bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Comparative Study of Cerium and Aluminum Conversion Coatings on AZ31 Magnesium Alloy in Aqueous and Ethanol Solutions
Authors: Chu Yu-Ren , Lin Chao-Sung 
Published: February 2020

Regarded as a potential replacement for chromate conversion coating, cerium-based conversion coating system for magnesium alloys has been widely discussed for many years. As revealed in previous research, trivalent cerium conversion coating formed in aqueous solution is found to have a loose structure with a fibrous layer on the top, which leads to a limited barrier protection. To enhance the corrosion resistance of trivalent cerium conversion coating, some approaches that include non-aqueous system and quadrivalent cerium conversion coating have been investigated. In contrast, an aluminum conversion coating based on aluminum nitrate, which is expected to have a protection effect similar to that of cerium nitrate, has also been proposed. However, the corrosion behavior of aluminum conversion coating and its feasibility of being conducted in non-aqueous solution have not been well studied so far. Hence, this study is focused on a comparative understanding through a combination of electrochemical analysis and microstructural characterization.
Prior to conversion coating process, the AZ31 plates were abraded using emery paper up to 2500 grit and rinsed with deionized water. The conversion coating process was conducted in aqueous or ethanol solution for 60 s under room temperature, after which the coated plates were heated by hot air of approximately 75 °C for drying.
Gray coatings can be observed after both cerium and aluminum coating processes conducted in aqueous solution. As observed in electrochemical impedance spectroscopy (EIS), cerium conversion coating slightly increases the total impedance from around 5,000 to 7,000 Ωcm2 and exhibits a partially blocked electrode behavior, which is coherent with its loose microstructure. However, aluminum conversion coating shows a different behavior with an apparent barrier protection, which strongly elevates the total impedance to over 50,000 Ωcm2.
As conducted in ethanol solution, the formation of cerium and aluminum conversion coatings are both retarded. Without the existence of citric acid, aluminum conversion coating can still provide certain corrosion protection, while cerium conversion coating can barely formed. With citric acid added, however, cerium conversion coating formed in ethanol solution exhibits an impedance even higher than that of the coating formed in aqueous solution in EIS, while the total impedance of aluminum conversion coating is further decreased.
Deposition of Magnetite on 304 SS Under Phosphate & Caustic Treatment Regimes in Boiler Environments
Authors: Raman Balaji , Hall Derek M. , Shulder Stephen J. , Caravaggio Michael F. , Lvov Serguei N. 
Published: February 2020

Under the high pressure high temperature (HPHT) conditions in boilers, iron oxides, like magnetite and hematite, are the most common corrosion products. Apart from just degrading the base metal in the feedwater system, corrosion products can also be transported downstream, where they can potentially deposit on surfaces in the boiler. Deposition of magnetite on orifice plates in lower headers of forced circulation boilers leads to improper flow patterns, poor heat transfer and in some cases lead to tube failures. Field data suggests that the boiler operating conditions, like temperature, pressure and boiler water chemistry could influence the deposition of magnetite from the aqueous stream on to the metal surface. It has been experimentally shown previously that boiler water conditioned to pH25
⁰C 9.3 using NH4OH, favors the deposition of suspended magnetite nanoparticles on 304 stainless steel surfaces at 300 ⁰C and 100 bar. As an extension, the work presented here, explores the effects of additional chemistries on the deposition process and behavior of suspended magnetite particles. This study looks at the influence of all-volatile treatment (AVT) regime with the addition of solid alkali to the boiler water. The aim is to understand the influence of the phosphate treatment-addition of sodium triphosphate-and caustic treatment-addition of sodium hydroxide- on the deposition process with respect to the conventional AVT regime. In addition, the study also investigates the influence of solid alkali addition on the suspended magnetite and hence the nature of the deposits formed on the stainless steel substrate. The boiler environment was simulated in an autoclave pressure vessel. The test solutions were prepared in de-aerated conditions to closely match the boiler feedwater in terms of chemistry. The concentrations of sodium triphosphate and sodium hydroxide used were decided based on the standard operating guidelines followed in the industry. A standard three electrode assembly was used to monitor the deposition process using Electrochemical Impedance Spectroscopy (EIS). The nature of the deposits were investigated using surface characterization techniques. The results showed a clear influence of the zeta potential and double layer compression on the behavior of the suspended particles and their affinity to deposit at 300 ⁰C and 100 bar. The results will add to the existing work on understanding magnetite deposition and suspended particle behavior in high pressure high temperature environments.
Corrosion and Redox Potential Control of High Temperature Materials in Fluoride and Chloride Molten Salts
Authors: Fuentes Roderick Eliel , Olson Luke Christopher , Martinez-Rodriguez Michael Joe , Gray Joshua R. , Garcia-Diaz Brenda Lee 
Published: February 2020

