bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrochemical Evaluation of Hydrogen Permeation through Iron Sheets
Authors: Fanjul Pablo , Ibáñez David , González-García María Begoña , Pérez-Junquera Alejandro , Hernández-Santos David
Published: November 2022

Devanathan-Stachurski or H cell is successfully used to the evaluation of hydrogen permeation in sheets or membranes. H cell consists of two electrochemical compartments separated by a sheet which acts as working electrode (WE) in both cells. This setup allows the generation of hydrogen in the charging cell, applying a controlled potential or constant current. It diffuses though the sample and is electrochemically detected in the oxidation compartment where the hydrogen gas is oxidized applying a constant potential [1]. The anodic current is directly proportional to the amount of hydrogen penetrating through the membrane with time. As small amounts of hydrogen pass through the membrane, a very sensitive potentiostat is required for its detection. In addition, since the two electrochemical cells use the same WE, two equipments with floating mode with galvanostatic isolation should be used.

Taking into account the instrumental requirements, the study of the hydrogen permeation properties of different iron sheets have been analyzed in this work. Different electrochemical profiles are obtained depending on the sample (Figure 1): sample 1 (red line) exhibits a larger diffusivity of the hydrogen due to the higher current recorded, while sample 2 (blue line) not only shows lower current but also shows a delay in the hydrogen transport due to its lower permeability. The absorption of hydrogen by ferrous metals is a serious problem because the hydrogen embrittlement can produce modifications of the mechanical properties of the material with occasional stress corrosion cracking.

Figure 1. Hydrogen transients obtained using two different iron samples.

References

[1] ASTM G148-97, “Standard Practice for Evaluation of Hydrogen Uptake, Permeation, and Transport in Metals by an Electrochemical Technique.”

Figure 1
Anti-Corrosive and Anti-Bacterial Polymeric Coatings Consisting of PCL and Lawsone
Authors: Asadi Hamid , Duncan Austin , Ramasamy Ramaraja
Published: November 2022

The clinical application of magnesium (Mg)-based alloys as biodegradable orthopedic implants is highly restricted because of their rapid corrosion rate in the physiological environment [1]. Polymeric coatings have been recognized as one of the most effective methods to tailor the corrosion rate of Mg alloys without changing their bulk properties, while providing them with other functionalities such as enhanced biocompatibility and antibacterial properties [2]. In this study, a bi-layered anti-corrosive polymeric coating based on polycaprolactone (PCL) and lawsone, a natural corrosion inhibitor extracted from the leaves of Lawsonia inermis plant, was fabricated on AZ31 Mg alloy to improve its corrosion resistance. The result of electrochemical and in vitro immersion studies clearly demonstrated the corrosion inhibitory effect of lawsone and the enhanced corrosion resistance of AZ31 alloy by almost two orders of magnitude (inhibition efficiency of 98.3%) after being coated with PCL-lawsone. Moreover, coated AZ31 substrates exhibited significantly hampered local alkalization and excessive H2 generation. Apart from the corrosion inhibition properties, incorporation of lawsone imparted a strong antibacterial activity to the coating, which is helpful in the prevention of microbial infection and early implant failure. While most of the commonly used corrosion inhibitors are known to be toxic and have limited biomedical applications, no cytotoxic effect was observed for lawsone-containing coating toward human fetal osteoblast cells (viability of > 85%). The findings of this work highlighted the great potential of lawsone as a natural corrosion inhibitor for fabrication of corrosion protective, antibacterial, and biocompatible coatings on Mg-based biodegradable implants.

References

Wang, Jia‐Li, et al. "Biodegradable magnesium‐based implants in orthopedics—a general review and perspectives." Advanced science 7.8 (2020): 1902443.

Asadi, Hamid, et al. "A multifunctional polymeric coating incorporating lawsone with corrosion resistance and antibacterial activity for biomedical Mg alloys." Progress in Organic Coatings 153 (2021): 106157.
Bayesian Network Machine Learning Approach to Atmospheric Corrosion Modelling
Authors: Santucci Raymond J , Sanders Christine E. , Zhu Hongyu , Smith Kenneth D , Kelly Robert G
Published: November 2022

The performance degradation of materials exposed to corrosive atmospheric environments is a serious problem. Corrosion maintenance strategies and cycles are informed largely by historical trends in corrosivity dependent on the location of interest. Assessments are often made with sparse experimental data and are generalized to certain materials and baseline conditions observed in the past. The development of a predictive model which can better inform maintenance strategies and cycles offers opportunities for time savings and cost avoidance. Such a model would need to predict corrosion damage accumulation as a function of material of interest, location of interest, and atmospheric conditions during the period of exposure of interest.

