Corrosion Of Ferritic Steels Research Articles

Template-Free One-Step Electrodeposition Method for Fabrication of Robust Superhydrophobic Coating on Ferritic Steel with Self-Cleaning Ability and Superior Corrosion Resistance.

The corrosion of ferritic steel, a widely used structural material in the power and nuclear industries exposed to humid coastal environments, is a major concern. Here, we present a template-free one-step electrodeposition method for the fabrication of a robust superhydrophobic (SHP) coating on ferritic steel with excellent mechanical stability, enhanced corrosion resistance, and self-cleaning ability. By varying the electrodeposition time and potential, the micronanoscale hierarchical surface structures were optimized. The coated SHP surfaces were characterized by water contact angle measurement, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The coated surfaces showed a characteristic cauliflower morphology of cerium myristate with micronanoscale features. The maximum water contact angle achieved was 162.8 ± 2.4°. Shear abrasion testing showed good mechanical durability for the prepared coatings. The as-prepared SHP coating showed a five order reduction in corrosion current density (4.14 × 10-11 A/cm2) and corrosion rate (4.63 × 10-7 mm/y) as compared to the bare sample. Further, a six order enhancement in the polarization resistance (1.55 × 109 Ω) was also observed in agressive chloride solution, which confirmed the excellent corrosion resistance of the SHP coating. Electrochemical impedance spectroscopy (EIS) studies showed a high impedance modulus for SHP coated surfaces due to the presence of a compact protective layer of cerium myristate. This observed impedance modulus of the SHP surface was approximately four orders higher than the reported value on magnesium alloys. This study provides a new platform for obtaining a robust, mechanically stable, and corrosion resistant SHP coating with a self-cleaning ability on ferritic steel substrates that may be adapted for a range of materials in practical applications.

Microbiologically influenced corrosion of ferritic steel–zirconium-based metal waste form alloy under simulated geological repository environment

ABSTRACTThe present work focused on investigating the microbiologically influenced corrosion (MIC) susceptibility of ferritic steel–Zr-based metal waste form (MWF) alloy in simulated ground water media, cultured with a common biofilm former Bacillus sp. Total viable count studies showed a good bacterial attachment on the surface of MWF alloy. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) examination of the biofilm MWF surface revealed preferential adhesion of microbes on Fe–Zr-rich intermetallic phases. Anodic polarisation and electrochemical impedance spectroscopic (EIS) studies showed active corrosion potential (Ecorr), higher passive current density (Ipass) and decreased polarisation resistance (Rp) values, confirming the corrosion susceptibility of MWF alloy under Bacillus sp. biofilm.

Corrosion of Ferritic Steels in High Temperature Molten Salt Coolants for Nuclear Applications

ABSTRACTCorrosion of ferritic steels, including oxide dispersion strengthened (ODS) variants, in high temperature molten fluoride salts may limit the life of advanced reactors, including some hybrid systems that are now under consideration. In some cases, the steel may be protected through galvanic coupling with other less noble materials with special neutronic properties such as beryllium. This paper reports the development of a model for predicting corrosion rates for various ferritic steels, with and without oxide dispersion strengthening, in FLiBe (Li2BeF4) and FLiNaK (Li-Na-K-F) coolants at temperatures up to 800 °C. Mixed potential theory is used to account for the protection of steel by beryllium, Tafel kinetics are used to predict rates of dissolution as a function of temperature and potential, and the thinning of the mass-transfer boundary layer with increasing Reynolds number is accounted for with dimensionless correlations. The model also accounts for the deceleration of corrosion as the coolants become saturated with dissolved chromium and iron. Electrochemical impedance spectroscopy has been used for the initial in situ study of an ODS ferritic steel in high-temperature molten fluoride salt environments, with the complex impedance spectra obtained at its open circuit corrosion potential (OCP) interpreted in terms of the basic components of the equivalent circuit, which include the electrolyte conductivity, the interfacial charge transfer resistance, and the interfacial capacitance. Such in situ measurement techniques may provide valuable insight into the degradation of materials under realistic conditions.

