Corrosion Dissolution Research Articles

Synergistic inhibition to dissolution corrosion by de-twinning and precipitation in alumina-forming austenitic steel exposed to lead-bismuth eutectic with 10-8 wt.% oxygen at 600°C

This work investigated the original microstructure of cold-worked alumina-forming austenitic steel, along with its precipitation and dissolution corrosion behaviors in lead-bismuth eutectic with 10-8 wt.% oxygen at 600°C, using solution-annealed steel for comparison. Anomalously, cold-worked steel presented milder corrosion compared to solution-annealed steel, with average corrosion depths of 314.3 and 401.0 μm after 1700 h exposure. Cold working-induced de-twinning transformed the annealing twin boundaries into normal high-angle grain boundaries (NGBs), increasing NGBs proportion from 36% to 89%. The increased NGBs provided more nucleation sites for intergranular barriers composed of alternate NiAl and M23C6 precipitates, thus better obstructing the dissolution attack.

Study on the effect of Si content on the compatibility of F/M steels with lead-bismuth eutectic using small punch testing

This study investigates the impact of silicon (Si) on the corrosion resistance and post-corrosion toughness of ferrite/martensitic (F/M) steels in a liquid lead-bismuth eutectic (LBE) environment. Corrosion tests were performed on HT-9 and EP-823 (1.17 wt.% Si) steels at 550 °C for 1000 h under oxygen-controlled conditions. The resulting oxide layer consisted of an outer magnetite layer, a spinel layer and an inner oxide zone (IOZ). A Si-rich oxide layer was identified within the spinel and IOZ layers of EP-823, which slowed the growth rate of the oxide layer, enhanced antioxidant performance, and inhibited dissolution corrosion by the LBE. Post-corrosion mechanical properties were evaluated using a small punch test. Results showed a significant reduction in HT-9’s toughness within 240 h of corrosion, while EP-823 exhibited increased brittleness after 500 h due to Si-promoted carbide and Laves phase precipitation, significantly reducing its toughness.

Microstructure and corrosion property evolution of a surface-nanostructured 15–15Ti austenitic steel during immersion in liquid LBE at 550 °C

This study investigated the compatibility of surface-nanostructured 15–15Ti austenitic steel in 550 °C LBE with an oxygen concentration of 5 × 10−7 wt.% for various exposure durations (759, 1638, 2404, and 3012 h). The results demonstrate that the grain size was reduced from 33.50 μm to the nano-scale after shot-peening (SP), achieving 17.62, 15.44, and 14.25 nm under SP pressures of 0.06, 0.15 and 0.25 MPa, respectively. The untreated steel experienced severe oxidation and dissolution corrosion, whereas the surface-nanostructured steel exhibited only mild oxidation and was resistant to dissolution corrosion. The enhanced corrosion resistance of surface-nanostructured steel is attributed to the higher protectiveness of the Cr-rich spinel layer and the less defective Ni-rich layer beneath it. Recrystallization occurred exclusively in the Ni-rich region, while the deformed steel underwent recovery during exposure. The thickness of the recrystallization layer was 2.9 μm at 759 h, increased to 8 μm at 1638 h, and remained stable thereafter. The size of recrystallized grains in SP-samples processed under pressure of 0.06 MPa and 0.15 MPa was approximately 2.92 μm, whereas it was about 1.32 μm for 0.25 MPa processed sample.

A study on the fretting corrosion of 316L in static lead-bismuth eutectic (LBE): The role of slip amplitude and normal force on damage mechanism at 350 °C

Fretting corrosion of stainless steel in the LBE affects the safety of lead-cooled fast reactors. Slip amplitude and normal load are the main mechanical factors affecting fretting wear behavior. Thus, the damage mechanism of 316L stainless steel at 350 °C LBE influenced by slip amplitude and normal load was investigated by jointly utilizing multiple characterization methods. The results indicate that the normal load and slip amplitude essentially affect the tangential stress and relative sliding value in the contact area, leading to different slip regions and damage mechanisms. In the mixed slip region, the damage mechanism is adhesion and delamination cracks. The increase in tangential stress leads to decrease in relative sliding. The thick wear debris layer attached to the worn surface can protect the substrate from being attacked by the LBE. In the gross slip region, the damage mechanism is abrasive wear and dissolution corrosion. The increase in relative sliding causes more damage and Ni dissolution, leading to the transformation from austenite to ferrite and internal strain, making the substrate more susceptible to damage and increasing the risk of liquid metal embrittlement (LME) of austenitic stainless steel at 350 °C. Accordingly, a model for different damage mechanisms was proposed. These results can provide important information on the fretting damage related to the LBE environment.

