Corrosion Of Ferritic Stainless Steels Research Articles

Elucidating the effect of titanium alloying on the pitting corrosion of ferritic stainless steel

Ferritic stainless steels have been utilized in marine atmosphere and are found to be susceptible to pitting corrosion in our field investigation. Alloying is an important to modify the passive film on the surface and improve the pitting corrosion resistance. Nevertheless, how the addition of titanium modifies the passive film and affects the pitting corrosion resistance of ferritic stainless steels remain controversial. This study has elucidated these topics through microstructure analysis and corrosion properties analysis. The results demonstrate that titanium addition increases the pitting potential almost linearly. Titanium forms TiO2 in the passive film and reduces defect density of the passive film. Moreover, titanium addition induces the precipitation of the Laves phase, which promotes micro-galvanic corrosion. For the titanium-alloyed ferritic stainless steels, pitting corrosion predominantly occurs in the ferrite phase adjacent to the Laves phase. The influence mechanism of titanium on the pitting corrosion of the ferritic stainless steel has been established, which takes micro-galvanic corrosion induced by titanium addition into account.

A Combined Experimental and Computational Approach to Study Crevice Corrosion of Stainless Steels

In the present work, a dual experimental and computational technique is used to study crevice corrosion of ferritic stainless steels in chloride-containing media. A specifically designed three-electrode set-up is developed to monitor current and potential during the incubation, initiation and propagation stages. At the same time, a 3D finite element model is implemented to examine the galvanic coupling prevailing in the experimental set-up and to provide a mechanistic interpretation of the obtained results. The asymptotic current and potential measured at the end of the experiments are thought to be more realistic indicators of crevice corrosion kinetics than the commonly used depassivation pH. The technique also allows highlighting several physicochemical effects including chloride concentration, pH, temperature as well as the effect of surface pretreatment. Finally, an in-depth examination of the simulated current and potential distributions inside the crevice reveals that any extension of the propagation outside the confined geometry will report the ohmic drop out of the crevice, which radically impacts the initiation and propagation modes.

Inhibitory Effect of Ethanolic Extract of Propolis on Corrosion of Ferritic Stainless Steel in Chloride Media

This work evaluates the inhibitory effect of ethanolic extract of propolis (EEP) on the corrosion of AISI 409 stainless steel (SS) in chloride media. Additions of 100, 200, and 500 μL of EEP in an aqueous sodium chloride solution were performed. The inhibitory effect on the SS was evaluated using electrochemical impedance spectroscopy (EIS) measurements up to 720 hours in immersion. EEP additions of 200 μL and 500 μL increased the polarization resistance of the SS. After 720 hours of immersion, the highest impedance was identified for the SS in solution with 500 μL of EEP. The maximum inhibition efficiency observed for addition of 500 μL of EEP in solution was 98.1 %, after 360 h of immersion.

Temperature dependence of corrosion of ferritic stainless steel in dual atmosphere at 600–800 °C

The ferritic stainless steel AISI 441 (EN 1.4509) is exposed for 1000 h to air - 3% H2O on one side and to Ar - 5% H2 – 3% H2O on the other at temperatures 600, 700, and 800 °C. Conditions are chosen to mimic the environment of metallic interconnects in an operating solid oxide fuel cell (SOFC). At 600 °C, ∼25 μm thick Fe2O3/(Fe,Cr)3O4 forms on large parts of the air side of the samples. Reference samples exposed to air - 3% H2O on both sides form thin protective layers of (Cr,Mn)3O4/Cr2O3 at the same temperature. At higher temperatures, 700 and 800 °C, all samples form protective layers of (Cr,Mn)3O4/Cr2O3 regardless of exposure to single or dual atmosphere. It is concluded that corrosion resistance in a dual atmosphere has an inverse dependence on temperature. Different hypotheses for the underlying cause for the dual atmosphere effect are discussed and compared to the experimental data.

