Severe Localized Corrosion Research Articles

Developing high elongation of Ca-containing Zn alloys with superior osteogenic and antibacterial properties

The development of high-strength zinc (Zn) alloys significantly contributes to the field of orthopedics by enhancing their osteogenic properties. Calcium (Ca) is pivotal for bone composition; however, its incorporation into the Zn matrix often hampers elongation due to the formation of large-sized CaZn13 phases. In this study, two Zn alloys with different Ca contents were prepared, and their microstructures, mechanical properties, corrosion behavior and biocompatibility were investigated. Results indicate that the Zn alloy with high Ca content exhibits large-sized and high-volume-fraction CaZn13 phases, which do not significantly change during equal channel angular pressing (ECAP). The grain sizes of ECAPed Zn alloys decreased from 36.75 μm and 35.81 μm of as-cast state to 4.32 μm and 1.71 μm, respectively. Refined microstructures contributed to the improvement of mechanical properties of Zn alloys, which have elongation over 15 % higher than that of all Zn-Mg-Ca alloys reported so far. The high elongation of Zn alloys originates from the inhibition of the propagation of microcracks which generated from the Zn/CaZn13 interphase. Moreover, the formation of large-sized CaZn13 phases leads to the severe local corrosion through enhancing galvanic effect, finally increasing corrosion rate. During degradation, the release of metallic ions, such as Zn2+, Mg2+, and Ca2+, are beneficial to the cell viability and osteogenic properties. And the accelerated release of Zn2+ plays a role in antibacterial performance. These results are very helpful for promoting the application of biodegradable Zn alloys in the field of orthopedics.

Understanding the Effect of Corrosion Resistance in Welded AA2198‐T8 Alloy: Microstructural‐Electrochemical Insights

ABSTRACTIn this study, we explore the corrosion resistance of AA2198‐T8 alloy in friction stir‐welded zones, focusing on microstructure changes and resulting corrosion susceptibility. Macrogalvanic coupling effects are observed in weldment under corrosive conditions, particularly in the welding joint (WJ), heat‐affected zones, and base metal (BM). Severe localized corrosion is prevalent in anodic zones, revealing intricate trenching patterns around micrometric particles in cathodic domains. Investigating isolated zones exposes SLC across all welding‐affected regions and BM, underscoring the involvement of microgalvanic cells in corrosion. The novel utilization of a syringe cell as an electrochemical tool proves to be instrumental in delineating the electrochemical characteristics of welding testing zones. Notably, stir zone within WJ emerges as the region depicting the lowest corrosion resistance, a critical finding substantiated by localized electrochemical impedance spectroscopy. These insights into the interplay of electrochemical phenomena and microstructural attributes have implications for advancing corrosion mitigation strategies and alloy engineering in materials science.

Investigation on localized corrosion behavior of pipeline steel under AC interference in alkaline earth metal environment using wire beam electrode

The localized corrosion behavior of X65 steel under AC interference in alkaline earth metal environment was investigated using the detachable wire beam electrode (WBE). The AC/DC current distribution, electrochemical properties, and elemental distribution were traced through the WBE to characterize the localized corrosion behavior and mechanism. The results show that hydrogen evolution under high cathodic protection (CP) conditions leads to an uneven distribution of calcareous deposits, and areas not covered by calcareous deposits have higher JAC and Cl− concentrations. The synergistic effect of Fe3O4 dissolution reprecipitation process, hydrogen evolution and Cl− leads to severe localized corrosion.

