bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Characterizing Crevice Corrosion Processes Electrochemically, Microscopically, and Spectroscopically
Authors: Ebrahimi Nafiseh , Noel Jamie , Shoesmith Dave 
Published: February 2020

Due to the occluded nature of the process, crevice corrosion is difficult to investigate electrochemically, microscopically and spectroscopically. The electrochemistry/chemistry occurring within propagating crevices can be highly localized and difficult to characterize. With an emphasis on Ti and Ni alloys, we have developed a range of methodologies to determine the electrochemical/chemical details of crevice corrosion processes and how they are influenced by the compositional and microstructural properties of the materials.
On both alloy categories crevice propagation can be supported by both external and internal cathodic processes. The kinetics of the external process (O2 reduction) can be followed electrochemically using a galvanic coupling technique, while the internal process (H+ reduction), although detectable by its influence on the O2 reduction kinetics, cannot be directly followed in real time. Which of these two reactions is dominant is very dependent on alloy composition and microstructure.
For Ti alloys, the microstructure is very dependent on the added alloying elements (e.g., Ni, Pd, Ru) and the content of unavoidable impurities such as Fe, and perhaps also Mo and Cr. Their distribution in the uncorroded alloy can be determined using atomic probe tomography and their redistribution, as a consequence of a period of crevice propagation, by dynamic secondary ion mass spectrometry.
By comparison to Ti alloys, Ni-based alloys (in particular Ni-Cr-Mo alloys) are free of segregated secondary phases, and possess high quality, low energy grain boundaries. These two qualities can be demonstrated using electron backscatter diffraction, transmission electron microscopy and electron energy loss spectroscopy. However, while the quality of the grain boundaries is a key feature in controlling the initiation of crevice corrosion, it is the alloy composition which exerts the dominant influence on the accumulation and distribution of corrosion damage by depositing Mo oxides at propagating sites, a process that can be demonstrated by correlating the damage distribution, determined by confocal laser scanning microscopy, with the accumulation of molybdates, confirmed by microRaman spectroscopy.
Using this combination of electrochemical, microscopic and spectroscopic techniques we are presently determining the influence of alloy composition on the relative importance of internally and externally supported crevice propagation. Also, we are developing the technique of X-ray photoelectron spectroscopic imaging to demonstrate the self-healing capability conferred on these alloys by the inclusion of Mo.
Formation Mechanism of Alumina Nanotubes By Anodization of Aluminum Alloy
Authors: Ono Sachiko , Hashimoto Hideki , Asoh Hidetaka 
Published: February 2020

Anodic porous alumina film, a typical self-ordered nanohole material formed by anodizing aluminum in an appropriate acidic solution, is used as a starting material of nanofabrication of functional devices besides a corrosion resistant surface oxide. In contrast to anodic titania nanotubes, anodic porous alumina is generally compact without spacing between the cell boundary. The tubular shape of anodic titania is resulted in enrichment of fluoride between cells which is originated form electrolyte and more soluble than anodic titania. In the case of aluminum, it is reported that enrichment of only sulfate or ethylene glycol originated form electrolytes produces alumina nanotubes by anodization. In the present paper, the formation mechanism of anodic alumina nanotubes will be discussed.
STEM image of vertical cross section prepared by ion-milling of the anodic film, which was formed on 99.99 % pure aluminum in oxalic acid at 160V, indicated close-packed hexagonal cell arrays with small voids of 15-20 nm at the triple cell points. Dark field STEM image clearly revealed a bright particle in the each void suggesting the presence of a heavy metal because of Z-contrast. By EDX point analysis, Cu enriched particles were found in the voids at the triple points. Nevertheless, in the case of anodic film formed at the similar condition on AC8A cast alloy including 0.97 % of Cu, tubular cells with the space of approximately 50 nm between cell boundary were formed unlike the case of pure aluminum including 60 ppm of Cu. Numerous branching of pores were also observed. EDX mapping revealed that Si was enriched in the outer layer of the cells and Cu was enriched at the area near cell boundaries. Therefore, it is deduced that enrichment of Cu at the cell boundaries produces the tubular cells by accelerating oxide dissolution similar to the cases of enrichment of sulfate and ethylene glycol.
Effect of Adsorbed Organic Thin Films on Electrochemical Interaction Mechanisms of Metal Reducing Bacteria with Steel Surfaces
Authors: Wurzler Nina , Ozcan Ozlem 
Published: February 2020

