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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Steam Corrosion Investigation of Single Silicon Carbide Nanostructures

Silicon carbide (SiC) has been advanced as an alternative to zircaloy for use as an accident-tolerant fuel cladding material in next-generation water-cooled reactors. This is due, in large part, to the predicted superior corrosion resistance of SiC, as compared to zircaloy, particularly at the high temperatures that are obtained in a nuclear reactor under accident conditions. The other favorable performance metrics of SiC include its enhanced mechanical stability, low neutron absorption, low chemical reactivity, and high radiation stability. Past reports, which include theoretical and isolated experimental activities, have studied the corrosion of bulk-scale SiC in reactor-like conditions. This report will present high-temperature steam corrosion results from single SiC nanofiber-based constructs. The changes in microstructure, and the evolution of oxide thickness and SiC recession with progressive corrosion will be characterized at the atomic-to-nanoscale using transmission electron microscopy (TEM). Furthermore, the corrosion-induced degradation in mechanical properties of the SiC nanofibers will be characterized using three-point bending tests involving an atomic-force microscope (AFM) in the contact mode.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Mechanical Properties and Corrosion Behavior of Spray-Formed 7075 Alloy with One-Stage Aging

The mechanical properties, corrosion resistance and microstructure of the spray-formed 7075 alloy after one-stage aging treatments were studied by using a tensile tester, hardness tester, slow strain rate test, electrical test, intergranular corrosion test, electrochemical corrosion test, scanning electron microscope and transmission electron microscope. The results show that the strength and hardness of the alloy have double peaks with the one-stage aging treatments. With aging at 120 °C for 24 h (first peak), abundant tiny η′ phases and η phases precipitate in the matrix. The tensile strength of the alloy increases to 760 MPa, and the elongation is 4.8%. After aging at 120 °C for 132 h (second peak), blocky η phases appear. The tensile strength and elongation of the alloy are 757 MPa and 5.9%, respectively. The grain boundary precipitates dissociate, and the precipitate-free zones are widened. The corrosion resistance of the alloy increases.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Laser Surface Processing of Alloys for Corrosion Protection (Final Project Report of Marine Energy Seedling Project)

This is the final project report for the MHK Seedling project. The report describes use of laser surface processing (LSP) to modify the surface of test materials (Al, steel) and the corrosion testing performed on the resulting samples in different corrosion environments. Data shows that LSP improved the corrosion resistance of Al and steel used in this work relative to respective non-LSP samples. The data also showed that each material had a specific range of laser processing conditions where the beneficial effects of LSP (i.e. improvement in corrosion protection) were observed. Application of LSP to enable low-cost materials in marine environments, additional microstructural analysis and long-term testing are proposed to further develop this technology for marine renewable energy and systems.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Fireside Corrosion of Alumina-Forming Austenitic (AFA) Stainless Steels

Here, the performance of four alumina-forming austenitic alloys was tested in simulative fireside corrosion atmospheres. The alloys were exposed at 700 °C to gas atmospheres of oxygen with varying amounts of SO 2 with two deposits, one which contained Na 2 SO 4 /K 2 SO 4 /Fe 2 O 3 in a 1.5:1.5:1.0 molar ratio (SCM) and the other Na 2 SO 4 /K 2 SO 4 in a 1:1 molar ratio (M1). The specimens were placed into alumina crucibles and submerged halfway in the powder deposits. Corrosion first initiated in the region where the deposit was thinnest. In the SCM, most alloys exhibited two-stage kinetics: an initiation stage during which degradation was slow followed by a propagation stage during which degradation was rapid. Exposures in the SCM deposit showed a significant effect of alloy composition and microstructure. In the as-processed state, OC4 suffered severe scale spallation and was not protective, while OC8, which contains a higher Cr content, remained protective. The exposures with the various microstructures indicate the significance of the factor on fireside corrosion. The OC8 alloy was extremely resistant in the as-processed state but was rapidly degraded when the microstructure had been equilibrated prior to exposure. Conversely, the OCS and OCT alloys, which were borderline in the as-processed state were quite resistant after their microstructures had been equilibrated. The results indicate that corrosion resistance in these environments comes from alumina, but the alloys need more Cr and in a very accessible microstructure location to get the third-element effect to promote the alumina. The weight changes and the amount of degradation were more severe with M1 than with the SCM. Furthermore, there was more corrosion when the alkali iron trisulfates must be formed from a thermally grown iron oxide scale, than when the iron oxide was already in the deposit. In the latter case, the rate of degradation by “synergistic fluxing” was reduced.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Variation of the Passive Film on Compositionally Concentrated Dual-Phase Al 0.3 Cr 0.5 Fe 2 Mn 0.25 Mo 0.15 Ni 1.5 Ti 0.3 and Implications for Corrosion

