Protective Layer Of Corrosion Products Research Articles

Corrosion Behavior of Homogenized and Extruded 1100 Aluminum Alloy in Acidic Salt Spray.

The 1100 aluminum alloy has been widely used in many industrial fields due to its high specific strength, fracture toughness, excellent thermal conductivity, and corrosion resistance. In this study, the corrosion behavior of the homogenized and hot-extruded 1100 aluminum alloy in acid salt spray environment for different time was studied. The microstructure of the 1100 aluminum alloy before and after corrosion was characterized by an optical microscope (OM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and a laser scanning confocal microscope (LSCM). The difference in corrosion resistance between the homogenized and extruded 1100 aluminum alloy was analyzed via the electrochemical method. The results indicate that after hot extrusion at 400 °C, the microstructure of the 1100 aluminum alloy changes from an equiaxed crystal structure with (111) preferentially distributed in a fibrous structure with (220) preferentially distributed. There was no obvious dynamic recrystallization occurring during extrusion, and the second-phase particles containing Al-Fe-Si were coarse and unevenly distributed. With the increase in corrosion time, corrosion pits appeared on the surface of the 1100 aluminum alloy, and a corrosion product layer was formed on the surface of the homogenized 1100 aluminum alloy, which reduced the corrosion rate. After 96 h of corrosion, the CPR of the extruded samples was 0.619 mm/a, and that of the homogenized samples was 0.442 mm/a. The corrosion resistance of the extruded 1100 aluminum alloy was affected by the microstructure and the second phase, and no protective layer of corrosion products was formed on the surface, resulting in a faster corrosion rate and deeper corrosion pits.

In vitro and vivo biocompatibility and degradability of low-alloyed Mg-Zn-Ca-MgO composite as bone repair biomaterials

Abstract Magnesium alloys have gained attention as biodegradable bone repair biomaterials. Unlike non-biodegradable materials like titanium and tantalum, biodegradable implants offer advantages in promoting bone healing and minimizing chronic inflammatory reactions. However, the impact of the implant's degradation on the osteogenic environment remains a concern. The Mg-Zn-Ca-MgO composite, being biocompatible and containing osteogenic ions, is a promising candidate. This study assesses the degradability and in vitro/in vivo biocompatibility of two Mg-Zn-Ca-MgO composites with varying degradation rates. The Mg-1Zn-0.2Ca-1.0MgO composite was prepared, and leaching solutions were created following standard protocols. MC3T3-E1 cell cultures were conducted to assess cell toxicity, alkaline phosphatase (ALP) staining, cytoskeleton morphology, and osteogenic protein expression. In vivo biodegradation and bone regeneration capacity were evaluated in rat femoral condyles. Benefiting from the more protective corrosion product layer on the surface, the ultra-fine grained (UFG) composite showed better corrosion resistance and lower Mg2+ release than the coarse-grained (CG) composite. UFG material exhibited higher cell viability, cytoskeleton integrity, ALP secretion, and osteogenic protein expression. In vivo, UFG composites led to greater bone regeneration and exhibited excellent biocompatibility. The UFG Mg-Zn-Ca-MgO composite demonstrates enhanced biocompatibility, corrosion resistance, and bone regeneration potential. This study highlights the importance of controlling Mg ion release for optimal bone healing in biodegradable materials.

Probabilistic Analysis of Corrosion Rates and Degradation of Weathering Steel Bridges

AbstractCorrosion of weathering steels in outdoor conditions has been observed since their pioneering applications in construction in the 1960s. Changing environmental conditions such as decreasing SO2 concentration and changes in temperature and relative air humidity affect the formation and development of a protective layer of corrosion products on the surface of these steels. The study compares the long‐term corrosion rates of weathering steels according to EN ISO 9224 with the measured rates for various environments in the Czech Republic and abroad, with a focus on sites with high concentrations of chlorides from de‐icing salts. When considering related uncertainties, the corrosion rate models provide estimates in a wide range, and in‐situ measurements can significantly improve corrosion loss predictions. The reliability of bridges made of weathering steels with a well‐developed protective layer is insignificantly affected by corrosion. However, low reliability levels may be experienced in critical details where for example leakage may damage the protective layer of patina.