The interface of a metal substrate and a biofilm can differ significantly from the surrounding environment. Metal reducing bacteria (MRB), for instance, are capable of utilizing various metallic compounds as electron acceptors. Besides chromium, uranium and manganese as well as many organic compounds, Fe(III) is converted to the soluble form Fe(II) during the bacterial metabolism. This could lead to a weakening of the protective passivation layer on stainless steel and thereby facilitate microbiologically influenced corrosion (MIC). Even tough the processes of electron transfer are not yet entirely explained, the contribution of flavins and other humic substances as electron shuttles is widely discussed in the literature. Moreover, the adsorption of organic thin films on steel surfaces can lead to surface preconditioning and thus to changes in adhesion behavior of bacteria.
The aim of this work is to understand the chemical and electrochemical interaction mechanisms of MRB with steel surfaces by combining electrochemistry and surface-analytical techniques. The investigations primarily focus on the effect of pre-adsorbed thin organic films and self-assembled monolayers (SAMs) on the electron transfer processes between bacteria and steel surfaces. Electrochemical Quartz Crystal Microbalance (eQCM) studies have been performed to investigate the adsorption/desorption kinetics of organic films as well as the formation of biofilms on FeCr electrodes. Furthermore, the evolution of the biofilms on steel surfaces has been analyzed by means of electrochemical impedance spectroscopy (EIS) to support the QCM studies with information on structural changes during different stages of biofilm growth. Electron transfer and corrosion processes have been analyzed by means of square wave voltammetry (SWV) and linear sweep voltammetry (LSV), respectively. The results of electrochemical studies are complemented with microscopic and spectroscopic characterisation of organic adsorbates and analysis of changes in the passive film chemistry and surface morphology.
This presentation will summarize our results on the chemical and electrochemical interaction mechanisms of MRB on steel surfaces leading to passive film degradation. The role of flavins in accelerating corrosion processes will be elucidated in detail to provide useful insights from a fundamental aspect for the understanding of the initial stages of microbiologically influenced corrosion in the presence of MRB.
Inhibition of Filiform Corrosion on Organic-Coated Magnesium-Containing Galvanized Steel By Smart-Release Ion Exchange Pigments
Authors: Michailidou Emmanouela , McMurray Hamilton Neil , Williams Geraint 
Published: February 2020

Zinc-(1-2 w%) Magnesium-(1-2 w%) Aluminium coated galvanized steel presents a superior corrosion resistance over conventional galvanized steel as a result of the Al and Mg additions to the bulk composition of the coating. It has been previously demonstrated that cathodic delamination does not occur on organically-coated ZMA galvanized steel due to the unfavourable potential gradient formed between the intact interface and the defect. Contrary, the potential at the intact interface is more negative than the potential at the defect thus triggering anodic undermining in the form of filiform corrosion. Smart-release exchange pigments have been proven to be a promising approach towards the suppression of undermining corrosion. In the current research, the ability of hydrotalcite (HT) based pigments on the inhibition of induced filiform corrosion on organic coated ZMA galvanized steel has been investigated.
This paper describes a systematic kinetic study on the inhibitory effect of anion exchange HT-based pigments on filiform corroding hot dipped Zn-(1-2 w%)Mg-(1-2 w%)Al galvanized steel. The samples were alkaline degreased in 1M KOH and 1M NaOH at 70oC and 3 min immersion time and were coated with a model organic coating of 15.5% PVB containing the exchange pigments via bar casting. Filiform corrosion was then initiated via scribing the samples and introducing a corrosive electrolyte in the defect. The kinetics of filiform corrosion were followed by optical recording over a period of six weeks.
It is positively demonstrated that the addition of smart-release pigments in the organic coating greatly suppresses the rate of filiform corrosion. The inhibitory effect of the pigments has been further investigated by systematically varying the volume fraction of the pigment on the organic coating presenting the reduction of filiform corrosion rate with respect to the concentration of the pigment in the organic coating. The effect of anion exchange HT-based pigments on filiform kinetics is analysed and described in terms of an inhibition mechanism.
Investigation of the “Protection Zone” Phenomenon Established By Conducting Polymers in Coatings for Corrosion Protection
Authors: Merz Anna , Rohwerder Michael 
Published: February 2020

