Joe Tylczak | Department of Energy, National Energy Technology Laboratory (original) (raw)

Papers by Joe Tylczak

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Jul 15, 2023

Poster presentation titled Ni-based alloys in direct-fired supercritical CO2 power cycle environm... more Poster presentation titled Ni-based alloys in direct-fired supercritical CO2 power cycle environments at the 2023 High Temperature Corrosion Gordon Research Conference

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Oct 10, 2022

MS&amp;T22, Pittsburgh PA, October 8-12, 2022

High Temperature Corrosion of Materials

Future technologies require structural materials resistant to environmental degradation in high-t... more Future technologies require structural materials resistant to environmental degradation in high-temperature CO2-rich environments. In this work, we exposed several commercially available Ni-based alloys (230, 263, 282, 617, 625, and 740H) to atmospheric pressure gases intended to simulate the compositions expected in future direct-fired supercritical CO2 power cycles. The alloys were exposed to 95% CO2 + 4% H2O + 1% O2 and the same gas containing 0.1% SO2 at temperatures of 600, 650, 700, 750, and 800 °C for 2500 h. With minor exceptions, chromia scales formed on all alloys at all temperatures in the SO2-free gas, yielding parabolic growth rates that followed an Arrhenius temperature dependence. Behavior in the SO2-containing gas was more complex. Generally, the alloys performed well at temperatures of 650, 750, and 800 °C. While some alloys further performed relatively well across the whole temperature range, several of the alloys experienced chromia failure resulting in non-protective duplex oxide scales and high oxidation rates, at temperatures of 600 and 700 °C. Deviation from protective behavior was associated with internal sulfide formation and, additionally for the case of 600 °C, external sulfate formation. Extensive carburization accompanied growth of the non-protective duplex oxide scales, which made it more difficult for the alloy to recover after initiation of the sulfur-induced accelerated corrosion process. The thermodynamic and kinetic factors influencing the accelerated corrosion in the presence of sulfur are discussed. The results suggest that caution is required when assessing compatibility of Ni-based alloys for CO<sub>2</sub>-based systems when sulfur-based impurities are expected.

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Oct 10, 2022

The Bureau of Mines studied the effect of alloy additions on abrasive wear of low-alloy steels. A... more The Bureau of Mines studied the effect of alloy additions on abrasive wear of low-alloy steels. A dry-sand, rubber-wheel abrasion test: apparatus using ASTM G65-81 procedure B was used for the abrasive wear tests. Eighty-six material heat-treatment combinations were abrasion tested. Results of these tests were analyzed statically using regression analysis to see if addition of Cr, Mn, Mo, Ni, Si, Al, Cu, and S were significant in affecting the abrasive-wear rate of low-alloy steels. Regression analysis was also used to confirm hardness and C effect on the abrasive wear rate of these steels. It was found that for all the steels taken as a group, increased amounts of Mn significantly reduced the wear rate, while increased amounts of Mo and Si Increased the wear rate. analysis also confirmed previous research done by others, that increasing hardness and amounts of C reduced the wear rate. For the hardened steels taken as a class, only increasing amounts of C and Mn reduced the wear rate, while increases in Si increased the wear rate. In the class of unhardened steels, increases in C, Mn, and S reduced the wear rate, whereas inereas'e8 in Mo increased the wear rate. The steels with the best resistance to wear were two hardened experimental steels similar to AISI 1055 and AISI 1078.

Wear of Materials 1987, 1987

The Bureau- of Mines investigated the effects of composition on abrasive wear in four substitutio... more The Bureau- of Mines investigated the effects of composition on abrasive wear in four substitutional and two interstitial binary systems. The substitutional systems studied were Hf-Zr, Cu-Ni, Cr-V, and Fe-Ni. Abrasive wear and hardness were measured on arc-melted specimens over the complete range of compositions in each substitutional system. The interstitial systems Ti-N and Ti-O were investigated up to 3 wt pct interstitial. The abrasive testing machine utilized a load of 66.7 N on a 6.35-mm-diam pin running on 105-µm garnet abrasive cloth.
Wear of the Hf-Zr alloys correlated with solidus temperature, that of Cu-Ni alloys with solidus and hardness, and that of Cr-V and Fe-Ni alloys with hardness. An increase in the solute, Fe or Ni, in the Fe-Ni system resulted in decreased wear except in the region of the bcc to fcc phase transformation. In the Ti-N and Ti-O interstitial systems, wear decreased with the first 0.5 to 0.9 wt pct nitrogen and oxygen added respectively and remained nearly constant to about 3 wt pct interstitial. The effects of solidus temperature, lattice strain, and thermal diffusivity on abrasive wear are discussed.

The laboratory wear testing capabilities of the Bureau of Mines are described. Wear tests are use... more The laboratory wear testing capabilities of the Bureau of Mines are described. Wear tests are used to support the Bureau's research efforts toward reducing the wear of equipment used for mining and minerals processing and any wear involving a loss of strategic or critical materials. The emphasis is on abrasive wear because it accounts for most of the wear losses that occur in mining and minerals processing equipment. Spalling wear, caused by repetitive Impact in grinding equipment, also is included. Ten abrasive wear tests, including high— stress and low—stress and two—body and three—body conditions, are described: dry—sand, rubber—wheel abrasive wear; Taber Abraser; abrasion resistance of refractory materials; dry—particle erosive wear; elevated—temperature, dry—particle erosive wear; low—angle slurry pot; jaw crusher gouging wear; ball mill wear; pin—on—drum abrasive wear; and high—speed impact gouging. Two repetitive impact tests are described: ball—on—block impact—spalling and ball—on—ball Impact— spalling. Test equipment, procedures, and specimens are described, and typical test results are presented and discussed.

Laboratory wear testing was conducted by the Bureau of Mines on a variety of typical wear—resista... more Laboratory wear testing was conducted by the Bureau of Mines on a variety of typical wear—resistant alloys used in mining and mineral processing equipment to establish their relative spalling and abrasion resistance. Test specimens in the form of 7 balls were subjected to repeated impacts until they broke, spalled excessively, or received several hundred thousand impacts. Pin specimens removed from the balls were evaluated for high—load abrasive wear. The alloys included commercial forged steels, cast steels, manganese steels, and four types of white cast iron, with a range of heat treatments. The effects of hardness and microstructure on impact wear and abrasive wear are discussed. The data should help mine operators select the compositions and heat treatments that best suit service conditions.