Corrosion Resistance and Biological Properties of Pure Magnesium Modified by PEO in Alkaline Phosphate Solutions

Magnesium (Mg) has been explored during the last few decades in the biomedical industry as a biodegradable implant. However, mechanical properties and corrosion resistance are still big concerns for clinical use. Therefore, this study proposes a suitable surface modification of the Mg by plasma electrolytic oxidation (PEO) to improve its corrosion resistance and biological performance. Mg samples were processed in a galvanostatic mode using an electrolytic solution of a phosphate compound supplemented with either potassium pyrophosphate or sodium-potassium tartrate. The obtained coatings were physiochemically characterized by SEM, XRD, EDS, and micro-Raman spectroscopy. The corrosion resistance of the coatings was studied using a hydrogen evolution setup and electrochemical tests. Finally, the biological performance of the material was evaluated by using an indirect test with osteoblasts. Obtained coatings showed a porous morphology with thicknesses ranging from 2 to 3 µm, which was closely dependent on the PEO solution. The corrosion resistance tests improved the degradation rate compared to the raw material. Additionally, an unreported active–passive corrosion behavior was evidence of a protective layer of corrosion products underneath the anodic coating. Indirect in vitro cytotoxicity assays indicated that the coatings improved the biocompatibility of the material. In conclusion, it was found that the produced coatings from this study not only lead to material protection but also improve the biological performance of the material and ensure cell survival, indicating that this could be a potential material used for bone implants.

Effect of Heat Treatment on the Corrosion Behavior of a Supermartensitic Stainless Steel in Sour Solution.

In the present research work, the influence of heat treatment on the corrosion behavior of a supermartensitic stainless steel (SMSS) in sour solution (H2S gas was replaced by sodium thiosulfate) was studied using polarization curve electrochemical techniques (CP) and Electrochemical Impedance Spectroscopy (EIS), along with microstructural characterization using optical microscopy and X-ray diffraction (XRD) measurements. The CP results revealed that the samples subjected to quenching and tempering process exhibited the formation of a more protective corrosion product layer. However, the EIS results showed that this layer accelerated the corrosion process as immersion time increased. Finally, according to XRD and electrochemical test results, the lower the percentage of volume fraction of retained austenite in the microstructure of SMSS, the lower the corrosion resistance.

Inhibition of the erosion-corrosion of elbow by synergistic action of swirling flow and inhibitor

The experiments of using inhibitors to inhibit the erosion-corrosion of elbows under the conditions of liquid-solid non-swirling flow and swirling flow were designed to evaluate the inhibition of erosion-corrosion of elbows under the combined action of swirling flow and inhibitors. The experiments were carried out by a circulating loop system in combination with a variety of test methods and computational fluid dynamics (CFD) simulation. It is demonstrated that the addition of inhibitors under non-swirling flow and swirling flow conditions can inhibit effectively the erosion-corrosion rate and its four components (pure corrosion, pure erosion, corrosion-enhanced erosion, and erosion-enhanced corrosion). The comprehensive inhibition efficiencies of the synergistic action of swirling flow and inhibitor on the four components of erosion-corrosion are higher than the inhibition efficiencies of inhibitor acting on the four components alone. The hydrodynamic characteristics of swirling flow produce the sand suspension effect and mass transfer enhancement effect which facilitate the adsorption of inhibitor on the working electrode surface and acting in conjunction with the oxide film to form a lamellar protective corrosion product layer with stronger integrity and compactness.