Initiation of Localized Corrosion of Ferritic Stainless Steels by Using the Liquid-Phase Ion Gun Technique

The initiation of localized corrosion of types 430 and 443J1 ferritic stainless steels was evaluated in 0.15 mol dm−3 Na2SO4 solution. A liquid-phase ion gun (LPIG), a silver microelectrode covered with a silver chloride layer, was cathodically polarized to generate Cl− in the vicinity of the stainless steel polarized at 0.4 VSSE. Contact of the stainless steel surface with the Cl−-concentrated environment by the LPIG operation induced a rapid increase in anodic current flow through the stainless steel electrode after the induction period td and consumption of the cathodic electric charge Qd by the LPIG microelectrode. Numerical modeling using the LPIG microelectrode current for td gave a critical Cl− concentration [Cl−]d needed for the initiation of localized corrosion. These parameters obtained by LPIG tests showed that type 443J1 stainless steel was superior to type 430 stainless steel in localized corrosion resistance. AES depth profiling of the stainless steel surfaces after the LPIG operation revealed enrichment of Cl in the outermost oxide film as well as decreased film thickness. The mechanism of degradation of the stainless steel surface due to contact with the Cl−-concentrated solution is discussed. The adsorption of Cl− on the oxide surface is thought to be a trigger of the oxide degradation.

Effect of Sn on the Pitting Corrosion Behavior of Ultra‐Purified 17% Cr Ferritic Stainless Steel

The influence of Sn on pitting corrosion of ferritic stainless steels has been investigated by AC and DC electrochemical methods in 3.5 wt% NaCl and gravimetric tests in 6 wt% FeCl3 at 25 °C. 0.14 wt% Sn addition can improve pitting potential, while excessive addition (about 0.33 wt%) can deteriorate pitting corrosion resistance. Sn‐bearing steels have higher passive film resistance and faster growth rate of more compact passive film, in which the charge carrier density is reduced probably due to the presence of SnO2. Dissolved Sn2+ can inhibit elementary anodic reactions. Therefore, the content of Sn should be optimized within 0.1–0.23 wt% to obtain better corrosion resistance.

Literature Review on Analysis of Sensitization and Corrosion of Ferritic Stainless Steel (FSS) by Different Welding Processes

This paper deals with the review of different literature. The review focuses light on analysis of sensitization and corrosion by the different authors for controlling sensitization and corrosion in ferritic stainless steel by using different welding processes. Besides the problem of low ductility and poor toughness of ferritic stainless steel, welds due to the microstructures characteristics of the weld section as a result of weld heat input rate and heat transfer rate factor , susceptibility to intergranular corrosion caused by the depletion of the chromium content of the weld matrix particularly in the HAZ is a major concern limiting the full deployment of the material in certain engineering application regardless its attractive economics combined with moderate strength and excellent corrosion characteristics of AISI 409 M. Ferritic stainless steel during welding (TIG,MIG, and SMAW) have been investigated. Its sensitization and corrosion can be evaluated by chemical exposure of the weld cross section. Then the characteristics of sensitization and corrosion can be analyzed using scanned electron microscope. This review concluded that variation in heat input resulted in significant changes in the mechanical properties of the weld which results on the sensitization and corrosion.

High-Temperature, Dual-Atmosphere Corrosion of Solid-Oxide Fuel Cell Interconnects

High-temperature corrosion of ferritic stainless steel (FSS) surfaces can be accelerated and anomalous when it is simultaneously subjected to different gaseous environments, e.g., when separating fuel (hydrogen) and oxidant (air) streams, in comparison with single-atmosphere exposures, e.g., air only. This so-called “dual-atmosphere” exposure is realized in many energy-conversion systems including turbines, boilers, gasifiers, heat exchangers, and particularly in intermediate temperature (600–800°C) planar solid-oxide fuel cell (SOFC) stacks. It is generally accepted that hydrogen transport through the FSS (plate or tube) and its subsequent integration into the growing air-side surface oxide layer can promote accelerated and anomalous corrosion—relative to single-atmosphere exposure—via defect chemistry changes, such as increased cation vacancy concentrations, decreased oxygen activity, and steam formation within the growing surface oxide layers. Establishment of a continuous and dense surface oxide layer on the fuel side of the FSS can inhibit hydrogen transport and the associated effects on the air side. Minor differences in FSS composition, microstructure, and surface conditions can all have dramatic influences on dual-atmosphere corrosion behaviors. This article reviews high-temperature, dual-atmosphere corrosion phenomena and discusses implications for SOFC stacks, related applications, and future research.

