bluuebunny/crossref_metadata_2025 huggingface dataset:
Water Vapour Effects on Wustite Scale Growth at High Temperatures
Authors: Yin Huaying , Young David John
Published: February 2020

High purity iron and a low carbon, low silicon steel were oxidised at temperatures of 800 to 1200oC, in atmospheres of N2-H2-H2O and N2-O2-H2O. Scales of wüstite grew at low oxygen potentials, and of FeO/Fe3O4/Fe2O3 at high potentials. In both cases, kinetics were parabolic after an initial transient period. The iron and steel behaved similarly in O2/H2O gases, but not in H2/H2O. Weight uptake kinetics for both metals were initially linear, changing to parabolic with time as diffusion slowed and became rate-controlling [1]. Iron generally reacted faster than steel, but eventually developed parabolic kinetics. The effect of p(O2) at fixed p(H2O) on kw
for iron and steel is seen in Fig. 1 to be functionally similar. However, whereas the oxidation rate of steel is strongly dependent on p(H2O), that of iron is not [2,3]. The Arrhenius plot in Figure 2 shows that activation energies for the two materials are rather similar at 157 kJ mol-1 for temperatures of 800 to 1100oC, but iron oxidises almost three orders of magnitude faster than steel. However, at 1200oC, oxidation rates are closely similar.

The predictions of the Wagner model of rate control by lattice diffusion of iron vacancies is shown to be quantitatively successful for reaction of pure iron in H2/H2O. The slower rates observed for steel are attributed to defect interactions with impurity species, perhaps including a hydrogen-bearing species. Gas composition effects on the parabolic rate constant, kw
, for steel can be described by the expression:

 kw = A p(O2)1/4 + B p(H2O)1/2 (1)

where p denotes partial pressure and A, B are constants. A model based on simultaneous diffusion of singly charged vacancies on cation sites and hydroxyl ions on anion sites is shown to account for this relationship.

Scaling rates in O2/H2O also increased with water vapour level, a result attributed to gas phase transport within oxide pores which were present in the scales, but absent in wüstite grown in H2/H2O. Rates for iron and the steel were the same, in each case reflecting mainly the growth of a thick wüstite layer. The lack of impurity effects on the steel oxidation is attributed to the failure of hydrogen-bearing species to penetrate the outer layers of magnetite and hematite which form in these gases.

References

1. H. Yin, S.L.I. Chan, W.Y. D. Yuen and D.J. Young,
Oxid. Met.
, 77 (2012) 305-323.

2. H. Yin, W.Y.D. Yuen and D.J. Young,
Mater. Corros
., 63 (2012) 869-877.

3. H. Yin and D.J. Young,
Oxid. Met
., 79 (2013) 445-460.

Figure 1
Measurement of Cr Evaporation in Several Nickel Based Alloys at Moderate Velocities
Authors: Tylczak Joseph H , Holcomb Gordon R
Published: February 2020

Chromium is the principle basis of corrosion protection in most moderate-to-high temperature oxidation resistant alloys. The loss of Cr from an alloy is significate in its expected operational lifetime, as its loss can lead to beak-way oxidation. Gas flow rate is an important parameter in the loss of Cr. Most laboratory Cr evaporation experiments have used relatively low gas flow rates. In this research the Cr loss rate was investigated at 760 °C, in an air plus 57 vol pct water environment with an apparent gas flow rate of 26.5 m·sec-1. This speed was achieved by spinning the samples on the end of a disc in a gas filled, heated retort. Since secondary alloy additions can have an effect on chrome activity and diffusion, three nickel based alloys with similar (~21 wt pct) Cr levels were investigated. The alloys chosen were HAYNES 230, 282, and Inconel 625. Moving and static samples (hung near the moving samples) were exposed for times up to 1000 hrs.

Samples were first measured gravimetrically and then the surfaces examined via SEM. Finally the samples were cross sectioned and examined via SEM with EDS to determine Cr depletion. Results show a noticeable difference for the IN 625 surface, as viewed via SEM, between the surface scale formed on the respective static and moving samples. The viewed surfaces of the HAYNES 230 and 282 samples did not show as substantial of a difference between each’s respective static and moving sample. The moving IN 625 sample showed both higher mass loss and deeper Cr depletion than the static sample. The HAYNES 282 showed the least mass change, both in the static and moving conditions. At 1000 hr the HAYNES 282 had near zero total mass change while the static sample had some mass gain. At 1000 hr both HAYNES 230 and the IN 625 moving samples had gained about twice as much mass as their respective static samples. Analysis showed the Cr depletion was deeper in all the moving samples, as compared to their respective static ones. The IN 625 had the deepest Cr depletion, followed by HAYNES 282, and then the HAYNES 230.
Nano-Structured Coatings for Supercritical Steam Turbines Application: High Temperature Corrosion Studies By TG-Mass Spectrometry
Authors: Perez Trujillo Francisco Javier , Mato Maria Sonia , Illana Andrea , Lasanta Isabel , Castañeda Saul , Alcala German , De Miguel Teresa
Published: February 2020

Supercritical Steam Turbines will be operated at 3.00 Bar and 650 C. It meas that the ferrritic substrate steels must be coated in order to resist the oxidation processes that appears in those operation conditions. At the present time, there are metallic coatings canidates that are one option for this problem, but a new way to obtain better performances is the application of nano-structred coatings composed by metallic nitrides on ferritic steels such as P92.

