The properties of hot-dip galvanised and electroplated zinc coatings on steel have been widely studied, but the corrosion mechanisms of zinc flake coatings have not yet been investigated in similar detail. Here, we investigate the protective effect of inorganic lamellar zinc coatings, comparing the metallic dissolution rates of different zinc, aluminium and alloyed flakes using an inductively coupled plasma mass spectrometry (ICP-MS) flow cell. These experiments were carried out on both intact and predamaged coatings with different electrolytes. Data were also compared to accelerated laboratory corrosion tests and outdoor weathering results. The chloride concentration, and its effect on the passive oxide film, appears to be a key aspect moderating the dissolution rate and hence sacrificial zinc dissolution under various conditions. The complementary use of accelerated tests and ICP-MS flow cell analysis provides new insights into both the influence of the corrosive environment and the impact of the zinc flake (alloy) used. Based on this approach, tailored coating solutions using zinc flake coatings can be developed.

The inherent defective morphology of the physical vapor deposition (PVD) hard coatings limits their corrosion protective ability. We examined the impact of nitride-based PVD coatings, including TiN, TiAlN, and CrN deposited on inert substrates by cathodic arc PVD method (CA-PVD), on the galvanic corrosion of carbon steel. Their contribution was evaluated by zero-resistance ammeter (ZRA) and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl at pH 2 and 6, with and without aeration. The results indicated the prominent role of the coating type and the coupling environment on the generated galvanic currents. Immersion tests for the TiN-, TiAlN-, and CrN-coated steel cross-sections visually verified these results. The galvanic current contribution was distinct in environments where oxygen reduction is the dominant cathodic reaction. However, the layers' contribution to galvanic corrosion was minimal in deaerated acidic solutions, which is attributed to the high bonding strength of adsorbed intermediates to the coating surfaces.

The hot corrosion behaviour of the γ-Y2Si2O7 ceramic exposed to NaVO3 or V2O5 molten salt was studied at 1000–1300°C. YVO4 was identified as the corrosion product due to the chemical interaction of the two corrosive agents with the γ-Y2Si2O7 ceramic. Although YVO4 produced in the two corrosion reactions had the same crystallographic structure, they had different morphologies. YVO4 produced by the corrosion of NaVO3 with the γ-Y2Si2O7 ceramic showed a rod-like shape, whereas it was particle-shaped in the corrosion reaction of V2O5 with the γ-Y2Si2O7 ceramic. Additionally, the degradation of γ-Y2Si2O7 ceramic by V2O5 was more severe than that by NaVO3, and the thickness of the corrosion layer significantly increased with temperature. In this study, a model describing the formation of the corrosion product was established, and the formation of YVO4 with different morphologies in the two corrosion reactions was explained based on the growth characteristics of the YVO4 crystals.

Corrosion inhibition mechanism of two aromatic amino acids, phenylalanine (Phe) and tryptophan (Trp), was explored for steel in an alkaline pore solution simulating a carbonated concrete environment. The electrochemical impedance spectroscopy and potentiodynamic polarization test results revealed that both compounds can be used effectively as corrosion inhibitors for carbonated concrete environments with high inhibition efficiency. The dissolution of steel got controlled as Phe and Trp acted as anodic-type inhibitors. Phe and Trp adsorbed on the steel surface by physiochemisorption process following the Langmuir isotherm. The inhibitive solution analysis through UV–visible technique confirmed the formation of inhibitor–Fe complexes. The surface of steel was analyzed after submergence in corrosive solutions with and without inhibitors by means of optical microscopy, scanning electron microscopy–energy-dispersive X-ray spectroscopy, Fourier transformed infrared, and X-ray photoelectron spectroscopy, which highlights the formation of a compact, barrier layer comprised of metal–inhibitor complex. Subsequently, with the help of the aforementioned techniques, an inhibition mechanism for Phe and Trp was conjectured, which revealed that the presence of additional heterocycle in amino acids can raise the chances of chelation and formation of a more adherent and thermodynamically stable layer. Phe bound with Fe ions through the carboxylate functional group only, while Trp chelated the Fe ions via a nitrogen atom of the pyrrole ring and carboxylate functional group.