Machine learning has recently gained attention as a way to model complex systems and processes. Atmospheric corrosion is certainly a complex process as there are many parameters that influence it which are uncontrolled and vary in difficult to predict ways. A machine learning algorithm would require data to learn from which might include environmental conditions such as temperature, relative humidity, UV light exposure, time of wetness, salt concentration, applied loads, and electrochemical data for substrates, inhibitors, and coatings. The ability of machine learning to determine models and relationships from large data sets is well demonstrated; however, a Bayesian model approach can be more suitable when data is limited, expensive or time consuming to obtain, and expert knowledge can be leveraged to construct the relationships. While certain meteorological variables are well categorized and easy to retrieve other variables like corrosion damage or salt deposition are sparsely reported if measured at all. For this reason, a Bayesian Network Model has been developed to better predict the corrosion damage accumulation of C1010 steel and three different aerospace coating systems applied over AA2024-T351.

The network map was constructed from parameters (nodes) which are known to influence corrosion. Mathematical relationships were used to develop relationships between nodes or to calculate new nodes as available. Finite element analysis was used to refine the network map and provide supplemental inputs for features that are difficult to measure experimentally. The model was initially trained from historic corrosion data gathered from collaborators across the DoD. Contemporary experimental data was also gathered in a 19-site survey of field exposure sites across the world. This dataset provided further inputs for training and also data for validation and testing. The methodology behind model construction will be highlighted and model predictions will be compared against experimental results. To date, there has been good correlation between model predictions and experimental results for C1010 steel mass loss, which provides a basis to further extend the model to aerospace coating systems.

Figure 1
DFT Analysis of Ethanol Electro-Oxidation on Fe(110) and Fe3c(110) and Its Correlation with the Stress Corrosion Cracking of Carbon Steel
Authors: Ashrafriahi Ali , Seifitokaldani Ali , Newman Roger
Published: November 2022

Stress Corrosion Cracking (SCC) of carbon steel in fuel-grade ethanol is typically intergranular in service, but it is nearly always transgranular, in short-term laboratory experiments. While this might be considered an inconvenience, it provides an important clue about the SCC mechanism. The important point is that the transgranular cracking occurs under much milder mechanical conditions than any known form of hydrogen embrittlement in ordinary carbon steel. For this and other reasons, hydrogen is not considered to be the cause of this form of SCC. Transgranular SCC of carbon steel occurs in a very particular set of environments. Anhydrous liquid ammonia, anhydrous ammonia-methanol and CO-CO2-H2O are the key systems to be considered, apart from alcohols. High-temperature water containing oxygen also causes transgranular SCC, but is a less severe environment, probably because a magnetite film imposes a compressive stress that partially opposes any embrittlement effect. In our view, the important factor connecting these examples is embrittlement by interstitials. Just as hydrogen can embrittle iron, so can nitrogen or carbon (or oxygen). The main distinction is the diffusivity of the interstitial in iron. Ammonia can be oxidized to N, and CO can be reduced to C (or, in the language of surface chemistry, this could be dissociative adsorption). Still, at ambient temperature, those interstitials can only diffuse a few nm in relevant times of seconds. But we know little about the effect of such near-surface embrittlement on the propagation of a crack, and research on such surface effects is very important. Striking mechanical and morphological similarities of the SCC of carbon steel in ethanolic media with those governed by a cleavage-like mechanism in CO-CO2 aqueous solutions prompted the investigation of the possibility of ethanol electrochemical oxidation into CO on ferrite (Fe) and cementite (Fe3C) surfaces. Density functional theory computations on (110) surfaces revealed that the catalytic activity of Fe and Fe3C through the α dehydrogenation pathway can significantly reduce the energy barrier of electro-oxidation of ethanol and production of CO to 0.575 and 0.480 eV, respectively. These first principle calculations indicate that at the anodic potentials applied during potentiostatic slow strain rate testing, ethanol electro-oxidation to CO is thermodynamically viable on carbon steel, giving further credit to the involvement of cleavage type SCC of carbon steel in ethanolic environments.
Electrochemical Behavior of Additively Manufactured 7050 Aluminum Alloy in Chloride Environments
Authors: Rajendran Rupesh , Owens Crosby T , Eisenhaure Jeffrey D , Singh Preet M
Published: November 2022

The benefits of additive manufacturing (AM) process combined with the high-strength, corrosion resistant and fracture toughness properties of the 7xxx series aluminum alloys make them promising candidates for the aerospace and defense industries. However, these alloys undergo unconventional thermal cycles during additive manufacturing process like laser powder bed fusion (LPBF) as well as during post-processing treatments like hot isostatic pressing, resulting in microstructures different from equivalent wrought alloys.

In our work, we investigate how the effects of microstructural differences in a modified LPBF 7050 aluminum alloy compared to an equivalent wrought alloy, results in differences in electrochemical behavior. A series of AM 7050 aluminum alloy samples with different post-processing treatments and subsequent microstructures are tested for polarization and electrochemical impedance behavior in varying chloride ion concentrations. The effects of underaging and overaging treatment on the electrochemical behavior is also studied. Localized corrosion behavior of the alloys is investigated using immersion tests and scanning vibration electrode technique (SVET), which showed differences in pitting behavior and pit stability. The results indicate that AM 7050 alloy in general, showed less corrosion susceptibility compared to an equivalent wrought alloy.
(Digital Presentation) Advanced Intercalation Electrode Materials for Calcium Rechargeable Batteries
Authors: Xu Zheng-Long
Published: November 2022

