Formation Of Corrosion Products Research Articles

Enhanced electrochemical corrosion resistance of SS(304L) alloy with nano-pyramids c-TiN layer for saline media application

The present work evaluates the impact of the cubical titanium nitride (c-TiN) coating on the corrosion characteristics of the 304 L stainless steel SS(304 L). A thick and crystalline c-TiN layer with a hierarchical nano-pyramid-like structure was prepared by a single-step sputtered method at RT on a mechanically polished SS(304 L) substrate. Most of the basic characterization techniques were employed to understand the growth mechanism of c-TiN coating. The corrosion characteristics of the prepared coating were executed in two distinct ways, Tafel and EIS plots, in terms of polarization resistance (Rp) under saline water ambient [3.5 % NaCl]. The obtained results reveal the superior corrosion resistance of coated substrate compared to the bare substrate after a long immersion (∼6 h) of the sample in saline water. The c-TiN coated sample offers low corrosion current density (Icorr) (19.8 µA/cm2) compared to the bare substrate (213 µA/cm2). Similarly, EIS and equivalent circuit results also indicate superior corrosion resistance of c-TiN-coated SS-304 L, resulting in a significantly low corrosion rate (CR) of ∼ 0.0213 µmpy. The formation of corrosion products was discussed by using surface morphology analysis, while the electrochemical ion kinetic study was also presented to understand the anti-corrosion mechanism of c-TiN coating.

Characterization of microstructural and corrosion behavior of cold sprayed Zn11Al3Mg alloy coating

This study investigated the microstructure and corrosion behavior of the cold-sprayed Zn11Al3Mg zinc alloy coating through analysis of phase composition, microstructures, and electrochemical behaviors. The results demonstrate that the CS-Zn11Al3Mg coating primarily consists of a finely structured ternary eutectic phase of Zn/Mg2Zn11/Al, with uniformly distributed submicron-sized Al phases. Additionally, a small amount of coarse Zn/Mg2Zn11 eutectic phase coexisted with MgZn2 was also observed. The enhanced corrosion resistance of the coating was obtained when compared with cold sprayed Zn coating. The rapid sacrificial dissolution of MgZn intermetallic compounds was observed in saline solution, leading to localized corrosion in the coating layer. Fortunately, the cooperative interaction of dissolved Mg2+ and Al3+ promotes the formation of protective corrosion products, namely Zn5(OH)8Cl2·H2O and Zn/Mg-Al layered double hydroxides, provided long-term corrosion protection for mild steel.

Comparison of microstructure, mechanical property, and degradation rate of Mg-1Li-1Ca and Mg-4Li-1Ca alloys.

Mg-1 wt.% Li-1 wt.% Ca (LX11) and Mg-4 wt.% Li-1 wt.% Ca (LX41) alloys share the same hexagonal closed-packed crystalline structure. However, the differences in microstructure, mechanical properties, and degradation rates between the two alloys are not well understood. Hereby, the above three aspects of LX11 and LX41 alloys were studied via optical microscopy, tensile tests, and electrochemical polarization and electrochemical impedance spectroscopy, together with hydrogen evolution. The concentration of the released Mg2+, Ca2+, and Li+ ions was analyzed using a flame atomic absorption spectrophotometer. Results demonstrated that the LX11 alloy was composed of finer α-Mg grains, fewer twins, and smaller volume fractions of the intermetallic phases Mg2Ca than the LX41 alloy. The increasing Li concentration generated a weak decrease in the yield strength of the Mg-Li-Ca alloys, a remarkable increase in elongation to failure, and a stable ultimate tensile strength. The LX11 alloy had better corrosion resistance than the LX41 alloy. The release rate of the cations (Mg2+, Ca2+, and Li+) varied significantly with time. The release rate of metallic ions in Hank's solution cannot reflect the true corrosion rate of Mg-Li-Ca alloys due to the formation of the precipitated corrosion products and their difference in solubility. The dealloying corrosion mechanism of the Mg2Ca phase in Mg-Li-Ca alloys was proposed.

