Corrosion Of Austenitic Steel Research Articles

Accelerated corrosion tests of a contact pair austenitic stainless steel – titanium alloy

The results of accelerated corrosion tests of a pair of austenitic stainless steel — titanium alloy under conditions of elevated temperatures and high concentrations of corrosive agents are presented, conditions for the developing the mechanism of local corrosion being the same. The proposed approach included provoking the appearance of microstress concentrators by three-point loading of test samples with subsequent forced development of local types of corrosion through simultaneous exposure to an increased concentration of corrosive agents and temperatures at a fixed exposure in an autoclave. The results of modeling the corrosion process in a titanium alloy being in contact with stainless steel are assessed proceeding from the data obtained from metallographic studies of the state of surface layers of the metal and the morphology of corrosion products on prepared sections of the surface of templates cut from the samples under study. We considred a pair of steel 08Kh18N10T — titanium alloy VT-5. It is shown that the contact of samples under conditions of accelerated corrosion tests does not lead to a significant development of local types of corrosion of the titanium alloy. On the contrary, analysis of the state of the surface layers of the samples of stainless steel revealed the presence of deep corrosion pits, triggering the intergranular corrosion. In this case, corrosion of austenitic steel, both in the presence and in the absence of contact with titanium, proceeded in three stages: the initiation and fusion of pitting; formation of knife corrosion ulcers; propagation of intergranular cracks into the depth of steel. The proposed methodology of corrosion testing can be used to predict the possible nature of the development of metal corrosion under operating conditions that form local zones of static stresses in structural materials, and for prompt response to extend the design life of the equipment at thermal and nuclear power facilities.

Corrosion tests on austenitic samples with alumina and alumina-forming coatings in oxygen-containing stagnant Pb and turbulently flowing PbBi

Two differently produced alumina coatings (by pulsed laser deposition (PLD) and detonation gun (DG)) and one alumina-forming coating realised by pack cementation are proposed as a protection barrier against corrosion of austenitic steels in Pb and PbBi. Samples were tested in oxygen-controlled stagnant Pb (10−7 wt.%) at 480 °C and 550 °C for up to 10,000 h and in turbulently flowing (up to 1.6 m/s) PbBi eutectic at 490 °C with 10−9–10−8 wt.% oxygen for about 500 h. All exposed coatings showed a good behaviour in flowing PbBi and in stagnant Pb at around 480 °C independent of the oxygen content. At 550 °C, the PLD coating failed most probably due to incomplete coating of the sample, while the DG sample protected the base material.

Experimental investigation on corrosion of structural steels in molten Pb-Mg and LBE

• A comparative investigation on two F/M steels and two austenitic steels exposed to LBE and Pb 83 Mg 17 was conducted. • High temperature Pb-Mg results in slight dissolution corrosion in F/M steels and strong dissolution corrosion in austenitic steels. High temperature LBE causes oxidation in all structural steels. • Pb-Mg should be carefully considered if it will be deployed in future LFRs. Lead and its alloys are commonly used as coolant and liquid spallation neutron targets for advanced nuclear reactors and ADS systems. Pb-Mg alloy may be a potential coolant and maintain an acceptable corrosion rate without additional oxygen control in comparison with LBE. A comparative study on corrosion behavior of two F/M steels (SIMP, T91) and two austenitic steels (316L, 15-15Ti) in liquid Pb-Mg and LBE at 550°C for 1000h has been studied in this work. In Pb-Mg, F/M steels show slight dissolution corrosion and austenitic steels show severe dissolution corrosion. In LBE, all steels form oxide layers and a three-layer structure is observed in F/M steels.