The Albany Research Center (ARC) has a long history of studying abrasive wear, related to mineral... more The Albany Research Center (ARC) has a long history of studying abrasive wear, related to mineral testing, handling, and processing. The center has also been instrumental in the design and development of wear test procedures and equipment. Research capabilities at ARC include Pin-on-Drum, Pin-on-Disk, and Dry Sand/Rubber Wheel abrasion tests, Jaw Crusher gouging test, Ball-on-Ball Impact test, and Jet erosion tests. Abrasive and erosive wear studies have been used to develop both new alloys and improved heat treatments of commercial alloys. As part of ARC’s newest iteration on wear testing to evaluate materials for use in new and existing pulverized coal combustion and gasifier power systems, the ARC has designed and constructed a new High Temperature Hostile Atmosphere Erosion Wear Test (HAET). This new piece of test apparatus is designed for erosive particle velocities of 10-40 m/sec and temperatures from room temperature (23°C) to 800+°C, with special control over the gas atmosphere. A variable speed whirling arm design is used to vary the impact energy of the gravity fed erosive particles. The specimens are mounted at the edge of a disk and allow a full range of impingement angles to be selected. An electric furnace heats the specimens in an enclosed retort to the selected temperature. Tests include both oxidizing conditions and reducing conditions. A range of gases, including CO, CO2, CH4, H2, H2S, HCl, N2, O2, and SO2 can be mixed and delivered to the retort. During the erosion testing a stream of abrasive powder is delivered in front of the specimens. This apparatus is designed to use low abrasive fluxes, which simulate real operating conditions in commercial power plants. Currently ~270 μm SiO2 particles are being used to simulate the abrasive impurities typically found in coal. Since operators are always striving for longer lifetimes and higher operating temperatures, this apparatus can help elucidate mechanisms of wastage and identify superior materials. This talk will present some initial results from this new environmentally controllable erosion test apparatus.

The resistance of FeAl-40%TiB[sub 2] and FeAl-80%WC cermets to solid particle erosion at 25, 180,... more The resistance of FeAl-40%TiB[sub 2] and FeAl-80%WC cermets to solid particle erosion at 25, 180, 500 and 700 C was evaluated and compared to the behavior of WC-6%Co (Co-90%WC) cemented carbides. Even though the WC-Co contained a higher volume fraction of the hard phase, the erosion rates of the FeAl-cermets were similar in magnitude to the erosion rates of the WC-Co. However, the erosion rates of the FeAl-cermets either were constant (FeAl-TiB[sub 2]) or decreased (FeAl-WC) with increasing test temperature; whereas, the erosion rates of the WC-Co cemented carbides increased with increasing test temperature. This indicated that once the microstructures of the FeAl-cermets are optimized for wear resistance, these materials might make promising candidates for high-temperature wear application.

The sequestration of CO2 is an important technology to be promptly developed if fossil fuels are ... more The sequestration of CO2 is an important technology to be promptly developed if fossil fuels are continued to be used and CO2 emission to the atmosphere is to be reduced. Low alloy carbon steel pipelines are being considered to transport the supercritical CO2 from power plants to underground sequestration sites. However, the CO2 stream will not be pure and dry, but will contain a number of corrosive contaminants. We have developed an experimental system that allows the use of a number of in-situ electrochemical techniques, such as electrochemical impedance spectroscopy, linear sweep voltammetry, and cyclic voltammetry, at elevated temperature and pressure. These methods are used to measure the parameters of the real time corrosion process without removing the sample from the system. This paper describes the design of the apparatus and presents the results of our first measurements of corrosion of carbon steel in supercritical CO2 doped with H2O at 50 ºC and 15 MPa. The first conductivity measurements in the dry and water-saturated supercritical CO2 fluid are also presented in this paper.

Mater Sci Eng a Struct Mater, 1999

The solid particle erosion behavior at room and elevated temperatures (180, 500, 700 and 900°C) o... more The solid particle erosion behavior at room and elevated temperatures (180, 500, 700 and 900°C) of an Si3N4–MoSi2 composite was studied. Alumina particles entrained in a stream of nitrogen gas impacted the target material at a velocity of 40 m s−1. Impingement angles of either 60, 75 or 90° were used. It was found that the erosion rate for the Si3N4–MoSi2 composite (measured at room temperature) was a maximum at the 90° incident angle, erosion behavior typical of brittle materials. The erosion rate of the composite at a 75° impingement angle increased slightly with increasing test temperature up to 700°C (i.e. from 4.1 to 4.9 mm3 g−1). At 900°C, the measured erosion rate decreased to 2.9 mm3 g−1. The erosion behavior of the Si3N4–MoSi2 composite was compared to that of commercially available Si3N4, WC–6%Co, 304 SS, IN-800 (Ni–Fe–Cr alloy) and Stellite-6B (Co–Cr–W–Mo alloy).

A new series of high nitrogen-carbon manganese stainless steel alloys are studied for their wear ... more A new series of high nitrogen-carbon manganese stainless steel alloys are studied for their wear resistance. High nitrogen and carbon concentrations were obtained by melting elemental iron-chromium-manganese (several with minor alloy additions of nickel, silicon, and molybdenum) in a nitrogen atmosphere and adding elemental graphite. The improvement in material properties (hardness and strength) with increasing nitrogen and carbon interstitial concentration was consistent with previously reported improvements in similar material properties alloyed with nitrogen only. Wear tests included: scratch, pin-on-disk, sand-rubber-wheel, impeller, and jet erosion. Additions of interstitial nitrogen and carbon as well as interstitial nitrogen and carbide precipitates were found to greatly improve material properties. In general, with increasing nitrogen and carbon concentrations, strength, hardness, and wear resistance increased.

The wear-corrosion behavior of a high chromium white cast iron in a Na 2 SO 4 solution was invest... more The wear-corrosion behavior of a high chromium white cast iron in a Na 2 SO 4 solution was investigated. Disk samples of the high chromium white iron, a model matrix, and a model carbide were abraded against SiC electrodes in a 1 N solution of Na 2 SO 4. Both open circuit and cathodically polarized conditions were investigated. In the case of cathodic polarization, uniform wear was observed. In the case of open circuit (with no electrochemical control), it was found that the chrome carbides in the white cast iron were attacked, and thus were unable to protect the surface from abrasion.

