the TiZrHfMo alloys exhibited high cell viability ratios, which were close to that of CP-Ti. The present work demonstrates the huge potential of TiZrHfMo MPEAs as implant material for biomedical applications.

Enhancing electrochemical corrosion resistance in Al–6Ni alloys through trace Sc additions

Al–Ni-Sc alloys exhibit superior mechanical properties at both room and elevated temperatures, owing to the high thermal and chemical stability of Al3Ni microfibers, and Al3Sc nanoprecipitates. This study explores the impact of scandium additions (0.2 and 0.4 wt%) in eutectic Al–6Ni casting alloys and the influence of aging treatment on electrochemical corrosion behavior in a 0.05 M NaCl solution. Scandium addition did not alter the polarization curve direction but reduced the anodic current density, slowing corrosion. Scandium strengthened the passive film, evident in Electrochemical Impedance Spectroscopy (EIS) with higher Rp values. Sc addition influences the susceptibility to localized corrosion in Al–Ni alloys by promoting the coherence of passive films through the formation of Al3Sc nanoprecipitates and affecting the distribution of Al3Ni. XPS results show that as-aged Sc-containing increases the density of coherent Al3Sc nanoprecipitates, which could result in the formation of Sc2O3 film along with films like Ni2O3 and Al2O3. These synergistic effects contribute to improving the overall corrosion resistance with Sc additions subjected to aging treatment. The microgalvanic effects between the matrix and reinforcement phases, as a result of the formation of nobler Al3Ni and Al3Sc that serve as cathodes within anode Al matrix, cause severe pitting. Nevertheless, after aged treatment, the corrosion resistance dramatically drops for alloys with 0.2 wt% Sc and remains unchanged for 0.4 wt% Sc, due to higher density of nobler Al3Sc nanoprecipitates phase that can counteract the microgalvanic effects and lead to less extensive pitting than as-aged Al–6Ni-0.2Sc.

The industrial SO2-induced corrosion: Investigation of the corrosion onset

The stability of the passivation film on reinforcing steel is significantly influenced by the internal chemical environment of concrete under industrial sulfur dioxide (SO2) corrosion. This study aimed to investigate the electrochemical state of the reinforcing steel and the internal chemical environment (corrosion products, phase composition, and pore structure) of concrete by conducting indoor simulations of reinforced concrete specimens exposed to industrial SO2 environment. The results indicated a consistent trend in open circuit potential (OCP) and corrosion current density (icorr) of steel rebar in different types of concrete. A sudden reduction in OCP is accompanied by a significant increase in icorr when the rebars reach an active state. At this time, the ratio of sulphation depth to protective layer thickness ranges from 0.47 to 0.63. The main sulphation products were gypsum and ettringite, with their content decreasing as the cover layer depth, water-to-binder ratio, and fly ash content increased. Due to crystallization pressure and expansion, the impact of SO2 corrosion on the capillary pores of concrete was the most significant, followed by its effect on larger pores. After 96 days of corrosion, there was an increase of 191.7 % and 116.2 % in the quantity of pore sizes, respectively. Furthermore, the porosity growth rate in concrete with the incorporation of fly ash is lower than that of Portland concrete. This suggests that the rational use of fly ash to partially replace Portland cement is beneficial for enhancing the resistance of concrete to SO2 corrosion.

Electrochemical oscillation behaviors of gold during its recovery from waste printed circuit boards through slurry electrolysis

Slurry electrolysis is an effective technology for recovering gold from waste printed circuit boards (WPCBs). However, electrochemical oscillation during the gold recovery process is a potential factor affecting power consumption. As a result, the potential oscillation behaviors of gold dissolution at a constant current were studied. These results showed that the periodic formation and dissolution of the Au-OH passive film on the anode induced electrochemical oscillation. The amplitude and frequency of electrochemical oscillation were affected by hydrochloric acid concentration, current intensity, electrode spacing, and sodium chloride concentration, among which the concentration of sodium chloride had a significant inhibitory effect. Under the following conditions: hydrochloric acid concentration of 8 mol/L, current of 0.03 A, and electrode spacing of 1.5 cm, the obtained maximum amplitude potential and frequency were 1.17 V and 0.56 Hz, respectively. The phase space reconstruction results showed that the systems evolved between the near-linear equilibrium region and the periodic oscillation region. Different factors induced two oscillation modes: top-down and bottom-up. The top-down and bottom-up oscillations induced by current intensity, hydrochloric acid concentration, and electrode spacing reduced the relative power consumption by 11.8, 17.2, and 11.8 %, respectively, and increased the relative power consumption by 14.3, 21.2, and 30.1 %, respectively. A critical value was obtained, which varied oscillation patterns and gained a region of lower power consumption. The addition of trisodium citrate and PVP can improve gold recovery rate and current efficiency by regulating process of electrochemical oscillation. This work will provide theoretical support for recovering valuable metals from WPCBs with reduced energy consumption by controlling the external conditions to switch the oscillation mode.