The passive film on a dual-phase Al 0.3 Cr 0.5 Fe 2 Mn 0.25 Mo 0.15 Ni 1.5 Ti 0.3 FCC + Heusler (L2 1 ) compositionally concentrated alloy formed during extended exposure to an applied potential in the passive range in dilute chloride solution was characterized. Each phase, with its own distinct composition of passivating elements, formed unique passive films separated by a heterophase interface. High-resolution, surface sensitive characterization enabled chemical analysis of the passive film formed over individual phases. The film formed over the L2 1 phase had a higher concentration of Al, Ni, and Ti, while the film formed over FCC phase was of similar thickness but contained comparatively higher Cr, Fe, and Mo concentrations, consistent with the differences in bulk microstructure composition. The passive film was continuous across phase boundaries and the distribution of passivating elements (Al, Cr, and Ti) indicated both phases were independently passivated. Spatially resolved analysis of the surface chemistry of the dual-phase CCA revealed that the cation with the highest composition in passive film formed on the FCC phase was Cr (52.4 at. pct) and for the L2 1 phase was Ti (53.1 at. pct) despite the bulk concentration of each element being below 20 at. pct in their respective phases. Al, Cr, and Ti were enriched in both phases within the passive film relative to their respective bulk compositions. In parallel studies, single-phase alloys with compositions representative of the FCC and L2 1 phases were synthesized to evaluate the corrosion behavior of each phase in isolation. The corrosion behavior of the dual-phase alloy showed passivity evidenced by a pitting potential of 0.615 V SCE in 0.01 M NaCl. The pitting potential and other electrochemical parameters suggested a combination of behaviors of both single-phase samples, suggesting that the global corrosion behavior may be represented by a composite theory applied to phases, their area fractions, and interphase length. However, the interphase in the dual-phase CCA was a local corrosion initiation site and may limit localized corrosion protectiveness. The alloy design implications for optimization of second phase structure and morphology are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Analysis of the Corrosion Behavior of an A-TIG Welded SS 409 Weld Fusion Zone

AISI 409 (SS 409) ferritic stainless steel is generally used as the thick gauge section in freight train wagons, in ocean containers, and in sugar refinery equipment. Activating the flux tungsten inert gas (A-TIG) welding process can reduce the welding cost during fabrication of thick sections. However, corrosion behavior of the A-TIG weld fusion zone is a prime concern for this type of steel. In the present work, the effect of the A-TIG welding process parameters on the corrosion behavior of a weld fusion zone made of 8-mm-thick AISI 409 ferritic stainless-steel plate has been analyzed. Potentiodynamic polarization tests were performed to evaluate the corrosion behavior. The maximum corrosion potential (E{sub corr}) was shown by the weld made using a welding current of 215 A, a welding speed of 95 mm/min, and a flux coating density of 0.81 mg/cm{sup 2}. The minimum E{sub corr} was observed in the weld made using a welding current of 190 A, a welding speed of 120 mm/min, and a flux coating density of 1.40 mg/cm{sup 2}. The current study also presents the inclusive microstructure–corrosion property relationships using the collective techniques of scanning electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray diffraction.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Improving Corrosion Resistance of 316L Austenitic Stainless Steel Using ZrO{sub 2} Sol-Gel Coating in Nitric Acid Solution