As a high-efficiency laser additive manufacturing technology, laser powder bed fusion (LPBF) has unparalleled advantages in the manufacture of titanium matrix composites. In this work, the effect of laser energy density (LED) on the forming quality, microstructure evolution, and corrosion resistance of LPBF-fabricated nanographene oxide reinforced titanium matrix nanocomposites (GO/TC4) was investigated. The results show that the optimal surface roughness and relative density of GO/TC4 nanocomposites fabricated by LPBF are 11.8 μm and 99.40%, respectively. The microstructure is mainly acicular α/α′-Ti, accompanied by a small amount of β-phase grain boundaries. When the LED is increased to 58.33 J/mm3, the self-corrosion potential of GO/TC4 sample reaches 0.345 V in 3.5 wt% NaCl solution, and the GO/TC458.33 nanocomposite exhibits the highest corrosion resistance. The results revealed that the corrosion products on the surface of the samples were mainly composed of a passivation film of TiO2 and a small amount of Al2O3.

Copper has been proposed as a corrosion barrier for used fuel containers due to its thermodynamic stability under the anoxic conditions relevant to a deep geological repository. Laboratory simulations of anticipated repository conditions have demonstrated the production of small quantities of hydrogen gas, which have been interpreted as being indicative of an oxidation (corrosion) process. This work reports new corrosion results for repository-relevant materials: electrodeposited copper, cold spray copper and junction material under Canadian and Swiss simulated ground waters. The attribution of the recorded hydrogen suggests corrosion is limited to the outermost atomic layers of copper cladding. However, the origins of the hydrogen have not been conclusively determined. Three thermal desorption methods have been used to investigate the outgassing of hydrogen from electrodeposited copper which may permit a more accurate interpretation of the hydrogen evolution profile from corrosion cells.

Highly formable interstitial-free steel has been subjected to corrode in wet-dry salt spray (WDSS) and immersion corrosion (IMCC) conditions in 5, 10, 20, 30, and 45 days to investigate its corrosion behavior in simulated-marine environment at the same temperature using 5 wt.% NaCl. The corrosion mechanisms and their effects have been studied and compared on the basis of weight loss and mechanical properties. Results revealed that corrosion rate in WDSS is about 9.5 times higher than IMCC. The corrosion coefficient (n) values for WDSS and IMCC have been observed as 0.99 and 0.35, respectively, which are evident for the protective nature of rust. The corrosion mechanisms and rust constituents may attribute different corrosion kinetics in both conditions. Moreover, the rate of degradation in yield strength and fracture strain in WDSS is 2 and 2.5 times higher than IMCC respectively; however, in the case of ultimate tensile strength the degradation rate is nearly same. It has also been observed that the higher pitting corrosion in WDSS may lead to change the failure mode from ductile to mix-mode after 30 and 45 days of corrosion as authenticated from scanning electron microscopic images.

This paper evaluated the inhibitory effect of Ce-chloride and Na-lactate mixture on the AA2024 aluminum alloy in 0.1 M NaCl solution. Electrochemical impedance spectroscopy (EIS) was applied for testing the general corrosion resistance, while potentiodynamic polarization measurement was applied for determining the alloy pitting corrosion resistance in NaCl and inhibitive solutions. The presence of cerium on the cathodic intermetallic particles was confirmed by scanning electron microscope/energy-dispersive X-ray spectroscopy analysis. The mixture of Ce-chloride and Na-lactate was a more effective corrosion inhibitor than Ce-chloride alone. The inhibitors mixture is a mixed-type corrosion inhibitor with a higher influence on slowing down the cathodic reaction of oxygen reduction. The adsorption of the inhibitor, the presence of cerium in different oxidation states (Ce3+ and Ce4+), and lactate anion (C–C/C–H, C–OH, C═O, and O–C═O group) were confirmed by X-ray photoelectron spectroscopy analysis. A mechanism of inhibitor adsorption on the surface of AA2024 alloy in NaCl solution was proposed.

The long-term disposal of low- and intermediate-level radioactive waste is anticipated to involve the encapsulation of the material within a cementitious matrix before placement in a deep geological repository. After sealing, the waste repository will become anoxic and the corrosion of emplaced metals will result in the production of hydrogen gas. Knowledge of the rate at which this hydrogen is generated is valuable in that it permits the assessment of pressure build-up within the repository. The corrosion behavior of mild steel has been monitored through the generation of hydrogen gas, under simulated repository conditions that mimic various stages of cement evolution. It was found that, when cement is used to encapsulate steel, the passage of several years is required for the steel and cement to reach a steady hydrogen production rate. Steel that is directly immersed in simulated cement pore water requires only months to stabilize. All measured steel uniform corrosion rates were significantly below 1 nm year−1 at 50°C, regardless of the test environment, after more than 4 years of exposure.