Effect of Cu addition on the mechanical properties and corrosion behaviours of Al–9.2Mg–0.8Mn alloy

Microalloying is an effective method to improve the properties of Al–Mg alloys. The microstructure, mechanical properties and corrosion behaviours of Al–9.2Mg–0.8Mn– xCu ( x = 0–1.2 wt-%) alloys are studied to promote the application of Al–Mg alloys. The addition of Cu increases the strength of the alloy, where the ultimate tensile strength of 0.6 wt-% Cu alloy is improved by 43 MPa. Moreover, the addition of Cu significantly affects the corrosion behaviours of alloys. For as-sensitised alloys, compared to the matrix, the 0.1 wt-% Cu alloy shows a 28.3% reduction in pitting corrosion mass loss, which is attributed to the Cu element can form a stable passivation film, and the 0.3 wt-% Cu alloy shows a 15% reduction in intergranular corrosion mass loss, which is attributed to the addition of Cu can restrict the β phase precipitation at grain boundaries. The study shows that Cu-alloying can improve the comprehensive properties of Al–9.2Mg–0.8Mn alloys.

A high-power narrow-linewidth microlaser based on active-passive lithium niobate photonic integration

We demonstrate an on-chip integrated Fabry-Perot (FP) resonator laser with high output power and narrow linewidth. The laser chip is fabricated on monolithically integrated active (i.e., Er3+-doped) and passive (i.e., non-doped) thin film lithium niobate (TFLN) substrate in which the laser cavity is constructed with two Sagnac loop reflectors fabricated on the passive TFLN. The monolithically integrated FP resonator laser achieves an output power of 126.35 μW and a linewidth of 47.5 kHz.

Advancements in Modelling the Tribocorrosion Current

AbstractTribocorrosion in passive metals involves a complex and interactive mechanism between mechanical and electrochemical actions at a rubbing contact in a corrosive environment. The mechanical wear mechanism disrupts the passive film on the metal surface; and instantly, the metal repassivates and dissolves in the corrosive environment. This surface damage failure can occur in various components such as marine structures and medical implants which can force significant downtime and repair costs. In this article, historical advancement in the well‐known theories and models which have been developed for passivation and tribocorrosion current (as a measure for wear‐accelerated corrosion) is presented and discussed. The strengths and limitations associated with the models are reviewed to generate an overall picture of the progress in the field. The links between different models are also discussed and finally, some possible directions for future research are suggested.

Corrosion and Biological Behaviors of Biomedical Ti-24Nb-4Zr-8Sn Alloy under an Oxidative Stress Microenvironment.

Biomaterials can induce an inflammatory response in surrounding tissues after implantation, generating and releasing reactive oxygen species (ROS), such as hydrogen peroxide (H2O2). The excessive accumulation of ROS may create a microenvironment with high levels of oxidative stress (OS), which subsequently accelerates the degradation of the passive film on the surface of titanium (Ti) alloys and affects their biological activity. The immunomodulatory role of macrophages in biomaterial osteogenesis under OS is unknown. This study aimed to explore the corrosion behavior and bone formation of Ti implants under an OS microenvironment. In this study, the corrosion resistance and osteoinduction capabilities in normal and OS conditions of the Ti-24Nb-4Zr-8Sn (wt %, Ti2448) were assessed. Electrochemical impedance spectroscopy analysis indicated that the Ti2448 alloy exhibited superior corrosion resistance on exposure to excessive ROS compared to the Ti-6Al-4V (TC4) alloy. This can be attributed to the formation of the TiO2 and Nb2O5 passive films, which mitigated the adverse effects of OS. In vitro MC3T3-E1 cell experiments revealed that the Ti2448 alloy exhibited good biocompatibility in the OS microenvironment, whereas the osteogenic differentiation level was comparable to that of the TC4 alloy. The Ti2448 alloy significantly alleviates intercellular ROS levels, inducing a higher proportion of M2 phenotypes (52.7%) under OS. Ti2448 alloy significantly promoted the expression of the anti-inflammatory cytokine, interleukin 10 (IL-10), and osteoblast-related cytokines, bone morphogenetic protein 2 (BMP-2), which relatively increased by 26.9 and 31.4%, respectively, compared to TC4 alloy. The Ti2448 alloy provides a favorable osteoimmune environment and significantly promotes the proliferation and differentiation of osteoblasts in vitro compared to the TC4 alloy. Ultimately, the Ti2448 alloy demonstrated excellent corrosion resistance and immunomodulatory properties in an OS microenvironment, providing valuable insights into potential clinical applications as implants to repair bone tissue defects.