Conducting polymers (CPs), such as polypyrrole (PPy), polyaniline (PANi) or poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS), can be employed for the corrosion protection of metals when certain design rules are followed [1, 2].
Based on the capability of a conducting polymer to work as a strong oxidant to the metallic substrate, which induces the potential to shift to a noble direction, several possible protection mechanisms based on different electrochemical effects have already been reported. However, these mechanisms often seem to work only under certain special conditions. For instance, a CP containing coating might be very effective in preventing corrosion in pin holes by passivating the metal exposed therein to the corrosive environment, while it fails disastrously in the presence of larger defects [2]. So this work focuses on the investigation of an innovative protection system which provides a long term coating stability. It was found that separated particles of conductive polymer when distributed on a zinc or iron matrix establish a “protection zone” around their boundary. The above proposed effect hinders the oxygen reduction rate at the very delamination front, establishing a region where no or only very slow delamination occurs, i.e. a degradation free zone is created. This phenomenon was investigated for the following CPs: polyaniline, polypyrrole as well as PEDOT.
Homogeneous and strongly adherent conducting polymer deposits (dots of conducting polymer) have been prepared with different thickness. Evaluation of the anticorrosion performance of the deposits covered by an organic coating was investigated with Scanning Kelvin Probe (SKP) and the role of the conducting polymer thickness and kind of metal on the corrosion performance was also examined. The experiments carried out revealed that the investigated deposit configurations are highly efficient, in fact provide a real break-through for the design of corrosion protection coatings based on conducting polymers.
Keywords: Corrosion protection; Conducting polymer; Protection zone; Scanning Kelvin Probe.
[1] Rohwerder, M.; Duc, L.; Michalik, A.: In situ investigation of corrosion localised at the buried interface between metal and conducting polymer based composite coatings. Electrochimica Acta 54 (25), pp. 6075-6081 (2009)
[2] Rohwerder, M. (2009). Conducting polymers for corrosion protection: A review. International Journal of Materials Research, 100(10), 1331-1342. doi:10.3139/146.110205.
Effect of Passive Film on Corrosion Behavior of Passivated Electroless Ni-P Coating
Authors: Sun Chong , Leitch Michael , Zeng Hongbo , Luo Jing-Li 
Published: February 2020

In heavy oil wells, carbon steel casing and tubing often suffers from severe corrosion due to the presence of corrosive gases, chlorine compounds and solid particles in the corrosive medium. An electroless Ni-P coating (EN coating) has been applied to the carbon steel surface, which presents better corrosion resistance than the substrate. However, defects such as microscopic pores, as the corrosion paths, will be inevitably present in EN coating, which can cause the corrosion of carbon steel substrate despite the coating. To solve this problem, passivation treatment can be used to create a passive film on EN coating surface and improve the corrosion resistance of the coating. However, erosion-corrosion also occurs when solid particles are suspended in the corrosive medium, and the erosion-corrosion mechanism of the passivated Ni-P coating is not known.
In this work, a passive film was formed on the EN coating in the K2Cr2O7-containing bath with and without an applied passivation potential. The corrosion properties of passive films were evaluated by means of electrochemical measurements and compared to the non-passivated EN coating. SEM, XPS, and EDS were employed to analyze the chemical composition and surface morphology of the films. The results showed an obvious passive region of passive film on EN coating in the potential range of -0.1 – 0.45 V (vs. SCE). The corrosion current of the passivated EN coating through chemical passivation treatment (CPT) was reduced by 61 % than that of non-passivated EN coating film, while it was reduced by 79 % through a combination of CPT and electrochemical passivation treatment (EPT) with an applied passivation potential of 0.2V (vs. SCE). These results demonstrate how EPT can significantly improve the corrosion resistance of the passive film.
Erosion-corrosion of passivated EN coatings through CPT and EPT was studied under an applied passivation potential by means of a single particle impingement technique. The transient current response to disruption of the passive film was obtained at different impact angles and velocities, which was the result of different damaged surface area produced by solid particle impingement. Correspondingly, the hydrodynamic effects on erosion-corrosion of passivated EN coating were predictable with a theoretical model based on kinetic analysis.
Malic-Sulfuric Acid Anodizing of AA 2024 Compared to Other Dicarboxilic-Sulfuric Acid Anodizing Processes
Authors: Dick Luís Frederico Pinheiro , Knörnschild Gerhard , Atz Dick Pedro , Vignoli Machado Thiago 
Published: February 2020

Aiming to develop hexavalent chromium (CrVI)-free anodizing baths for Al-alloys, the porous anodizing of AA2024 was studied in different mixtures of sulphuric acid-organic acid formulations with similar concentrations. Mixtures of sulphuric with dicarboxylic acids as malic, malonic, oxalic and tartaric and with the tricarboxylic citric acid were tested. The corrosion behavior of the unsealed anodized layers exposed to 0.1M NaCl were compared by voltammetry and chronoamperometry at polarizations slightly above the pitting potential of blank AA2024 with the behaviour of standard chromic acid anodizing. The obtained oxide layers were characterized by SEM, FTIR and micro-Raman spectroscopy, which confirmed the incorporation of organic acids in relative different amounts. Best corrosion resistances expressed in terms of pitting nucleation time were observed for malic-sulphuric, followed by tartaric-sulphuric anodizing. However, none of the formulations achieved the resistance conferred by the chromic acid anodizing. A direct correlation between mesoporosity of the anodizing layer and corrosion resistance was verified.
3D Impedance Mapping of Internal Concrete Block By Using Multichannel Wire Grid
Authors: Azumi Kazuhisa , Saito Shu 
Published: February 2020