The advanced technologies of modern civilization produce radioactive wastes that require careful disposal if they cannot be recycled. These materials can originate from a variety of activities, such as scientific research, medicine, or nuclear power generation and, as such, can result in numerous waste forms. In this paper, the corrosion behavior of several less-common metals is studied, specifically: aluminum, copper, lead, magnesium, zinc, and zirconium, all under simulated cementitious environments. The data reported rely on the production of hydrogen as a corrosion end-product to calculate the uniform corrosion rate as a function of time. At 50°C, in either young cement water (pH 13.5) or saturated portlandite (pH 12.5) and after approximately 2 years of exposure, magnesium was found to corrode at ∼10 µm/year; aluminum at 1 µm/year (portlandite only); zinc at ∼100 nm/year; lead at <1 nm/year and both copper and zirconium at less than 0.1 nm/year.

Cathodic protection allied to a polymeric coating is one of the most employed techniques to protect buried steel pipelines against corrosion. Nevertheless, cathodic disbondment, a phenomenon associated with such protection in high-performance coatings such as (three-layer polyethylene [3LPE]), still concerns the oil and gas segment regarding pipeline integrity. The present work was part of a Program of Integrity Management and studied in field-like conditions the influence of cathodic potential, type of soil and coating system on the coating disbondment of buried pipelines for 450 days. The coating systems herein studied simulated the patching between aged (coal tar) and new coatings (3LPE), a standard procedure during damaged pipeline repair. Results pointed out that the combination between aged (coal tar) and new coatings (3LPE) in a pipe segment reduced coating disbondment when compared to the systems where 3LPE was the sole type of coating. Moreover, it was shown that more cathodic potentials (<−1100 mV) and the aggressiveness of the industrial soil herein tested induced disbondment diameters as high as 15.5 mm.

Cerium molybdate and aluminum molybdate were synthesized by precipitation at controlled pH. The inhibitory properties of these solids on the corrosion process of aluminum in near-neutral aqueous NaCl solutions were studied. Potentiodynamic polarization curves showed that both molybdates act as mixed-type inhibitors. This is due to molybdate anion acts as an anodic inhibitor, while the trivalent cations Ce(III) and Al(III) have an inhibitory effect on the cathodic reaction. Linear polarization tests demonstrated a large increase in polarization resistance when these solids are added, resulting in an inhibition efficiency of 97% in both cases. Scanning electron microscopy and X-ray energy dispersive microanalysis of the exposed surfaces revealed the formation of compact protective films rich in Mo and with no detectable Cl levels.

Due to their excellent biocompatibility, titanium alloys are the preferred materials for manufacturing bioimplants. Low-cost titanium alloys have been developed as cheaper and less toxic alternatives for Ti–6Al–4V in the biomedical industry, but their suitability for diabetes patients is yet to be evaluated. With the growing number of diabetes patients globally, this research investigated the corrosion performance of low-cost Ti–3Fe, Ti–4.5Al–1V–3Fe, and Ti–6Al–1V–3Fe alloys in 0.9 wt.% sodium chloride solution and glucose-containing Hanks balanced salt solution (HBSS) compared with Ti–6Al–4V. Glucose was added to simulate the body fluids of patients with prediabetic and diabetic conditions. Open circuit potential and potentiodynamic polarization tests were performed. The results reveal that Ti–4.5Al–1V–3Fe and Ti–6Al–1V–3Fe alloys show superior corrosion resistance compared with the other alloys in the glucose-containing solutions, as they had the lowest corrosion rate and higher corrosion potential. Consequently, these alloys hold promise as effective implants, particularly for people living with diabetes.

In this study, the leaf extract of the plant Daphne gnidium L. (Thymemeacea) was used as a corrosion inhibitor for mild steel in 0.1 M NaCl. The content of total polyphenols was evaluated by UV visible spectrophotometry and with cyclic voltammetry. The results show that the extract contains a high content of total phenols estimated at 90.26 (mg GAE/g). Besides this, the plant extract was characterized via Fourier transform infrared spectroscopy. Electrochemical impedance spectroscopy and polarization techniques were used to investigate the extract's anticorrosive performance. The results indicated that the addition of 3% of the extract increased the inhibition efficiency to 90.8% after 4 h of immersion. In addition, the results of the polarization tests showed that the extract acted as a mixed-type inhibitor, mainly affecting the anodic reaction. Scanning electron microscopy was used to study the morphology of the metal surface. The results revealed a less corrosion impact on mild steel in an inhibited solution.