Effects of H2S content on the corrosion behavior of gas storage reservoir injection and production pipeline steel in CO2-H2S environment

The effects of H2S content on the corrosion behavior of gas storage reservoir injection and extraction pipeline steel in a CO2-H2S environment were investigated by surface characterization and ultrasonic thickness measurement. The results show that the corrosion products of gas injection and extraction pipelines under real conditions are more complex. In the CO2-H2S environment, with the increase of H2S content, the corrosion rate of gas storage reservoir gas injection and extraction pipeline steel firstly increases and then decreases. At a partial pressure ratio of CO2 to H2S of 550, corrosion resulted mainly in the formation of FeCO3, FeS2, and Fe3O4, with limited generation of stabilizing protective films. This led to severe localized corrosion, mainly driven by CO2. In contrast, when the CO2 to H2S partial pressure ratio was reduced to 5.2, the corrosion mainly produced Fe7S8, FeS2, and BaSO4, which promoted the formation of a more stable protective film on the inner wall of the tube, while the presence of gums reduced the severity of the localized corrosion and shifted the corrosion control to H2S.

Enhancing corrosion resistance of AZ31B magnesium alloy substrate in 3.5 % NaCl solution with Al-Si coating prepared by cold metal transfer-based wire arc additive manufacturing

In this study, we explored an innovative approach to enhance the corrosion resistance of AZ31B magnesium alloy in 3.5 wt% NaCl solution by applying an Al-Si coating using cold metal transfer (CMT)-based wire arc additive manufacturing (WAAM) technology. The findings indicate that the Al-Si coating improved the alloy’s corrosion performance, with a more noble self-corrosion potential (- 0.97 VSCE) and lower self-corrosion current density (3.68 μA/cm2) compared to untreated AZ31B. Long-term immersion tests demonstrated that AZ31B suffered from severe localized corrosion, while Al-Si coating maintained a uniform corrosion profile. Analysis of the corrosion products showed that the Al-Si coating primarily comprised oxidized Mg and hydroxide Al, with minimal oxidized Al and Si, in contrast to the mainly metallic and hydroxide Mg on AZ31B. By reducing the electrochemical activity and enhancing the stability of corrosion products, the Al-Si coating significantly improved the corrosion resistance of AZ31B substrate. This study suggests a promising avenue for advancing the durability of magnesium alloys in corrosive environments.

Study of the corrosion behavior of N80 and TP125V steels in aerobic and anoxic shale gas field produced water at high temperature

In this study, the corrosion behavior of N80 and TP125V steels was delved firstly into produced water from shale gas fields containing CO2-O2. Moreover, the localized corrosion of these steels was investigated to elucidate the effects of aerobic and anoxic on steel corrosion. The results indicated that the corrosion rates of N80 and TP125V steels under aerobic conditions were lower compared to those in the presence of CO2-O2. Specifically, at temperature of 100 °C and with dissolved oxygen (DO) concentration of 4 mg/L in the CO2-O2 environment, the N80 and TP125V steels exhibited the highest corrosion rate, with values of 0.13 mm/y and 0.16 mm/y, respectively, as determined by specific weight loss measurements. Conversely, these rates decreased to 0.022 mm/y and 0.049 mm/y under aerobic conditions. Furthermore, severe localized corrosion of N80 and TP125V steels with a DO concentration of 4 mg/L was also observed in the CO2-O2 environment. Finally, it was evident that pitting corrosion is the predominant type of corrosion affecting N80 and TP125V steels in the produced water from shale gas fields.

Development of highly corrosion-resistant Mg-Al-Y extruded alloy via regulating the Mg17Al12 phase

A highly corrosion-resistant AW90 extruded alloy (Mg-9Al-0.2Y wt %) was developed via alloying and solution-aging treatment (PW = 0.14 mm/y). The solution-treated AW90 alloy exhibits the most severe localized corrosion due to the strong micro-galvanic acceleration effects. The finely dispersed Mg17Al12 phase promotes the strong quasi-passive behavior and uniform corrosion of the aged AW90 alloy due to the formation of a dense and uniform corrosion product film. The high corrosion resistance of the aged AW90 alloy is attributed to the formation of a Mg-Al layered double hydroxide film, which has stronger resistance to chloride ions.