Effect of micro-alloying elements on the microstructure and properties of Ti-1300 alloy fabricated by directed energy deposition

In this research, Al0.5CoCrFeNi high-entropy alloy (HEA) multi-element micro-alloyed Ti-1300 alloy is fabricated by directed energy deposition. The microstructure, mechanical and electrochemical properties of Ti-1300 alloys are investigated. The average grain size of the Ti-1300 alloy is considerable reduced by 32.8% to 77.3 μm after micro-alloying. In addition, micro-alloying elements significantly improves the mechanical properties of the Ti-1300 alloy, with an increase in ultimate tensile strength of 13.4%, yield strength of 14.9% and average microhardness of 6.6%, while elongation remains essentially unchanged. Solution strengthening and refined crystalline strengthening are the dominant strengthening mechanisms. Electrochemical tests show that the micro-alloying elements results in a thicker and denser passivation film of Ti-1300 alloy in NaCl solution. This increases the resistance of the passivation film, leading to a reduction in both the corrosion current density and the corrosion rate. Multi-element micro-alloying is an effective strategy to improve the microstructure, mechanical and electrochemical properties of Ti-1300 alloy.

ZIF-8 modified the anode of the magnesium battery to improve the problems of voltage hysteresis and corrosion resistance

Magnesium is a promising anode material. However, the magnesium anode will quickly react with the electrolyte to form an ion-insulated passivation film, resulting in voltage hysteresis. Because the magnesium anode is easily corroded, it leads to a decrease in its electrochemical performance. In this paper, the anode of the magnesium battery was modified by ZIF-8 coating. The ZIF-8 coating can largely prevent contact between water in the solution and the surface of the magnesium anode, which can inhibit the passivation of the magnesium anode. The voltage hysteresis time is significantly reduced from 4 s before modification to 0.3 s, which also effectively reduces the resistance of the battery. Compared with the unmodified magnesium battery, the modified magnesium battery has a larger initial voltage and a longer discharge platform. The anode utilization rate is doubled compared with that before modification, and the specific energy density is also greatly improved. The ZIF-8 coating with porous network structure and hydrophobicity can slow down the infiltration of corrosive substances to some degree, prolong its transmission path, and provide better protection for the magnesium anode.

Influence of electrochemical descaling treatment in simulated cooling water on the corrosion behavior of stainless steel

The electrochemical descaling treatment of circulating cooling water can effectively reduce the content of scaling ions, chloride ions and produce strong oxidizing substances with bactericidal properties in the water, which is beneficial for operation at high concentration ratio (N) of circulating water, meets the goal of clean production and has a good prospect. However, changes in ion concentration and type in water can have an impact on the corrosion behavior of metals. Currently, there is limited understanding of the impact of electrochemical treatment on the corrosion behavior of stainless steel, a commonly used material in cooling water systems, which increases the application risk of this technology. In this study, the effects of electrochemical treatment of simulated cooling water on the corrosion behavior and the passive film properties of Type 304 stainless steel with different N values were investigated by analysis of water composition, polarization curve and X-ray photoelectron spectroscopy. The results showed that the pitting potential of stainless steel decreased with the raise of N in untreated simulated water, while the pitting potential increased with the raise of N in electrochemically treated simulated water, and the highest pitting potential was observed when N was 10. The electrochemical treatment effectively reduced the Cl− content in the simulated water. With the increase of N, the concentration ratio of [Cl−]/[SO42−] decreased, and the content of ClO− generated by Cl− oxidation in the water increased, which affected the corrosion behavior of stainless steel. Appropriate concentrations of the ClO− can effectively inhibit pitting corrosion of the stainless steel in simulated water, and the best inhibitory effect observed when ClO− concentration was 50 mg⋅L−1. The inhibition of pitting corrosion by ClO− was attributed to the effective improvement of the Cr/Fe ratio and the oxides/hydroxides ratio in the passive film on the surface of stainless steel, thus the compactness and the protection performance of the passive film was enhanced. The results can provide reference for the design of electrochemical treatment devices and processes.