The growing demand for electric vehicles and stationary energy storage systems calls for developing next-generation batteries that combine high energy, high power and low cost. Among many post lithium-ion batteries, calcium rechargeable batteries utilizing divalent Ca2+ ion charge carriers are expected to offer clear benefits in affordability of batteries along with the potentially high energy density, due to the abundance of calcium in earth crust (46600 ppm versus 20 ppm for lithium) and the low redox potential of Ca/Ca2+ (-2.9 V vs. standard hydrogen electrode). Recent efforts on the development of negative electrodes, such as elemental calcium metal and natural graphite, has brought the rechargeable calcium chemistries a step closer to a practically feasible battery system. However, the lack of suitable cathode is the Achille’s heal of the calcium rechargeable battery technology.[1] The relatively large ionic radius and divalent nature of Ca ions make the intercalation kinetics generally sluggish in intercalation hosts. Moreover, a large Ca2+ intercalation is supposed to cause extended volume changes of the host, triggering a premature degradation of the electrode structure. In this talk, I would like to present our recent findings in graphite anode and polyanionic cathode materials as intercalation electrodes in high performance non-aqueous calcium rechargeable batteries. We demonstrated that a large amount of Ca ions can be reversibly (de)intercalation in graphite for Ca ion batteries by identifying a proper electrolyte to promote the solvated-ion co-intercalation reactions.[2] The solvated-Ca-ion co-intercalation chemistry is comprehensively investigated by combining first principle calculations and synchrotron in-situ X-ray diffraction. For cathodes, we find that the open-framework sodium vanadium fluorophosphate can function as a stable and fast-kinetic Ca2+ intercalation host with an extremely low capacity degradation rate of 0.02% per cycle over 500 cycles.[3] This value records the best stability reported for Ca ion battery cathodes so far. Through this talk, it is believed that the new findings in discovering novel materials or intercalation chemistries will be of great interest of the community working on multivalent ion batteries and other energy storage technologies.

Reference:

[1] C Chen, F Shi, ZL Xu, Advanced electrode materials for nonaqueous calcium rechargeable batteries, J. Mater. Chem. A, 2021, 9, 11908-11930

[2] Z.L. Xu, J. Park, J. Wang, H. Moon, G. Yoon, J. Lim, Y.J. Ko, S.P. Cho, S.Y. Lee and K. Kang, A new high-voltage calcium intercalation host for ultra-stable and high-power calcium rechargeable batteries, Nat. Commun. 2021, doi:10.1038/s41467-021-23703-x.

[3] J. Park,† Z.L. Xu,† G. Yoon,† S.K. Park, J. Wang, H. Hyun, H. Park, J. Lim, Y.J. Ko and K. Kang, Stable and High power calcium ion batteries enabled by calcium intercalation in graphite, Adv. Mater. 2020, 32.4: 1904411.
Localized Corrosion Mechanisms – a Bayesian Reasoning Perspective
Authors: Sridhar Narasi
Published: November 2022

The mechanisms for localized corrosion proposed over the last several decades are fall into two two major categories: (1) defect generation in the passive film of the open surface leading to breakdown and enhanced local dissolution and (2) the maintenance of a local electrolyte chemistry that promotes continued localized corrosion. A qualitative argument was proposed by Frankel et al. [1] to bridge the gap between passive film and local chemistry mechanisms. They suggest that passive film breakdown was more important for alloy-environment situations where pit initiation was more difficult, whereas local chemistry was more relevant for situations where pit initiation was more facile. Another difficulty arises when modeling the effect of local chemistry on stabilization of local corrosion. Is it the formation of critical pH, critical metal-anion complexes, or metal-anion salt film that is responsible for the stabilization of localized corrosion? These effects are interrelated because high concentration of metal cations can lead to acidification and salt film formation. Specific experimental techniques may bias conclusions with respect to one mechanism or another. Furthermore, uncertainties exist in the data used to validate models as conditions assumed in the models may be difficult to access. It is convenient under these circumstances to take a probabilistic approach based on Bayesian network (BN) to assess the likelihood of validity of a causal mechanism [2]. In this presentation, the importance of local acidity versus metal-salt formation on localized corrosion is examined through a Bayesian network model. The Bayesian network consists of nodes connected through cause-effect relationships characterized by conditional probabilities. The network computes the marginal probability of an event given causal events. Conversely, given an evidence, the preceding causes are evaluated using Bayes theorem. Thus, BN provides a probabilistic framework for cause-effect evaluations based on experimental evidence. Results from the literature and recent experiments are presented to illustrate the approach. Limitations of the approach are also presented.

Frankel, G.S., T. Li, and J.R. Scully, Localized Corrosion: Passive Film Breakdown vs Pit Growth Stability. J. of The Electrochemical Society, 2017. 164(4): p. C180-C181.