Crevice corrosion behavior of 316L austenitic steel in static liquid lead-bismuth eutectic at 550°C

Crevice corrosion is a significant form of localized corrosion that can lead to failures in structural components. However, there is a lack of research on this phenomenon in liquid lead-bismuth eutectic (LBE). In this study, the crevice corrosion behavior of 316 L exposed to stagnant LBE with the oxygen concentration of 1 × 10–6 wt.% at 550 °C for 500 h was examined for the first time. Microstructural characterizations indicated 316 L is susceptible to crevice corrosion and reducing the crevices size facilitates a transition from oxidation to dissolution corrosion. Grain boundaries are able to provide more diffusion channels for oxygen, thereby promoting the development of Cr-rich oxides and chemical segregations beneath the surface scale. A simplified model elucidating the transportation of dissolved oxygen within the crevice environment of LBE has been developed.

Tensile and cracking behavior of thin-walled 316Ti austenitic steel after exposure to 550 °C lead-bismuth eutectic with different oxygen concentration

The corrosion evolution of 316Ti steel in 550°C lead-bismuth eutectic (LBE) with oxygen concentrations (Co) of 5×10-6 wt.% and 5×10-8 wt.% and their impact on the tensile behavior were investigated in this study. The steel primarily underwent oxidation at Co of 5×10-6 wt.%, slightly influencing the tensile strength and elongation of specimen within 1000 hours exposure. In contrast, the structural integrity and tensile strength of specimen were significantly deteriorated at Co of 5×10-8 wt.% where the steel mainly experienced dissolution corrosion. The cracking behaviors of oxide layer and ferrite layer, and their influences on the failure of thin-walled specimen were discussed. Special concerns should be raised on the detrimental effect of localized corrosion, such as intergranular oxidation, LBE-wetted precipitate bands and dissolution pits, since cracks are expected to initiate easily in these zones and propagate into steel matrix under tension, potentially leading to the premature failure of thin-walled components.

Microstructural Evolution of Pre-oxidized T91 Steel During LBE Dissolution Corrosion

Microstructural Evolution of Pre-oxidized T91 Steel During LBE Dissolution Corrosion

New insights into selective leaching and ferritization in 15-15Ti austenitic steel in lead-bismuth eutectic through parent phase reconstruction

Selective leaching accompanied by ferritization is widely observed in the dissolution corrosion of austenitic steels exposed to lead-bismuth eutectic. This study proposes a refined mechanism for selective leaching involving solid-state diffusion followed by dissolution-reprecipitation processes. Pole figure analysis reveals that ferritization follows the Nishiyama-Wassermann orientation relationship, independent of corrosion environment or corrosion behavior. Moreover, austenite reconstruction analysis shows that the growth of ferrite is hindered by the misfits at random high-angle grain boundaries. Hence the above results suggest that ferritization is initially driven by solid-state diffusion. As LBE channels open within the grains, further growth of ferrite is assisted by the dissolution-reprecipitation mechanism. Additionally, the formation of dual-oriented ferrite grains at Σ3 twin boundary is observed, and the selectivity of this formation with respect to grain boundary and ferrite orientation is discussed.

Corrosion behavior of the second phase in Mg–9Gd–3Y–2Zn–0.5Zr alloy under simulated coastal storage environment

The Mg–9Gd–3Y–2Zn–0.5Zr alloy was studied for its long-term corrosion behavior in a simulated coastal storage environment. The results show that the Mg12 (Y, Gd) Zn phase in the Mg–9Gd–3Y–2Zn–0.5Zr alloy forms a galvanic couple with α-Mg, and the Mg12 (Y, Gd) Zn phase acts as a cathode to accelerate α-Mg during the corrosion initiation period. The corrosion of the anode is subsequently transformed into corrosive dissolution of the anode. With the dissolution of the Mg12 (Y, Gd) Zn phase, elements such as Gd and Y are gradually distributed into the entire corrosion product layer, improving the protective performance of the corrosion product layer by forming dense Gd2O3 and Y2O3.