Microstructure and corrosion behavior of a hot-rolled pure Mg after annealing at various temperatures

The microstructure and corrosion behavior of a hot-rolled pure Mg in the rolled state and after annealing at various temperatures was studied in this paper. It was found that the hot-rolled pure Mg after annealing at 250 °C, 350 °C, 400 °C, 500 °C and 550 °C showed homogeneous microstructures and the presence of a partially recrystallised tissue in hot rolled pure Mg. Corrosion of annealed Mg mainly occurred at grain boundaries, which stemmed from the relatively higher energy and chemical activation on the grain boundaries. Initial corrosion sites were provided by different proportions of High angle grain boundaries (HAGBs). The corrosion rate tends to increase and then decrease with increasing grain size. The Mg annealed at 450 °C showed a non-uniformed microstructure, with a lower fraction of the recrystallization grains and higher fraction of HAGBs, leaving to the severe localized corrosion and the highest corrosion rates. Corrosion rate measurement indicated that there existed a curvilinear relationship between the corrosion rate and grain size.

Research on the Multifactor Synergistic Corrosion of N80 and P110 Steel Tubing in Shale Gas Wells in Sichuan Basin

We aimed to investigate the corrosion patterns and the main controlling factors of N80 steel and P110 steel tubing under different sections. Conducting weight loss corrosion experiments for 168 h using high-temperature and high-pressure autoclaves to simulate the corrosion behavior of two types of casing materials, N80 steel and P110 steel, in different well sections under specific conditions of CO2 content, chloride ion concentration, temperature, pressure, and sulfate-reducing bacteria population in highly mineralized formation water. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) were used to analyze the corrosion products, surface morphology, and elemental composition of the two steel pipes. Additionally, 3D microscopy was employed to observe the morphology and measure the dimensions of localized corrosion pits. Under different well sections, the corrosion products formed on N80 steel and P110 steel mainly consist of FeCO3, and crystalline salts of chlorides present in the solution medium. Under low-water-cut conditions, narrow and deep corrosion defects were observed, while narrow and shallow corrosion defects were found under high-water-cut conditions. In the upper wellbore section, both steel pipes exhibited dispersed and thin corrosion product films that suffered from rupture and detachment, resulting in severe localized corrosion. In the middle wellbore section, the corrosion product film on N80 steel comprised irregularly arranged polygonal grains, some of which exhibited significant gaps, leading to extremely severe corrosion. For P110 steel, the corrosion product film was also dispersed and thin, with extensive detachment and extremely severe corrosion. In the lower wellbore section, both steel pipes were covered with a dense layer of grains, with smaller gaps between them, effectively protecting the metal matrix from corrosion. Consequently, the corrosion rate decreased compared to the middle section but still exhibited severe corrosion. In low-water-cut conditions, attention should be given to the risk of column safety due to corrosion from condensate water and CO2, as well as the size of narrow and deep corrosion defects in the middle wellbore section. In high-water-cut conditions, it is recommended to use corrosion inhibitors in combination while focusing on SRB bacteria corrosion in the upper wellbore section, condensate water in the middle section, CO2 content and chloride ion coupling in the lower section, and the size of narrow and shallow corrosion defects causing column safety risks.

Corrosion Behavior of 30 ppi TAD3D/5A05Al Composite in Neutral Salt Spray Corrosion