Concentrating solar power (CSP) systems that can operate at higher temperatures can achieve higher efficiencies and power production using high temperature power cycles. Operating at these higher temperatures requires identifying heat transfer fluids and materials of construction for heat transfer systems that will provide good operating characteristics and long system lifetimes under these conditions. Advanced power cycles such as the supercritical CO2 Brayton cycle can operate above 800°C and molten salts are one of the best options to transfer heat at these conditions due to their very high boiling points and good heat transfer properties. However, a potential drawback with using high temperature molten halide salts is materials corrosion. Therefore, it is important to identify pairs of heat transfer materials and molten salts that will have the mechanical properties and chemical stability that will provide long system lifetimes. Several alloys that can be used for high temperature operation includes alloys with high nickel and chromium content, such as Haynes 230, and high cobalt and chromium content, such as Haynes NS-163. However, weight loss by dealloying of Cr from high temperature alloys containing Cr was observed. In this work, several high temperature alloys were exposed to molten KCl-MgCl2 and FLiNaK (LiF-NaF-KF) at several temperatures ranging from 750 to 950 °C for 100 hours. For redox potential control, Mg and Zr were added into the test. The alloys were examined via SEM/EDS post corrosion at the surface and cross-section to account for the corrosion attack and element depletion from bulk. The salts were analyzed via ICP-OES to quantify the elements that were depleted and diffused into the salt.
Electrochemical Study of Corrosion in High Temperature Molten Salts
Authors: Garcia-Diaz Brenda Lee , Olson Luke Christopher , Martinez-Rodriguez Michael Joe , Fuentes Roderick Eliel , Gray Joshua R. 
Published: February 2020

Concentrating solar power systems are projected to need to produce energy with a cost of $0.06/kWh when implemented on a very large scale. It is generally believed that temperatures of the heat transfer fluids will need to be higher than 800oC to drive an advanced Brayton cycle or Rankine cycle with superheated steam to reach this target. However, current state-of knowledge of corrosion science indicates a lack of published data on the impact of molten salts at temperatures above 800°C on corrosion of molten salt contacting materials such as steels or high temperature alloys and ceramics. This work investigates the corrosion mechanism of selected alloys and ceramics in chloride and fluoride molten salts used for high operating temperature heat transfer fluids using a combination of electrochemical techniques, theoretical calculations, and thermodynamic predictions. The electrochemical characterizations included linear polarization resistance scans, electrochemical impedance spectroscopy, and cyclic potentiodynamic polarization. Results show that the Fe-Ni-Cr alloys tested have high general corrosion and require corrosion inhibition. Advanced materials, such as SiC-SiC and TZM, have been shown to have much lower corrosion and good passivation behavior. Experimental tests using coupon immersion in the molten salts support the mechanism determined from electrochemical testing that the main element being oxidized is Cr. Analysis of samples also indicates selective Cr oxidation concentrates along grain boundaries and creates porous networks in the sample. The electrochemical impedance tests suggest that the corrosion is diffusion controlled and this assumption correlates well with corrosion modeling studies. The electrochemical testing data combined with thermodynamic modeling led to the development of a reaction mechanism for high temperature corrosion in molten salts.
The Effect of Nickel Alloy Corrosion Under Cathodic Protection inside High Temperature Molten Salt Systems
Authors: Tavakoli Bahareh Alsadat , Shimpalee Sirivatch , Weidner John W. , Garcia-Diaz Brenda L. , Martinez-Rodriguez Michael J. , Olson Luke Christopher 
Published: February 2020