Influence of Alkyd Composite Coatings with Polyaniline Doped with Different Organic Acids on the Corrosion of Mild Steel

Composite coatings prepared by mixing 5 wt.% polyaniline with commercial alkyd-based paints were applied on carbon steel. The polyaniline emeraldine chloride salt was prepared by procedure recommended by IUPAC, including deprotonation by ammonia hydroxide, and reprotonation with sulfamic, succinic, citric, and acetic acids with different doping degrees or oxidation states. The steel samples with base and composite coatings were immersed in 3% NaCl and the corrosion current density was determined after 96 h in situ using the ASTM 1,10-phenanthroline method. The samples were also inspected by optical microscopy. It was shown that the composite coatings reduced the possibility of blister formations and delamination. The corrosion current density and the appearance of the corrosion products, whose area was determined by ImageJ software, closely followed the initial oxidation state of the polyaniline. It was also shown that damaged composite coatings with higher degrees of oxidized (doped) polyaniline were more prone to formation of corrosion products. The role of the initial state of the polyaniline is discussed. It is suggested that such behavior could be connected to the oxygen reduction reaction mechanism that proceeds mainly via two electron paths on the polyaniline particles, releasing a much smaller amount of hydroxyl ions, which is responsible for the delamination and blister formation of the commercial coatings.

Investigation on deterioration mechanism of geopolymer cemented coal Gangue-Fly ash backfill under combined action of high temperature and salt corrosion environment

The geopolymer cemented coal gangue-fly ash backfill (GCGFB) is pumped to the goaf to maintain the stability of surface subsidence, which is inevitably affected by the high temperature caused by geothermal heat and ion erosion of mine water. To study the deterioration mechanism of GCGFB caused by salt corrosion and high temperature of mine water, in this study, a customized temperature-controlled corrosion chamber was used to carry out the corrosion experiment of GCGFB. A three-factor and three-level orthogonal experiment was designed. The uniaxial compressive strength (UCS), relative dynamic elastic modulus (RDEM) and weight deterioration of GCGFB under different combinations of temperatures, solution concentrations, and solution types were analysed. The deterioration mechanism of GCGFB was analysed through the testing of scanning electron microscopy (SEM)-energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). From the results, the most significant factors on the deterioration of GCGFB is solution type. Cl− and SO42− caused chemical-physical erosion on GCGFB, and the UCS, RDEM and weight of GCGFB increased first and then decreased with ages. The reason for the increase was due to the compacting effect of Friedel 's sat, ettringite, and gypsum filled in GCGFB. The reason for the decrease was due to the expansion pressure on the inner wall of the pores of the GCGFB caused it to crack or even peel off. The GCGFB was corroded in 20 % Na2SO4 solution at 40 °C for 90 days, and the UCS increased by 164.90 % compared to that of the uncorroded specimen. Mg2+ brought chemical erosion on GCGFB, and a decreasing law of the UCS, RDEM and weight with ages was shown. During the Mg2+ erosion, there are more and more M−S−H in matrix, which reduced the density of specimen apparently. The GCGFB was corroded in 5 % MgCl2 solution at 40 °C for 180 days, and the macropore area distribution of GCGFB is increased to 23.499% than that of uncorroded group. The expansion stress of corrosion products would squeeze the inner pore wall, resulting in microcracks inside GCGFB and high temperatures would accelerate the migration of ions and the formation of corrosion products. Overall, this study can provide a new insight or valuable data for the designing of ultra-high performance, low-caron, eco-friendly, and durable GCGFB structures in the harsh mining environments.

Ultrasonic impact treatment of Ti-based amorphous alloy: Improved tribological performance in air and 3.5 % NaCl solution

The inherent brittleness of amorphous alloys limits their tribological properties. Ultrasonic impact treatment (UIT), applied without preloading, has been used to improve the tribological performance of Ti-based amorphous alloys. Following UIT, the impacted surface softened, whereas the sample cross-section hardened. The change in hardness could be controlled by varying the UIT duration and ultrasonic power. UIT leads to an increase in relaxation enthalpy, suggesting higher free volume and enhanced plasticity. This improved plasticity is evidenced by the Vickers indentation morphologies and the pop-in phenomena of the nanoindentation curves. Regardless of whether the tribology testing was performed in air or in a 3.5 % NaCl solution, UIT led to noticeable reductions in both the coefficient of friction (COF) and the wear rate. The corrosion resistance improved noticeably in both static and sliding states. The primary wear mechanisms were adhesion, abrasion, and delamination. Compared to sliding in air, the COF and wear rate were lower in the NaCl solution. Post UIT, the higher free volume facilitates oxidation in air and the formation of protective corrosion products in the NaCl solution, which is beneficial in reducing adhesion. Simultaneously, the improved plasticity of UIT may contribute to resistance to fatigue and delamination. Therefore, UIT is a simple and feasible method for significantly improving the tribological performance of amorphous alloys.