Effect of a Small Amount of Cr and Mo on Aqueous CO2 Corrosion of Low-Alloyed Steel and Formation of Protective FeCO3 in Near-Saturation Conditions

The effect of a small amount (1 wt%) of Cr or Mo on aqueous CO2 corrosion of low-alloyed steel and the formation of protective FeCO3 corrosion product layers was investigated under controlled water chemistry conditions, where the bulk saturation value of FeCO3 was maintained at near-saturated condition. Changes in CO2 corrosion rate with exposure time were monitored by linear polarization resisitance measurements. The surface morphology and the composition of the corrosion product layers were analyzed by scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction, and transmission electron microscopy. Results showed that the emergence of a continuous Fe3C layer created favorable conditions at the surface of nonalloyed steel (containing no Cr and Mo) for semiprotective FeCO3 to form even though the bulk saturation value of FeCO3 was maintained at near-saturated condition. However, semiprotective FeCO3 was not observed on the surface of 1% Cr steel and 1% Mo steel, but rather discontinuous and porous corrosion product layer was formed. Due to the hydrolysis reactions of Cr3+ and Mo3+, and the discontinuous structure of the corrosion product layers, the surface conditions for 1% Cr steel and 1% Mo steel were not favorable for the formation of FeCO3 under the experimental conditions of this study.

Effect of O2 contamination on carbon steel pseudo-passive scales in CO2 aqueous solutions

Waters containing CO2 can lead to the formation of a “pseudo passive” protective corrosion product layer on carbon steel, however an oxygen contamination can significantly alter the corrosion behavior. The carbon steel API 5 L X65 specimens were tested in a CO2 saturated solution with small concentrations of O2 (90−270ppb). Electrochemical techniques, Raman spectroscopy and SEM were used for determining the corrosion product layer properties. Oxygen contamination induces pits that result in a significant increase and instability of the open circuit potential. Removing the oxygen contamination, stops pits propagation and the carbon steel surface regains its “pseudo-passive” behavior.

Corrosion Damage to Joints of Lattice Towers Designed from Weathering Steels

The article dealt with the load-bearing capacity and durability of power line lattice towers designed from weathering steel. Attention was paid in particular to the bolted lap joints. The article evaluates the static and corrosion performance of bolted lap joints in long-term operating towers, and also presents and evaluates design measures that can be applied in the design of new lattice towers, or in the reconstruction of already operating structures. Power line lattice towers are the most extensive realization of weathering steel in the Czech Republic. On the basis of the inspections carried out to evaluate the working life of the transmission towers in operation, it can be stated that a sufficiently protective layer of corrosion products generally developed on the bearing elements of the transmission towers. However, the development of crevice corrosion at the bolted joints of the leg members is a significant problem. In this paper, the corrosion damage of bolted joints was evaluated considering two basic aspects: (1) the influence of crevice corrosion on the bearing capacity of the bolted joint was evaluated, using experimental testing and based on analytical and numerical calculations; (2) appropriate design measures applicable to the rehabilitation of developed crevice corrosion of in-service structures, or the elimination of crevice corrosion in newly designed lattice towers, was evaluated. Calculation analyses and destructive tests of bolted joints show that the development of corrosion products in the crevice does not have a significant effect on the bearing capacity of the joint, provided that there is no significant corrosion weakening of the structural elements, and bolts of class 8.8 or 10.9 are used. The results of the long-term experimental programme, and the experience from the rehabilitations carried out, show that, thanks to appropriate structural measures, specified in detail in the paper, the long-term reliable behaviour of the lattice towers structures is ensured.

Engineering of corrosion product-polymer hybrid layers for enhanced CO2 corrosion protection of carbon steel part two: Computational investigation and surface characterisation