Among the different processes, an important degradtaion process that appeaars at this temperature is the volatilization process; in order to analyse a TG-Mass spectrometry set up is used to monitor the vlatilization of coatings. A comprehensive analysis will be perform, jointly with gravimetric tests.

A detailed characterization by SEM, GD-Analysis abd XR-Difraction will be show.

A complete degradation mechanism in comparison with metallic-microestrucrured coatings will be povided.
Corrosion Investigation of Ni-Free Nitrided Stainless Steel Material As Bipolar Plate for Polymer Electrolyte Fuel Cell
Authors: Shironita Sayoko , Yu Yang , Nakatsuyama Kunio , Souma Kenichi , Umeda Minoru
Published: February 2020

Bipolar plates are particularly required mechanical strength and corrosion resistance for automobile application of polymer electrolyte fuel cell (PEFC). Thin metallic bipolar plates enable to realize small-size and light-weight PEFC stacks. However, there is some problem for cost, durability, and so on. In this study, we report an improvement of the corrosion resistance of Ni-free stainless steel (SUS445) by a nitriding heat treatment.

Nitriding heat treatment of Ni-free stainless steel (SUS445) was performed using a vacuum furnace under nitrogen atmosphere at 1473 K. Electrochemical measurements were carried out using a three-electrode electrochemical cell having a Pt counter electrode, an Ag/Ag2SO4 reference electrode, the SUS445 and the nitrided stainless steel (SUS445N) as a working electrodes in Ar-saturated 0.5 mol dm-3 H2SO4 solution at room temperature. Linear sweep voltammogram was obtained from a rest potential to 1.1 V vs. SHE at a sweep rate of 0.33 mV s-1.

Linear sweep voltammograms of SUS445, SUS445N, and SUS316 are shown in Figure 1. The voltammogram of SUS445 has current peak corresponds to a formation of passivation layer at -0.2 V vs. SHE. The onset potential of the SUS445N voltammogram shifts toward the positive direction and there is no current peak of the passivation layer formation. The current density of SUS445N is one order of magnitude lower than that of SUS445 and SUS316. It is found that the corrosion resistance of SUS445 improved by the nitrogen heat treatment. Moreover, PEFC operation test was performed using SUS445N bipolar plates and graphite one for a comparison. The two cell voltage at 0.25 A cm-2 were almost the same up to 2500 h power generation. Therefore, the Ni-free nitrided SUS445 exhibited a high durability as the bipolar plate of PEFC.

Figure 1
Maskless Direct-Write Etching of Nanopit Arrays in Si Using Focused Electron Beam Induced Etching
Authors: Wanzenboeck Heinz , Bertagnolli Emmerich
Published: February 2020

We have used a focused electron beam and chlorine injection in order to etch nanopits on predefined positions of a Si sample. With other methods it is often difficult to get exactly positioned nanopits. With this maskless, resistless direct-write approach nanopits with a diameter below 100 nm has been fabricated. We will report on the optimum processing conditions and present different geometries fabricated wit this technique. Finally, application examples will be given.
Fabrication of Commercially Viable AAO/Al Composite Membranes By Using Pre-Patterned Al Substrates
Authors: Jeong Dae-Yeong , Athinarayanan Balasankar
Published: February 2020

The anodization is a well-known and powerful technique to fabricate nanoporous anodic aluminum oxide (AAO) membranes with straight pore channels with uniform diameters. However, such AAO membranes are expensive and mechanically weaker, so that need to be fabricated a composite form by using a cost-effective method. In our previous study, we had successfully fabricated relatively strong AAO/Al composite membranes by introduction of an aluminum mesh-like supporting layer by using UV-lithography, which is a relatively expensive and lengthy process, followed by wet-etching. As a result, we could fabricate AAO/Al composite membranes of 60 nm average pore diameter with a water-permeability above 450 L/m2.bar and a breaking pressure above 11 bar. In this study, we introduce new ways to fabricate the cheap and mechanically stronger AAO/Al composite membranes by incorporating pre-patterned Al substrates fabricated by using two different processes - lamination of Al foil with Al mesh, followed by heat-treatment, and rolling of Al foils using a micro-patterned roller. The AAO/Al-mesh composite membranes with a porosity up to 52%. The water permeability’s and the breaking pressure of 3,765 L/m2·h and 6 bar, 2,146 L/m2·h and 6 bar, and 1,117 L/m2·h and 7.5 bar were obtained in AAO/Al-mesh composite membranes with 390, 175 and 57 nm pore dimeters, respectively. The dependence of the water permeability and the breaking pressure on pore dimeters and porosity in micro-patterned AAO/Al composite membranes is on the way of investigation. The results will be shown and discussed in this presentation.
Dictating Organolead Perovskite Nanostructure Size Using Silicon Nanotube Templates
Authors: Coffer Jeffery L , Gonzalez-Rodriguez Roberto , Arad-Vosk Neta , Rozenfeld Naama , Sa'ar Amir
Published: February 2020

A class of alkyl ammonium lead halide structures that readily crystallize as perovskite phases of the generic formula CH3NH3PbX3 have been discovered, and their relative ease of crystallization and formation into robust films have led to the development of an exciting new class of photovoltaic and lasing platforms. To our knowledge, however, synthetic methods that permit an evaluation of the fundamental size dependent properties with the requisite level of control of any of these perovskite structures have not yet been achieved. The key element to achieving feature size control in the synthesis of these perovskite phases is the use of hollow semiconducting silicon nanotubes as templates for perovskite growth; i.e. viewing the nanotube interior as a nanoscale reaction vessel. We have recently reported a facile strategy for the formation of SiNTs of a broadly tunable inner diameter, as well as Si wall thickness. These nanotubes are currently under evaluation for a diverse range of additional uses, such as loading with magnetic nanostructures, drug loading and subsequent delivery, Li storage and discharge phenomena associated with battery technology, etc. In principle, these nanotubes permit structural control of perovskite width through nanotube inner diameter.

