Long-term Corrosion Tests Research Articles

ZrO 2 and TiO 2 membranes for nanofiltration and pervaporation : Part 1. Preparation and characterization of a corrosion-resistant ZrO 2 nanofiltration membrane with a MWCO < 300

This paper reports the sol–gel preparation and subsequent characterization of ceramic multilayer membranes, comprising a mesoporous γ-Al 2O 3 or ZrO 2 interlayer and a microporous ZrO 2 toplayer. The optimized membranes show a molecular weight cut-off (MWCO) of 200–300 in standard nanofiltration tests after firing the ZrO 2 toplayer at 400 °C. For the all-ZrO 2 membrane, a detailed study was made of its corrosion behaviour. PEG-retention, MWCO and permeability were studied in dynamic corrosion tests using aqueous solutions both at low and high pH values. Long-term corrosion tests (4 weeks) at successive pH values of 2, 13 and 1 demonstrated no significant loss in performance for the membranes showing a MWCO in the range 200–300.

Inhibition Effect of Rhodanine for Corrosion of Mild Steel in Hydrochloric Acid Solution

The inhibition effect of Rhodanine on the corrosion performance of mild steel (MS) was studied in 0.5 M HCl solution. For this purpose, potentiodynamic polarization, electrochemical impedance spectroscopy, and long-term corrosion tests including hydrogen evolution and change in open-cirquit potential during immersion time were used. To determine activation energy of corrosion process, potentiodynamic polarization curves were also obtained in a temperature range from 298 to 328 K. The results show that Rhodanine effectively inhibits the MS corrosion in hydrochloric acid solution.

Corrosion of Be-based fusion-specific waste materials

Future fusion power reactors will generate activated metallic waste. Although the majority of this waste will be cleared or recycled, there will remain an important volume for which the solution may be surface or geological disposal. In current reactor concepts, the most important remaining fractions will be constituted by neutron irradiated beryllium, EUROFER, Li 4SiO 4, and tungsten. In particular, the beryllium presents a disposal problem because of its chemotoxicity in addition to its radiotoxicity. In order to support waste management decisions and environmental impact studies of fusion waste, data are needed on the corrosion of metallic wastes in a disposal environment. Therefore, we started a research programme aimed at providing such data. In a first phase, we focus on the corrosion of beryllium in argillaceous and cementitious environments. In these environments, the main form of corrosion attack on beryllium is pitting. To determine the susceptibility of Be to pitting, we used both short-term (potentiodynamic polarisation measurements) and long-term corrosion tests (monitoring the evolution of the corrosion potential over extended periods of time).

High temperature corrosion properties of SiNx and CrNx coatings deposited by IBAD method

SiNx and CrNx coatings (thickness 1–2 μm) were deposited by IBAD method at a nitrogen ions energy of 90 keV on low-alloy, AISI 310 and 316 substrate. The samples were subjected to long-term high temperature corrosion tests at cycled reducing–oxidizing atmosphere and in air. Corrosion rate was evaluated gravimetrically. The corrosion rate of coated alloy steels was significantly decreased at temperatures up to 800 °C. At 900 °C exposure the nitrides were subjected to fast decomposition and oxidation.

Pitting Resistance of Diffusion-Alloyed Carbon Steels

Pitting corrosion is a dangerous type of corrosion fracture of metals observed, as a rule, in solutions containing oxidizers (e.g, oxygen) and, at the same time, activating chlorine ions and ions of other halogens. In this case, bounded regions of the metal suffer fracture. However, since the surface damaged by pitting plays the role of an anode, the corrosion process runs at a high rate due to the contact with the remaining part of the surface playing the role of a practically nonpolarized cathode. This leads to the formation of deep point defects and pits. The principal electrochemical condition required for the development of pitting is the shift of potential to a value more positive than a certain critical value called the potential of pitting formation EPT . According to the generalized experimental data, pitting corrosion is typical of the metals and alloys readily susceptible to passivation, i.e., of iron, stainless steels, aluminum and its alloys, titanium, etc. [1–5]. The resistance of metals and alloys to this type of corrosion is determined, on one hand, by the nature, composition, structure, and state of the surface and, on the other hand, by the solution, its composition (i.e., aggressive ions), and temperature. In the present work, to study the pitting resistance of carbide layers obtained on 35, 45, and U7A steels after treatment according to the technology of diffusion carbide surface alloying (DCSA), the specimens were subjected to electrochemical and long-term corrosion tests in chloride-containing solutions.