Carbon dioxide internal corrosion of carbon steel pipelines remains a major issue that is typically mitigated via the addition of corrosion inhibitors. In specific operational environments, a protective natural corrosion product layer known as iron carbonate (FeCO 3 ) can evolve on internal pipeline walls, providing comparable corrosion inhibitionefficiency to that achieved from surfactants. However, in some instances, incomplete corrosion product coverage can initiate localised corrosion. In our previous work, we demonstrated the ability of Poly (allylamine hydrochloride) (PAH) to act synergistically with FeCO 3 when the corrosion product exhibits partial coverage of ×65 carbon steel surfaces in an aqueous CO 2 corrosion environment. In this work, we employ density functional theory (DFT) to show that PAH is able to coordinate with both FeCO 3 and the bare carbon steel surface, producing a FeCO 3 -PAH hybrid structure. The surface and chemical properties of a naturally formed FeCO 3 and the FeCO 3 -PAH hybrid layers are characterised employing scanning electron microscopy (SEM) coupled with focused ionic beam (FIB), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD) and X-ray photoelectron spectroscopy (XPS). • The PAH molecules adsorb onto the carbon steel surface and corrosion product (FeCO 3 ) via chemisorption and physisorption. • The PAH molecules interact with FeCO 3 through coordination and hydrogen bonding producing a hybrid layer. • The PAH centres of interaction with film-free carbon steel and FeCO 3 film are protonated and neutral amine groups. • The crystal structure and layer thickness of FeCO 3 and FeCO 3 -PAH hybrid layers are characterised and compared.

Influence of dissolved oxygen on the corrosion of mild steel in a simulated cement pore solution under supercritical carbon dioxide

To understand the influence of oxygen on initiation of the localized corrosion of mild steel in the underground casing/cement system for carbon capture and sequestration, the corrosion behavior of P110 steel was systematically investigated by means of electrochemical and analytical measurements in a simulated cement pore solution under supercritical carbon dioxide at 80 °C and 10 MPa. With the increasing concentration of dissolved oxygen from < 150 to 300 μg/L, the protective corrosion product layer on the steel was locally destabilized, producing a reactivation current peak and a lower repassivation potential on the potentiodynamic polarization curve. The presence of more oxygen did not change the cathodic reaction mechanism and the formation of the corrosion product layer. The localized corrosion protrusion would expansively grow as the formation of iron hydroxides at the interfacial region with the penetration of dissolved oxygen and chloride through the preformed corrosion product layer on steel substrate.

Application of Scratch Testing for the Assessment of the Adherent Properties of Scales and CO2 Corrosion Product Layers and their Relation to Corrosion

Protective corrosion product layers, such as iron carbonate, can govern pipeline corrosion; their formation being associated with operational conditions (high [Fe2+], pH > 6.0, T > 70 °C). Brines contain Ca2+ that can incorporate as a substitutional cation in the iron carbonate lattice, potentially compromising the mechanical integrity of the protective layer. This work utilized scratch testing as an analytical technique that provides more information on layer adherence than indentation methods. It was demonstrated that the presence of iron calcium carbonate layers contributes to the formation of a protective and mechanically stable iron carbonate layer adjacent to the steel surface.

Effects of pre-filmed FeCO3 on flow-induced corrosion and erosion-corrosion in the absence and presence of corrosion inhibitor at 60 °C

In CO2 environments, an increase in the temperature can influence carbon steel flow-induced corrosion (FIC) and erosion-corrosion (EC) degradation processes. Increasing temperature typically results in the acceleration of electrochemical degradation mechanisms in the absence of protective corrosion product layers. Furthermore, the presence of sand in corrosive process fluids could aggravate the service conditions. Although protective iron carbonate (FeCO3) film or/and corrosion inhibitors are capable of suppressing corrosion in CO2-containing environments typical of oil and gas production, their ability to suppress degradation and their associated mechanisms in erosion-corrosion environments is less understood. This work focuses on understanding the ability of FeCO3 to protect the steel surface in the absence and presence of corrosion inhibitor and their interactions in flow-induced and erosion-corrosion systems at 60 °C. The effect of the temperature increase is investigated based on results obtained in a previous study performed at 25 °C. FeCO3 filmed carbon steel specimens were developed using an autoclave at 60 °C, pH 6.6 and 30 bar in a 1.5 wt% NaCl CO2-saturated solution over 48 h. The FeCO3 covered specimens were evaluated in FIC and EC environments at 60 °C and a flow velocity of 15 m/s in the presence and absence of 1000 mg/L sand and 100 ppm of a commercially available corrosion inhibitor. Results indicate that the sole presence of an FeCO3 layer is not sufficient to retard the corrosive process of carbon steel at 60 °C under EC conditions. However, the commercial corrosion inhibitor was observed to worked synergistically with the FeCO3 layer to reduce the corrosion degradation component in both the presence and absence of sand particles. The erosion component is also reduced in erosion-corrosion environments as a result of the combined presence of FeCO3 and corrosion inhibitor.