     In this work, we describe the formation of methylammonium lead iodide nanostructures inside porous silicon nanotubes with a wall thickness of 10 nm and possessing inner diameters of either 70 nm or 200 nm. After structural characterization, the photophysical properties of these perovskite nanostructures, in terms of optical absorption and photoluminescence as a function of temperature, are evaluated. Spectroscopic comparisons with relatively larger one-dimensional microwires of the same composition are also carried out. We seek to interrogate not only the presence of size dependent shifts in absorption/emission features associated with a given perovskite structure, but also the effects of physical confinement on possible size-dependent phase behavior of these one dimensional semiconductors.
Formation of Self-Organized Nanohole Arrays on Stainless Steels
Authors: Tsuchiya Hiroaki , Hamada Shoken , Yamada Natsuko , Fujimoto Shinji
Published: February 2020

Self-organized nanotubular and nanoporous oxide layers have been reported on a variety of valve metals and their alloys by anodization in fluoride-containing electrolytes due to a wide range of their applications. In addition to valve metals and alloys, the formation of the porous oxide layer is achieved also on stainless steel in a fluoride-containing electrolyte[1]. Nanotubular oxide layers have been formed not only in fluoride-containing electrolytes but also in chloride or perchlorate containing electrolytes. In the case of valve metals, the formation of bundles of nanotubes are fabricated on Ti and W in chloride or perchlorate containing electrolytes whereas the highly ordered nanohole arrays consisting of circular dimple are obtained on stainless steels in perchlorate containing electrolytes[2, 3]. In the present work we examine the formation of nanohole arrays on various stainless steels and report how chemical composition of the steels affect the morphology of nanohole. In addition, the other properties of the stainless steel with nanohole arrays are briefly presented.

References

[1] K. Kure, Y. Konno, E. Tsuji, P. Skeldon, G.E. Thompson, H. Habazaki, Electrochem. Commun. 21 (2012) 1.

[2] V. Vignal, J.C. Roux, S. Flandrois, A. Fevrier, Corros. Sci. 42 (2000) 1041.

[3] H. Tsuchiya, T. Suzumura, Y. Terada, S. Fujimoto, Electrochim. Acta 82 (2012) 333.
Modeling of Porous Metal Oxide Layer Growth in the Anodization Process
Authors: Habera Michal
Published: February 2020

Most of the works on nanotubes growth are oriented on exploring suitable setups for optimal growth for the structures. Substantially less interest is devoted to first principles based mathematical modelling of the growth. We present a simple mathematical model of porous metal oxide layer growth in the anodization process.

The mathematical model is essentially the model used by [Sample, Golovin: Formation of porous metal oxides in the anodization process, Phys. Rev. E 74, 2006]. The dynamics of the system is determined by the solution of the continuity equation for the electric current density, while the boundary conditions for the overpotential are given by the Butler-Volmer relation.

The arising system of partial differential equations is solved using the finite element method. Unlike in the other works, the continuity equation for the electric current density is solved not only in the oxide layer, but also in the metal and the electrolyte. The positions of the interfaces are not known a priori and must be found in the process of the numerical solution of the problem.

The core technical difficulty is the tracking of the metal/oxide and oxide/electrolyte interface. This issue is addresed via the application of the level-set method. The main benefit of using the level-set method is that it can easily handle topology changes and that the computation is done on a fixed mesh.

Another important ingredient of the developed numerical scheme is that the problem is solved using the mixed formulation. The mixed formulation allows one to succesfully handle the boundary condition arising from the Butler-Volmer relation even in the level-set setting. It is shown that the chosen methodology correctly captures the discontinuities of the electric potential at the interfaces.

The advocated numerical scheme has been implemented in FEniCS (software for the automated solution of differential equations by finite element methods). Results of the simulations with the physical parameters corresponding to the growth of aluminium oxide layer are presented.