Strain corrosion of glass fibre-reinforced plastics pipes

In this contribution, results of long-term strain corrosion tests on glass fiber reinforced unsaturated polyester (GRP) pipe ring samples are reported. The pipe sections tested had a nominal diameter of 500 mm, an external diameter of about 520 mm, and a wall thickness of about 11 mm. The pipes had been produced by a filament winding process. The nominal ring stiffness was 10 000 N/m 2. In the inverse creep tests, each ring section was subjected to a specified constant diametric deflection, which was applied by a deformation-controlled device constructed for the purpose. The samples were exposed to 5% sulfuric acid on the inside of the pipe at the bottom zone of the ring. Stress relaxation tests were carried out under specified constant diametric deflection up to the failure of the sample. At the beginning of each test, the equivalent diametric compressive force in the samples was measured and, in addition, the time to failure of each sample was recorded. For long-term extrapolation of the experimental data, a regression analysis was used and the trend of relative vertical deflection versus time to failure of test samples was established. The long-term 1000 h tests showed that the deformation capacity of the GRP pipe section in acid environment would be reduced by about 75% compared with the deformation at break of the dry samples under short-term static loading. The theoretical correlation showed that under the influence of constant diametric deflection and sulfuric acid, the maximum strain after 1000 h would be reduced. Furthermore, the long-term extrapolation showed a strain at failure after 50 years under continuous exposure to the acid environment of less than 0.2%.

Corrosion properties of alumina and titania NF membranes

The chemical stability of multilayer alumina and titania nanofiltration (NF) membranes, prepared by a sol–gel procedure was investigated. The membranes have toplayers of γ-AlOOH fired at 400 °C, anatase–TiO 2 fired at 300 °C and anatase–TiO 2 fired at 450 °C, respectively. The solvent stability of the membranes was proven in a series of stability tests with different types of organic solvents. In order to provide information about the corrosion properties, the membrane performance (PEG-retention, molecular weight cut-off (MWCO), permeability) was studied in a series of dynamic corrosion tests with aqueous solutions at low pH (HNO 3) and at high pH (NaOH). For the membrane with a γ-AlOOH toplayer (low crystallinity), the MWCO increased from 200 to 1700 after 7 days of operation at pH 2, indicating serious membrane corrosion. For the anatase–TiO 2 membrane fired at 300 °C (low crystallinity), the MWCO increased from 200 to 800 at pH 2. On the contrary, corrosion tests performed with the highly crystalline anatase–TiO 2 membrane fired at 450 °C demonstrated no significant loss in membrane performance in the pH range studied (1.5–13). Long-term corrosion tests (6 weeks) at pH 2 and 1.5 confirmed the high corrosion resistance for this type of NF membrane.

Grouts for Bonded Post-Tensioning in Corrosive Environments

Problems with corrosion of prestressing steel in post-tensioned structures due to inadequate grouting have become more apparent in recent years. To improve grouting practices, a series of fresh property tests, accelerated corrosion tests, simulated field tests, and long-term corrosion tests were used in this study to develop optimum grouts for post-tensioning. Grouts possessing adequate workability and bleed resistance were tested in an accelerated corrosion test to evaluate relative corrosion protection properties. This paper focuses on the accelerated corrosion test results. The most promising of these grouts were then tested for placeability under simulated field conditions. A fly ash grout and a thixotropic grout are recommended from this testing program. Fluidity, bleed, and corrosion resistance data was also acquired for a number of different combinations of pozzolans and admixtures.

Corrosion Behavior of Zinc-Nickel Alloy Electrodeposited Coatings

Abstract Various types of zinc-electrocoated steel sheets are used to improve the durability of car bodies. Among these coatings, the Zn-Ni alloy has higher corrosion resistance than pure Zn, as well as better welding and painting properties. The corrosion mechanism of the Zn-Ni alloy has been investigated mainly on the basis of accelerated tests and electrochemical measurements. There are few data about long-term corrosion tests. In the present study, the behavior of unpainted Zn-Ni alloy coated steel was studied during 3 years of exposure in industrial and marine environments. Electrochemical impedance spectroscopy (EIS) and surface analysis (scanning electron microscopy [SEM] and Auger electron spectroscopy [AES]) were the experimental techniques used. Long-term atmospheric corrosion mechanism of Zn-Ni coatings was discussed and compared with that proposed based on short-term tests.

Long-term corrosion tests on Nd–Fe–B sintered magnets

Long-term corrosion tests were performed on sintered magnets in an environment similar to their working conditions. It was found that the corrosion process proceeds faster for magnets containing higher Nd contents. A small degree of oxidation slows down the corrosion rate and improves the corrosion resistance. However, high oxidation of magnets leads to degradation of the microstructure and the magnetic properties during their subsequent service. Small oxygen contents, which improve the resistance to oxidation, do not affect the magnetic properties. The critical oxygen concentration, which causes deterioration of the properties, depends on both the Nd content and the solute elements added to the starting alloy. Additions of Co, Al, Zr, C or Cu substantially improve the resistance to atmospheric corrosion.