Corrosion of Austenitic Steels and Nickel Alloys in Molten KNO3–NaNO3 at Different Temperatures: Role of Alloying Elements

Corrosion of Austenitic Steels and Nickel Alloys in Molten KNO3–NaNO3 at Different Temperatures: Role of Alloying Elements

Influence of Seawater Salinity on Corrosion of Austenitic Steel

Abstract Due to the paramagnetic properties and the ability to passivation, for the production of hulls of some vessels (mainly warships), corrosion-resistant (stainless) steels with austenitic structure are used. This article describes the influence of seawater salinity on selected corrosion properties of high-alloy steel X5CrNi 18-10 (304). The average salinity of the seas is taken as 3.5% content of sodium chloride. Corrosion rate of the tested material was evaluated in an aqueous solution of sodium chloride was evaluated. The NaCl concentration in corrosive solutions was 0.7%, 1.4%, 2.1%, 2.8%, 3.5%, 4.2%. Corrosion tests were performed using the potentiodynamic method. The range of electrochemical potential changes was Ecorr ±150 mV. Corrosion rate was assessed on the basis of corrosion current density measurements. Corrosion potential values against the saturated calomel electrode were also determined. Based on the obtained measurement results and non-parametric significance tests carried out, a significant influence of seawater salinity on the value of corrosion current density and corrosion potential was found. The highest value of corrosion current density (jcorr), and thus the highest corrosion rate, was recorded for 3.5% NaCl solution. In the concentration range from 0.7 to 3.5% NaCl in solution, the corrosion rate of austenitic steel increases. A further increase in salinity of electrolyte results in the inhibition of corrosion rate of steel. There is almost a full negative, linear correlation between the proportion of sodium chloride in the corrosive solution and the value of corrosion potential. Along with the rise in the salinity of seawater, increase the electrochemical activity, and thus the corrosion susceptibility, thus the corrosion susceptibility, of the austenitic steel X5CrNi 18-10 was observed.

Corrosion of Austenitic Steels and Their Components in Uranium-Containing Chloride Melts

The corrosion resistance of AISI 316L, 12Kh18N10T (analogue of AISI 321) austenitic stainless steels and their basic components (metallic iron, nickel, chromium, molybdenum) was investigated in the melts based on the NaCl–KCl equimolar mixture at 750 ºC. Austenitic stainless steels underwent high temperature sensitization, and it was shown that this phenomenon determined the intergranular type of the steel corrosion. It was demonstrated that the presence of uranium ions in the electrolyte intensified corrosion processes. Metallic molybdenum demonstrated the highest corrosion resistance among the construction materials studied.

Corrosion of Austenitic Steels and Their Components in Molten Nacl–Kcl–UCl3

The fused halides can be used for nuclear fuel reprocessing and as working media for molten salt nuclear reactors. However practical implementation of such technologies is limited by the problem of finding suitable corrosion resistant materials capable of long-term working in contact with molten salts. From the economical point of view the application of stainless steels as construction materials for the molten salt media is one of the most prospective ways. In the present study the corrosion behaviour of metallic iron, nickel, chromium, molybdenum, AISI 316L and 12Kh18N10T (analogue of AISI 321) austenitic steels was studied in NaCl–KCl–UCl3(1 wt.% U) melts at 750 ºC. Gravimetric measurements served as a basis for estimating corrosion resistance of studied materials. Quenched melts were analyzed using ICP-AES method. The surface of the alloy samples after corrosion tests was characterised using XRD, SEM and Х-ray microanalysis. The foils of corroded materials were examined by TEM. The corrosion rates of studied metals in NaCl–KCl–UCl3melt decrease in the following order: Cr>Fe>Ni>Mo, which correlates well with the formal standard potentials of metals in chloride melts indicating electrochemical nature of the corrosion processes. Molybdenum is the only corrosion resistant metal in the uranium-containing chloride melts and it can be used as a construction material for molten salt reactors. The major products of stainless steel corrosion in chloride melts are iron, chromium and manganese species. The surface of the corroded samples of austenitic stainless steels was depleted in manganese and chromium and enriched in nickel and molybdenum. Intergranular corrosion was observed for all types of austenitic steels. In terms of intensity and depth of the corrosion layer in NaCl–KCl–UCl3 the studied steels can be ranged in the order AISI 321>AISI 316L that correlates with the amount of excessive phases formed (figure). Figure 1

Corrosion in austenitic steels and nickel-based alloys caused by liquid tin at high temperature

Austenitic steels as well as nickel-based alloys were exposed to liquid tin, the former at nominally 500 and 700°C and the latter at nominally 700 and 1000°C, using sealed tube samples that were filled with liquid tin. The duration of the tests ranged from 25 to 100h. In the evaluation of the experimental findings, special emphasis is laid on the identification of principal corrosion modes and possible influences of the applied experimental technique, most notably non-uniform temperature across the sample capsules. Indicative corrosion rates are presented.