The computational methodology based on the level-set method and on the mixed formulation can be easily applied in two dimensional as well as in three dimensional setting. The successfully developed method for the interface tracking which is the core technical difficulty in the modelling of oxide layer growth allows one to think about further extensions of the model. In particular the flow in the electrolyte, the deformation inside the oxide layer as well as surface tension effects could be possibly numerically simulated in the future.
Oil-Impregnated Nanoporous Oxide Layer of Anodized Stainless Steel for Omniphobic and Anti-Corrosive Surfaces
Authors: Lee Junghoon , Jiang Youhua , Choi Chang-Hwan
Published: February 2020

Oil-impregnated surfaces have a promising potential to be used for anti-corrosion, anti-bacterial, anti-icing, and anti-contaminative surfaces by reducing the contact of undesired liquids onto the solid surface. The key technology to facilitate the oil-impregnation into the surface is to create porous structures to retain the oil with a good chemical affinity. In order to make the oil-impregnated surface on stainless steel, which has not been explored much, an anodizing process of stainless steel with ethylene glycol followed by Teflon coating was employed for the fabrication of nanoporous hydrophobic structures with good chemical affinity with peflourinated oil. We examined the omniphobic properties of the oil-impregnated nanoporous surface of stainless steel, compared with the air-impregnated (without oil-impregnation) porous layer, by measuring static and dynamic contact angles of liquids with different surface tensions including water and hexadecane. The oil impregnation into the Teflon-coated hydrophobic nanoporous layer on the stainless steel enhanced repellency to the liquids despite the different surface tensions. The corrosion resistance of the oil-impregnated stainless steel surface was also evaluated in chloride-containing liquids. The results demonstrate that the oil-impregnated hydrophobic nanoporous layer on stainless steel can effectively inhibit the penetration of corrosive media into the pores, leading to a significant improvement of corrosion resistance compared with the air-impregnated (without oil-impregnation) porous layer and bare stainless steel.
Influence of Corrosion Product on Corrosion Behavior of Carbon Steel in Atmospheric Environment
Authors: Shinoda Honami , Katayama Hideki , Hoshi Yoshinao , Shitanda Isao , Itagaki Masayuki
Published: February 2020

Atmospheric corrosion proceeds under thin water film, and it is affected by many environmental factors such as temperature, relative humidity, rainfall, deposition of airborne sea salt. Most of the previous study of atmospheric corrosion of carbon steel has been focused on the corrosion behavior in initial corrosion process. However, corrosion products are formed on the surface at an early stage in case of carbon steels. Thus it is important to clarify the influence of corrosion products on atmospheric corrosion behavior.. While corrosion products may easily lead to wet condition with absorption of moisture, it is reported that corrosion products inhibit the corrosion physically or chemically. In this study, we focus on dew condensation which occurs on the surface of carbon steels with rust layer.

The electrodes with corrosion products were prepared by wet/dry cyclic corrosion test. The remodeled concentric corrosion sensor was used as the electrodes. The temperature of electrode materials can be controlled from the backside of electrode because the backside of the remodeled sensor is exposed to atmosphere. The corrosion test was carried out in a chamber at 25℃ and 60％RH by adding the droplet of 0.1M NaCl solution or distilled water. During the corrosion test, the corrosion rate of the electrode was monitored by electrochemical impedance method. The electrode covered with corrosion products was cooled with a cooling equipment in the chamber at 25 ℃ and 60 ％ RH in order to measure the dew point. The dew point was evaluated by measuring solution resistance using electrochemical impedance method. The dew point of the electrode before corrosion test was measured. The solution resistance dropped sharply to a low value at around 17 ℃. The dew point was calculated at 17℃ under the 25℃ and 60％RH from the curve of saturation water vapor pressure and Tetens’s equation, indicating that the experimental and calculated values are in good agreement. The amount of corrosion products increased with an increase of the cycle number. The solution resistance of the electrode after corrosion test went down at the temperature higher than the calculated value.

In addition, the deposition of corrosion products occurred an increase of the dew point of the electrode.

This is attributed to the diameter of pore in rust layer. It is known that equilibrium water vapor pressure in the crevice increases with a decrease of the crevice size. This means that the humidity in crevice increases in comparison with relative humidity of atmosphere. It is predicted the deposition of corrosion products leads to the formation of smaller size of pores. The chloride ion is included in the rust layer, and thus the water absorption of chloride ion occurs even at higher surface temperature.
The Effect of Carbon Dioxide Pressure in Carbon Steel Corrosion in 5 Wt.% NaCl Solution Using Flow Loop
Authors: Kim Hyoung Chan , Lee Sang Joon , Cho Seong Jun , Lee Ju Dong , Lee Young Cheol , Moon Hyeong Soon , Park Kyung Tae
Published: February 2020

The pipelines transport a raw, unrefined well stream, usually consisting of a multiphase flow of gas, oil and water contained carbon dioxide, hydrogen sulfide and chlorides at elevated temperatures. Internal corrosion is the important factor affecting the reliability and longevity of subsea oil and gas pipelines in the oil and gas field. In the pipeline design, the measurement of corrosion rate was evaluated under similar corrosion environments using flow loop.

The flow loop installed at KITECH located in Korea was made of UNS 31603 with internal diameter 1 inch and corrosion tests can be performed up to 7 m/s liquid velocity and up to 12 m/s gas velocity under maximum pressure 10 MPa. The flow loop system was comprises of a progressive cavity pump, separator, corrosion test section and corrosion monitoring equipment such as electrical resistance probes, linear polarization resistance probes. Corrosion inhibitor performance test, gas hydrate test etc. can be conducted with the system.

Material of the coupon was API 5L X52 and weight loss coupon method was adopted based on NACE Standard RP 0775-2005. Measurement of corrosion rate was conducted under test conditions, 0 and 0.5 MPa, dissolved oxygen concentration less than 10 ppb, temperature 313 K, for 24 hours in NaCl 5wt. % solution at the velocity of 3 and 4 m/s respectively.