Monitoring of corrosion environment for reinforced steel inside the concrete structure was investigated using 3D impedance mapping method. In this method many iron wires in grid alignment were embedded in a test cement block and impedance between two iron wires sequentially chosen from the grid was measured to obtain the resistance map inside the cement block. From the resultant 3D impedance map, corrosion environment for steel inside the concrete such as penetration of water or salt can be speculated.
In the experiment, test cement block of 200 mm x 200 mm x 60 mm in size was made in which iron wires of 99.5% impurity and 0.2mmφ in diameter were embedded in a grid alignment of 8 line with 20 mm spacing in lateral direction and 4 layer with 10 mm spacing in depth, a total number of iron wires was 8 x 4 = 32. Top face of cement block was open to air and the other faces were covered with PVC plates as a casting mold. Impedance was measured for a combination of crossing two wires in two neighbor layers, and a number of combination was 8 x 8 x 3 = 192. To choose the appropriate two wires from 32 embedded wires to connect impedance analyzer, computer controlled analog multiplexer array was used. Impedance analyzer was built in laboratory using one-chip impedance converter (Analog Devices, model AD5933) which integrates components necessary for impedance analysis as direct digital synthesizer (DDS) as AC source, digital signal processor (DSP) engine for FFT (DFT, discrete fourier transformation), operational amplifier as AC output driver and input current / voltage converter, and 12bit analog digital converter. In this study, impedance was measured at a fixed frequency of 270Hz with modulation voltage of 20mV. About 1400 s was required to complete a single impedance mapping.
Example of impedance map inside the test cement block is shown in Fig.1. The value of resistance was in the range from ca. 3kΩ at the central area of deep (30-40 mm) cement block to a several 100kΩ close to the surface (10-20 mm). Relatively low resistance deep inside the cement block indicates that the inside of the cement block was not dried out. On the other hand, not only the surface but also the side faces of cement block were dried because a gap was formed between the PVC mold and side faces of the cement block due to volume shrinking when a cement block had set. Transition of impedance map during drying and penetration of water from the top face were also investigated.

Figure 1
(Invited) Amorphous Zr-Doped HfO2 high-K Dielectric Thin Film for Electronic and Optoelectronic Applications
Authors: Kuo Yue 
Published: February 2020

Metal oxides have been used as the high-k dielectric materials in ICs and TFTs for several decades. Recently, they are used as the gate dielectric in the nano-sized MOSFET to take the advantage of the low leakage current and other device properties.
HfO2 is the most popular high-k gate dielectric for sub 1 nm EOT transistors and circuits. One of its main drawbacks is the low crystallization temperature, i.e., < 700°C, which can be a serious reliability problem. We have solved this problem by adding Zr into HfO2 to form the Zr-doped HfO2 (ZrHfO) film. This kind of high-k film can remain amorphous after been heated to above 900ºC. The material and electrical properties can be optimized by controlling the concentration of Zr in the film and the post deposition annealing (PDA) condition. In this talk, the author reviews his works in dielectric and non-dielectric applications of the amorphous ZrHfO thin film. They are highly dependent on the structure of the film.
The amorphous ZrHfO high-k thin film can be transformed into heterogeneous structures for non-dielectric applications. For example, one or more of the nanocrystalline materials have been embedded into the ZrHfO thin film to serve as charge trapping media. Electrons and holes can be stored in this kind of film separately with the selection of the proper nanocrystal materials and the gate bias condition. This kind of nonvolatile memory device has a lifetime more than 10 years
The amorphous ZrHfO high-k thin film can be prepared into another type of heterogeneous structure. After the hard breakdown process, many nano-resistors can be permanently and uniformly formed in the high-k thin film. Light can be emitted from nano-resistors upon the application of a voltage. This is a solid state incandescent light emitting device (SSI-LED) became the principle of light emission is the black body emission. The emitted light has the broad-band spectrum covering the whole visible and part of the near-IR wavelength range. Applications of SSI-LEDs include lighting, on-chip optical interconnect, and others. The nano-resistor structure can also be used as one-time-programmed memory devices, i.e., antifuses, because the leakage current ratio after and before the breakdown process can be larger than 105. Separately, the nano-resistor structure has the current rectification function, which makes it a diode device. However, different from the on-off function of the conventional p-n junction diode, which has a drastic change of the current upon a small increase of the driving voltage, the nano-resistor based diode has the gray-scale capability because of the gradual change of the current vs. voltage curve.
There are many other possible applications of the amorphous ZrHfO high-k thin film beyond the conventional electronics and optoelectronics, which will also be discussed.
This talk is dedicated to the memory of Prof. Samares Kar for his seminal contribution to this important ECS symposium series.