The Bureau of Mines, U.S. Department of the Interior, compared the abrasive wear conditions of fo... more The Bureau of Mines, U.S. Department of the Interior, compared the abrasive wear conditions of four types of laboratory wear tests. The conditions include two-and three-body, low-and high-stress, open-and closed-systems. Over 50 steel and cast iron alloys and several other materials were tested in a slurry-erosion wear test, dry-sand/rubber-wheel test, and pin test. Ten of the alloys were tested by a jaw crusher test. Factors such as ease of preparing specimens, ease of conducting tests, testing time, and reproducibility of results are compared. Wear parameters of the Archard equation were estimated for the four types of tests. The wear path ranged from 12.8 to 56,000 m and the applied load from 0.024 to 12,500 N; nevertheless, the relative wear values of the alloys agree within a factor of 2 or less among the four tests. The specific wear for the dry-sand/rubber-wheel and jaw crusher tests, representing three-body wear, is only about 4 pct of that of the slurry and pin tests, representing two-body wear. Based on test results and observations of wear scars, the conditions of high or low stress and open or closed system are not pertinent. The results raise serious questions about the usefulness of some laboratory wear tests and indicate a need for better correlations with field wear conditions.

The history of brittleness and spalling problems of white cast irons used for the grinding of min... more The history of brittleness and spalling problems of white cast irons used for the grinding of minerals is reviewed. Development of improved alloys was slow because of lack of meaningful laboratory tests. A new test developed by the Bureau of Mines, Department of the Interior, that simulates ballmill impact conditions is described. A spalling study was conducted jointly with the Special Irons Committee of the American Foundryman's Society. Specimens were cast into 3-inch balls from a commercial white iron containing 3 wt-pct C, 18 wt-pct Cr, and 1 wt-pct Mo. Eleven different heat treatments were used to provide a range of hardness, spalling resistance, and microstructure. In the test, balls were impacted against each other until they broke or lost over 100 g by spalling. The number of impacts to cause failure ranged from 5,000 to over 200,000. Heat-treatment was found to increase the spalling resistance up to 24 times over the as-cast condition. It is important to optimize both spalling resistance and abrasion resistance to match a particular application.

U.S. Bureau of Mines research is reported on spalling and abrasion of commercial grinding balls a... more U.S. Bureau of Mines research is reported on spalling and abrasion of commercial grinding balls and white cast irons, abrasion resistance of low-alloy steels, cast-on hard-surfacing, slurry wear of materials, and ball mill erosion-corrosion.

Minerals and Metallurgical Processing

As part of its research on wear of mining and mineral processing equipment, the US Bureau of Mine... more As part of its research on wear of mining and mineral processing equipment, the US Bureau of Mines evaluated the erosion -corrosion characteristics of 1f alloys in phosphoric acid waste water. Tests were conducted on .e. and 5-cm-diam specimens in 12- and 60-cm-diam ball mills by grinding phosphate rock in gypsum pond water with an initial pH of 1.6. For comparison, grinding tests also were conducted in tap water. Static corrosion tests in gypsum pond water also were carried out. For all alloys tested, the wear by erosion-corrosion was greater than the sum Of erosion plus static corrosion. A low-alloy, high-carbon steel and a high-manganese, nitrided stainless steel were the most cost-effective materials.

The new method for measuring wear developed by the Bureau of Mines, U.S. Department of the Interi... more The new method for measuring wear developed by the Bureau of Mines, U.S. Department of the Interior, was applied to an ore chute feeding a primary jaw crusher. The wear of reference specimens adjacent to each test specimen was used to correct for local variations in the wear intensity. After applying the corrections, the wear of randomly located duplicate specimens agreed within± 5 pct. Field tests on 24 steel, cast iron, and composite materials were compared with four types of laboratory abrasion tests. The pin test agreed reasonably well with field wear for all specimens except the hard facing and composite materials.

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Jul 15, 2023

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Oct 10, 2022

MS&amp;T22, Pittsburgh PA, October 8-12, 2022

High Temperature Corrosion of Materials

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Oct 10, 2022

Wear of Materials 1987, 1987

Mater Sci Eng a Struct Mater, 1999

Minerals and Metallurgical Processing

Presented by NETL at MS&T 19, 10/19

Novel cold spray zinc-based alloy coatings have been investigated for corrosion protection of API... more Novel cold spray zinc-based alloy coatings have been investigated for corrosion protection of API 5L low carbon steel pipelines used in transporting natural gas. These different zinc alloy coatings are designed for use to help prevent internal corrosion and improve the lifespan of steel pipelines via sacrificial anodic protection. The corrosion behavior of these cold deposited zinc alloy coatings was investigated in CO2 saturated 3.5 wt.% NaCl solutions under simulated natural gas pipeline conditions. Electrochemical tests were conducted at 25 and 40 °C to determine the polarization resistance and galvanic current between each coating and the steel substrate in the galvanic couple. Tests were conducted at atmospheric, 1 bar, pressure. The results indicate that use of these coatings has the potential to increase the lifespan of steel pipelines above what a zinc coating alone could provide. Introduction In the US, natural gas accounts for one third of the energy consumed [1]. The gas pipeline network consists of more than 210 individual pipeline systems and nearly 300,000 miles, Figure 1, which makes it the most the most extensive pipeline delivery system in the world [2] [3]. The majority of the line pipe in current service was installed in the 1950's and 1960's. These pipelines are made of high grade carbon steel regulated by the American Petroleum Institute (API) [3] [4]. Failure of this pipeline can cause disruption in service and gas release into the environment. Corrosion is a primary failure concern, as carbon steel does not resist corrosion particularly well. Developing inexpensive, practical methods to increase the life of new and existing pipelines is of significant importance. Natural gas pipelines are usually buried underground, which puts them in contact with potentially corrosive soils. Currently coatings and impressed current systems are used to protect the external pipe from corroding [5]. The impressed current method works by supplying a remote external anode with a direct current, with the soil acting as the electrolyte. However, this only protects the external surface of the pipeline. Natural gas consists primarily of methane (CH4); some hydrocarbons, water; and gases, such as carbon dioxide (CO2); and dissolved ions, such as Cl− [3] [6]. While designed to be dry, usually less than 7 lbs. of water per MMCF of gas, it is not unusual to find liquid water. It has been shown when CO2 dissolves in water it forms a corrosive solution that can cause severe internal corrosion [7]. When transporting natural gas that contains corrosive species, the internal pipe has neither an anode nor an abundant electrolyte on which an impressed current can be utilized, but rather pockets of localized areas of attack.