This study created ceramic preforms with a 3D network structure (TAD3D) by using treated aluminum dross (TAD) and kaolin slurry, with 30 ppi polyurethane foam as a template via the sacrificial template method. TAD3D/5A05Al composites were then produced via pressureless infiltration of 5A05Al aluminum alloy into TAD3D. The corrosion behavior and resistance of TAD3D/5A05Al in salt spray were assessed via neutral salt spray corrosion (NSS), scanning electron microscopy (SEM), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) tests. The results showed that after 24 to 360 h of NSS corrosion, the corrosion of the 5A05 matrix was primarily pitting, with pits expanding and deepening over time, and showing a tendency to interconnect. The main corrosion products were MgAl2O4, Al(OH)3, and Al2O3. As corrosion progressed, these products increased and filled cracks, pits, and grooves at the composite interface on the material’s surface. Corrosion products transferred to the grooves at the composite interface and grew on the ceramic surface. Corrosion products on the ceramic framework and the Al matrix can form a continuous passivation film covering the composite surface. PDP and EIS results indicated that the composite’s corrosion resistance decreased by 240 h but increased after that time. After 240 h, the surface passivation film can weaken corrosion effects and enhance the composite’s resistance, although it remained weaker than that of the uncorroded samples. Additionally, grooves at the composite interface deepened over time, with loosely structured corrosion products inside, potentially leading to severe localized corrosion.

Die soldering and corrosion failure of high temperature tool steel for high-pressure die casting Al alloy

High-pressure die casting (HPDC) is regularly used to produce aluminum components. The die-casting molds are subjected to severe localized corrosion due to contact with the hot melted aluminum (700 °C) and accelerated by the intense thermal cycling generated by the cooling system. The correct understanding of each failure mode that occurs during the operation of these molds can increase tool life and reduce operational costs. Different components used in aluminum components production were evaluated after completing their useful tool life, and the failure modes were compared with two high-temperature laboratory tests, molten aluminum corrosion and die soldering tests. The primary crack mechanism observed in the HPDC die was heat checking, with a surface reaction of the tool steel with the molten aluminum. PVD coating increases the die's tool life, reducing the reactivity with the molten aluminum, which was observed in both laboratory tests. Die soldering tests represent the die mold behavior in HPDC production, showing a similar intermetallic phase and crack formation. Laboratory corrosion tests showed a more aggressive corrosion behavior than that observed in molds and dies used in HPDC industrial production.

A spatiotemporal “bulk erosion” mode in selective laser melted magnesium alloys and the resulting adverse cell & tissue responses

Selective laser melting (SLM) has attracted great attention in the fabrication of magnesium-based biodegradable implants. However, current SLMed magnesium alloys are generally suffered from rapid corrosion, which is deadly detrimental to their use. Herein, we thoroughly revealed why they are so vulnerable to corrosion through a typical SLMed AZ91D material model. An abnormally spatiotemporal “bulk erosion” mechanism was found, not the well-known “surface corrosion” mode of traditionally plastic-deformed alloys. The unique microstructure derived from SLM possesses high chemical reactivity, which is favorable for interactional attacks of fast fluid penetration, severe local corrosion and intensive micro-galvanic corrosion. Thus, it brings two orders of magnitude in corrosion rates compared with its plastic-deformed counterparts. In vitro, such fast-corrosion induced apparent cytotoxicity, cell damage, and further apoptosis to rat and mouse derived mesenchymal stem cells. In vivo, the material disintegrates into small pieces in a short period, and results in unexpected bone destruction and long-lasting foreign body reactions in Sprague Dawley rats. Close attention should be paid to this issue before SLMed Mg-based implants being applied in patients.

Correlation between the micro-shot peening coverage and surface microstructural evolution and fluoride-induced corrosion behavior in Monel 400 alloy