The Mechanism of Corrosion of Steel 304L in the Presence of Copper in Industrial Installations / Mechanizm Korozji Stali Austenitycznej 304L W Obecności Miedzi W Instalacjach Przemysłowych

This paper presents the mechanism of corrosion of austenitic steel in the presence of copper. It has been found that when corrosion occurs, the presence of copper in the corrosive solution in the neighbourhood of austenitic steel results in the intensification of the corrosion processes. In the macroscopic scale, austenitic steel constitutes a cathode, but since copper precipitates can deposit on it, the steel can locally pass to the active state and become an anode in the places where copper deposited, which leads to its local corrosion due to galvanic corrosion.

Corrosion of austenitic steels and their components in vanadium-containing chloride melts

The corrosion of austenitic 12Kh18N10T, 10Kh17N13M2T, and 03Kh17N14M3 steels and their components (Cr, Fe, Ni, Mo) in NaCl-KCl-VCl2 melts with 5 wt % V at 750°C is studied. The rates and mechanisms of corrosion of the materials under these conditions are determined. The processes that occur during contact of the metals and steels with vanadium-containing chloride electrolytes are investigated.

Corrosion of austenitic steel in leakage lithium

High-temperature lithium, which is used as the neutron source in the International Fusion Material Irradiation Facility, reacts with oxygen, nitrogen, and moisture in the atmosphere. We estimated which lithium compounds might be stable under environmental conditions by using chemical equilibrium calculations, then performed austenitic stainless steel corrosion tests with the selected lithium compounds. The lithium compounds (reagents) and a steel specimen were heated to 1120K in an Al2O3 Tammann crucible. After the test, the steel specimen was cleaned with alcohol and water and then weighed and metallurgically examined. We found that the steel was significantly corroded in Li3N, LiOH, and Li2O2 environments. Because Li2O2 is not stable according to the chemical equilibrium calculations, corrosion by Li3N and LiOH needs to be considered in high-temperature lithium applications.

Corrosion of Austenitic Steels and Their Components in Vanadium-Containing Chloride Melts

Corrosion behavior of stainless steel types AISI 316L, 316Ti and 321 and their components (iron, chromium, nickel and molybdenum) was studied at 750 0C in NaCl-KCl-VCl2 melts. It was found that iron, chromium and manganese species constitute the major corrosion products of austenitic steels and Fe2+, Cr2+, Ni2+, and Mo3+ ions are formed as a result of interaction of corresponded metal and vanadium-containing chloride melts. It was found that austenitic stainless steels are subjected to high temperature sensitization and this phenomenon determines the intergranular character of steel corrosion. Presence of vanadium ions in electrolyte leads to intensification of corrosion processes due to increased oxidation of electronegative steel components and alloy formation. Metallic molybdenum has highest corrosion resistance among studied construction materials.

Corrosion of Austenitic Steels and Their Components in Vanadium-Containing Chloride Melts

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Metallurgical study on corrosion of austenitic steels in molten salt LiF–BeF 2 (Flibe)

Static corrosion tests for SS304 and SS316L austenitic steels in high purity LiF–BeF 2 (Flibe) were carried out at 500 and 600 °C for 1000 h. After the exposure, the steel surfaces were corroded due to the fluoridation by HF dissolved in Flibe. The grain boundary of the steel surfaces was preferentially attacked. The mechanism of corrosion including selective intergranular attack was discussed. The corrosion rate of SS304 and SS316L in Flibe at 600 °C was estimated as 10.6 and 5.4 μm/year, respectively.