The test results showed that corrosion rate increased at higher flow rate and the predominant factor of corrosion was not chloride concentration but pH of the internal liquid of the flow loop.
Hydrogen Entry into an AISI 4135 High Strength Steel in Tribocorrosion Environment
Authors: Doi Kotaro , Akiyama Eiji , Hayakawa Masao
Published: February 2020

High strength steels are susceptible to hydrogen embrittlement which decreases long-term reliability. Suspension coil springs for automobile are made of high strength steel and have high tensile strength. The end turns of springs are considered to be suffered from both corrosion and wear and the synergistic effect of them, tribocorrosion. To examine the possible enhancement of hydrogen entry by tribocorrosion, we recently investigated hydrogen entry in a simulated tribocorrosion environment, and found that the amount of entered hydrogen in tribocorrosion environment was larger than that in simple corrosion environment in a NaCl solution. For further understanding of the role of wear and corrosion on hydrogen entry into steels, hydrogen entry caused by tribocorrosion and in corrosion in a low pH solution has been investigated in this study. The effects of low pH solution, corrosion and wear on the amount of hydrogen entry will be discussed in our presentation.

Tribocorrosion test was conducted using samples of an AISI 4135 with 1300 MPa of tensile strength with 20 mm diameter and 5 mm thickness. In the tribocorrosion test, pin-on-disk type wear apparatus equipped with a cell containing corrosive solutions was used and the sample was worn by a SiC ball with 10 mm diameter in a NaCl solution or a NaCl+H2SO4 solution for 48 h. The rotation diameter of SiC ball was 10 mm and the rotation speed was 150 rpm. The tests were conducted at room temperature. For comparison, corrosion test without wear was also conducted by samples immersion in the NaCl solution or the NaCl+H2SO4solution. Changes in pH of solution were measured during the test. After tribocorrosion test and corrosion test, the amount of hydrogen in the sample was measured by means of hydrogen thermal desorption analysis.

The result of hydrogen thermal desorption analysis showed that the amount of entered hydrogen in the worn sample was lower than that of the immersed sample in the acidic NaCl+H2SO4 solution, though the amount of entered hydrogen in the worn sample was larger than that of the immersed sample in the neutral NaCl solution as mentioned above. This is because that pH of the acidic NaCl+H2SO4 solution during the tribocorrosion test increased with time.
Hydrogen Entry into Pure Iron Treated By Plasma Nitriding
Authors: Sugawara Yu , Muto Izumi , Hara Nobuyoshi
Published: February 2020

In order to prevent hydrogen embrittlement of steels, it is effective to decrease the amount of hydrogen entry into steel matrix under atmospheric corrosion environments. In this study, the nitrided layer was formed in the surface of pure iron by plasma nitriding to inhibit the hydrogen entry, and the hydrogen permeation tests were conducted to clarify the barrier effect of nitrided layer on the hydrogen entry into pure iron.

Pure iron sheets of 1 mm thickness with 99.99 mass% purity were used as the specimens. The specimens were heat-treated at 1173 K for 18 ks and then furnace-cooled. The surfaces of the specimens were polished with diamond paste down to 1 μm. Plasma nitriding was performed in a nitrogen-hydrogen atmosphere composed of 75 % N2 and 25 % H2 for 3.6 ks at 673 K and at 600 Pa. The one side of the specimens was nitrided by masking another side. Figure 1a shows the cross-sectional image of the specimen etched with 3 % nital solution after the plasma nitriding. The layer with a different etching behavior from the matrix was observed in the surface region. The thickness of the surface layer was ca. 2.8 μm. Figure 1b shows the XRD patterns of the plasma-nitrided specimen. The peaks assigned to ε-Fe2-3N and γ
’-Fe4N were detected. The peaks of ε-Fe2-3N were larger than that of γ
’-Fe4N, suggesting that the surface layer was mainly composed of ε-Fe2-3N phase.

In order to investigate the property of hydrogen entry in the surface of the nitrided specimen, the hydrogen permeation tests using the Devanathan-Stachurski cell1 were carried out. The hydrogen entry was conducted by galvanostatic polarization at −100 μA (i
c) in deaerated boric-borate buffer solution with 0.01 M NaCl (pH 8.45) for 10.8 ks. The Pd-coated surface of the specimens in the hydrogen detection side was polarized at 0.2 V vs. SHE in deaerated 0.1 M NaOH solution. Figure 1c and 1d show time variation of the potential on the hydrogen entry side and the hydrogen permeation current density (i
p), respectively. In the initial 30 s, the potential of both the untreated and the nitrided specimen drastically decreased to approximately the same value (ca. −0.75 V vs. SHE). In the case of the untreated specimen, the permeation current drastically increased to ca. 300 nAcm-2 in the period from 0.5 to 1.0 ks. After that, it gradually increased and reached to 450 nAcm-2 at 10.8 ks. On the other hand, the permeation current of the nitrided specimen slightly increased to 10 nAcm-2 in the period from 1.6 to 4.0 ks and stayed at ca. 10 nAcm-2 from 4.0 to 10.8 ks. The hydrogen permeation test revealed that the plasma nitriding treatment strongly inhibited the hydrogen entry into pure iron under the cathodic polarization.