Influence of CrFeCoNiCu high-entropy alloy and ultrasonic stirring on the thermal, electrochemical and mechanical properties of Zn-30Sn high-temperature solder alloy

In this study, the thermal, electrochemical and mechanical properties of Zn-30Sn solder alloy with different contents of CrFeCoNiCu high-entropy alloy (HEA) (0, 0.5 and 1 wt%) were investigated. At the same time, ultrasonic stirring was introduced into the melting process. The results suggested that the addition of HEA could refine the microstructure and the Zn matrix phases accelerated to dissolve to form more precipitation phases with the increase of HEA content from 0 to 1.0 wt%. The application of ultrasound could make the distribution of the phases disperse and facilitate the formation of dense and uniform corrosion products during the corrosion process. The electrochemical corrosion test and tensile test results showed that the ultrasonically treated Zn-30Sn solder alloy containing 1.0 wt% HEA had the lowest corrosion current density (Icorr = 1.11 μA·cm−2), the highest ultimate tensile strength (101.13 MPa) and yield strength (25.55 MPa), indicating that the corrosion resistance and mechanical properties were most outstanding. Moreover, the melting temperature of the composite solder alloys was slightly decreased from 379.5 °C to 377.5 °C.

Investigation of corrosion behavior of galvanized steel as submarine cable armor in seawater under weak magnetic fields

Submarine cables are the main transmission channel for offshore wind power technology. In the actual work of submarine cables, it is inevitable that an induced magnetic field will be generated in the submarine cable armor. The induced magnetic field generated will have a certain impact on the corrosion of the submarine cable armor, thus affecting the service life of the submarine cable. In this paper, the corrosion behavior of submarine cable armor with galvanized steel structure in seawater under different weak magnetic fields is investigated by electrochemical corrosion experiments. The results show that the galvanized layer does not play a protective role when the structure of submarine cable armor is damaged, and the magnetic field environment plays a role in promoting the corrosion behavior of submarine cable armor. Through the analysis of its corrosion mechanism, it is found that the magnetic field promotes the corrosion behavior of submarine cable armor by affecting charge transfer and the formation of corrosion products, which provides a reference for the accurate evaluation of the actual service life of submarine cable.

Water Chemistry Impact on Activated Corrosion Products: An Assessment on Tokamak Reactors

Activated Corrosion Product (ACP) formation and deposition pose a critical safety issue for nuclear fusion reactors. The working fluid transports the ACPs towards regions accessible by worker personnel, i.e., the steam generator. The code OSCAR-Fusion has been developed by the CEA (France) to evaluate the ACP generation and transport in closed water-cooled loops for fusion application. This work preliminary assesses the impact of water chemistry on the transport, precipitation, and deposition of corrosion products for the EU-DEMO divertor Plasma Facing Unit Primary Heat Transfer System. Sensitivity analyses and uncertainty quantification are needed due to the multi-physics phenomena involved in ACP formation and transport. The OSCAR-Fusion/RAVEN code coupling developed by the Sapienza University of Rome and ENEA are used. This work presents the perturbation results of different parameters chosen for a closed water-cooled loop considering a continuous scenario of 1888 days. The aim of this work is to preliminarily assess the variation of build-up of ACPs, perturbing the alkalizing agent concentration into the coolant, and the corrosion and release rates of different materials. The assessment of ACP formation deposition and transport is fundamental for source term identification, reduction of radiation exposure assessment, maintenance plan definition, design optimization, and waste management.