This study examines the influence of micro-shot peening (MSP) on Monel 400 alloy, focusing on surface microstructural evolution and fluoride-induced corrosion behavior compared to its solution annealed (SAed) counterpart. MSP treatments were conducted at various surface coverages (100%, 200%, 500%, 1000%, 1500%, and 2000%). Characterization encompassed microhardness, surface roughness, grazing incidence x-ray diffraction (GI-XRD), field emission scanning electron microscopy (FE-SEM) with electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). With increasing the MSP coverage to 2000%, the surface crystallite size decreased from approximately ∼30 µm in the SAed sample to 60 nm. TEM analysis emphasized dislocation slip and formation of dislocation structures as the primary mechanisms for the grain refinement. However, the 2000% coverage exhibited microcrack formation, compromising its hydrofluoric (HF) corrosion resistance. Electrochemical tests revealed severe localized corrosion in all MSP-treated samples except the 1500% coverage, which exhibited a minimum passive current density of 0.2–1.0 µA/cm2. Inductively coupled plasma optical emission spectroscopy (ICP-OES) of immersion solutions showed lower copper and nickel ion concentrations (<150 ppm) in the 1500% MSP-treated sample, indicating its enhanced corrosion resistance. X-ray photoelectron spectroscopy (XPS) identified NiO, NiF2, CuO, CuF2, and Cu(OH)2 phases in SAed and 1500% MSPed samples, with a higher concentration of copper oxide (CuO) in the corrosion film of the 1500% MSP-treated sample, contributing to its superior corrosion resistance.

Study on hydrogen permeation and stress corrosion cracking behaviors of AISI 4135 high-strength steel with macrofouling adhesion in marine immersion zone

A field exposure test was set up to study the effect of macrofouling adhesion on hydrogen permeation and stress corrosion cracking (SCC) behaviors of a high-strength steel in marine immersion zone, and the results were further verified by laboratory electrochemical simulation tests. The results indicated that the crevices formed by macrofouling adhesion can promote localized corrosion pits and change the local chemical environment. More severe localized corrosion can increase the hydrogen permeation current density and promote the SCC of high-strength steel. As a comparison, the hydrogen permeation current density of steel under cathodic protection state was slightly decreased owing to the shielding effect of macrofouling.

The effect of solution aggressiveness on the corrosion-induced degradation mechanism of Al-Cu-Li 2198 alloy

Investigation on the corrosion-induced degradation mechanisms of Al-Cu-Li 2198 alloy is critical for the aircraft maintenance protocol. This article aims to identify the corrosion-induced degradation mechanisms of AA2198-T8; three (3) different accelerated corrosion tests with electrolytes of various aggressiveness, namely sodium chloride (NaCl), Harisson’s and exfoliation corrosion (EXCO) solution were exploited. Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and immersion tests were used in this context. The EIS analyses revealed that exploitation of different electrolytes essentially affects corrosion-degradation mechanism. Intergranular corrosion attack was found to dominate in EXCO solution, while transgranular attack was evident in both, 3.5 wt. % NaCl and Harrison’s solutions. Severe localized corrosion in Harrison’s solution led to higher degradation of elongation at fracture (Af) throughout immersion duration; EXCO exposure led to higher corrosion attack rate for the short exposure times (≤ 6 hours). Correlation between the different electrolytes regarding tensile ductility decrease was attempted through a linear coefficient for the initial, small exposure times; 1-hour EXCO exposure of AA2198-T8 was found to be equivalent to 107 hours exposure to 3.5 wt. % NaCl solution, while the respective correlation with Harrison’s solution showed that 1-hour EXCO exposure is equivalent to 27 hours Harrison exposure.

In-situ electrochemical testing and fluid dynamics simulation of pipeline defects under flow accelerated corrosion

The pipeline defects of flow accelerated corrosion (FAC) on the corrosion behaviors and localized corrosion mechanisms on different locations of the depressions and the welded joint with weld reinforcements were investigated using wire beam electrode (WBE) techniques and fluid dynamics simulations. The results revealed that the swirling vortex inside the depression and the local jet impact by the fluid separation in the weld reinforcement can accelerate the localized corrosion. Also, the depressed upper and trailing edge regions and the weld toes on both sides of the weld reinforcement experience considerable pressure fluctuations, enhancing interfacial mass transfer processes and inducing cavitation for severe localized corrosion failure. Furthermore, the galvanic corrosion strength factor (g) indicated an enhanced susceptibility of localized corrosion in depression and welded joints with weld reinforcement.