Pearl, J., Causality. 2009: Cambridge university press.
Use of Multielectrode Arrays and Statistical Analysis to Investigate the Influence of Chloride on the Pitting Probability of Copper
Authors: Matin Sina , Tahmasebi Arezoo , Momeni Mojtaba , Behazin Mehran , Davison Matthew , Shoesmith David , Noël James J.
Published: November 2022

Under some conditions, copper and copper alloys are either immune from corrosion or undergo slow uniform corrosion, generally considered a favourable situation, since predicting the damage incurred by the metal during a period of uniform corrosion is relatively straightforward. However, under conditions leading to surface passivation of Cu, localized corrosion might occur in the presence of aggressive oxidants. As a result, the susceptibility of Cu to localized corrosion must be considered carefully to avoid unpredictable failures in Cu-based structures. Understanding the pitting probability of Cu is important for various applications, including the use of Cu-coated containers for the permanent disposal of used nuclear fuel. In this study, the pitting probability of Cu in chloride-containing solutions crudely representing the groundwater that might be found in a deep geologic repository (DGR) was investigated using electrochemical techniques and statistical analysis. The probabilities of both pitting and repassivation of Cu were found to increase with increasing [Cl-]. The surface morphologies of copper electrodes in the same solution were also evaluated using scanning electron microscopy (SEM). The passive film on the surface of the copper electrode with the highest breakdown potential (Eb) was found to be more protective than that on the electrode with the lowest Eb.
(Digital Presentation) Corrosion Resistance of 55%Al-Zn Alloy Fabricated By Ball Milling and Spark Plasma Sintering
Authors: Nishimoto Masashi , Kobayashi Tetsuro , Muto Izumi , Tokuda Shimpei , Nishida Yoshikatsu , Sugawara Yu
Published: November 2022

Hot-dip 55mass%Al-Zn coated steels show good corrosion resistance because the 55%Al-Zn alloy coating layer acts as a sacrificial anode and protects the steel substrate from atmospheric corrosion.1 The balance between sacrificial behavior and dissolution resistance is important for improving the corrosion protection ability of the Al-Zn coating. In this study, 55%Al-Zn alloy was fabricated by ball milling and spark plasma sintering, and the effect of microstructure on the dissolution behavior of the 55%Al-Zn alloy was investigated.

The 55%Al-Zn alloy specimen was fabricated by ball milling of Al and Zn powders and subsequent spark plasma sintering. The coating layer on the hot-dip 55%Al-Zn coated steel was used to compare the dissolution behavior. The dissolution behavior of 55%Al-Zn alloys was analyzed by galvanic current measurements and polarization measurements in a diluted synthetic seawater.

In the sintered 55%Al-Zn alloy, Zn-rich phases with diameter less than 500 nm were dispersed in the Al matrix. The galvanic current measurements between the sintered 55%Al-Zn alloy and the steel substrate showed that the sintered 55%Al-Zn alloy acted as a sacrificial anode. In the galvanostatic polarization measurements, the potential of the sintered 55%Al-Zn alloy remained lower than that of the hot-dip 55%Al-Zn coating layer.

Reference:

S. Tokuda, I. Muto, Y. Sugawara, M. Takahashi, M. Matsumoto, and N. Hara, Corros. Sci., 129, 126–135 (2017).
Effect of the End-of-Life (EOL) Content in High-Pressure Vacuum-Assisted Die Cast (HPVADC) Aural2 (AlSi10Mg) on Corrosion Behaviour
Authors: Ando Yuki , Kish Joey , Shankar Sumanth
Published: November 2022

Al cast alloys are widely used in automotive applications due to their high strength-to-weight ratio. The castability of Al alloy is known to be excellent; the idea of implementing the End-of-Life (EOL) Al alloy parts to fabricate new Al alloys is determined to be feasible. In contrast, the fabrication of Al cast alloys with the EOL content increases the propensity of introducing the impurity element to the Al cast alloys. It is expected to affect the microstructure such as the distribution and morphology of intermetallic particles. The mechanical properties of those alloys, also known as the secondary alloys, are comparable to primary alloys, however, the corrosion behaviour of secondary alloys is not fully characterized and understood. It is anticipated that the corrosion behaviour is affected by the EOL content introduced to the Al cast alloys.

In this research, HPVADC Aural2 alloy with different EOL contents (0%, 40%, 75%, and 90%) are subjected to various electrochemical characterization techniques and microstructure characterization. Cyclic polarization measurements were conducted on both skin and core parts of the alloys. The breakdown potential (Eb) of the primary alloy was found to be the lowest, however, the potential difference between the breakdown (Eb) and repassivation (Er) of the primary alloy was significantly smaller than the secondary alloys. Potentiostatic polarization was also performed on both skin and core parts to observe the corrosion modes, and it was determined that both initiation and propagation corrosion modes were inter-granular/inter-dendritic corrosion. Galvanostatic polarization measurements were performed, and the behaviour of the potential responses differed between the primary and the secondary alloys, as well as the core and skin. Scanning Vibrating Electrode Technique (SVET) will be performed on the cross-section, skin, and core region to observe the local anodic/cathodic current density. The passive layer characteristics of each EOL alloy will be investigated by X-ray Photoelectron Spectroscopy (XPS). Microstructure analysis through Light Optical Microscope (LOM) and Scanning Electron Microscopy (SEM) was conducted. The distribution of Si eutectic and Fe-containing intermetallic particles on the secondary alloys was found to be different from the primary alloy; the mean size of intermetallic particles observed on the skin in the secondary alloys was higher than the primary alloy. No significant difference was observed at the core region in terms of intermetallic distribution. The morphology and chemistry of intermetallic particles will be further investigated with Energy Dispersive Spectroscopy (EDS).