ABSTRACTHigh-entropy alloys (HEAs), are multicomponent alloys composed of at least five elements ... more ABSTRACTHigh-entropy alloys (HEAs), are multicomponent alloys composed of at least five elements with compositions of 5-35 atomic % for each element. These alloys are being investigated for corrosion protection of natural gas transmission pipelines by studying their behavior under aqueous acidic conditions. Electrochemical and immersion experiments were carried out in 3.5 weight % NaCl solution at pH 4 and 40°C. Oxygen was purged out from the solution by using CO2 as stripping gas. The electrochemical experiments included potentiodynamic and electrochemical impedance spectroscopy tests, used to calculate corrosion rates. Potentiodynamic polarization curves, including cyclic voltammograms, were used to explain active, active-passive, and passive regions of these alloys and susceptibility to localized corrosion. Surface characterization of the corroded samples were performed using scanning electron microscopy (SEM) and x-ray diffraction (XRD). The results of the immersion and electrochemical testing indicate that some of the HEAs have better corrosion performance than commercial alloys UNS N10276, UNS K03014, and UNS 31600.INTRODUCTIONResearch on multicomponent solid solutions in near-equal molar ratio helped to the development of high-entropy alloys (HEAs), a new family of alloys composed of at least five alloying elements with an atomic composition of 5-35 % each. HEAs can also be defined by a configurational entropy of mixing (?Sconf) of at least 1.5R, where R = 8.314 Jmol-1 K-1 is the gas constant. ?Sconf has the most predominant role on the total mixing entropy, and is calculated using Equation 1 for ideal and regular solutions. This equation is a good representation for liquid alloys and many solid alloys in the melting temperature range. Atomic fraction of element i is described as Xi.1-4equation>At a greater mixing entropy of an alloy, the formation of single-phase solid solutions is increased and the concentration of intermetallic compounds is minimized.1,3 High composition of several number of elements offer unique physical and metallurgical aspects with superior mechanical, electrochemical, magnetic characteristics.5

Presentation at MS&T 2023 titled "Effect of temperature and impurities on the oxidation ... more Presentation at MS&T 2023 titled "Effect of temperature and impurities on the oxidation behavior of Ni-based alloys in hot CO2-rich gases."

Presented by NETL at TMS 2020, 02/20

7th International sCO2 Power Cycles Symposium, Virtual, February 21-24, 2022

Presented by NETL at High Temperature Corrosion Gordon Research Conference, 07/19

Presented by NETL at 2019 Annual Project Review Meeting for Crosscutting, Rare Earth Elements, Ga... more Presented by NETL at 2019 Annual Project Review Meeting for Crosscutting, Rare Earth Elements, Gasification and Transformative Power Generation, 04/19

Presented by NETL at The Nuclear Materials Discovery and Qualification Initiative (NMDQi) Working... more Presented by NETL at The Nuclear Materials Discovery and Qualification Initiative (NMDQi) Working Meeting, 10/19

The effect of HCO3−(aq) on CO2 corrosion of carbon steel was investigated in deaerated 3.5 wt% Na... more The effect of HCO3−(aq) on CO2 corrosion of carbon steel was investigated in deaerated 3.5 wt% NaCl solutions at 30 °C from pH 3.96 to 7.15. In the CO2-saturated solutions, the pH was adjusted with different HCO3−(aq) concentrations, c[HCO3−(aq)]. The corrosion rate decreased by a factor of 2 as the pH and c[HCO3−(aq)] increased. The cathodic current density during polarization increased at higher pH with higher c[HCO3−(aq)], indicating that HCO3−(aq) acted as an additional hydrogen source for the hydrogen evolution reaction. As the pH increased, the active dissolution regions displayed similar anodic Tafel slopes and suggested a modified Bockris mechanism for the Fe oxidation reaction. The exchange current densities for the half reactions were calculated to study kinetics of the anodic and cathodic half reactions independently. The anodic exchange current density (j0,a) increased by one order of magnitude in the presence of CO2, indicating the involvement of CO2(aq) in the Fe oxidation reaction. As the pH and c[HCO3−(aq)] increased, the cathodic exchange current density (j0,c) decreased by a factor of 50 because the increase in j0,c[HCO3−(aq)] was not high enough to compensate the decline from the other hydrogen sources, especially j0,c[H+(aq)]; and j0,a decreased by a factor of 2.4 because HCO3−(aq) may have competed with CO2(aq) for the surface coverage and the increase in j0,a[HCO3−(aq)] could not compensate the decrease in j0,a[CO2(aq)]. It suggests that the reaction rate constant of HCO3−(aq) was smaller than CO2(aq) for the anodic half reaction and was smaller than H+(aq) for the cathodic half reaction. The XPS results verified that the corrosion products transitioned from iron carbonate to hydroxide as the pH increased while iron carbonate remained the major product. As the pH increased with HCO3−(aq), a second time constant was observed at lower frequencies of the electrochemical impedance spectroscopy (EIS) results.

While corrosion protection of the exterior of natural gas pipeline has developed to be a routine ... more While corrosion protection of the exterior of natural gas pipeline has developed to be a routine process, including use of coatings and cathodic impressed current systems; the protection of the inside of the pipe is not as straightforward. This work explores the use of sacrificial metal coatings to protect the pipes inner surface. Coatings, applied by techniques including hot dip, electroplated, and thermally spray, were applied to one side of low carbon steel plates which were similar in composition to an API 5L pipeline steel. Coatings evaluated included Zn, alloys of Zn (95 Zn-5 Al, 85 Zn- 15 Al), Al, and an alloy of 95 Al- 5 Mg. Existing models suggest that any residual water, which often contains chlorides and CO2 from the gas, will be the primary contributors to any corrosion. Gravimetric corrosion tests were conducted in autoclaves to simulate the partial pressure of CO2 found in a natural gas pipeline. A test condition of; immersed samples in a 3 ½ wt. % NaCl brine, with a pressure of 300 kPa (45 psig) of CO2, and a temperature of 40 °C; was used. Tests of 168 h duration with, and without, a nonconductive masking of the steel substrate were conducted. For the tests where the steel surfaces were exposed, on the back side of the coated side of the steel test coupons, did not show significant corrosion after the tests with any of the sacrificial coatings. For the Zn, or Zn alloy, samples; a layer of ZnCO3 formed on coated and uncoated steel surfaces. The results indicated that for these conditions, the thermally sprayed coatings showed less weight loss than the hot dipped or electroplated coatings, and the Zn alloy with 15% Al had less weight loss than either the pure Zn or the Zn with 5 % Al. Visual examination indicated that while AlMg alloy successfully protected the uncoated steel from corrosion, it showed heavy corrosion including pitting in these conditions.