In this study, thin-film coating of zirconium oxide (ZrO{sub 2}) was prepared by sol-gel method and subsequent heat treatment process. The sol was prepared by controlled hydrolysis of zirconium tetrapropoxide using acetic acid and ethanol/acetylacetone mixture as catalyst and chelating agent, respectively, and finally deposited onto the 316L austenitic stainless steel (316L SS) using dip coating method in order to improve its corrosion resistance in nitric acid medium. The composition, structure, and morphology of the coated surface were investigated by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The obtained results from XRD and FTIR state the formation of tetragonal and monoclinic ZrO{sub 2} phase. Also, the obtained results from surface morphology investigation by SEM and AFM indicate the formation of smooth, homogeneous and uniform coatings on the steel substrate. Then, the corrosion behavior of stainless steel was investigated in a 1 and 10 M nitric acid solutions using electrochemical impedance spectroscopy and linear polarization test. The obtained results from these tests for ZrO{sub 2}-coated specimens indicated a considerable improvement in the corrosion resistance of 316L stainless steel by an increase in corrosion potential and transpassive potential, and a decrease in passive current density and corrosion current density. The decrease in passive current density in both the concentration of solutions was two orders of magnitude from bare to coated specimens.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Localized Corrosion on Fatigue–Crack Growth in 2524-T3 and 2198-T851 Aluminum Alloys Used as Aircraft Materials

Corrosion and fatigue of aluminum alloys are major issues for the in-service life assessment of aircraft structures and for the management of aging air fleets. The aim of this work was to evaluate the effect of localized corrosion on fatigue crack growth (FCG) resistance of the AA2198-T851 Al-Li alloy (Solution Heat Treated, Cold Worked, and Artificially Aged), comparing it with the FCG resistance of AA2524-T3 (Solution Heat Treated and Cold Worked), considering the effect of seawater fog environment. Before fatigue tests, the corrosion behavior of 2198-T851 and 2524-T3 aluminum alloys was verified using open circuit potential and potentiodynamic polarization techniques. Fatigue in air and corrosion fatigue tests were performed applying a stress ratio (R) of 0.1, 15 Hz (air) and 0.1 Hz (seawater fog) frequencies, using a sinusoidal waveform in all cases. The results showed that the localized characteristics of the 2198-T851 and 2524-T3 aluminum alloys are essentially related to the existence of intermetallic compounds, which, due to their different nature, may be cathodic or anodic in relation to the aluminum matrix. The corrosive medium has affected the FCG rate of both aluminum alloys, in a quite similar way. Graphical Abstract: .

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Different Cooling Rates on the Corrosion Behavior of High-Carbon Pearlitic Steel

The present work discusses the effect of pearlitic morphology on the corrosion behavior of high-carbon fully pearlitic steel in 3.5% NaCl solution. Four different types of pearlitic steels (furnace-cooled, as-received, air-cooled and forced-air-cooled) consisting of coarse, medium, fine and very fine microstructures, respectively, were tested. Electrochemical behavior of these steels was studied with the help of dynamic and linear polarization and AC impedance spectroscopic tests. The corrosion resistance improved with fineness of the microstructure in general. However, with further reduction in interlamellar spacing beyond a limit, the corrosion resistance reduced slightly. Formation of homogeneous distribution of microgalvanic cells between cementite and ferrite lamellae of fine pearlitic steel improved the corrosion resistance. However, entanglement of the lamellae of pearlite in very fine pearlitic structure as well as breaking of cementite lamellae due to finer pearlitic colonies was attributed to the higher corrosion of the forced-air-cooled steel as compared to the air-cooled steel.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Corrosion Behavior of B and Ti Grain-Refined Sr-Modified A356

Corrosion behavior of A356 aluminum alloy with different grain refiners was evaluated. For this purpose, the Sr-modified A356 alloy was grain refined with Al5Ti1B and Al3B, and then, the corrosion characteristics were determined. For the mechanical properties, impact and Vickers hardness tests were carried out. To determine the corrosion behavior, both the electrochemical impedance spectroscopy technique and by potentiodynamic polarization plots were carried out in a 3.5 wt.% NaCl solution at 25 °C. The corrosion resistance of A356 alloy was dramatically improved in sequence with the following modifications compared to the unmodified castings: Sr, Ti and B additions. This situation applies to both different cooling rates, namely die and sand casting. The increase in corrosion rate was more than 80% for all alterations of the microstructure. Additionally, charge transfer resistance was increased ten times in die cast samples, while this value was 2.5 for sand cast samples compared to the unmodified alloy. It is important to note that sand casting of the unmodified alloy was improved four times with regard to the die cast unmodified A356.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The Effect of Flowing Velocity and Impact Angle on the Fluid-Accelerated Corrosion of X65 Pipeline Steel in a Wet Gas Environment Containing CO{sub 2}