This research is conducted to characterize the effect of EOL content on their microstructures which is essential to understand the corrosion behaviour of the secondary alloys, ultimately enhancing the utilization of EOL parts in the Al cast alloy manufacturing.
On the Nature of Critical Potentials for Aluminum Repassivation
Authors: Kiosidou Evangelia (Lila) , Srinivasan Jayendran , Noell Philip James , Schindelholz Eric John
Published: November 2022

Repassivation (Erp) and pitting transition potential (Eptp)1,2 are considered critical parameters in aluminum pitting, because they have been associated with repassivation phenomena3,4. The physical meaning of Erp has long been well-established in the literature as the threshold between stable pitting and complete repassivation of the material5–7. The nature of Eptp, however, has not been thoroughly explained in the current literature apart from the primary assumption that it represents the commencement of repassivation4. Moreover, experimental investigation and evidence to expand this argument as well as to explore the relationship between these two potentials has been scarce4.

The present work aims to address these open questions with cyclic potentiodynamic polarization (CPP) and potentiostatic experiments conducted on high purity Al in NaCl. Repassivation trends at and below Eptp were explained based on the assumption of actively corroding fractions which were dependent on the applied potential. Morphological transformation was also observed during polarization as evidenced by electron microscopy and X-ray microtomography after the electrochemical tests. The observation of a distinct Erp separate from the Eptp during slow CPP scans was related to the charge passed and was hypothesized to be the net effect of the gradually decreasing actively corroding area at potentials below Eptp, which resulted in morphology that restricted mass transport out of the pits, which delayed complete repassivation. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

References

K. Nisancioglu and H. Holtan, Corrosion Science, 18, 1011–1023 (1978).

K. L. Moore, J. M. Sykes, and P. S. Grant, Corrosion Science, 50, 3233–3240 (2008).

S. T. Pride, J. R. Scully, and J. L. Hudson, J. Electrochem. Soc., 141, 3028 (1994).

M. Yasuda, F. Weinberg, and D. Tromans, J. Electrochem. Soc., 137, 3708 (1990).

A. Broli and H. Holtan, Corrosion Science, 13, 237–246 (1973).

G. S. Frankel, J. R. Scully, and C. V. Jahnes, J. Electrochem. Soc., 143, 1834 (1996).

G. S. Frankel, J. Electrochem. Soc., 145, 2186 (1998).
Corrosion Analysis of Al-Ce-X Cast Alloys in Dilute Boric Acid and 3.5 Wt.% NaCl Solutions
Authors: Jun Jiheon , Nam Seungjin , Ott Ryan , Kesler Michael
Published: November 2022

New compositions of Al-Ce-X cast alloys have been developed to offer higher material performances than the conventional Al alloys for nuclear and other industrial applications. To assess the corrosion behavior of these new Al-Ce-X alloys, mass change measurements and electrochemical analysis were conducted using 0.23 wt.% boric acid solution, relevant to the water chemistry for the storage pool of spent nuclear fuels, and a 3.5 wt.% NaCl solution approximating sea water. Pre- and Post-corrosion Al alloy specimens were characterized by electron microscope systems including SEM, TEM and EDS. The initial electrochemical and mass change results suggest that Al-Ce-X alloys are resistant to corrosion in 0.23 wt.% boric acid but can be susceptible to corrosion in 3.5 wt.% NaCl solution. The initial characterization of post-corrosion samples indicated that one Al-Ce-X alloy type experiences uniform corrosion without any preferential or local attacks. Further corrosion analysis and characterization are underway for comprehensive understanding of corrosion phenomenon in these new alloys.
In-Service Corrosion Performance of Automotive AA7075 Sheet Alloy
Authors: Wang Shanshan , Piroteala Tudor , Ryan Kevin , Kamat Rajeev , Yuan Yudie
Published: November 2022

Aluminum alloys offer higher specific strength than advanced high strength steels, making them preferred material choice for automotive light weighting. Among them, AA7075 sheet alloy offers significantly higher strength than 5xxx and 6xxx alloys and has been developed to provide high in-service strength for automotive structural applications. However, there is a need to understand the stress corrosion cracking (SCC) susceptibility of AA7075 under “in-service” conditions for the automotive market. Currently there are no commonly accepted corrosion testing specifications or evaluation criteria for AA7075 sheets among material suppliers and automotive original equipment manufacturers. Furthermore, there is a lack of in-service data to validate the accelerated laboratory exposure testing. In this study, in-service SCC performance of the AA7075 test coupons was evaluated by road exposure for a two-year period under harsh Canadian winters. The SCC specimens were loaded using four-point bending frames, and were investigated in various tempers and surface conditions (bare vs. e-coated). Overall, the road exposure results were consistent with the lab accelerated testing such as slow strain rate tensile testing in specific environments. Coating provided sufficient corrosion protection such that the stressed coupons survived after 2-year road exposure without reduction in strength. For bare metals, overaged T73 and in-service (T6+paint bake) tempers outperformed T6 temper. Localized corrosion of AA7075 sheets with various tempers was also studied using potentiodynamic polarization technique.