Corrosion Behaviors of Outdoor Bronze Sculptures in an Urban–Industrial Environment: Corrosion Experiment on Artificial Sulfide Patina

Copper alloys interact with air pollutants to form corrosion products and, consequently, a patina on outdoor bronze sculptures. In this study, corrosion experiments were conducted to clarify the corrosion behaviors of artificial sulfide patina in an urban–industrial environment on a quaternary bronze alloy (Cu–Zn–Sn–Pb) with a composition and metallurgical properties similar to those of outdoor bronze sculptures. The correlation between the chromaticity and reflectance of the patina revealed increasing brochantite with the corrosion of the patina and an association between the chromaticity a* and patina growth. Cuprite and brochantite were distinguished, and the point at which brochantite covered the patina surface was determined. The quantitative changes in brochantite were mainly influenced by physical causes such as the crystal size and patina layer thickness as well as by Cu2+ ions working as color formation ions moving to the outermost layer. Atmospheric corrosion of the alloy resulted in reduced Cu and Zn contents and increased Sn and Pb contents. The patina consisted of brochantite in the outermost layer and cuprite and cassiterite in the inner layers. These findings should clarify corrosion characteristics such as the surface color, composition, and changes in corrosion products of outdoor bronze sculptures and contribute toward their preservation.

Ni-Al Bronze in Molten Carbonate Manufactured by LPBF: Effect of Porosity Design on Mechanical Properties and Oxidation.

Fuel cell technology has developed due to diminishing dependence on fossil fuels and carbon footprint production. This work focuses on a nickel-aluminum bronze alloy as an anode produced by additive manufacturing as bulk and porous samples, studying the effect of designed porosity and thermal treatment on mechanical and chemical stability in molten carbonate (Li2CO3-K2CO3). Micrographs showed a typical morphology of the martensite phase for all samples in as-built conditions and a spheroid structure on the surface after the heat treatment, possibly revealing the formation of molten salt deposits and corrosion products. FE-SEM analysis of the bulk samples showed some pores with a diameter near 2-5 μm in the as-built condition, which varied between 100 and -1000 μm for the porous samples. After exposure, the cross-section images of porous samples revealed a film composed principally of Cu and Fe, Al, followed by a Ni-rich zone, whose thickness was approximately 1.5 µm, which depended on the porous design but was not influenced significantly by the heat treatment. Additionally, by incorporating porosity, the corrosion rate of NAB samples increased slightly.

Investigation into durability degradation and fracture of cable bolts through laboratorial tests and hydrogeochemical modelling in underground conditions

Premature failures of cable bolts caused by durability degradation in underground reinforcement systems have been more and more often observed. To identify various factors affecting the corrosion process, the corrosion processes were examined through laboratorial testing programs as well as hydrogeochemical modelling. Experiments were carried out in simulated underground conditions in “corrosion cells” containing stressed cable bolt specimens as well as groundwater, clay, coal or a combination of the materials. Water chemistry and corrosion pattern analysis of specimens in different testing conditions were conducted. Hydrogeochemical models were established and the formation of corrosion products, the change of ion concentration and factors related to corrosion rates were studied. The results showed the corrosion degree of specimens could be classified into three categories. The dissolved oxygen was the main factor affecting the general corrosion and stress level, pH and electrical conductivity were secondary factors. Erosive ions were main factors affecting localised corrosion which was mainly observed to form at high stress areas. A ‘staple’ like crack initiated at localised corrosion were observed which was identified as a potential site for stress corrosion cracking. The modelling results showed sulphide iron generated in presence of microorganisms which would also accelerate stress corrosion of specimens. The obtained results and proposed methodologies would establish quantifiable data to compare variable mine conditions and help understand the corrosion mechanisms in underground conditions.

Numerical Investigation of the Corrosion and Fatigue Behavior of Clinched Joints

AbstractThe application area of clinched joints is steadily increasing. They are vastly used in the automotive industry to join car body parts. Clinched components are often exposed to different environmental conditions as well as cyclic mechanical loading. Those environments are common originators of multiple corrosion and material fatigue phenomena. It is thus important to include possible environmental factors into the design of the joining process, to ensure full functionality of the clinched joint during its service life. In order to estimate material failure in such joints, several experimental and numerical tools are available. However, the literature provides little knowledge about the combined influence of corrosion and high‐cycle fatigue on the service life of clinched joints. In this work, a modeling framework is given that combines the effects of corrosion products formation on the fatigue life of clinched EN AW‐6014/HCT590X+Z joints by means of numerical simulations.