The effect of gas speed on chromium loss, which is significant in a high temperature alloy’s life... more The effect of gas speed on chromium loss, which is significant in a high temperature alloy’s lifetime, was explored. Cr loss rate at 760 °C, in a combined air and 57 vol pct water environment with an apparent gas flow rate of 26.5 m·s-1 were measured for durations up to 1,000 h. Three alloys were investigated, HAYNES 230, 282, and Inconel 625. Samples were measured gravimetrically and examined via scanning electron microscopy. While the exposed surfaces were quite similar between the static and the moving samples, the degree of depletion of Cr in the metal near the surface and the gravimetric losses were significant. At 1,000 h, both the HAYNES 230 and Inconel 625 moving samples had lost about twice the mass of their respective static samples. Analysis showed Cr depletion was always deeper in the moving samples compared to their static equivalents.

Chromium is the principle basis of corrosion protection in most moderate-to-high temperature oxid... more Chromium is the principle basis of corrosion protection in most moderate-to-high temperature oxidation resistant alloys. The loss of Cr from an alloy is significate in its expected operational lifetime, as its loss can lead to beak-way oxidation. Gas flow rate is an important parameter in the loss of Cr. Most laboratory Cr evaporation experiments have used relatively low gas flow rates. In this research the Cr loss rate was investigated at 760 °C, in an air plus 57 vol pct water environment with an apparent gas flow rate of 26.5 m·sec-1. This speed was achieved by spinning the samples on the end of a disc in a gas filled, heated retort. Since secondary alloy additions can have an effect on chrome activity and diffusion, three nickel based alloys with similar (~21 wt pct) Cr levels were investigated. The alloys chosen were HAYNES 230, 282, and Inconel 625. Moving and static samples (hung near the moving samples) were exposed for times up to 1000 hrs. Samples were first measured gravimetrically and then the surfaces examined via SEM. Finally the samples were cross sectioned and examined via SEM with EDS to determine Cr depletion. Results show a noticeable difference for the IN 625 surface, as viewed via SEM, between the surface scale formed on the respective static and moving samples. The viewed surfaces of the HAYNES 230 and 282 samples did not show as substantial of a difference between each’s respective static and moving sample. The moving IN 625 sample showed both higher mass loss and deeper Cr depletion than the static sample. The HAYNES 282 showed the least mass change, both in the static and moving conditions. At 1000 hr the HAYNES 282 had near zero total mass change while the static sample had some mass gain. At 1000 hr both HAYNES 230 and the IN 625 moving samples had gained about twice as much mass as their respective static samples. Analysis showed the Cr depletion was deeper in all the moving samples, as compared to their respective static ones. The IN 625 had the deepest Cr depletion, followed by HAYNES 282, and then the HAYNES 230.

Internal metallic and non-metallic coatings are being considered as parts of answers to allow cur... more Internal metallic and non-metallic coatings are being considered as parts of answers to allow current natural gas transmission pipelines to safely batch transport a variety of products, including natural gas, carbon dioxide and hydrogen. Sacrificial anode coatings, that contain Zn, are being considered for internal corrosion protection of standard carbon steel pipeline as they are known to galvanically protect steel. However, this can lead to the creation and ingress of hydrogen into the line pipe material, resulting in increased susceptibility to cracking under high static and cyclic loads associated with both steady state as well as startup and shut down conditions. The current study simulates the conditions expected to be encountered in field by performing crack growth rate measurements under static and fatigue loading conditions on fracture mechanics-based specimen extracted from API 5L X-65 steel. The effect of cyclic loading frequency on fatigue crack growth rate (FCGR) and the effect of applied cathodic polarization on static crack growth rates (SCGR) was investigated in a 3.5% NaCl solution in contact with CO2 at 25°C. The partial pressure of CO2 (pCO2) was 101.325 kPa. The applied cathodic potentials were those associated with mixed potential of the Zn- based coatings.

Natural gas transmission pipelines are a known to leak and thus release methane which is a greenh... more Natural gas transmission pipelines are a known to leak and thus release methane which is a greenhouse gas (GHG). There are several mechanisms for these emissions, including venting of lines, mechanical damage, and corrosion failure. With the projected pipeline life being described as “virtually forever”, slow corrosive attack can be an issue. The corrosive failure can be by either the exterior or interior attack. While there are practices in place to protect the exterior of the pipelines, including organic coatings and impressed cathodic protection, these techniques are not practical for the pipe’s interior. While dry natural gas is considered non-corrosive, the maintenance/inspect process of pigging of pipelines typicality results in black corrosion deposits being removed. These corrosion deposits are most likely a result of inadvertent water reacting with residual carbon dioxide (CO2) forming carbonic acid and attacking the pipeline, particularly wherever this water pools. This research examined the use of sacrificial coatings on the interior of natural gas pipelines to protect the pipeline from corrosion. These tests simulated the case where trapped water is in the bottom of the pipeline. A typical natural gas pipeline can have 100 bar of pressure. The gas stream can have 3 to 4 vol % CO2. This can result in a CO2 partial pressure of 3 to 4 bars. NACE SP0106 says that CO2 at a partial pressure of greater than 2.1 bar in the presence of water is usually corrosive. Compression of the gas, which occurs every 40 to 100 miles, heats the gas which will accelerate the corrosion rate. The work examined the corrosion of an API 5L grade X65 steel in a test, 3 ½ wt. pct. NaCl solution with a 3.1 bar pressure of CO2 at 40 °C. Results of the corrosion rate of the bare steel were compared with that of several sacrificial metals, including Al and Zn. The corrosion rate of the steel coupled to sacrificial metals was measure for both parts of the couple.