Austenitic steel corrosion in IGCC environment. Characterisation by photon and nuclear microprobes

An austenitic steel sample was treated simulating particular working conditions of an integrated gasification combined cycle (IGCC) power plant. Several classical characterisation techniques were used to investigate the oxide scales. In addition, micro-particle-induced X-ray emission (PIXE) and Rutherford backscattering spectrometry (RBS) analyses were performed and permit us to identify several phases constitutive of the oxide. Moreover, micro-X-ray absorption near edge structure (XANES) experiments allow us to determine the valence of the vanadium incorporated in the scale in the form of microscopic islets. The comparison of all these results leads to the proposal of a corrosion mechanism for this alloy.

Effect of stresses and strains on the intergranular corrosion of austenitic steels in nitric acid

We show that tensile stresses close to the yield limit and small strains (up to 5 %) facilitate an increase in the density of grain-boundary dislocations in sensitized austenitic steels 03Kh18N11, 08Kh18N10T, and 12Kh18N10T, create favorable conditions for repassivation of grain boundaries, and accelerate the intergranular corrosion (IC) of these steels in 50 % and 65 % solutions of nitric acid. The changes in the activation energy caused by stresses and strains indicate kinetic control of the dissolution of steel grain boundaries. This means that, in manufacturing and maintenance of stainless steel equipment used in nitric acid production, it is necessary to avoid stress concentration and reduce the IC susceptibility of the steels.

To the Corrosion of Austenitic Steel in Sodium Loops

We investigated whether it is possible to predict corrosion effects for austenitic steels exposed to liquid sodium with an analytical diffusion model The comparison between experimental measurement...

Corrosion of austenitic steels in molten sulphate deposits

Thermal analysis has been used to determine the melting behaviour of alkali metal sulphate deposits typical of those found on superheater tubes in coal-fired power station boilers. Additions of 5–30 m/o Fe 2(SO 4) 2 to Na 2SO 4K 2SO 4 mixtures under a simulated flue gas (N 2 + 15 v/o CO 2 + 1 v/o O 2 + 0.3 v/o SO 2) are shown to reduce the melting point from 820°C to below 550°C. Alkali-iron trisulphates are formed which re-solidify on heating above 720°C by decomposition of Fe 2(SO 4) 3 at low thermodynamic activity. It is suggested that the effect of heat flux and SO 3 potential gradient on the melting behaviour of a superheater deposit could account for the observed ‘bell-shaped’ temperature dependence of corrosion rate in the range 550–750°C. Results are presented of laboratory corrosion tests on three commercial austenitic stainless steels using a melt of composition 74 m/o Na 2SO 4 + 20 m/o K 2SO 4 + 6 m/o Fe 2 (SO 4) 3. A model is proposed for corrosion by an acid fluxing mechanism involving refractory metal alloy elements in the steels. The model offers a quantitative basis for prediction of fireside corrosion resistance in coal-fired boilers, and a comparison of relative corrosion rates of a range of steels in laboratory tests, probe trials and service performance confirms the validity of the present model.

Intercrystalline corrosion of austenitic steels with different amounts of chromium, nitrogen, and carbon

1. The relative effect of nitrogen on the susceptibility of steels Kh(18-27)N20 to ICC is substantially greater than that of carbon. This is evident at nitrogen concentrations larger than the carbon concentration. 2. Chromium increases the resistance to ICC of nitrogen-containing steels more than that of carbon steels.

Effect of chromium and carbon on the susceptibility of austenitic steels to intercrystalline corrosion

1. In the lower region of the dangerous temperature range the development of intercrystalline corrosion in austenitic steels does not depend on the carbon concentration and is accelerated with increasing chromium concentrations. These results cannot be explained by the impoverishment theory. They are quite well explained if we assume that susceptibility to intercrystalline corrosion in the lower region of the dangerous temperature range depends on the diffusion rate of chromium. 2. In the upper region of the dangerous temperature range the time necessary for development of intercrystalline corrosion decreases with increasing carbon concentrations; it increases somewhat with increasing chromium concentrations.