Galvanic Corrosion of Ferritic Stainless Steels Used for Dental Magnetic Attachments in Contact with an Iron-platinum Magnet

This study was an examination of the galvanic corrosion of ferritic stainless steels, namely SUS 444, SUS XM27, and SUS 447J1, in contact with a Fe-Pt magnet. The surface area ratio of each stainless steel to the Fe-Pt magnet was set at 1/1 or 1/10. Galvanic corrosion between the stainless steels and the magnet was evaluated by the amount of released ions and the electrochemical properties in 0.9% NaCl solution. Although each stainless steel showed sufficient corrosion resistance for clinical use, the amount of ions released from each tended to increase when the stainless steel was in contact with the magnet. When the surface area ratio was reduced to 1/10, the amount of Fe ions released from the stainless steels increased significantly more than when there was no contact. Since contact with the magnet which possessed an extremely noble potential created a very corrosive environment for the stainless steels, 447J1 was thus the recommended choice against a corrosion exposure as such.

Effect of Heat History on the Corrosion of Ferritic Stainless Steels Used for Dental Magnetic Attachments

This study investigated the effect of heat history on the corrosion of keepers used for dental magnetic attachments. Ferritic stainless steels of SUS 444 and 447J1 were prepared with heat treatments in the temperature range of 550-850 degrees C for 1-5 hours. The stainless steels were electrochemically and metallurgically examined by anodic polarization curves in a 0.9% NaCl solution and by microstructural observation using an electron probe microanalyzer with WDS. Heating both kinds of stainless steel at 650-750 degrees C for two hours or more led to the deterioration of their corrosion resistance. For example, there was evidence of a reduction in the breakdown potentials and an increase in the current densities of the anodic polarization curves. These phenomena were attributed mainly to the precipitation of the sigma (FeCr) or chi (Fe18Cr6Mo5) phase, which sometimes resulted in intergranular corrosion. When dental alloys are cast in investment molds embedding the keepers, the heat time required for thermal expansion of the molds should be kept under one hour.

Corrosion of ferritic stainless steel during metal-organic chemical vapour deposition growth using a fluorinated precursor

The growth of Ce 1−xGd xO 2−x 2 films, which are of interest as electrolytes in solid oxide fuel cells, by metal-organic chemical vapour deposition has been studied. The precursors [[Ce(fod) 3] 2(tetraglyme)]and [*lcub;Gd(tmhd) 3] 2(tetraglyme)](where fod-H is 1,1,1,2,2,3,3-heptanuoro-7,7-dimethyloctane-4,6-dione, tmhd-H is 2,2,6,6-tetramethyl-3,5-heptanedione and tetraglyme is tetraethylene glycol dimethyl ether) have been used. Type 430 ferritic stainless steel was used as the substrate. Although the overlayer thickness appeared to be substantial, cross-sectional analysis revealed an intermediate oxide layer had formed. This paper details the experimental work used to ascertain the conditions that caused oxidation. A corrosion mechanism based on existing theories is presented. Halogenated precursors may be incompatible with alloy metal substrates.

Effects of nitrogen on corrosion of stainless steels in a liquid sodium environment

The corrosion of ferritic stainless steels using sodium at 650 ° C in a maximum isothermal region contained in a non-isothermal sodium loop constructed of a Type 316 stainless steel has been examined. Also, previous results on corrosion of austenitic stainless steels in sodium at 700 ° C in the same loop have been reproduced. The selective dissolution and absorption of nickel, the selective dissolution of chromium, and the resultant increase in iron in the surface of stainless steels in the loop mainly determine the corrosion loss of the stainless steel specimens. The austenitic steels hardly decarburize, but denitride. The ferritic steels decarburize and denitride and the denitriding is more remarkable than the decarburizing. The vanadium and niobium, carbide and nitride formers, in the ferritic steels inhibit the decarburizing to some extent, but barely inhibit the denitriding. The nitrogen in the steels rapidly diffuses to the grain boundaries, and rapidly dissolves into sodium, which will lower surface energy of the steels to enhance the dissolution of other elements. The dissolved N in sodium would then be transported to the free surface of the sodium adjacent to the argon cover gas of sodium and easily be released into the cover gas. This mechanism would cause the rapid dissolution of nitrogen into sodium and the enhancement of the corrosion rate of the steels containing nitrogen.