Chemical reactions of caesium, tellurium and oxygen with fast breeder reactor cladding alloys: Part IV — The corrosion of ferritic steels

A study of the corrosion of the steels FV448 and DT2203Y05 by Cs/Te mixtures in sealed capsules containing oxygen buffers at 948 K after 168 h shows that the oxide dispersion strengthened steel is more resistant to corrosion than is FV448 at Cs:Te ratios of 1:1 and 2:1. Both steels generally corrode evenly and show more resistance to the more damaging intergranular penetration than do PE16 and M316 alloys. Corrosion is most severe at 1:1 compositions irrespective of oxygen potential, and the corrosion products are Cs 2Te + transition metal tellurides. The corrodants Cs 2Te, Cs 2Te + Cs and Cs are inert to FV448 in the absence of O 2 but corrosion increases with increasing oxygen potential. At low potentials the dominant corrosion products are caesium chromâtes + Cr 2Te 3 and these are augmented by CsFeO 2 + FeTe 0.9 at higher potentials. The various types of corrosion are summarised.

Corrosion of ferritic steels by molten lithium: Influence of competing thermal gradient mass transfer and surface product reactions

An Fe-12Cr-1MoVW steel was exposed to thermally convective lithium for 6962 h. Results showed that the weight change profile of Fe-12Cr-1MoVW steel changed substantially as the maximum loop temperature was raised from 500 to 600°C. Furthermore, for a particular loop experiment, changes in the structure and composition of the exposed surfaces did not reflect typical thermal gradient mass transfer effects for all elements: the surface concentration of chromium was often a maximum at intermediate temperatures, while nickel (present at low concentrations in the starting material) tended to be transported to the coldest part of the loop. Such data were interpreted in terms of a qualitative model in which there are different dominant reactions for the various constituents of the ferritic steels (surface product formation involving nitrogen and/or carbon and solubility-driven elemental transport). This competition among different reactions is important in evaluating overall corrosion behavior and the effects of temperature. The overall corrosion rate of the 12 Cr-1MoVW steel was relatively low when compared to that for austenitic stainless steel exposed under similar conditions.

Corrosion of ferritic steels (Fe-Cr-Al) in sulfur vapor and H2S/H2 mixtures

The high-temperature corrosion (700–1000°C) kinetics and processes in sulfur vapor and hydrogen sulfide were investigated for ferritic steels containing Cr and Al. Observation and analysis of the reaction curves obtained allowed the various corrosion steps to be clarified. Formation of compact, protective layers, at either the alloy-sulfide or at the sulfide-gas interface, occurred in the early stages of reaction and subsequently, most of the layers formed were microcrystalline and porous. The influence of the system parameters, i.e., temperature, pressure of the sulfidizing agent, and alloy composition, is reported in this paper.

Effect of Ni Additions Upon the Stress Corrosion of Ferritic Steels in a Chloride Environment

Abstract Although mild steels will not fail by stress corrosion cracking (SCC) in a boiling MgCl2 solution, the addition of only 1% Ni to such steels will promote a susceptibility that becomes more marked at higher Ni contents. Constant strain rate stress corrosion tests, together with fractographic examination of failed specimens and the determination of relevant polarization curves, have been employed in order to ascertain the roles of both Ni and Cl− in the cracking mechanism. It seems that failures of Ni containing “mild steels” in concentrated chloride solutions are most readily explicable in terms of Ni promoting Cl adsorption which subsequently inhibits anodic dissolution. The mechanism of crack propagation is thought to be dependent on dissolution processes, possibly aided by mechanical tearing.

An Electrochemical Investigation of Corrosion of Ferritic Steels in Molten Sulfates

Abstract The corrosion behavior of four ferritic steels in molten sulfates was evaluated by potential measurements of freely corroding electrodes as well as by potentiodynamic polarization measurem...