Corrosion of F/M steels and austenitic steels in Pb-Mg at different temperatures

Pb83Mg17 is expected to be a potential coolant for lead cooled fast reactors because of its less toxic radioactive products and possible acceptable corrosion rate without additional oxygen control in comparison with LBE. In order to evaluate the compatibility of structural steels and Pb-Mg, two F/M steels (SIMP, T91) and two austenitic steels (316L, 15-15Ti) were tested in Pb-Mg at 350, 450 and 550 °C with exposure time ranging from 100 h to 2000 h in this work. Compared with the slight corrosion or no obvious corrosion of F/M steels, austenitic steels have suffered very serious dissolution corrosion which is significantly influenced by temperature and exposure time. The corrosion rate of austenitic steels is controlled by dissolution or diffusion mechanism at different temperatures.

Oxygen-enhanced dissolution corrosion of austenitic stainless steel 316 L in static lead-bismuth eutectic at 500 °C

The corrosion process of 316 L austenitic stainless steel in liquid lead-bismuth eutectic at 500°C with dissolved oxygen concentrations ranging from below 10−11 to 10−5 wt% was investigated. The maximum dissolution corrosion damage and the highest oxygen consumption during the experiments occurred at intermediate dissolved oxygen concentrations (10−7 and 10−6 wt%). An assumption of a governing role of Fe3O4 equilibrium and diffusion-limited processes on the steel surface explains quantitatively this observation. The proposed mechanism suggests that oxygen-enhanced dissolution is a result of the combination of solid steel dissolution and the oxidation of dissolved steel constituents in the liquid metal bulk.

Corrosion behavior of (Cr2/3Ti1/3)3AlC2 and Ti3AlC2 in static liquid lead–bismuth eutectic

AbstractCorrosion behavior of (Cr2/3Ti1/3)3AlC2 and Ti3AlC2 in static oxygen‐saturated liquid lead–bismuth eutectic (LBE) at 550°C and (Cr2/3Ti1/3)3AlC2 in static oxygen‐depleted LBE at 500°C were investigated. In oxygen‐saturated corrosion, the loose and porous corrosion layer consisting of (PbTiO3 + TiO2) was generated on the surface of Ti3AlC2. In contrast, (Cr2/3Ti1/3)3AlC2 formed the protective Cr2O3 layer with better corrosion resistance. Moreover, dissolution corrosion of (Cr2/3Ti1/3)3AlC2 in oxygen‐depleted corrosion was intensified without a protective oxide film. And impurity phase TiC on the surface also caused the decomposition of matrix, thus impairing corrosion resistance.

Enhancing LBE corrosion resistance through inhibition diffusion approach for AlTixCrFe HEA coating

High-entropy alloy (HEA), when used as coating materials for structural steel in lead–bismuth eutectic (LBE) nuclear reactor, faces severe dissolution corrosion due to the diffusion of their constituents along grain boundaries. In order to mitigate dissolution corrosion, a method to enhance the LBE corrosion resistance of HEA is proposed by utilizing a second phase to inhibit elemental diffusion at grain boundaries. Herein, we used the laser cladding technique to prepare a series of biphase AlTixCrFe HEA coating with a body-centered cubic primary phase and a TiAl second phase. During the LBE corrosion process, a single-layer oxide layer (OL) formed on the HEA coating surface, and meanwhile there existed an internal oxidation zone (IOZ) formed beneath the single-layer OL at AlTixCrFe HEA coating interface, which gradually converted into the single-layer OL as the corrosion time prolonged. After 2000 h of corrosion, AlTi0.75CrFe HEA coating exhibited the lowest OL thickness (8.1 μm) and oxidation rate (0.065 μm2/h) because Al, Ti, and Cr acted as protective elements, rapidly forming a protective OL on the surface. Meanwhile, the presence of TiAl second phase at the grain boundaries impeded the mobility of elements, which improved the dissolution corrosion resistance and diminished its destructive impact on the protective OL.