One way to potentially reduce the costs of concentrated solar power (CSP) central receiver systems is to operate the central receiver at high temperatures that allow for more efficient thermodynamic power conversion cycles. Molten salts are one potential heat transfer fluid at that can operate efficiently at these temperatures, but their use will introduce other technological challenges, such as corrosion and mass transfer reactions. The corrosion of alloys at high-temperature (700-1000°C) in the receivers and heat exchangers cause a reduction in heat transfer efficiency and durability. Cathodic protection may mitigate corrosion of metal surfaces by shifting the potential of the alloy below its oxidation potential. The behavior of molten salt cooled concentrated solar power (CSP) systems under cathodic protection can be obtained by developing a 3-D model. A simplified model was designed for and benchmarked against a thermosiphon reactor. This thermosiphon reactor exposed alloy coupons to non-isothermal conditions expected in concentrated solar power (CSP) plants. When the cathodic current density is equal to the protection current density and the potential is a protective, the model calculates the corrosion rate and the corrosion potential. Magnesium was used as a sacrificial anode. The rate of Mg consumption, the corrosion potential, and the corrosion current are dependent on several studied variables. Kinetic parameters were obtained from experimental coupon exposures conducted between 700-1000 °C in molten salt in the thermosiphon reactor. Results were in good agreement with experimental values at different conditions.
Fig. 1 shows a comparison of the model prediction of corrosion rate distribution, i (A/cm2) at coupon surfaces for both Hot-Zone and Cold- Zone without (a) and with (b) cathodic protection.

Acknowledgements

The authors gratefully acknowledge the financial support for this work from the DOE EERE SunShot Initiative (DE-AC36-08GO28308) under a subcontract from SRNL to the University of South Carolina. The authors also thank the University of South Carolina Center for Fuel Cells and the CD-adapco group for their support.

Figure 1
Evaluating Water Corrosivity of Water Treatment Plants in Korea
Authors: Park Ju-hyun , Huh Yujeong , Min Byungdae , Choi In-cheol , Chung Hyen-Mi , Park Young-bog , Choi Young-june , Park Eunhee , Lee Mrs. 
Published: February 2020

Introduction

Corrosion control of treated water is an important aspect of safe drinking water supplies. Highly corrosive water can cause system failures or result in health problems because of dissolved lead and other heavy metals from plumbing utilities. This paper is to evaluate corrosivity of water flowing in the distribution systems from water treatment plants in Korea

Experimental

The langelier Saturation index(LI), a measure of solution’s ability to dissolve or deposit calcium carbonate, is often used as an indicator of the corrosivity of water. LI is an equilibrium model derived from the theoretical concept of saturation. It indicates the degree of saturation of water with respect to calcium carbonate and can be calculated from
LSI = pHa -pHs
Where:
pHa : the measured water pH
pHs : the pH at which water with a given calcium and alkalinity as CaCO3 is an equilibrium with calcium carbonate.
The LI was calculated from the chemical parameters including Temperature, Alkalinity, Calcium, pH and Conductivity at major 70 WTPs in Korea from July 2014 to October 2015.

Result
s

Water quality parameters of treated water in Korean WTPs are shown in Fig. 1. From the recorded data , alkalinity ranged between 4.7 and 108.0 mg/L on average 31.6 mg/L as CaCO3. The concentration of Ca ranged between 1.86 and 44.8 on average 19.1mg/L in all WTPs. The result of pH varied from 6.33 to 8.40 on average 7.12, indicating sub-acid to sub-akaline in nature.
The calculated LI of raw and treated water were low (Fig.2). Mean LI values in raw water of WTPs were -0.93, -1.41, -1.68, and -1.80 for the Han, Nakdong, Keum, and Sumjin river basin, and values in treated water were -1.37, -1.78, -1.86, and -2.50 respectively.
LI of raw water from tributaries of four major rivers were relatively low and the geological characteristics of granite in Korea was considered as a main cause of it. Increased corrosivity of treated water resulted from the decrease of pH and alkalinity, which occurred during the purification process especially coagulant treatment. If the corrosion management guidelines were set to the Japan’s guideline(LI≥ -1.0), 61 water treatment plants among 70 were classified as which were required corrosion control(87%).
Based on the correlation results between LI and water quality parameters, pH and calcium concentration were confirmed as the major components for LI(Table 1).
Therefore, pH and Calcium concentration control is considered as an effective method for the management of corrosivity of tap water
According to investigated LI, the treated water in Korean WTPs during 2014~2015 can be classified as corrosive water. This result indicates that the further treatment will be needed for the safe domestic use of water.