Passive Films and Blistering of Titanium

AbstractCoupons of titanium alloys under consideration as components of the Engineered Barrier System in the proposed repository at Yucca Mountain have been evaluatedfor their passive film composition and stability. Oxide depths and compositions on specimens exposed in long-term corrosion testing for one year were determined with x-ray photoemission spectroscopy. The specimens removed from long-term testing, as well as separate coupons polarized cathodically in an electrochemical cell, exhibited blistering associated with hydride formation in both scanning electron microscopy and atomic force microscopy.

A high performance Nd-Fe-B magnet with improved corrosion resistance

Various alloy modifications have been examined in order to improve the corrosion resistance and temperature stability of Nd-Fe-B magnets. Such alloy modifications are generally accompanied by a reduction in magnetic properties. Therefore, modifications which satisfy the criteria for both high magnetic properties (B/sub r/ and H/sub cj/) and good corrosion resistance are desired. It is found that when the three elements Co, Al, and Zr are simultaneously substituted for Fe in Nd-(Dy)-Fe-B magnets, both the corrosion resistance and the magnetic properties are significantly improved. The optimum Zr content is about 1.0 wt.%. A long-term (100 days) corrosion test in an autoclave environment has not disintegrated or attacked the surface of some Nd-(Dy)-Fe-Co-B-Al-Zr magnets. This indicates that corrosion-free high-performance magnets can be readily produced from Nd-(Dy)-Fe-Co-B-Al-Zr.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Demands for turbo-molecular pumps in the aluminium etching process

Turbo-molecular pumps used in etching processes have to fulfil special demands concerning corrosion stability. The rotor and stator are usually manufactured out of aluminium alloys. Chlorine containing etching gases such as Cl 2, BCl 3 or CCl 4 strongly attack the rotor and stator. The problem can be solved by coating with corrosion-resistant layers. We tested different coatings in an extreme long-term corrosion test by pumping Cl 2 enhanced by plasma. The nickel coating and Al 2O 3 layer produced in standard oxidation processes are not suitable for this application. Al 2O 3 layers produced by a new anodization process in aqueous electrolyte are very effective. After the 1000 h corrosion test, there was no visible attack.

A Novel Corrosion Test Cell for Predicting the Long-Term Corrosion Behavior of Metal Aerosol Containers

Abstract A transparent test cell that can be pressurized by laboratory or commercial propellant filling equipment has been designed for electrochemical corrosion testing with potentiodynamic scanning (PDS). PDS data from this cell are used to predict the outcome of long-term aerosol container corrosion tests. The analytical method for interpreting PDS data to make a prediction is outlined, and correlations between the predictions and storage test results are demonstrated for (1) oil in water (o/w) emulsions, (2) water in oil (w/o) emulsions, (3) water base formulas, (4) alcohol-water base formulas, and (5) high-viscosity gel formulas.

Long-term corrosion tests of materials for thermal decomposition of sulphuric acid

The corrosion resistance of tubes of Incoloy 800 and AISI 310 SS has been studied in a mixture of air and H 2SO 4 vapours at 1 bar pressure. The duration of the test was one year (8500 h). The temperatures of the tubes ranged from 400 to 700°C for SS AISI 310 and from 400 to 900°C for Incoloy 800. The extent of the attack was determined by measuring the scale thickness and the penetration depth on cross-sections of samples taken from several zones of the tubes. X-ray diffraction and S.E.M. X-ray microanalysis techniques were used.

Long-term high-velocity oxidation and hot corrosion testing of several NiCrAl and FeCrAl base oxide dispersion strengthened alloys

Several oxide dispersion strengthened (ODS) alloys have been tested for cyclic, long-term, high gas-velocity resistance to oxidation at 1100°C and hot corrosion at 900°C. Both nominally Ni-16Cr-4Al and Fe-20Cr-4.5Al ODS alloys were subjected up to ∼2500 cycles, where each cycle consisted of 1 hr in a hot, Mach 0.3 combusted gas stream followed by a 3-min quench in an ambient temperature, Mach 0.3 air blast. For comparison to existing technology, a coated superalloy was simultaneously tested. The ODS iron alloy exhibited clearly superior behavior, surviving ∼3800 oxidation and ∼2300 hot corrosion cycles essentially unscathed. While the ODS nickel alloys exhibited adequate oxidation resistance, the long-term hot corrosion resistance could be marginal, since the best life for such alloys under these conditions was only ∼1100 cycles. However, the hot corrosion resistance of the ODS Ni-base alloys is excellent in comparison to that of traditional superalloys.

A method for testing the corrodibility ofheat-affected zones in steel

A new method for testing the corrodibility of heat-affected zones (h.a.z.) has been developed. Test bars with different heat-affected zones are prepared according to the Norén Weld Hardening test, and submitted to potentiostatically controlled anodic dissolution. It has been observed that in sea-water, the corrosion rate of the h.a.z. in mild steel increases when the Mn content of the steel increases, or when the heat input equivalent used in welding decreases. These results have been verified by long-term corrosion tests of welded plates.