The corrosion behavior of high-entropy alloys (HEAs) from the CoCrFeMnNi family was evaluated in ... more The corrosion behavior of high-entropy alloys (HEAs) from the CoCrFeMnNi family was evaluated in CO2 containing 3.5 weight percent sodium chloride (NaCl) at pH 4 and temperature of 40°C by electrochemical and immersion methods. Their corrosion parameters were compared to those of Hastelloy® C276 (UNS N10276) and stainless steel 316L (UNS 31600). Corrosion rates were determined by weight loss analysis and corrosion current methods for each of the alloys. During immersion testing experiments, HEA-1 (high Cr content) had the lowest corrosion rate and HEA-8 (no Cr content) underwent metal dissolution and exhibited the highest corrosion rate. On the other hand, after potentiodynamic polarization measurements, significant pitting corrosion was developed on the surface of all the alloys except HEA-8 and C276, where scanning electron microscopy (SEM) analyses depicted general corrosion. HEA-6 exhibited the lowest corrosion rate while HEA-2 had the highest. Scanning electron microscopy (SEM) analyses of the corroded surfaces after electrochemical testing revealed that HEA-8 underwent general corrosion while the rest of HEAs and stainless steel 316L underwent pitting corrosion. X-ray diffraction (XRD) on immersion testing samples revealed the presence of oxide-rich phases in formed corrosion products of HEA-8.

Research on new technologies in the field of advanced materials have contributed to the developme... more Research on new technologies in the field of advanced materials have contributed to the development of high-entropy alloys (HEAs), a relatively new family of multicomponent alloys composed of at least five alloying elements with an atomic composition of 5-35 % each by offering a configurational entropy of mixing ΔSconf of at least 1.5R, where R is the gas constant. The incorporation of a larger number of elements with high concentrations leads to new material properties by changing physical and metallurgical aspects that offer superior magnetic, mechanical, and electrochemical characteristics. Literature data indicate that the oxidation resistance of eight HEAs in the CoCrFeMnNi family was studied by monitoring mass change oxidation kinetics at 650°C and 750°C for 1100 hours in comparison with the performance of commercially available alloys, nickel-based superalloy 230 (N06230) and austenitic stainless steel 304H (S30409) [1]. Results from this investigation revealed greater oxidation resistance from some multicomponent alloys compared to 230 and 304H alloys; and it is influenced by HEAs Cr or Mn compositional dependence, gaining valuable knowledge for their future use in commercial applications. The purpose of this research was to evaluate the corrosion behavior of these advanced materials under aqueous acidic conditions by exposing the multicomponent alloys to immersion testing, and study their electrochemical kinetics versus the corrosion performance of Hastelloy® C276 (UNS N10276) and stainless steel 316L (UNS 31600). The HEAs selected are considered for corrosion protection applications of natural gas transmission pipelines. Weight loss analysis revealed the corrosion rates of these materials while changes on the metal surface were characterized by scanning electron microscopy (SEM) and x-ray diffraction (XRD). Potentiodynamic polarization curves elucidated active, active-passive, and passive regions of these alloys to determine the presence of localized corrosion. Experiments were carried out under deaerated aqueous conditions of 3.5 wt.% NaCl solutions at pH 4 and temperature of 40°C. Oxygen content is suppressed from the environment by using CO2 as stripping gas. Reference: G.R. Holcomb, J. Tylczak and C. Casey, JOM, 67 (2015) 2326-2339

The effect of hydrogen charging of carbon steel API 5L X65 (UNS K03014) used in natural gas pipel... more The effect of hydrogen charging of carbon steel API 5L X65 (UNS K03014) used in natural gas pipelines was investigated. Metal specimens were cathodically charged at potentials below Ecorr at 40°C in CO2-saturated 3.5 wt.% NaCl solution, pH 4 for 24 hours prior to carrying out potentiodynamic polarization and tensile tests. Electrochemical experiments were used to calculate corrosion rates and elucidate active, active-passive, and passive regions. Furthermore, fracture and fatigue of the alloy was determined at 1 × 10−6 s−1 strain rate. Surface characterization of the fractured and corroded samples was conducted using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Results from hydrogen embrittlement-induced specimens were compared to a parallel study of uncharged specimens to understand the effect of hydrogen cathodic charging on carbon steel API 5L X65.

Future technologies require structural materials resistant to environmental degradation in high-t... more Future technologies require structural materials resistant to environmental degradation in high-temperature CO2-rich environments. In this work, we exposed several commercially available Ni-based alloys (230, 263, 282, 617, 625, and 740H) to atmospheric pressure gases intended to simulate the compositions expected in future direct-fired supercritical CO2 power cycles. The alloys were exposed to 95% CO2 + 4% H2O + 1% O2 and the same gas containing 0.1% SO2 at temperatures of 600, 650, 700, 750, and 800 °C for 2500 h. With minor exceptions, chromia scales formed on all alloys at all temperatures in the SO2-free gas, yielding parabolic growth rates that followed an Arrhenius temperature dependence. Behavior in the SO2-containing gas was more complex. Generally, the alloys performed well at temperatures of 650, 750, and 800 °C. While some alloys further performed relatively well across the whole temperature range, several of the alloys experienced chromia failure resulting in non-protective duplex oxide scales and high oxidation rates, at temperatures of 600 and 700 °C. Deviation from protective behavior was associated with internal sulfide formation and, additionally for the case of 600 °C, external sulfate formation. Extensive carburization accompanied growth of the non-protective duplex oxide scales, which made it more difficult for the alloy to recover after initiation of the sulfur-induced accelerated corrosion process. The thermodynamic and kinetic factors influencing the accelerated corrosion in the presence of sulfur are discussed. The results suggest that caution is required when assessing compatibility of Ni-based alloys for CO₂-based systems when sulfur-based impurities are expected.

Future power plants will require Ni-based superalloys resistant to high-temperature corrosion in ... more Future power plants will require Ni-based superalloys resistant to high-temperature corrosion in CO2-rich environments containing impurities. In this work, several commercially available Ni-based alloys (617, 230, 625, 263, 740H) were exposed at 600°C, 650°C, 750°C and 1 atm to 95% CO2, 4% H2O, 1% O2 without/with 0.1% SO2 to simulate compositions expected in a direct-fired supercritical CO2 power cycle. The results indicate no effect of SO2 at 750°C, a small negative effect at 650°C, and a large negative effect at 600°C. Alloys exposed at the higher temperatures (650–750°C) formed thin Cr-rich oxide scales, whereas the lowest temperature (600°C) resulted in thicker scales consisting of non-protective oxides and sulfates. Thermodynamic analysis indicates this increased corrosion is associated with a transition in the stable compounds in contact with the gas. Understanding the factors that affect this transition will aid in the selection or design of alloys for future CO2-based power systems.