This study investigated the effect of flowing velocity and impact angle on the fluid-accelerated corrosion (FAC) of X65 pipeline steel in a wet CO{sub 2}-containing environment by corrosion morphology analysis, electrochemical measurement, and hydromechanical numerical analysis. It has been found that the corrosion behavior was controlled by the ion diffusion rate and shear stress due to the flowing gas. With an increase in the flowing velocity, the pitting corrosion initially decreased and then increased when the flowing velocity exceeded 14 m/s; this increase is caused by the augmentation of shear stress. When the impact angle decreased, the position of serious corrosion gradually moved outwards.

36 MATERIALS SCIENCE↗
DOE OSTI2019

The Effect of Jet Flow Impingement on the Corrosion Products Formed on a Pipeline Steel in Naturally Aerated Sour Brine

Corrosion was generated by the action of a jet impingement flow of sour brine on pipeline steel samples of X70. Flow-assisted corrosion affected nature, number and peak intensity of the chemical species formed as corrosion products. Iron sulfides predominated in static and low flow rate conditions (1.1 m/s), whereas at 2.4 m/s iron oxides were mainly formed, which led to higher corrosion rates and suggested that oxides are less protective than sulfides. On inhibition, imidazoline seems to mitigate oxide formation and support sulfide formation balancing both species on steel surface. Ferrite phase in laminar pearlite was preferentially dissolved with/without inhibitor, and mackinawite (FeS{sub 2}) was formed at every flow rate, angle with and without inhibitor. Theoretical stresses determined by computational flow dynamics for corrosion product removal showed a fair approximation to those proposed in the literature.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Corrosion Behavior of Q235 Steel in Atmospheres Containing SO{sub 2} and NaCl

The atmospheric corrosion of metals is a severe problem in marine environments. However, the effects of SO{sub 2} and NaCl on the atmospheric corrosion of Q235 steel have not been widely studied. In the present work, electrochemical impedance spectroscopy was conducted to exploit the initial corrosion properties of Q235 in simulated atmospheric environments containing different contents of SO{sub 2} and NaCl. The solution resistance (R{sub s}) and polarization resistance (R{sub p}) of electrodes covered with pre-deposited NaCl were continuously monitored. The results showed that both SO{sub 2} and NaCl promoted the corrosion rate of Q235 steel. The pre-deposited NaCl maintained the moisture of the metal surface to ensure continued corrosion. The thickness of the electrolyte layer on the metal surface decreased with increasing SO{sub 2} content. A thin electrolyte layer could increase the Cl{sup −} concentration and reduce the pH value of the layer. The thin electrolyte layer could also promote the mass transfer of oxygen, thereby accelerating the cathodic reduction reaction. However, the NaCl content played a more important role than that of SO{sub 2} in the simulated environments.

36 MATERIALS SCIENCE↗
DOE OSTI2019

An Investigation of the Corrosion Mechanisms of Cu-7Ni-3Al-1Fe-1Mn Alloy in Chloride-Containing Environment

The corrosion mechanisms of Cu-7Ni-3Al-1Fe-1Mn (wt.%) alloy in a 3.5% NaCl solution are investigated through a multi-analytical approach. The formation, growth and stable corrosion stage of the stable corrosion layer are reflected by the change of electrochemical response with time. EDS and GI-XRD results show the presence of Cu{sub 2}(OH){sub 3}Cl and Cu{sub 2}O that are the main corrosion products, with the former predominantly present at topmost corrosion layer, and Cu{sub 2}O is mainly located in the inner part, followed by aluminum oxide closer to the alloy substrate.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Relationship Between Microstructure and Marine Corrosion Resistance of Martensitic Stainless Steels: A Multiscale Approach