Yb doping effects on CMAS corrosion resistance of Yb-doped GdPO4 by first-principles calculation and experimental investigation

GdPO4 is an attractive CMAS-resistant thermal barrier coating material due to the rapid GdPO4/CMAS reaction forming an interface reaction layer. However, this layer is weakly adhered to the GdPO4 surface weakening its function on inhibiting CMAS penetration. In this study, Yb-doped GdPO4 (Gd0.75Yb0.25PO4) was explored and its CMAS corrosion resistance was investigated. The Yb doping effects on the corrosion products formation enthalpy, the interface reaction layer construction and evolution, and the adhesion of the layer to Yb-doped GdPO4 were clarified based on first-principles calculation and experimental investigation. Yb-doped GdPO4 is verified to be more resistant to CMAS attack than GdPO4.

Carbon dioxide-Induced Corrosion of AISI 4140 Steel in Acidified Artificial Geothermal Brine

Carbon dioxide (CO2)-induced corrosion often occurs in the structural materials of geothermal industry. The presence of CO2 influences the formation of various corrosion products. This research investigates the effect of dissolved CO2 in acidic brines on the corrosion behavior of AISI 4140 steel at atmospheric pressure. The brines were the standard brine, Ca-free brine, and high-salinity brine. The corrosion behavior was studied using electrochemical and immersion tests. A cyclic polarization test showed that the corrosion rate was higher in dissolved CO2 brine than in non-CO2 brine, and an immersion test demonstrated a similar result. In the absence of CO2, the presence of Ca ions in the brine reduced the corrosion rate of the alloy from 26.8 to 24.6 mmpy and further to 20.7 mmpy in the high-salinity brine. A similar trend was demonstrated during immersion in the CO2-containing brine, with higher rates of 37.1, 30.9, and 24.9 mmpy for the Ca-free, standard, and high-salinity brines, respectively. However, the Ca ions and high-salinity brines induced a more localized corrosion as pit and filiform. A surface analysis using an optical microscope revealed that immersion in CO2 brines generated 4–10-fold higher surface roughness than the non-CO2 brines. In all specimens, a protective layer was not established during the tests. No new phase was detected using X-Ray diffractometer after the immersion test. Moreover, no tendency of passivation was observed in the reverse scan of the cyclic polarization test.

Understanding of the Interaction Between Crystallographic Orientation and Service Environment on Nonoriented Silicon Steel Corrosion

The effect of crystallographic orientation and environmental factors on the corrosion behavior of 35TWV1900 nonoriented silicon steel at various temperatures (25°C, 40°C, and 60°C) and Cl− concentrations (0.1 mol/L, 0.6 mol/L, and 1 mol/L) were investigated by electrochemical tests and immersion experiments. The results have revealed that the (111) plane exhibits a higher corrosion rate compared with (001) and (101) planes. The increased temperature promotes the anodic dissolution of the substrate, accelerating the formation of corrosion products and the transformation of β/γ-FeOOH to α-FeOOH/Fe3O4. In the immersion environment, the corrosion mechanism is a typical oxygen-absorbing corrosion mechanism. During the electrochemical reaction phase, the corrosion rate shows a trend of first increasing and then decreasing with the increase of Cl− concentration, which can be explained by the catalytic dissolution effect and the protective effect of adsorbed Cl− on the surface. Meanwhile, with the injection of Cl−, the content of dissolved oxygen in the solution decreases and the adsorption competition between Cl− and oxygen increases, leading to the reduction of corrosion rate and inhibiting the formation of an oxide film. The two stages of corrosion in an immersion environment are described, and the corrosion mechanism is elucidated.