Future power systems require steels that resist corrosion in high temperature CO2 containing comb... more Future power systems require steels that resist corrosion in high temperature CO2 containing combustion products/impurities. Here we evaluate the corrosion behavior of several commercial steels exposed to 95% CO2-4 % H2O-1 % O2, with/without 0.1 % SO2, at 550 °C and 1 atm. High-Cr steels formed thin Cr-rich oxides and low-Cr steels thick Fe-rich oxides during SO2-free exposures. Additions of SO2 had little effect on low-Cr steels but enhanced corrosion of high-Cr steels, where S within the chromia scale led to its failure and subsequent Fe-rich oxide nodule growth. The results are rationalized by considering the thermodynamic and kinetic factors controlling the reaction.

Future power systems require steels that resist corrosion in high temperature CO₂ cont... more Future power systems require steels that resist corrosion in high temperature CO₂ containing combustion products/impurities. Here we evaluate the corrosion behavior of several commercial steels exposed to 95% CO₂-4 % H₂O-1 % O₂, with/without 0.1 % SO₂, at 550 °C and 1 atm. High-Cr steels formed thin Cr-rich oxides and low-Cr steels thick Fe-rich oxides during SO₂-free exposures. Additions of SO₂ had little effect on low-Cr steels but enhanced corrosion of high-Cr steels, where S within the chromia scale led to its failure and subsequent Fe-rich oxide nodule growth. Ultimately, the results are rationalized by considering the thermodynamic and kinetic factors controlling the reaction.

Next-generation power systems require structural alloys resistant to high-temperature oxidation i... more Next-generation power systems require structural alloys resistant to high-temperature oxidation in CO2 containing combustion impurities. Here we evaluate the oxidation performance of several commercial Ni alloys exposed to 95%CO2-4%H2O-1%O2, with/without 0.1% SO2, at 750 °C and 1 atm. All alloys formed protective chromia layers and showed no signs of carburization or sulfidation, and minimal chromia volatilization. The microstructural evolution of the alloy surface, secondary oxidants, and minor alloy additions all played a role in promoting protective chromia formation/growth. The results show that Ni alloys are promising candidates for high-temperature portions of next-generation CO2-based power systems.

Power cycles using supercritical CO2 (sCO2) as the working fluid are expected to offer significan... more Power cycles using supercritical CO2 (sCO2) as the working fluid are expected to offer significantly improved conversion efficiency and lower levelized cost of electricity over current power systems. In addition, sCO2 power cycles operated in a direct-fired configuration (where the combustion gases are used to turn the turbine) may allow for capture of 100% of the CO2 produced by combustion at almost no additional energy penalty. A broad materials evaluation effort is underway at the National Energy Technology Laboratory (NETL) to help enable direct-fired sCO2 power cycles as a promising next-generation energy conversion technology. Of primary interest is the corrosion behavior of structural alloys in the complex multi-oxidant environments expected for this application. In this study, the corrosion behavior of several candidate structural alloys was evaluated by simulating the conditions expected for the high-temperature regime of a direct sCO2 power cycle. Several commercial Fe (grades 22 and 91, 304, 310, 347H) and Ni (617, 230, 625, 740H, 282, 263) alloys were exposed at 1 atm and 550 °C (Fe alloys) or 750 °C (Ni alloys) to CO2 containing 4 vol% H2O and 1 vol% O2, with and without 0.1 vol% SO2. The alloys were massed at 500 h increments up to 2500 h to determine the oxidation kinetics. At 2500 h samples were removed from the test and characterized by XRD, SEM, and EDS, while duplicate samples continue to be exposed for longer times to assess for possible breakaway oxidation. Ni alloys all exhibited relatively low oxidation rates to 2500 h (<1 mg/cm2 in all cases) and XRD and SEM analyses revealed that Cr-rich oxides were the primary reaction products. For Fe alloys (current exposure time of 1500 h with tests ongoing), 304, 310, and 347H show minimal mass gains (<0.2 mg/cm2), while grade 91 and 22 show similar and more substantial mass gains (≈10 mg/cm2). In general, the presence of SO2 led to approximately twice the mass gain as the SO2-free condition for both Ni and Fe alloys. The results are used to assess the influence of impurities on the oxidation behavior of structural alloys in high-temperature CO2, and to evaluate the suitability of these alloys for direct sCO2 power cycles.

Future CO2 based power systems require steels resistant to corrosion in high-temperature CO2-rich... more Future CO2 based power systems require steels resistant to corrosion in high-temperature CO2-rich environments. Candidate 9Cr ferritic-martensitic steels degrade by surface oxidation and substrate carburization, both of which can be strongly affected by impurities in the CO2. Herein we studied Grade 91 steel exposed to 95%CO2-4%H2O-1%O2 with/without 0.1% SO2 at 1 atm and 550, 600, 650 °C for up to 3000 h to establish the temperature-dependence of these processes. SO2 showed little effect on oxidation at 550–600 °C but reduced carburization, while the combination of SO2 and faster alloy diffusion at 650 °C resulted in significant reduction in both oxidation and carburization.

Future direct-fired supercritical CO2 power cycles require steels resistant to oxidation/corrosio... more Future direct-fired supercritical CO2 power cycles require steels resistant to oxidation/corrosion in high-temperature CO2 environments containing various impurities. Herein we studied the oxidation behavior of 14 candidate steels in a simulated direct-fired CO2 power cycle environment consisting of 95% CO2, 4% H2O, 1% O2 with/without 0.1% SO2 at 1 atm and 550 °C, 600 °C, 650 °C for up to 2500 h. Steels with ≥ 11.5 wt% Cr exhibited at least partial coverage by Cr-rich oxide scales leading to a significant decrease in the oxidation rates in both gases. While SO2 had little effect on low-Cr steels that formed Fe-rich oxides, it generally worsened performance of high-Cr (> 11.5 wt%) steels by hindering the establishment of a protective Cr-rich oxide. This effect was most pronounced at the lowest temperature of 550 °C, which was attributed to strong preferential adsorption of sulfur-containing species within the oxide at relatively low temperatures.