Theoretical explanation of passivation behavior in OFP-Cu and OF-Cu

This research presents a comprehensive comparative analysis of the passivation kinetics of OFP-Cu and OF-Cu in simulated repository electrolyte. The study employs a range of techniques, including potentiodynamic polarization, multi-step potentiostatic polarization, electrochemical impedance spectroscopy, and Mott-Schottky analysis, to explore the intricacies of corrosion behavior. The Point Defect Model (PDM) is used to interpret the steady-state physicochemical processes. Utilizing the results of PDM optimization, defect distribution diagrams within the passivation film were constructed, shedding light on the pivotal transition from p-type to n-type semiconductor properties of the film. The study concludes with an interpretation of the experimental data, highlighting the enhancement of copper's corrosion resistance due to phosphorus doping, as elucidated by the Solute-Vacancy Interaction Model.

Effect of N2 partial pressure on ZrN coating orientation and tribocorrosion behavior and mechanism

The ZrN coatings were prepared using multi-arc ion plating (MAIP) under different N2 partial pressures ranging from 10 % to 80 %. A comprehensive analysis of the microstructure, electrochemical behavior, and tribocorrosion properties of these coatings showed a gradual deposition rate decrease with rising N2 partial pressure. Analysis using GIXRD revealed higher N2 pressure led to a shift in crystal orientation from (111) to (200), initially increasing corrosion resistance but later declining. At 70 % N2 pressure, the ZrN coating exhibited the lowest values of capacitance Cpo (8.89 μF cm−2) and double-layer capacitance Cdl (1.14 × 10−7 F cm−2), with the highest values for the two-time constants τ recorded as 0.274 s and 5.749 s. The tribocorrosion behavior correlated closely with the corrosion performance, with the ZrN-70 % coating demonstrating superior tribocorrosion resistance and a minimal wear rate of 4.25 × 10−5 mm3/Nm. While the ZrN-80 % coating exhibited the lowest wear rate of 2.67 × 10−5 mm3/Nm, but was more susceptible to friction and corrosion synergy, causing localized failure. The outcomes reveal crystal texture significantly affected on the electrochemical and tribocorrosion characteristics of the coatings, primarily attributed to the robust passivation tendency and stability of the passivation film associated with the (200) crystal orientation. The dominant wear mechanism identified involves the interplay of adhesive, abrasive, and corrosion-erosion wear processes. Based on these results, ZrN coatings prepared using MAIP are expected to emerge as candidate materials for critical friction components in marine equipment or other corrosion-erosion environments.

Effect of carbon nanotube content and annealing temperature on corrosion performance of carbon nanotube/Ni composite layer

Adding carbon nanotubes (CNTs) to metal composites changes their corrosion resistance, which is significantly affected by the distribution of CNTs. In this study, the effect of the content and distribution of CNTs on the corrosion resistance of composites was investigated by changing the electrodeposition process. The results indicated that could inhibit grain growth and act as an elemental channel for passivation film formation, which positively enhanced the corrosion resistance of the material. However, the annealing used to improve the bonding strength of CNTs to the matrix increased the grain size of the material, which had a weakening effect on the corrosion resistance. Using ultrasonic in electrodeposition had an obvious promoting effect on the uniform distribution of CNTs. The composites with 0.1 g/l CNT showed the best corrosion resistance after annealing for 30 min at 600 °C.

Electronic Structures of Passive Film Formed on Ti and Cr in a Phosphate Buffer Solution of pH 7

The electronic structures, including the semiconductive properties, of the passive films formed on Cr and Ti in a phosphate buffer solution of pH 7 were evaluated using photoelectrochemical response, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy (XPS). Based on the results, electronic band structure models of the passive films were proposed: the passive films on Cr consisted of an inner p-type oxide layer with a band gap energy, E g, of 3.6 eV and an outer p-type hydroxide layer with E g of 2.5 eV whereas those on Ti consisted of an inner n-type oxide layer with E g of 3.2 eV and an outer n-type hydroxide layer with E g of 2.5 eV. The type of semiconductor evaluated for the oxide and hydroxide layers was strongly supported by valence-band XPS, which can provide the energy difference between the Fermi energy of the underlying metal and the highest energy of the valence bands of the oxide and hydroxide layers in the passive films.