Acknowledgements: Dr. Danick Gallant, Aluminum Technology Center at National Research Council Canada; Kennesaw lab support in Novelis Global Research and Technology Center.
(Digital Presentation) Spark Plasma Sintering Fabrication of α/β Interface in Mg Alloys and Analysis of Corrosion Behavior
Authors: Shao Zheng , Nishimoto Masashi , Muto Izumi , Sugawara Yu
Published: November 2022

In Mg alloys, corrosion behavior is known to be related to the microstructure. For example, AZ91D alloy contains an α matrix phase (Mg solid solution), β phases (Mg17Al12) and lamellar α+β microstructures. During the real-time in situ observation of the corrosion process under galvanostatic polarization, filiform corrosion proceeded along the outside of the β-phase (in lamellar α + β microstructure and along the α-mother phase[1]. However, the detailed mechanism of the initiation and growth of filiform corrosion is still unknown. An electrode area contains simplified α + β structure is needed to clarify the corrosion mechanism of Mg alloys. The fabrication of such specimen could be actualized by Spark Plasma Sintering (SPS).

The advantage of SPS is that it can produce specimens with high efficiency and few pores. The energy from the pulsed current, self-heating of the workpiece, and particle-to-particle discharge are the combined driving force for sintering. In recent years, many experiments have been reported on the fabrication and strength evaluation of pure Mg and Mg alloys. However, only a few studies have been conducted on the fabrication and corrosion resistance of different phases.

In this study, we attempted to fabricate the interface of β and α phases by SPS using pure Al powder and pure Mg powder and other materials. The characterization of different phases was carried out by XRD, EPMA and TEM. The corrosion behavior of the sintered specimens was then observed using an in-situ observation system during open circuit potential measurements. After measurements, the specimen surface was assessed using OM, AES, and FE-SEM.

When a 0.25 mm thick Mg sheet was surrounded by pure Al powder, the temperature was set at 420 °C and kept for 30 minutes, a uniform white microstructure was found to form around the Mg sheet. The thickness is about 50 µm. EDS maps and point analysis show that this phase consists a β-phase (Mg17Al12) on the Mg sheet side and Mg23Al30 on the Al powder side. The thickness of the β-phase did not change obviously when the sintering time was extended to 1 hour. Finally, a β phase with a thickness of about 100 μm could be fabricated by using a specimen assembly method of outer Al powder, intermediate layer Mg powder. Analysis of corrosion behavior was done with this specimen.

Z. Shao, M. Nishimoto, I. Muto, and Y. Sugawara, Corrosion Science, 192, 109834 (2021).
Effect of Melt Pool Boundaries on Repassivation of Selective Laser Melted Stainless Steel
Authors: Hariharan Karthikeyan , Guo Xiaolei , Melia Michael Anthony , Rodelas Jeffrey Michael , Srinivasan Jayendran , Frankel Gerald S. , Schindelholz Eric John
Published: November 2022

Recent studies have shown that melt pool boundaries (MPBs) in selective laser melted (SLM) stainless steels (SS) can serve as preferential sites for pit initiation and corrosion propagation. In this study, we utilize electrochemical polarization experiments combined with detailed microstructural analysis to elucidate the role played by MPBs on localized corrosion in chloride media. Potentiodynamic polarization of artificial 1-D pits constructed from SLM SS316L grown to sufficient depth showed a sudden current drop below the salt-film dissolution potential on the downward scan, which was followed by an active Tafel-like behavior until the zero-current potential (ZCP) was reached. The observed current drop marks a critical potential for pit stability and characterizes the partial repassivation of the pit, as the current density value after the drop was significantly greater than the reported current density at complete repassivation. When the same 1-D pit was polarized upwards from a potential below the ZCP, it showed characteristic re-activation before salt film formation. This behavior was unique to SLM SS316L and was not found in conventional wrought SS316L. Moreover, 1-D artificial pit study on SLM SS316L using a modified ASTM G192 sequence showed a similar partial repassivation behavior. Scanning electron microscopy of SLM SS316L pit bottom morphology after long-term potentiostatic polarization at a potential between the partial repassivation potential and the ZCP showed selective, crystallographic attack along MPBs. The morphology also revealed melt pool fall-out due to the continued attack of the MPBs. Scanning transmission electron microscopy characterization of the SLM 316L material revealed Cr and Mo depletion at the MPBs. The observation of passivating element depletion at MPBs is in line with calculations of solute partitioning during melt pool solidification for the material under study. Based on our results, we conclude that localized corrosion under conditions at the edge of passivity can lead to selective attack of Cr- and Mo-depleted MPBs. The implications of inter-melt-pool corrosion on component structural integrity and protective repassivation potentials will be discussed.

SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. SAND2022-4016 A
A Comparative Study of Protective Film Formation of Additively Manufactured 316L SS and Conventional Wrought 316L SS in Aqueous, Gaseous and Steam Environments
Authors: Raja VS , C Sundaresan , Ghule Bhagwat
Published: November 2022

Additively prepared 316L SS using selective laser melting technique has been found to possess better passivation behavior in relation to its wrought counterpart in aqueous media such as chloride solutions, despite having cast structure. This has been attributed to the absence of manganese sulfide inclusions and higher chromium content of the passive film formed on the former. Not much work has been published on the behavior of this alloy in high temperature gaseous and steam environments though it is expected to be employed in such environments. Our studies show that the nature of the oxides formed on oxidation on the additively formed alloy has been found to be notably different from that formed on its wrought alloy counterpart. A talk will bring out the salient differences shown by these two types of alloys and their implication on the protection behavior.
Enhanced Crevice Corrosion of Stainless Steel 316 By Degradation of Cr-Containing Hollandite Crevice Former
Authors: Guo Xiaolei , Lei Penghui , Mohanty Chandi , Yao Tiankai , Lian Jie , Frankel Gerald S.
Published: November 2022

The disposal of high-level nuclear waste (HLW) is an important societal problem. It is also an extremely challenging corrosion research topic due to the highly complicated waste chemistry, long lasting radiation effect, and inevitable exposure to aqueous environments for hundreds of thousands of years. To safely accommodate some critical radionuclides such as volatile 129I and strongly heat generating 137Cs, numerous crystalline ceramic waste forms have been created and studied. Among the promising nuclear waste forms, hollandite was developed to isolate Cs waste and the corresponding decay product Ba due to the open tunnel structure capable of accommodating mono- or divalent cations. In this study, the synergistic corrosion interactions between a Cr-containing hollandite (Ba1.15Cr2.3Ti5.7O16) and stainless steel (SS) 316 is explored. This is relevant to the permanent disposal of HLW involving the encasement of glass or crystalline ceramic waste forms containing immobilized radionuclides in a metallic canister made from corrosion resistant alloys such as SS. The experiments performed in this study simulate the potential corrosion interactions occurring at the interface of the SS and ceramic. After corroding the SS316 and Cr-containing hollandite in proximity in 0.6 M NaCl at 90 oC for 28 days, severe crevice corrosion was identified on the surface of the SS, as evidenced by the presence of large pits and crevice damage with diameters of hundreds of microns. Similarly, localized damage was also found at matching sites on the Cr-hollandite surface, indicating interactions between the two materials. The synergistic corrosion interaction was likely due to the continuous release of Cr3+ cations from both materials, including the passive dissolution of the SS and the heterogenous degradation of the Cr-hollandite. The extra Cr3+ cations originated from the hollandite reduces the incubation time required to reach the critical crevice solution condition, thereby accelerating the breakdown of the passive film of SS and the subsequent onset of active dissolution. An adapted crevice corrosion model is applied to quantitively explain the accelerated corrosion of SS observed in this study.
The Effect of [Cu(EDTA)]2− on Crevice Corrosion of Type 316L Stainless Steel
Authors: Aoyama Takahito , Kato Chiaki
Published: November 2022

Alloyed Cu is known to inhibit the growth of pitting corrosion on stainless steels after pitting initiation. The Cu2+ dissolved from the stainless steel matrix acts as an inhibitor in acidic chloride environments which is formed in pits. The Cu2+ suppresses active dissolution rate inside the pits1. This suppression effect is supposed to be also effective for active dissolution which promotes crevice corrosion. Therefore, if it is possible to introduce Cu2+ to the inside of a crevice from the outside, introduced Cu2+ is supposed to inhibit crevice corrosion on stainless steel. However, diffusion of ions between inside and outside of the crevice is restricted by its geometry, and Cu2+ does not migrate to inside of a crevice according to the electroneutrality principle. [Cu (EDTA (ethylenediaminetetraacetic acid))] 2− is a chelated Cu2+ which has negative charge, and is expected to migrate to inside of a crevice from the outside by electrochemical migration. In addition, it is reported that Cu2+ in [Cu(EDTA)]2− could be easily substituted by Fe2+ in low pH2. Therefore, Cu2+ is considered to be introduced to the inside of the crevice as [Cu(EDTA)]2−, and to affect crevice corrosion of stainless steel. In this study, in situ observation of an inside of the crevice3 was performed to analyze the effect of [Cu(EDTA)]2− on crevice corrosion.

Type 316L stainless steel was used as specimen. The crevice corrosion tests were conducted in a flow cell3. 0.1 M NaCl or 0.1 M NaCl-10 mM [Cu(EDTA)]2− was flowed through the flow cell. The crevice was made by pressing the glass plate on the specimen surface. The specimen surface was perfused with 0.1 M NaCl before the glass plate was pressed. Therefore, inside of the crevice was filled with 0.1 M NaCl. The specimen was polarized at 0.35 V (vs. Ag/AgCl, Sat. KCl). After the crevice corrosion initiation, the different propagation morphology was observed between 2 conditions. In the case of 0.1 M NaCl, the gas bubbles were observed with corrosion propagation. On the other hand, little gas bubbles were observed in the case of 0.1 M NaCl-10 mM [Cu(EDTA)]2−. The gas bubbles observed in 0.1 M NaCl were considered to be H2 generated by the H+ reduction reaction inside the crevice. It was reported that the reduction reaction inside the crevice was changed by migrated anions which reacted with H+ inside the crevice3. Therefore, the results indicate [Cu(EDTA)]2− migrated to the inside of the crevice from the outside, and affected the crevice corrosion morphology.