Reference

A. B. Richard, E. M. Nancy, A. C. David, Strategies for assessing optimized corrosion control treatment of lead and copper, American Water Works Association, 2013, 105(5), pp. 62-75

Figure 1
The Technology of Corrosion Control with Corrosion Inhibitors in Water Pipes
Authors: Park Young-bog , Choi Young-june , Park Eunhee , Lee Jinsuk , Park Ju-hyun , Min Byungdae , Huh Yujeong , Choi In-cheol , Chung Hyen-Mi 
Published: February 2020

Introduction

The principle oxidants in the drinking system are dissolved oxygen and chlorine, and the corrosion of water pipe is going alone because of oxidants reaction. Since 1930, pH control chemicals such as NaOH, Ca(OH)2, NaHCO3, and phosphate corrosion inhibitors have been used to prevent the corrosion of water pipes. However, to directly add Ca(OH)2at inlet of water well in production process of drinking water may cause a problem to make clouding phenomenon in tap water. The objective of this study removes such problems as the turbidity, strengthen more safety of water.

Experimental

Materials – The iron(carbon steel) was in the form of sheet 0.04 cm in thick and the following analysis: Fe 99.62%, Mn 0.26%, Cu 0.08%, Ni 0.05%, Mo 0.01%. specimens cut from this sheet measured 15cm×1.2cm. The chemicals used as corrosion inhibitors were NaOH, Ca(OH)2, and H3PO4 and tap water used as blank. NaOCl was used to disinfect the drinking water made by the demo plant. In order to examine the effect of disinfectant residual concentration according to adding lime water and corrosion inhibitor such as ortho phosphate(H3PO4), the residual concentration of disinfectant was measured in carbon steel water pipe 50 m in length at the corrosion pilot plant and the temperature of solution was in room temperature between 5°C in the winter to 35°C in the summer. Chlorine residual concentration in the water pipes 50 m in length was measured for 5, 10, 20, 40, 60 min, respectively. The electrochemical tests was measured using Solartron Potentiostat 1480 and the test was performed in a typical three electrode cell which consist of carbon steel as working electrode, saturated calomel electrode as reference electrode, platinum counter electrode.

Result
s

HOCl and OCl- in drinking water which chlorine was added as disinfectant reach in equilibrium state at nearly pH 7.5. As pH increases, more of OCl- exists than the strong disinfectant, HOCl-, Increasing HOCl below pH 7.5 is more benefit in terms disinfectant efficiency. Figure 2 above shows the concentration of free residual chlorine with time. Running drinking water in the pipe, adding PO4 decreased concentration of chlorine from 0.48 to 0.28 ppm for 40 min, NaOH decreased concentration of chlorine from 0.45 to 0.10ppm, Ca(OH)2 decreased concentration of chlorine from 0.24 to 0.10 ppm, but tap water as blank degreased concentration of chlorine from 0.40 to 0.07 ppm for only 10 minutes. Of three corrosion inhibitors, PO4 showed the highest reduced efficiency for the concentration of residual chlorine. To inhibit the reaction of chlorine with metal water pipe is similar to inhibit the corrosion reaction.

Reference

US EPA, Disinfection Profiling and Benchmarking, EPA Guidance Manual, August 1999.
American Society for Testing and Materials, G 4-95(1996).

Figure 1
Adsorption and Corrosion Inhibition Behaviour of Some N-{n-[1-R-5-(quinoxalin-6-yl)-4,5-Dihydropyrazol-3-Yl]Phenyl}Methanesulfonamides on Mild Steel in 1 M HCl (n = 2, 3, 4; R = propanoyl, methylsulfonyl): Experimental and Theoretical Studies
Authors: Olasunkanmi Lukman Olawale , Ebenso Eno E 
Published: February 2020

Mild steel (MS) is a material of choice for diverse structural and industrial applications owing to its excellent mechanical strength and relatively low cost [1]. Certain requisite industrial activities involve the use of acidic solutions that constitute strong corrosive environment for MS. Therefore, corrosion of MS causes great economic loss and present huge safety threats to the concerned industries. Addition of corrosion inhibitors to aggressive solution has been identified as an economical and practical means of controlling metal corrosion. The existing data have shown that organic compounds containing O, N, S, and P heteroatoms, and pi-electron or aromatic systems often exhibit good anticorrosion properties [2,3]. Quinoxaline derivatives possess these features and their corrosion inhibition properties have been reported. These compounds form parts of many essential biological and pharmaceutical compounds and fit into the class of environmentally benign inhibitors [3].
In the present study, adsorption and corrosion inhibition properties of six quinoxaline derivatives namely, N-{n-[1-R-5-(quinoxalin-6-yl)-4,5-dihydropyrazol-3-yl]phenyl}methanesulfonamides: R = propanoyl & n = 2, 3, 4 for MS-2-PQPP, MS-3-PQPP, and MS-4-PQPP respectively; and R = methylsulfonyl & n = 2, 3, 4 for MS-2-PQPMS, MS-3-PQPMS and MS-4-PQPMS were investigated on MS in 1 M HCl solution. The techniques employed in the study include potentiodynamic polarization and electrochemical impedance spectroscopy. Quantum chemical calculations and molecular dynamic simulations studies were used to support experimental results.
All the studied compounds were found to exhibit appreciable inhibition efficiency and they are all mixed type inhibitors. The compounds inhibit MS corrosion by adsorbing on the steel surface and geometrically blocking the active sites for the corrosion reaction. Both MS-3-PQPP and MS-3-PQPMS showed higher inhibition performances, which suggests that the interplay of electronic and steric effects of the carbonyl/methylsulfonyl substituents ensures higher inhibition performance when n = 3 (meta-substitution). The adsorption of the studied compounds obeyed the Langmuir adsorption isotherm model. Theoretical quantum chemical calculations and molecular dynamic simulations corroborate experimental results.