1. M. A. V. Devanathan, and A. Stachurski, Proc. Roy. Soc. A, 270, 90 (1962).

Figure 1
Evaluating Coating Degradation of Ballast Tank By Electrochemical Impedance Spectroscopy
Authors: Hayashibara Hitoshi , Tada Eiji , Nishikata Atsushi
Published: February 2020

Water ballast tank (WBT) of commercial cargo ships is exposed to severe corrosive environment. In WBT, high significant coating degradation was observed at the part exposed to high temperature [1]. Corrosion of WBT steel causes the deterioration of structure’s strength. Therefore it is important to evaluate the protective performance of WBT coating. The inspection is usually carried out by visual observation, but more powerful toll is necessary to detect the coating degradation at earlier stage. Electrochemical impedance spectroscopy (EIS) is one of useful method to evaluate coating degradation. In the application, coating resistance was usually used as an index of the coating degradation. On the other hand, thick heavy-duty coatings like WBT coating have too high coating resistance to measure in applicable frequency range. Some studies proposed the evaluation methods by coating capacitance or constant phase element (CPE) [2,3].

In the present study, blast-processed steel panels applied with commercial epoxy paint of approximately 200 micro-meter thickness were used as specimen. The specimens were kept in the humid air (RH = 100%) at 343 K for 246 days and subsequent immersion in 0.05M NaCl solution at 343K for 79 days (total 325 days). Before the test and at 80th, 190th, 246th, 325th days after the test, EIS was measured in the frequency of 1 k to 1 mHz in 0.01M LiCl (water activity, aw = 1 ). After that, the solution was changed to 10M LiCl solution (aw = 0.3) and the coating capacitance was monitored by continuous measurements of impedance at 1 kHz to evaluate the change of water uptake in the coating due to the degradation. The EIS measurements were carried out at room temperature. The coating resistance decreased and the coating capacitance increased in the test. It was also confirmed absorbed water calculated by Brasher and Kingsbury’s equation [4] increased. Pull off test and SEM observation of the coating cross section after the corrosion test indicated the coating degradation and a trace amount of corrosion of the underlying steel. EIS will be useful for evaluating coating degradation of thick-coated steel at early stage.

Acknowledgement

This work was supported by JSPS KAKENHI Grant Number 25820427.

References

[1] H. Emi, M. Yuasa, A. Kumano, N. Yamamoto, T. Arima, M. Umino: J. Soc. Nav. Arch. Jpn., 174(1993), 735.

[2] L. Vallentinelli, J. Vogelsang, H. Ochs and L. Fedrizzi: Prog. Org. Coat., 45(2002), 405.

[3] E. P. M. van Westing, G. M. Ferrari and J. H. W. de Wit: Corros. Sci., 36(1994), 979.

[4] D. M. Brasher and A. H. Kingsbury: J. Appl. Chem., 4(1954), 62.
Strong Correlations Between Structural Order and Passive State at Water-Copper Oxide Interfaces
Authors: Narayanan Badri , Cherukara Mathew , Deshmukh Sanket , Harder Ross , Ramanathan Shriram , Sankaranarayanan Subramanian K. R. S.
Published: February 2020

Fundamental understanding of coupled electrochemical processes at metal-oxide/aqueous media interfaces, e.g., interfacial structure evolution, metal dissolution, and solvation dynamics at the atomic level are of immense interest to corrosion research, surface chemistry, and electrochemistry in general. Using reactive force field (ReaxFF) molecular dynamics (MD) simulations of CuOx passive thin film on Cu substrate, we investigated the impact of non-stoichiometry of passive oxide film on its breakdown, and aqueous corrosion (in sea water) of the underlying copper. Upon exposure to aqueous media (halide concentration similar to seawater), we find that halide ions adsorb on to the passive oxide layer, and cause dissolution of Cu atoms via formation of water-soluble Cu-halide complexes; eventually, this results in the breakdown of the passive oxide layer, and consequently leads to corrosion of underlying Cu. Our MD simulations indicate that oxygen rich CuOx films show enhanced resistance to breakdown via impeding halide ion adsorption as well as metal dissolution; for instance, increasing oxygen stoichiometry from 0.2 to 0.79 causes by halide adsorption to drop by half. Thus, O-rich Cu-oxide films provide better corrosion resistance than O-deficient ones. Interestingly, we find that high O-content in the oxide film promotes ordering of water molecules at the water/oxide interface leading to 2D “ice-like” layers. These ordered water layers inhibit the adsorption of halide ions via a phenomenon similar to brine rejection. These findings clearly indicate the oxygen stoichiometry, dissolution kinetics, and solvation dynamics at the water/oxide interface are strongly correlated to each other [Narayanan et al. Electrochimica Acta 179, 386 (2015)]. To validate the predictions of theory, and to probe the initiation of pits during aqueous corrosion of Cu, we employ coherent x-ray diffraction imaging. This imaging technique coupled with large scale molecular dynamics simulations identify localized strain fields that arise in the Cu nanoparticles; this in turn, provides atomic scale insights into pit formation during aqueous corrosion.
Virtual Design of Green Primers
Authors: Cole Ivan Stuart , Sapper Erik , Breedon Michael , Chu Clement , Chen Fiona
Published: February 2020

The paper reports on a collaboration between BOEING and CSIRO that aims to dramatically cut the time required to develop aircraft materials . At present the time required to develop material can be excess of 15 years, much longer than that required to develop a new craft .. One way to cut the time for materials development is design materials virtually. This virtual design does not eliminate the need for actual materials design and certification but it allows this process to focus only on material designs with a high probability of fulfilling their design function. Virtual design requires a platform that links models from the molecular scale to the engineered object scale. The project has two typical components