References

T. Sourisseau, E. Chauveu, and B. Baroux, Corros. Sci., 47, 1097-1117(2005).

W. Guan, B. Zhang, S. Tian, and X. Zhao, Appl. Catal. B, 227, 252-257 (2018).

T. Aoyama, Y. Sugawara, I. Muto, and N. Hara, J. Electrochem. Soc., 166, C250-C260 (2019).
Influence of Metal Cation and Temperature on Localized Corrosion Behavior of Steels in Aqueous Environments
Authors: Sakairi Masatoshi , Shen Tong , Han Xiaole
Published: November 2022

Steels are abundantly used in many areas because of their good formability and low price. Steels suffer from corrosion in aqueous environments with chloride ions. Corrosion of steels is also a serious problem for long-term usage of steel structures such as bridges and buildings. There are many studies focused on chloride ions. There are reports that metal cations have a tendency to inhibit the corrosion of steels in a chloride aqueous environment by forming a layer on the steel.

The other important factor for corrosion of steels in an aqueous environment is temperature. The corrosion rate of metal in cold regions is expected to slow because of low temperature. A recent study on atmospheric exposure tests carried out in different places in Hokkaido, it has elucidated that the corrosion rate in the cold region is the same as in the warm region.

However, it is not fully elucidated that temperature, especially below freezing point, and metal cations on corrosion behavior and distribution of active dissolution site. The purpose of this study is to investigate the influence of temperature and metal cations on thecorrosion behavior of steels.

Steel sheets of 15 x 20 mm and 20 x 20 mm were used as specimens. Three solutions of 0.1 mM ZnCl2, 0.5 mM ZnCl2 and 1.0 mM ZnCl2 were used for examination of the effect of metal cations, and 20 mass % NaCl solution was used for examination of effect of temperature. After the tests, the morphology of specimens was examined by optical microscope and scanning electron microscope.

After the wet/dry corrosion tests used 10 mL solutions droplets, corrosion products were formed on the specimens. The corrosion processes under NaCl and MgCl2 were similar. Yellow corrosion products were firstly observed in the solution during the wet period. In the case of under ZnCl2, after the formation of oxide layer on the specimens the corrosion proceeded in localized areas. The color of almost half area of the exposed surface was light, which might indicate less corrosion occurred in the area. The initial corrosion stage of steel preferred to form a brown area in the center of the droplet. There are no similar corrosion products thatcan be observed in comparison to the samples under MgCl2 and NaCl solutions.

A lot of corrosion products and localized corroded areas were formed on specimens after being immersed at 273 K, while less corrosion products and homogenously corroded surface were observed on specimens after being immersed at 293K.

The results indicated that corrosion morphology and preferentially corroded area were changed with the kind of metal cation and temperature.
Electrochemical Study of Pitting Corrosion of Corrosion Resistant Alloys in Supercritical CO2 Environment
Authors: Eslami Maryam , Wang Xi , Choi Yoon-Seok
Published: November 2022

Various types of corrosion resistance alloys such as 13 Cr, Super 13 Cr, and duplex stainless steels are typically used in oil and gas and CO2 capture and storage applications, especially the injection section, where the pipeline could be exposed to aqueous phase and the risk of localized corrosion is of high concern. The composition of these materials is engineered to provide high corrosion-resistant properties. The operating conditions in the above-mentioned applications can include high CO2 pressure and high temperature leading to the “so-called” supercritical CO2 condition. Under the supercritical CO2 conditions, the pH of the aqueous phase in the system can be as low as pH ~ 3 buffered by the dissolved CO2. The environment can also contain high salinity, and therefore, the passive layer on the stainless steel might be locally damaged resulting in pitting corrosion. While there are numerous studies available on the localized corrosion of different stainless steels in chloride-containing aqueous environment, the number of studies in supercritical CO2 conditions is limited. The objective of this work is to understand the effect of supercritical CO2 on the localized corrosion mechanism of corrosion resistant alloys.

Three different types of corrosion resistant alloys (13 Cr, Super 13 Cr, and duplex stainless steel) are studied under CO2 pressure (0 to 14 MPa) and at high temperature (150˚C) in 5 wt.% NaCl solution. The experiments are conducted in a high-pressure autoclave system at a consistent initial pH for comparison. The electrochemical behavior and the pitting corrosion are studied using cyclic potentiodynamic polarization and potentiostatic measurements. The surface of each specimen is investigated using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) before and after the electrochemical experiments to characterize the microstructural and localized corrosion features, respectively. All the tested materials show passive behavior under the conditions of the current study, however the pitting potential decreased in this order: duplex, Super 13 Cr and 13 Cr stainless steel.