Influence of Si addition on the corrosion behavior of 9Cr ferritic/martensitic steel in static liquid lead-bismuth eutectic

Abstract This study investigated the corrosion behavior of 9Cr ferritic/martensitic (F/M) steel with varying silicon contents when exposed to static lead-bismuth eutectic at temperatures between 450 °C and 550 °C. Except for samples corroded at 450 °C for 500 h, which developed a bilayer consisting of magnetite layer and Fe-Cr spinel layer, the oxide scale at 450 °C and 500 °C consists of exterior magnetite layer, Fe-Cr spinel layer, and disorganized internal oxide zone. Most of samples that corroded at 550 °C underwent dissolution corrosion. With the addition of Si, 9Cr F/M steel demonstrated enhanced corrosion resistance to LBE at low temperatures and effectively delaying the onset of dissolution corrosion at 550 °C.

A Turn-Off Fluorescent Sensor for Metal Ions Quantifies Corrosion in an Organic Solvent

We demonstrate that the corrosion of AISI 1045 medium carbon steel and pure aluminum can be quantified by the turn-off fluorescent sensor Phen Green-SK (PGSK) in ethanol-based solutions. We first evaluate the dependence of the chelation enhanced quenching of PGSK on iron and aluminum ion concentrations. Subsequently, we apply PGSK to examine the anodic dissolution of metal corrosion. The observed time-dependent PGSK-quenching quantifies the corrosion rates of two metals over 24 h of immersion in ethanol-based solutions. The PGSK-based quantification of corrosion is compared to scanning electron microscopy and electrochemical techniques, including open circuit potential and Tafel extrapolation. The corrosion rates calculated from PGSK-quenching and Tafel extrapolation are in agreement, and both indicate a decrease in corrosion rates over 24 h. Our work shows PGSK can efficiently sense and quantify anodic corrosion reactions at metal interfaces, especially in organic solvents or other non-aqueous environments where the application of electrochemical techniques can be limited by the poor conductivity of the surrounding medium.

Local mechanical properties of corrosion layers formed on T91 and SS316L steels after exposure to static liquid LBE at 500 °C for 1000 h obtained by nano-indentation

Static corrosion tests in LBE under oxygen-saturated and –depleted conditions at 500 °C for 1000 h were conducted to investigate the corrosion-induced diffusion layers on T91 and SS316L steels subject to dissolution and oxidation corrosion. Following nano-indentation experiments examined the variations of local mechanical properties within the corrosion layers. Under the present conditions, T91 steel showed better resistance to dissolution corrosion while higher susceptibility to oxidation corrosion against SS316L. For both steels, nano-indentation results showed a gradual decrease in mechanical properties from steel matrix to the corrosion side after dissolution corrosion. When subject to oxidation corrosion, the oxide scale formed on T91 steel showed lower Er-modulus and enhanced hardness in comparison with those of the steel matrix. An obvious decrease in both modulus and hardness was found at the interface between steel matrix and oxide scale.

Evaluating the dissolution corrosion resistance of Hastelloy exposed to liquid lead‐bismuth eutectic at 500°C

AbstractThe present study investigated the dissolution and oxidation corrosion behaviors of Hastelloy exposed to static liquid lead‐bismuth eutectic (LBE) at 500°C with an oxygen concentration of 1 × 10−6 mass%. Hastelloy exhibited better LBE corrosion resistance than the Monel alloy. Both dissolution and oxidation corrosion were observed in Hastelloy, and the maximum LBE penetration depth and spinel layer thickness in the corroded sample after 4000 h of exposure reached 120 ± 36 and 21 ± 12 µm, respectively. Annealing twin boundaries provided favorable paths of accelerated LBE penetration into the matrix, resulting in selective leaching of Ni. Microstructural characterization revealed that the spinel layer formed between penetrated LBE and base metal slowed down the elemental interdiffusion, thereby retarding the dissolution rate. Volumetric changes induced by LBE penetration promoted the formation of stacking faults and dislocations, which could provide more channels for elemental diffusion, leading to the propagation of dissolution attack.