The electrochemical properties of martensitic stainless steels may depend on complex aspects of their microstructure. Three alloys were considered in this study: X30Cr13 (AISI 420), a martensitic stainless steel with a low content of alloying elements; X17CrNi16-2 (AISI 431), chosen for its strong resistance to corrosion; and X5CrNiCu15-5 (AISI 630), chosen for its good mechanical resistance. Voltammetry tests have shown the influence of carbon and chromium content on corrosion resistance. Resistance to pitting appears equivalent for the both. However, heterogeneous corrosion, in relation to δ-ferrite precipitation and chromium carbides at the lath boundaries, appears in the case of X17CrNi16-2. Conversely, non-preferential corrosion occurs in the case of the X5CrNiCu15-5, and a superior passive film stability during immersion in artificial seawater. This counterbalance negative effect of the microstructure. Thus, it achieves an equivalent “macroscopically” corrosion behavior between the two steels.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Sulfide Concentration on the Corrosion and Cavitation Erosion Behavior of a Manganese-Aluminum Bronze in 3.5% NaCl Solution

The effect of sulfide concentration on the corrosion and cavitation erosion behavior of a cast manganese-aluminum bronze (MAB) alloy in 3.5% NaCl solution was investigated. The electrochemical results showed that when the sulfide concentration exceeded 50 ppm, hydrogen evolution reaction dominated the cathodic process because of the very negative corrosion potential of MAB, and the formation of a copper sulfide film on MAB was a diffusion-controlled process. The mass loss rate of MAB after longer-term immersion was ordered by the sulfide concentration as: 20/50 ppm > 100 ppm > zero > 200 ppm. In the 200 ppm sulfide solution, the mass loss rate of MAB was the lowest, because of the formation of a thin and homogeneous copper sulfide film. In the other sulfide solutions, the formation of a less-protective film with both oxides and sulfides resulted in higher mass loss rate of MAB. Moreover, selective phase corrosion occurred at the β and κ phases in solutions with sulfide addition less than 100 ppm. For all solutions, it was the mechanical attack that dominated cavitation erosion degradation. The cavitation erosion–corrosion synergy was lower in high sulfide solutions, because the corrosion products on MAB could reduce the mechanical impact under cavitation erosion.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Carbon Nanotube Concentration on the Corrosion Behavior of Electroless Ni-B-CNT Coating

In this study, Ni-B-CNT composite was deposited on AISI 4140 steel using different concentrations of CNTs ranging from 0.2 to 1 gr/lit in an electroless bath. The phase analysis and surface morphology of the samples were characterized using x-ray diffraction and FESEM. The corrosion behavior of the coated samples was investigated in a 3.5 wt.% NaCl solution through potentiodynamic polarization, EIS, and electrochemical noise (EN) analyses. The corroded surface of the samples was further analyzed via FESEM observation after 10 days of immersion in corrosive medium. It was found that although adding 0.2 gr/lit CNT in electroless solution improves corrosion resistance, increasing CNT concentration from 0.2 up to 1 gr/lit increases the corrosion rate. The FESEM observations and EN results imply that the formation of micro-galvanic cells in samples with high concentration of CNTs leads to nucleation and growth of the pits. The results revealed that no passive layer was formed on the surface of the Ni-B sample, and the corrosion occurred through ionic diffusion into the cracks and crevices. The results of potentiodynamic test show that adding CNTs into electroless bath facilitates the formation of passive layer. However, results of EN test imply that increasing CNT concentration causes repetitive breakdown and recovery of passive film.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Atomic Layer-Deposited Al{sub 2}O{sub 3} Interlayer for Improved Tribological and Anti-corrosion Properties of TiN Hard Coating on 316L Stainless Steel

A dense Al{sub 2}O{sub 3} interlayer was inserted into TiN to enhance the tribological and anti-corrosion properties of TiN hard coating via a hybrid process of magnetron sputtering and atomic layer deposition (ALD). The influence of the ALD-Al{sub 2}O{sub 3} layer on the microstructure, mechanical, tribological and anti-corrosion properties of TiN was examined. The TiN-Al{sub 2}O{sub 3} coating exhibits low friction coefficient and specific wear rate, due to the structure change and columnar refinement caused by the addition of amorphous ALD-Al{sub 2}O{sub 3} interlay which improves the mechanical properties of hard coating. The improved corrosion properties of TiN are attributed to the fact that the insulating ALD-Al{sub 2}O{sub 3} used as a sealing layer can prevent the corrosive chlorine ions migrating into the lower TiN layer and block the charge transport in coatings. Moreover, raising the insertion position of ALD-Al{sub 2}O{sub 3} layer away from the steel substrate results in a further increase in the anti-corrosion property of TiN-Al{sub 2}O{sub 3} composite coating.

36 MATERIALS SCIENCE↗