Detrimental effect of stray current on rails and fastening systems in urban railway tracks

In urban railway tracks, the rails serve not only to guide the vehicle, but also as a return conductor for the current the vehicle needs to run. If the rails are not properly insulated, stray current will flow from the rail to the lower part of the track and cause corrosion damage to metal structures near the track. In this study, the damaging effect of stray current on track components (rail and fastening system) was analyzed. The experiment was performed on two identical samples of a rail fastened to the concrete base with a direct fastening system. Both samples were immersed in water, and one of the samples was also treated with a constant direct current from the laboratory power supply via a stainless steel electrode. After 168 days of testing, 3D scans of the rails and clips were made using the ATOS measuring system, comparing the corroded with the reference samples. Applied current caused severe localized corrosion on the rail and rail clips, creating sharp edges that can lead to significant stress concentration under load, accelerate cracking, and contribute to fatigue failure.

Role of Fe oxide in the underdeposit corrosion of pipeline steel in oilfield produced water containing SRB

AbstractThe corrosion behavior of C20 pipeline steel was studied under Fe oxide and sand deposits in oilfield produced water containing sulfate‐reducing bacteria (SRB) via electrochemical techniques and surface analyses. A galvanic current of about 2 μAcm−2 was detected when the Fe oxide deposited sample and the bare steel were coupled in zero resistance ammeter (ZRA) mode, with the former being the anodic member of the couple. The Fe oxide deposited steel recorded severe localized corrosion after 14 days of testing in the SRB inoculated oilfield produced water. Corrosion severity decreased on the sand‐deposited steel, with general corrosion as the dominant morphology of surface attack. The development of product film was a vital factor in steel corrosion under the Fe oxide deposit.

Microstructural Understanding of Flow Accelerated Corrosion of SA106B Carbon Steel in High-Temperature Water with Different Flow Velocities.

All light or heavy water reactors fabricated with carbon steels suffer from flow-accelerated corrosion (FAC). The FAC degradation of SA106B with different flow velocities was investigated in terms of microstructure. As flow velocity increased, the major corrosion type changed from general corrosion to localized corrosion. Severe localized corrosion occurred in the pearlite zone, which can be the prior location for generating pits. After normalizing, the improvement in microstructure homogeneity reduced the oxidation kinetics and lowered cracking sensitivity, causing a decrease in FAC rates of 33.28%, 22.47%, 22.15%, and 17.53% at flow velocity of 0 m/s, 1.63 m/s, 2.99 m/s, and 4.34 m/s, respectively. Additionally, localized corrosion tendency was decreased by reducing the micro-galvanic effect and tensile stresses in oxide film. The maximum localized corrosion rate decreased by 21.7%, 13.5%, 13.8%, and 25.4% at flow velocity of 0 m/s, 1.63 m/s, 2.99 m/s, and 4.34 m/s, respectively.

Metagenomic insights into nutrient and hypoxic microbial communities at the macrofouling/steel interface leading to severe MIC

Adherent macrofouling in marine environments caused complex corrosion of steel surfaces, resulting in localized corrosion at the oyster/steel interface and uniform corrosion at the ascidian/steel interface. Sulfate-reducing bacteria (SRB) have been implicated in the microbiologically influenced corrosion (MIC) process at macrofouling-covered interfaces. To better understand the role of marine biofilms as key mediators in the MIC process, metagenomic techniques were used to study microbial communities and their response to macrofouling’s coverage. Compared to ascidians, the formed local anaerobic zone at oyster/steel interface stimulated the growth of SRBs, leading to higher FeS content and severe localized corrosion. SRB Desulfovibrio and Desulfobulbus, along with the SRB-related functional gene dsr, were found to increase, while oxygen-related function genes coxC, ccoN, ccoO, ccoP, and ccoQ decreased. In contrast, steel surfaces without macrofouling coverage had the richest microbial communities, yet experienced less severe MIC, suggesting no direct connection between microbial abundance/diversity and steel corrosion promotion.