1. Developing a platform that permits models to be linked

2. Selection and/or development of models across the relevant platform scales

The models developed include

a) Molecular scale models to define corrosion inhibitor and surface interactions

b) Molecular and continuum models to define inhibitor movement through a polymer and to a defect

c) Models of pit initiation and propagation on structural aluminium

d) Scenario builder to define the location and activity of an aircraft

e) Microclimate models defining the conditions within and exterior to an aircraft in service and on the ground

f) Damage accumulator that keeps track of the accumulation of damage

The models have been linked through the platform and the life of a range of primers with different inhibitors calculated for different flight patterns

Current and future activities consist of validating the models at each scale and validating the complete model by assessing how will it predicts the life in neutral salt spray tests. Future work will look at validating the model against life of components on actual aircraft and extending the model to composites.
Effect of Temperature on Behavior of Oxygen Transport through Solution Layer Formed on Metals
Authors: Sakairi Masatoshi , Sakaki Ryota
Published: February 2020

It is very important for investigate environmental corrosion behavior of steels to maintain and safely use of the steels structures. To understand environmental corrosion behavior of steels, environmental factors such as temperature, relative humidity, amounts of airborne salinity, SOx, and transport behavior of oxygen in thin water layer formed on the steels are also important. Therefore, exposure tests and measurement of some of the environmental factors were carried out in three counties, Japan, Vietnam and Thailand, under "Corrosion Mapping of Structural Materials in Asian Area with Understanding Effects of Environmental Factors, e-Asia Project". The corrosion results showed that the corrosion rate in heavy snow and cold region such as Hokkaido is higher than that expected from temperature. To clarify the unexpected corrosion rate in Hokkaido, transport behavior of oxygen in thin water layer formed on the metals at low temperature was examined.

The zinc and iron sheets were used for specimens, and specimens temperature was controlled by Peltier device form 298 K to 273 K. Three different solutions, 0.1 kmol/m3 NaCl, 1 kmol/m3 NaCl, and 1 kmol/m3 NaCl + 0.5 kmol m-3 H3BO3 / 0.05 kmol m-3 Na2B4O7 were used to form thin solution layers. The thickness of the solution layers were controlled by plastic tape from 200 µm to 1 mm. A Pt and AgCl coated Ag wires were used as counter electrode and reference electrode. The cathodic polarization curves were measured to obtain limiting current of oxygen with scanning rate of 20 mV/min. Before the polarization measurements, immersion potential was measured. In order to ensure the reproducibility, more than three times of electrochemical tests were carried out as same conditions.

The measured rest potential of both zinc and iron were strongly depends on concentration of used solution, while slightly change of the rest potential was observe by the thickness of the solution layers. A clear limiting current of oxygen was observed in every solution and it increased with increasing invers of the solution thickness. The clear increase was observed with thin solution layer at low specimen temperatures.
Corrosion Behavior of Al 6063 in Qatar's Desert and Marine Environments
Authors: Abdullah Aboubakr Moustafa , Sliem Mostafa H , Mohamed Adel M
Published: February 2020

Aluminum and its alloys have been widely used outdoors, especially in construction, electrical engineering and other applications, due to their high corrosion resistance, thermal and electrical conductivity and relatively low cost. The corrosion behavior of aluminum alloys indoor was significantly investigated compared to the outdoor studies. In addition, there is no investigation so far regarding atmospheric corrosion either in marine or desert areas in Qatar.

The aim of this article is to investigate the atmospheric corrosion behavior for different exposure times (six and twelve months) of welded and non-welded Al 6063 alloy with and without crevices at seven different sites in Qatar State that represent desert, industrial, coastal and marine environments. Avergae pit densities, pit depths, pit mouth areas and aspect ratios, pitting factor and corrosion rates for the alloy at each location were measured. In addition, electrochemical characterization techniques were used in non aggressive for the collected coupons to examine the effect of exposure on the naturally formed oxide layer. Furthermore, scanning electron microscope (SEM) coupled with energy dispersive X-ray (EDX) was used to study the susceptibility of studied alloys to intergranular corrosion (IGC) and the effect of sulfur compounds and chloride ions concentration on the suceptibility for this type of corrosion. The results showed that the number, the size and the depth of pits depend on the aggressiveness of the site environment. In addition, Al 6063 alloy has the tendency for IGC at the different environments. Chloride ions were responsible for the pitting initiation while, sulfur compounds were responsible for IGC propagation. The rate of corrosion for Al 6063 alloy specimens from different sites follows the following order: North field (marine) > Ras Laffan (on shore) > Seaside Mesaieed (on shore) > Halul Island (on Shore) > Industrial Mesaieed > Dukhan (on shore) > Desert.