Cr coatings were deposited on the Zircaloy-4 alloy by multi-arc ion plating under different bias voltages from −50 to −110 V, and the microstructure, mechanical properties, and high-temperature steam oxidation behavior of these coatings were systematically investigated. The results indicate that the bias voltage significantly affects the crystal orientation, surface morphology, deposition rate, nanohardness, and bonding strength of Cr coating on the Zircaloy-4 alloy. The high-temperature oxidation behavior of the Cr coating is closely related to its crystallographic orientation. Compared with the Cr coating with relatively random grain orientations, the Cr coating with (211) preferred orientation has a dense and uniform oxide scale and has the best oxidation resistance in the steam environment at 1200°C.

To improve the corrosion resistance of SIMP steel, we have investigated Si-ion implantation and preoxidation effects on the corrosion behavior of SIMP steel samples, which have been in stagnant lead-bismuth eutectic (LBE) with saturated oxygen at 55 0 ∘ $55{0}^{\circ }$ C for 1000 h. It was found that increasing Si content on the surface did not improve corrosion resistance performance. By contrast, the preoxidized sample demonstrated high resistance to LBE corrosion due to the presence of a thin Cr-enriched oxide layer.

Corrosion of steel in concrete can be characterized by measuring the galvanic current density when a macrocell is established. On nonpolarized steel, however, other electrochemical techniques like linear polarization resistance measurements may be used to characterize the electrochemical state of steel in concrete. On existing structures with their large dimensions and local differences in exposure conditions, local differences in the electrochemical state of the embedded reinforcement are established, leading to potential differences along the reinforcement and galvanic currents flowing. When it is possible to isolate anodic areas from the rest of the reinforcement, both galvanic current measurements, determination of polarization resistance on the separated anodic areas and the driving force between the anodic segments and the reinforcement are possible to obtain. In this work, this procedure is discussed and verified on a field structure on anodic areas caused by cracks in the concrete overlay and the results thereof are presented.

The long-term disposal of nuclear waste in deep geological repositories requires safe containment for up to one million years. To understand how the waste will respond to the gradually evolving environment, researchers can perform sensitive experiments in the laboratory to replicate the repository conditions at specific time points. In Belgium, spent nuclear fuel will be housed within a carbon steel overpack, which is encased within a cement buffer, which may include a stainless steel liner (the “envelope”). The range of corrosion behaviors for carbon steel, and to a lesser extent, stainless steel, has been studied through hydrogen evolution, an end-product of oxidation under repository conditions. Considerable time may be required for metallic surfaces to approach a steady hydrogen evolution and this is dependent upon the starting condition of the specimen surfaces. The use of nominally-similar materials can result in significant variation in the reported corrosion rates. The presence of cements, which generate their own hydrogen and influence water chemistry as a function of time, add complexity to even simple experimental configurations that requires careful interpretation.

This study investigates the influence of corrosion fatigue on the fatigue strength of an AlSi10MgMn high-pressure die-casting alloy with regard to the surface condition. Two different surface conditions are compared. First, an unmachined surface condition with a rough surface ( R a = 5.05   μm $\,{R}_{{\rm{a}}}=5.05\unicode{x0200A}\mathrm{\mu m}$ ) and second a machined and polished surface condition with a smooth, polished surface ( R a = 0.25   μm $\,{R}_{{\rm{a}}}=0.25\unicode{x0200A}\mathrm{\mu m}$ ) are tested. The specimens are loaded with a cyclic bending moment at a constant stress ratio of R = 0 till failure. A 5 wt% NaCl solution enables the corrosion fatigue tests. Corrosion fatigue leads to a significant reduction of the endurable stresses along the whole load spectrum independent from the surface condition. The applied corrosive solution prevents the formation of a pronounced long-life fatigue strength limit within the tested load cycle range. Hence, the reduction of the endurable stresses increases with the increasing number of load cycles, reaching approximately 37% at 2 × 1 0 6 $2\times 1{0}^{6}$ load cycles. No significant influence of the surface condition, independent of the environment (air, 5 wt% NaCl), on the fatigue behaviour is found.

In this study, the effect of TiC on the oxidation resistance of 304 stainless steel (304SS) at 650°C in air was investigated by examining oxidation kinetics and surface and cross-sectional scale microstructures, in comparison with TiC-free alloy. It was found that TiC addition deteriorated the oxidation resistance of 304SS at 650°C, in contrast with its improving effect on oxidation resistance at 850°C reported before. The variation of the TiC effect on the oxidation resistance of 304SS at different temperatures was attributed to the dual effect of TiC where the final results depended on if protective or nonprotective oxide scale formation occurred in TiC-free 304SS materials.