The corrosion of ferritic stainless steels and high-purity Fe-Cr alloys in basaltic lava and simulated magmatic gas

Three ferritic stainless steels, types 410, 430, and 446, containing 12, 17, and 26% Cr, respectively, and two high-purity binary alloys, Fe-19Cr and Fe-24Cr, were subjected to molten tholeiitic basaltic lava with a cover gas simulating magmatic gas at 1150°C for periods up to 400 hr. The oxygen and sulfur partial pressures were 9.8×10−10 and 7.0×10−3, respectively. All alloys formed Cr2O3 scales. Internal sulfidation occurred in the commercial alloys resulting in the formation of chromium and manganese sulfides. Internal oxidation of silicon also occurred. The extent of internal sulfidation decreased with increasing chromium content. There was a “critical” chromium content between 12 and 17%, above which internal sulfidation did not occur in 96 hr. However, the “critical” chromium level increased with exposure time to nearly 26% for 400 hr. Little internal sulfidation was observed in the high-purity alloys. The different behavior between the commercial and high-purity alloys may be attributed to (i) the formation of more perfect scales on the latter, which inhibited the inward migration of sulfur, and (ii) changes in the sulfur activity gradient across the scale caused by the presence of silicon and manganese.

Stochastic approach to the effect of alloying elements on the pitting resistance of ferritic stainless steels.

Birth and death stochastic processes are confirmed to operate in pitting corrosion of ferritic stainless steels containing Cr, Mo, Ti and Nb. Birth process corresponds to pit generation and death process to pit repassivation, each rate being determined as a function of potential by the analysis of survival probability vs. time curves based on the stochastic theory. Pitting potential is found to shift to the noble value with the addition of all the alloying elements examined. The cause of the shift, however, differs for each element. The shift by alloying Cr, Ti and Nb is caused by a decrease in the pit generation rate, while the pit repassivation rate remains constant. In contrast, the addition of Mo enhances the rate of repassivation and decreases the pit generation rate. These changes of both rates are contributing to the observed shift in pitting potential to the noble value.

Development of an Etching Technique for Determining the Intergranular Corrosion Resistance of Type 430 Stainless Steel

Abstract An etching technique has been developed for determining susceptibility of Type 430 stainless steels to intergranular corrosion after either heat treatment or welding. The test consists of a five minute chemical etching in boiling 60% (by volume) sulfuric acid plus 120 g/liter of copper sulfate (CuSO4·5H2O). Unlike austenitic stainless steels, the microstructures of most nonsensitized ferritic stainless steels contain chromium carbide precipitates. Hence, the use of the oxalic acid etch test (the ASTM Standard A262-A) for the intergranular corrosion of ferritic stainless steels is questionable, since the chromium carbide itself in nonsensitized samples may be attacked by the oxalic acid. The test described in this paper can be used as a substitute for the oxalic acid etch test for Type 430 stainless steel.

フェライトステンレス鋼の熱処理と腐食の関係

フェライトステンレス鋼の熱処理と腐食の関係

Intergranular Corrosion of Ferritic Stainless Steels

The susceptibility of both commercial and experimental ferritic stainless steels to intergranular corrosion was investigated. It was found that heating to 1700° F or higher and cooling rapidly sensitized a wide variety of ferritic steels to intergranular corrosion. The effects of Mo, Ni, Cb, and Ti additions to the steels were studied. It was found that Cb and Ti were effective in preventing intergranular corrosion in the Strauss test after high‐temperature heat treatment. However, in highly oxidizing media such as boiling 65% nitric acid, titanium‐containing steels could be sensitized to intergranular corrosion, while the columbium steels resisted intergranular attack even in boiling 65% nitric acid. Controlled potential polarization experiments gave results that agreed with the exposure results.