Study of cathodic reactions in defects of thermal spray aluminium coatings on steel in artificial seawater

Electrochemical and surface characterization techniques were used to study the corrosion protection provided by Thermal Spray Aluminium (TSA) coatings on carbon steel substrates with and without defects in artificial seawater. Results showed that the presence of defects accelerates the formation of a protective corrosion product layer on the TSA coating. Voltammetry and Electrochemical Impedance Spectroscopy (EIS) revealed that both calcareous deposits and aluminium corrosion products hindered diffusion of dissolved O2. Analysis of corrosion products by SEM-EDX, μ-Raman spectroscopy and XRD revealed Al oxides/hydroxides and hydrotalcite on top of TSA coating and a bilayer of calcareous deposits on the defect area.

Corrosion Behavior in Hank's Solution of a Magnesium–Hydroxyapatite Composite Processed by High‐Pressure Torsion

It is known that magnesium (Mg)–hydroxyapatite (HA) composites can be produced by the room temperature consolidation of particles. Herein, the corrosion behavior of an Mg–HA composite is analyzed, and a direct comparison with pure Mg is made. Samples of Mg–HA and of pure Mg are immersed in Hank's solution for up to 60 h, and the microstructure and corrosion products are characterized by scanning and transmission electron microscopy and X‐ray diffraction. Electrochemical tests are used to evaluate the corrosion behavior and a hydrogen evolution test is undertaken to determine the corrosion rate. The results show the corrosion rate of the Mg–HA composite is higher than for pure Mg but decreases significantly after ≈10 h of immersion in Hank's solution. The increase in corrosion resistance of the composite is attributed to the formation of a protective layer of corrosion products with an external surface layer rich in Ca, P, and O.

Corrosion performance, corrosion fatigue behavior and mechanical integrity of an extruded Mg4Zn0.2Sn alloy

Magnesium alloys are promising as load bearing components. They are inevitably exposed to cyclic loading and corrosive environment in actual service, which can consequently result in corrosion fatigue failure and loss of mechanical integrity of the material. Therefore, in the present study, the corrosion behavior, corrosion fatigue performance and mechanical integrity of an extruded Mg4Zn0.2Sn (wt.%) alloy were thoroughly studied in two corrosive electrolytes. Strong localized corrosion occurred when the alloy was immersed in deionized water based sodium chloride (NaCl) solution. The poor corrosion resistance of the alloy resulted in a fast deterioration of the tensile properties after pre-exposure to salt spray and a poor fatigue resistance in deionized water based NaCl solution. In comparison, the active dissolution of the substrate was sufficiently suppressed in artificial tap water based NaCl solution due to the formation of highly protective corrosion product layers. This consequently conferred longer fatigue life on the alloy in the electrolyte. Our results emphasized the influence of corrosion on the fatigue behavior and tensile properties of magnesium alloys.