Figure 1
Role of the Size of Iron- and Silicon-Rich Particles in the Atmospheric Corrosion Performance of Al-Mg-Si Alloys
Authors: Esmaily Mohsen , Svensson Jan-Erik , Johansson Lars-Gunnar
Published: February 2020

Aluminum-magnesium-silicon (Al-Mg-Si) alloys are vital lightweight materials partly owing to their excellent corrosion properties. While there is a wealth of knowledge in the literature on effect of chemical composition of second phase particles and constituents on their anodic/cathodic activity, there is little known on the influence of particles’ size on the corrosion behavior of Al alloys. Using friction stir welding/processing (FSW/P), which was combined with quantitative microstructural analyses, we were able to clearly uncover this previously less-recognized effect of intermetallic particles in an extruded Al-Mg-Si alloy. The exposures were performed at ambient temperature and in the presence of 95% relative humidity (RH) and 400 ppm CO2 for a time interval of 200-3200 hours. Prior to the exposures, samples were contaminated with 200 μg/cm2 NaCl, mimicking the environment that exists in marine atmospheres. The results showed that the size of the particles in the alloy microstructure plays extremely important role in the overall corrosion performance of the processed/welded materials. Thus, it was demonstrated that the extent of corrosion attack in the heat affected zone (HAZ) of the welded/processed alloys directly depends on the size of particles in the processed regions (a macro-galvanic corrosion process). In addition, using local corrosion analysis, it was clearly noted that the cathodic activity of intermetallic particles in this family of Al alloys is size-dependent.
Uncoupling the Mechanisms behind Tribocorrosion in Chloride Containing Media Using Spatially Resolved Friction and Electrochemical Measurements
Authors: Shockley J. Michael , Horton Derek John , Policastro Steven , Wahl Kathryn J.
Published: February 2020

Corrosion and wear damage are persistent, unavoidable problems in marine environments and are significant contributors to maintenance costs. When coupled, system or component lifetime can be severely decreased by the deleterious synergistic contributions between tribological and corrosion stresses applied to the contacting surfaces and protective oxide films. For example, material choices that separately meet standards for wear or corrosion resistance may, when exposed to marine environments, suffer from unexplained accelerated degradation.

This study focuses on understanding the mechanisms of the coupled damage process through spatially resolved measurements of friction and electrochemical response and correlation of behavior to the underlying microstructure features and properties. The repeated loss of passivity under wear conditions likely causes increased material loss due to an effective increased corrosion rate required to repassivate the metal surface, but also can cause an acceleration of wear by producing wear debris and changing the surface state of the underlying metal through dissolution of a hardened, plastically deformed area, among other mechanisms.

A common duplex stainless steel was used to study the role of multiple phases, composition segregation, grain boundaries and other microstructural features as initiation sites for the tribocorrosion process. This alloy system enabled controlled microstructural changes: varied grain size in a two phase field of austenite and ferrite, precipitation of sigma phase at the grain boundaries, and formation of nitrides and carbides. Using this approach each microstructural feature could be controlled and examined. An in situ tribometer was developed that enabled simultaneous friction and electrochemical measurements capable of resolving micron sized spatial features. Loss of passivity as a driving mechanism for tribocorrosion behavior was studied using simultaneous friction and electrochemical measurements at a high sampling rate that could then be correlated to specific microstructural features. Complementary analysis, performed ex situ, enables correlation of microstructure electrochemical properties to characteristic friction and wear behavior using analytical tools such as surface potential measurements (SKP) and electrochemical behavior (SECM, EIS).
The Influence of Non-Passivating and Passivating Alloys on the Galvanic and Local Corrosion Rates of 6061-T6 Al
Authors: Quiambao Kathleen , Hihara Lloyd H.
Published: February 2020

Galvanic corrosion of 6061-T6 aluminum-coupled metals was studied in marine, volcanic, and rainforest environments. In addition to outdoor exposure, the galvanic couples were subjected to the chloride-containing GM 9540 accelerated corrosion test. The galvanic couple types included 6061-T6 Al paired with Ti-6Al-4V, 316 stainless steel, silver, copper, 1018 steel, or Mg AZ31B using fiberglass-epoxy fasteners.

In this experiment, galvanic corrosion currents were measured through portable data loggers connected to each metal in the aluminum-coupled specimens. The total corrosion on the 6061-T6 Al in the galvanic couple resulted from the galvanic corrosion between the 6061-T6 Al anode and the cathode plus additional simultaneous local corrosion on the 6061-T6 Al caused by local cathodic reactions occurring on the 6061-T6 Al. The value of the total corrosion rate (i.e., local corrosion plus galvanic corrosion) was determined by mass loss of the galvanically coupled aluminum coupons. The local corrosion rate was determined using the difference between the total corrosion rate and the galvanic corrosion rate, as determined from the galvanic current data and Faraday’s law. The corrosion rates of the coupled 6061-T6 Al coupons were up to approximately 20 times greater than the uncoupled 6061-T6 Al coupons. Interestingly, less than 30% of the mass loss of the coupled 6061-T6 Al was directly due to the galvanic current, and accordingly 70% or more was due to local corrosion on the 6061-T6 Al. This implied that corrosion-product contaminants from the cathodic coupons (i.e., Ti-6Al-4V, 316 stainless steel, silver, copper, and 1018 steel) or byproducts such as excess H+ on the anodic 6061-T6 Al and excess OH- on the adjacent cathode may have had a major influence on the local corrosion of the 6061-T6 Al. In some cases, the type of cathodic coupon (i.e., Ti-6Al-4V, 316 stainless steel, silver, copper, and 1018 steel) made a significant difference on the corrosion rates of the 6061-T6 Al. Potentiodynamic polarization experiments were also conducted to study the mechanisms of galvanic corrosion for the couples described above.