Le Chatelier’s principle to stabilize intrinsic surface structure of oxygen-evolving catalyst for enabling ultra-high catalytic stability of zinc-air battery and water splitting

Well-designed highly active intrinsic surface structure of a catalyst for oxygen evolution reaction (OER) often faces the problem of corrosion dissolution, which severely deteriorates its catalytic stability, and breaking this activity-stability trade-off has always been a huge and long-term challenge. Herein, we employ Le Chatelier’s principle to address this dissolution problem of the catalyst to maintain its intrinsic surface structure for highly efficient and ultra-stable OER. Taking highly active but susceptible oxygen vacancy-rich Co-W oxide as the model catalyst for alkaline OER, its dissolving kinetics is significantly passivated by introducing homo ions into the electrolyte to regulate the dissolution equilibrium, thus achieving ultralong operating stability without sacrificing its high activity. The theoretical calculations and in-situ experimental results unravel the underlying mechanism of this strategy, that is, the homo ions (tungstate ions) can be preferentially adsorbed on the catalyst surface to construct a local non-corrosive environment, thus effectively stabilizing the well-designed unsaturated active cobalt sites to maintain the intrinsic surface structure of the catalyst and preventing them from being reconstructed or transformed toward the unfavorable direction. Importantly, this strategy is also effective in zinc-air battery and electrolytic water splitting, achieving ultra-stable performance over 1200 h, which is of great importance for promoting the practical applications of low-cost non-noble metal-based catalysts in energy devices.

Dissolution corrosion of FeCrAl alloy exposed to oxygen-depleted lead–bismuth eutectic containing Ni impurities at 600 ℃

FeCrAl alloy is one of the potential candidates of structural materials due to its high strength, low radiation swelling and good oxidation resistance for the application of lead-cooled fast reactors (LFRs). Particularly, FeCrAl alloy can form protective Al-containing oxide scales after exposure to liquid oxygen-rich Pb and lead–bismuth eutectic (LBE) at 400–800 ℃, showing better performance than traditional commercial stainless steels such as T91, 316L and 15-15Ti. Given the possibility that oxygen in liquid metal could be consumed and not be supplied timely in some quasi-static regions of the actual coolant circuit, to figure out the corrosion behavior of FeCrAl alloy in oxygen-depleted LBE is necessary. In this work, the commercial FeCrAl alloy was exposed to static liquid LBE containing Ni impurities with 10−9 wt% oxygen concentration at 600 ℃ for up to 5000 h, and the surface and cross-sectional morphology of the samples was characterized and analysed. It is found that FeCrAl alloy underwent severe dissolution corrosion, and the maximum penetration depth of LBE reached 161.4 μm after the test for 5000 h; PbBi infiltrated into alloy matrix along the GBs and selectively leached Al from the affected grains. Besides, an interesting discovery is the Cr-rich thin layer at LBE/matrix interface and Ni3Al precipitates in LBE penetration front which should be attributed to the deposition of impurity elements dissolved in liquid LBE during the cooling process.

Microstructure characteristics and degradation behaviors of Se/phosphate conversion coatings on Mg-Gd-Ag-Y-Zn alloys in the Hank's electrolyte

In the present study, a selenium-phosphate based conversion coating (SPCC) was successfully developed on the dual rare-earth Mg-Gd-Ag-Y-Zn by immersion in specific acid phosphate bath. The compositions, morphologies, degradation behaviors as well as the formation/deposition mechanism of the SPCC were deeply analyzed. The results declared that the compositions of conversion coatings were the mixture of Mg3(PO4)2/η-Se, with the shallow hill-like structure and dispersive distribution, which was beneficial to enhance the adhesion and corrosion resistance. The electrochemical and static-immersion tests both revealed that the lowest corrosion dissolution rates of the SPCC coatings were realized through pretreatment at 70 °C, with higher Rct value (507.4 Ω·cm2) and lower corrosion rate of 0.603 mm/y. On the one hand, the appropriate temperature was conducive to increasing the concentrations of H2PO4−/SeO32− and accelerating the exchange rates of molecule active-movement in the conversion solution; On the other hand, the dense/stable selenium-phosphate conversion layers formed by redox reaction and hydrolysis reaction retarded the adsorption sites and penetration channels for corrosive ions.