Corrosive Environment Factors and their Influence on the Development of Weathering Steel Corrosion Products

This article deals with the topic of atmospheric corrosion. Atmospheric corrosion causes damage to nearly 80% of all existing steel structures. The main parameters of atmospheric corrosion are the time of wetness (TOW), air temperature and aggressive corrosive agents such as chlorides, sulfur dioxide and others. Currently, low alloy steels with improved atmospheric corrosion resistance called weathering steels are used for the steel structures located in outdoor environment. A protective layer of corrosion products is created on the steel surface and this layer can reduce continuation of corrosion of steel. The time of wetness together with the effect of aggressive corrosive agents are various for surfaces oriented vertically or horizontally. Experimental tests of atmospheric weathering steel were carried out to monitor the impact of location and position of surface on the different constructions. These tests allow monitoring the development of corrosion products in real exposures. The article presents a part of the research, which includes monitoring the development of the thickness of corrosion products with regard to the position on the structure. Research is developed to refine of prediction models with the aim of improving determination of corrosion losses during the service life of the structure. Second part of these experiments is dedicated to measuring the deposition rate of chlorides. Chlorides have a corrosive impact on the steel surface. Under normal conditions the chlorides does not create suitable environment for the development of a protective layer of corrosion products.

Coupling Effects of pH and Dissolved Oxygen on the Corrosion Behavior and Mechanism of X80 Steel in Acidic Soil Simulated Solution.

In an acidic red soil environment, the corrosion mechanism of X80 steel may be closely related to the pH value and oxygen content, but it has not yet formed a systematic understanding. In this paper, the coupling effects of pH and dissolved oxygen on the corrosion behavior and mechanism of X80 steel in an acidic soil simulated solution were further analyzed by electrochemical methods and three-dimensional video microscope. Results showed that the hydrogen reduction reaction was almost the only cathode process in the anoxic and low pH system, and small and dense pits were present on the electrode surface. pH value increased, the pits decreased, but the size of pits increased. In the oxygen-adequate system, oxygen-consuming (OC) corrosion preferentially occurred, and a protective corrosion product layer (including FeOOH, Fe3O4, etc.) might be formed accordingly, but the proportion of hydrogen evolution (HE) increased and the product layer had defects at a low pH environment. The specific corrosion mechanism of X80 steel in an acidic soil simulated solution is described in the relevant models.

Effect of sulfate reducing Citrobacter sp. strain on the corrosion behavior of API X70 microalloyed pipeline steel

In this study, the effect of sulfate reducing Citrobacter sp. strain on the corrosion behavior of API X70 micro-alloyed pipeline steel has been evaluated in a simulated soil solution at different immersion times (varying from 7 days to 40 days) under both abiotic and biotic conditions using open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS). The corrosion products and biofilm morphology developed on the metal surface at various immersion times were evaluated by field emission scanning electron microscopy (FESEM). Formation of a protective layer of corrosion products including ferric oxide, sulfide and carbon-based compounds accumulated on the underlying steel leads to an increase of the corrosion resistance for the first 21 days under abiotic condition. The results of electrochemical impedance spectroscopy in the solution containing bacteria show a significant reduction in charge transfer resistance from 400 Ω cm2 after day 7–55 Ω cm2 after day 21 due to the biofilm formation. This reduction in corrosion resistance is consistent with the high concentrations of sulfide produced by the metabolism of bacteria and the formation of a relatively compact and thick biofilm that is heterogeneously dispersed over the surface. In addition, a higher susceptibility to pitting corrosion is observed for samples immersed in the bacteria containing medium.

Corrosion Processes on Weathering Steel Bridges Influenced by Deposition of De-Icing Salts.

The safety and durability of bridges designed from weathering steels are conditioned by the development of a sufficiently protective layer of corrosion products. Air pollution, microclimate around the bridge, time of wetness, structural solution of the bridge, and the position and orientation of the surface within the bridge structure all influence the development of protective layers on the surface of the weathering steel. In this article, attention is focused mainly on the microclimatic effects resulting from the road traffic under the bridge. The influence of chloride deposition on the development of corrosion products is evaluated using experimental in situ testing. Two neighboring bridges made of weathering steel and crossing different types of obstacles were selected for this experiment. Relations and dependences between the measured parameters (deposition rate of chlorides, corrosion rates, thickness of corrosion products and the amount of chlorides in corrosion products) are evaluated and discussed.