References

(1) De la Fuente, D.; Diaz, I.; Simancas, J.; Chico, B.; Morcillo, M. Corros. Sci.
2011, 53, 604.
(2) Mashuga, M.E.; Olasunkanmi, L.O.; Adekunle, A.S.; Yesudass, S.; Kabanda, M.M.; Ebenso, E.E. Materials
2015, 8, 3607.
(3) Olasunkanmi, L.O.; Obot, I.B.; Kabanda, M.M.; Ebenso, E.E. J. Phys. Chem. C
2015, 119, 16004.

Figure 1
(Invited) Trench-Gated MOSFET Instability Caused by High Temperature Reverse-Bias Stress
Authors: Hao Jifa 
Published: February 2020

The trench-gated MOSFET is widely used in power management applications because of its ultra-low on resistance [1]. Studies of trench-gate MOSFET reliability and degradation of blocking voltage and leakage current as well as edge termination effects are becoming increasingly important as the device dimensions shrink and its applications are diversified. The HTRB (high temperature reverse-bias) and HAST (highly accelerated temperature & humidity stress test) are often used in reliability assessment of planar discrete power MOSFETs [2] and are currently used in trench-gated MOSFET. The both HTRB stress and HAST stress apply a reverse bias voltage on the drain side with the source and gate grounded at elevated temperature in a MOSFET device. However, the HAST stress is at 85% HR relative humidity under pressure condition. The possible failure modes for HTRB and HAST stress are IDSS (drain to source) leakage current increase or shift, breakdown voltage shift or degradation, and Vth (threshold voltage) shift or instability. The failure mechanism under various failures is complex. They depend on not only device design and process, but also package process and its materials such as mold compound, as well as interaction between device and package.
In this paper, we discuss the instability of n-channel trench-gated MOSFET under HTRB and HAST reliability stresses. The devices are packaged by using state-of-the-art “low pitch” wafer-level-chip-scale package (WLCSP) without the use of mold compound or leads frame. We have observed that the HTRB and HAST stress increases gate oxide interface trap density. However humid HAST stress is observed to further introduce mobile positive charge in the gate oxide of the trench-gated MOSFET. This positive charge is argued to comprise protons (H+s) [3]. The proton is generated through electric-field assisted interaction and hole injection into the gate oxide at the bottom of the trench. The mobility of these protons is observed to cause gate-voltage induced modulation in the threshold voltage and leakage current of the trench-gated MOSFET.
In order to determine the mechanism by which H+s are introduced in the oxide, SEM inspection of the n-channel trench-gated MOSFET deprocessed to passivation showed the presence of passivation cracks in the device’s edge termination which cause moisture penetrated in the device during the HAST stress.
Furthermore, the experimental and simulation results lead us to conclude that in this study we are observing negative bias temperature instability (NBTI) in a parasitic p-MOSFET structure arising at the bottom of the trench in an n-channel trench-gated MOSFET during HTRB stress [4]. The NBTI is enhanced by the presence of moisture in the oxide.

References:

[1]: J. Zeng et al ISPSD 2002, pp. 147-150.
[2]: JEDEC, IESD22-A108D, November (2010).
[3]: J. Hao, M. Rioux, S. Suliman, O. Awadelkarim, Microelectronics Reliability, 54(2014) 374-380.
[4]: J.Hao, M. Rioux, and O. Awadelkarim, IIRW 2011, pp129-131.

Figure 1