Microstructure and Corrosion Behavior of ZnAl12Mg3Si0.3 Double-Batch Hot-Dip Coatings

This article presents the microstructure (SEM) and corrosion behavior of ZnAl12Mg3Si0.3 (ZAMS) coatings obtained by the double hot-dip method on Sebisty steel with increased strength. On the basis of chemical composition studies in micro-areas (EDS) and phase composition studies (XRD), structural components of the coating and corrosion products formed on the coating surface after exposure to the neutral salt spray (NSS) test (EN ISO 9227) were identified. The presence of the Fe(Al,Si,Zn)3 intermetallic phase was found in the Fe-Al intermetallic layer, while in the outer layer, dendrites rich in Al and Zn were identified. In these dendrites, the eutectics of Zn/MgZn2 and precipitates of the MgZn2 phase and Si were located. The NSS test showed better corrosion resistance of ZAMS coatings compared to conventional zinc hot-dip coatings. The increase in corrosion resistance is due to the formation of favorable corrosion products: simonkolleite-Zn5(OH)8Cl2·H2O and hydrozincite-Zn5(OH)6(CO3)2, and the presence of the MgZn2 phase in the coating, which is more anodic than other structural components.

Influence of the Martensite Phase of the Cu-9Al-3Ag Alloy and Its Corrosion Behavior in NaCl-Containing Media

The present investigation shows the influence of the microstructure resulting from the heat treatment termed betatization of an aluminum bronze containing Cu-9Al-3Ag alloy, in as-cast and heat-treated samples immersed in 0.5M NaCl-containing media with all experiments conducted at 25 ºC. The said treatment corresponds to heat saturation conditions in the phase region where the beta phase predominates in the microstructure. The corrosion behavior was recorded through using cyclic voltammetry and potentiodynamic polarization techniques, supplemented by OCP recordings. The results obtained through the polarization curves showed that at more positive potentials the current density decreases considerably, which is attributed to the formation of corrosion products on the surface of the working electrode.

Corrosion performance and possible mechanism of aluminium nitride-molybdenum gradient material in a simulated liquid metal battery environment

After being fabricated successfully by spark plasma sintering technology, corrosion performance of aluminum nitride-molybdenum gradient material was investigated using X-ray diffraction, scanning electron microscope, XPS techniques, etc. in a simulated liquid metal battery environment with LiF–LiBr–LiCl eutectic salt as electrolyte. The research results indicated that low temperature corrosion at 550 °C occurs mainly in pure aluminum nitride region with the corrosion products grown on the grain boundaries including alumina, nitrogen-lithium, aluminum-lithium intermediate phase or their complex compounds. Moreover, the formed corrosion product morphology is influenced significantly by aluminum nitride distribution. As the gradient compositions developed towards the pure molybdenum zone, the product morphologies tended to evolve in a sequence of sphere, flake and octahedron. At temperatures higher than 600 °C, alumina tends to be dissolved in molten salt vapor and molybdenum starts to be corroded simultaneously resulting in a substitute of the formed lithium aluminum molybdenum oxide phases for alumina in the final corrosion products. Mass change study on the samples suggested both the holding time and temperature have significant influences on the corrosion behavior of aluminum nitride-molybdenum gradient material. At temperatures higher than 700 °C, sudden change in sample mass accompanied by interface cracking would happen within the holding time of 100 h. Therefore, under long-term isothermal conditions, the serviced temperature of aluminum nitride-molybdenum functional gradient materials is suggested to be lower than 600 °C.

Speciation of iron(II/III) at the iron-cement interface: a review

Steel is used as reinforcement in construction materials and it is also an important component of cement-stabilized waste materials to be disposed of in deep geological repositories for radioactive waste. Steel corrosion releases dissolved Fe(II/III) species that can form corrosion products on the steel surface or interact with cementitious materials at the iron-cement interface. The thermodynamically stable Fe species in the given conditions may diffuse further into the adjacent, porous cement matrix and react with individual cement phases. Thus, the retention of Fe(II/III) by the hydrate assemblage of cement paste is an important process affecting the diffusive transport of the aqueous species into the cementitious materials. The diffusion of aqueous Fe(II/III) species from the steel surface into the adjacent cementitious material coupled with the kinetically controlled formation of iron corrosion products, such as by Fe(II) oxidation, decisively determines the extension of the corrosion front. This review summarises the state-of-the art knowledge on the interaction of ferrous and ferric iron with cement phases based on a literature survey and provides new insights and proper perspectives for future study on interaction systems of iron and cement.