The oxidation behavior of several Fe and Ni commercial alloys was evaluated in high-temperature e... more The oxidation behavior of several Fe and Ni commercial alloys was evaluated in high-temperature environments expected in next-generation supercritical carbon dioxide power cycles. The alloys were exposed to pure CO2 at 0.1 and 20 MPa and to CO2 containing H2O, O2, with and without SO2 at 0.1 MPa, at temperatures of 550°C (Fe alloys) and 700–750°C (Ni alloys). For comparison, the alloys were also exposed to air and supercritical steam. Low-Cr ferritic Fe alloys formed Fe-rich oxides leading to high oxidation rates in pure CO2, while high-Cr austenitic Fe alloys formed Cr-rich oxides leading to low oxidation rates. H2O and O2 impurities had negligible effect on the oxidation behavior of all Fe alloys. The addition of SO2 had negligible effect on the oxidation of ferritic Fe alloys, but significantly enhanced the rate for austenitic Fe alloys, where S in the oxide and underlying alloy contributed to the transition from Cr-rich to Fe-rich oxide growth. Ni alloys formed Cr-rich oxides and showed low oxidation rates in all CO2-containing environments which were very similar to those obtained in air and supercritical steam. Little or no effect of pressure was observed for any of the alloys exposed to pure CO2.

High-entropy alloys (HEAs), are multicomponent alloys composed of at least five elements with com... more High-entropy alloys (HEAs), are multicomponent alloys composed of at least five elements with compositions of 5-35 atomic % for each element. These alloys are being investigated for corrosion protection of natural gas transmission pipelines by studying their behavior under aqueous acidic conditions. Electrochemical and immersion experiments were carried out in 3.5 weight % NaCl solution at pH 4 and 40°C. Oxygen was purged out from the solution by using CO2 as stripping gas. The electrochemical experiments included potentiodynamic and electrochemical impedance spectroscopy tests, used to calculate corrosion rates. Potentiodynamic polarization curves, including cyclic voltammograms, were used to explain active, active-passive, and passive regions of these alloys and susceptibility to localized corrosion. Surface characterization of the corroded samples were performed using scanning electron microscopy (SEM) and x-ray diffraction (XRD). The results of the immersion and electrochemical testing indicate that some of the HEAs have better corrosion performance than commercial alloys UNS N10276, UNS K03014, and UNS 31600. INTRODUCTION Research on multicomponent solid solutions in near-equal molar ratio helped to the development of high-entropy alloys (HEAs), a new family of alloys composed of at least five alloying elements with an atomic composition of 5-35 % each. HEAs can also be defined by a configurational entropy of mixing (?Sconf) of at least 1.5R, where R = 8.314 Jmol-1 K-1 is the gas constant. ?Sconf has the most predominant role on the total mixing entropy, and is calculated using Equation 1 for ideal and regular solutions. This equation is a good representation for liquid alloys and many solid alloys in the melting temperature range. Atomic fraction of element i is described as Xi.1-4 equation> At a greater mixing entropy of an alloy, the formation of single-phase solid solutions is increased and the concentration of intermetallic compounds is minimized. 1,3 High composition of several number of elements offer unique physical and metallurgical aspects with superior mechanical, electrochemical, magnetic characteristics. 5

ABSTRACT Binary (Ni-Cr and Ni-Zn), and ternary (Ni-Co-Cr) Ni-based alloy coatings were electrodep... more ABSTRACT Binary (Ni-Cr and Ni-Zn), and ternary (Ni-Co-Cr) Ni-based alloy coatings were electrodeposited on carbon steel 1018 (UNS G10180). These metallic coatings are being investigated for use in providing corrosion protection of natural gas transmission pipelines by studying their behavior under aqueous acidic conditions. The corrosion resistance of the metallic coatings was investigated using immersion and electrochemical methods in a CO2-saturated solution of 3.5 wt.% NaCl at 40°C. Two types of electrochemical experiments were carried out: potentiodynamic and potentiostatic. The surface characterization of the investigated metallic coatings was performed before and after corrosion experiments using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray fluorescence (XRF). The effect of the coating composition on the corrosion performance of electrodeposited alloys in acidic aqueous conditions is discussed. INTRODUCTION Corrosion of mild steel in aqueous carbon dioxide (CO2)-containing solutions is associated with internal corrosion of oil and gas pipelines used for production and transportation. Although other factors such as temperature, presence of hydrogen sulphide (H2S), flow rates, material composition and exogenous ions also influence internal corrosion, the chemistry of H2O and CO2 is shown.1,2 Carbonic acid (H2CO3) is formed by the reaction of dissolved CO2 in water (Reaction [1]). Furthermore, H2CO3 dissociates according to reactions (2) and (3).(Equation-1)(Equation-2)(Equation-3)Metal dissolution proceeds with hydrogen evolution from reduction of dissociated hydrogen ions (H+) (Reaction [4]), H2O (Reaction [5]), H2CO3 (Reaction [6]), and bicarbonate ions (HCO3−) (Reaction [7]). The corrosion rate of the metal can depend upon mass transfer, pH, partial pressure of CO2, and temperature. On the other hand, corrosion of the metal can be limited by the reduction path from reactions (4) through (7).3,4(Equation-4)(Equation-5)(Equation-6)Corrosion control measures have been extensively used to protect the exterior surface of oil and gas pipelines to reduce the detrimental effects of environmental elements including type of soil, water, degree of aeration, pH, redox potential, resistivity, microbiological activity and soluble ionic species (salts and organics).5 Some of the most commonly used corrosion protection strategies involve protective coatings, cathodic protection, and inhibitors. Even though the internal composition of the environment is water-free by itself and non-corrosive, contaminants such as water and chlorides are accidentally introduced into the system creating a clear path to corrosion, and consequently affect pipeline integrity.

This disclosure provides alloy compositions comprising the main constituent elements iron, nickel... more This disclosure provides alloy compositions comprising the main constituent elements iron, nickel, cobalt, molybdenum, and chromium. In one embodiment, the alloy comprises 10.0 to 30.0 wt % iron; 30.0 to 60.0 wt % nickel; 10.0 to 25.0 wt % cobalt; 1.0 to 15.0 wt % molybdenum; 15.0 to 25.0 wt % chromium by weight; where the sum of iron and nickel is at least 50 wt %; and, where the balance comprises minor elements, the total amount of minor elements being about 5% or less by weight. The alloy compositions have use as coatings to protect metals and alloys from corrosion in extreme environments where corrosion is a major concern such as with exposure to sea water or sea water with CO₂.