Corrosion Evolution Research Articles

Effect of austempering temperature on corrosion evolution during immersion of high carbon nano-structured bainitic steel in aqueous chloride environment

Nano-structured bainitic (NSB) steels have a dual-phase structure comprising carbon-rich retained austenite (RA) and bainitic ferrite (BF). These steels exhibit high strength as well as sufficient ductility and damage tolerance and hence can find potential application in marine areas. However, a systematic study of the corrosion behavior is required to assess the reliability and longevity of these steels for the above applications. The role of austempering temperature (250 and 350 °C: specimens NB250 and NB350, respectively) and in turn the microstructural constituents on the corrosion response in aqueous chloride environment has been studied using immersion tests at different intervals of time (10, 20 and 30 days). Characterization of corrosion products has been done using microscopy and multiple spectroscopy techniques to reveal the attack mechanism and corroded layer composition. The corrosion rate, measured using weight loss experiments, decreases with a reduction in austempering temperature of the specimens and with an increase in immersion duration. Cross-sectional imaging of the corroded regions shows highly non-uniform but deeper penetration of corrosion with an increase in austempering temperature. In contrast, specimen transformed at the lowest temperature showed uniform and shallow penetration of corrosion. The corroded layer formed over NB350 after 10 days mostly comprised of oxyhydroxides but oxides took predominance after 30 days. However, NB250 showed mostly oxyhydroxides on the surface after 10 as well as 30 days. Hence, decreasing the austempering temperature while transforming austenite to nano-bainite not only provides higher strength but also greater corrosion resistance in saline environments.

Microstructure and corrosion evolution of aerospace aluminium alloy AA2024 thin wall structure produced through WAAM

Microstructure and corrosion evolution of aerospace aluminium alloy AA2024 thin wall structure produced through WAAM

The pitting to uniform corrosion evolution process promoted by large inclusions in mooring chain steels

The corrosion affects the service life of mooring chain steels in marine environments. The evolution of the corrosion process on mooring chain steels in simulated seawater was investigated through in-situ experiments, and the effect of sulfide-oxide complex inclusions on the pitting initiation is discussed. The matrix surrounding sulfide-oxide complex inclusions is enriched in iron sulfide using secondary ion mass spectrometry. The local dissolution of matrix enriched in iron sulfide triggers pitting corrosion. With the immersion time increasing, the corrosion is developed on the matrix around pits to form corrosion rings, resulting in uniform corrosion when corroded areas are connected. Under corrosion product film, the matrix around inclusions is more severely corroded than other areas to form pits. The corrosion behavior of mooring chain steels is a repeating cycle of pitting to uniform corrosion transition. Large inclusions more promote the process of pitting corrosion initiation than small inclusions and increase the rate of transition from pitting to uniform corrosion. • The corrosion evolution process of mooring chain steels is a repeating cycle of pitting to uniform corrosion transition; • The matrix around inclusions is enriched in iron sulfide, which preferentially dissolves and triggers pitting corrosion; • The average size of sulfide-oxide complex inclusions is larger due to high Mn content in material; • Large inclusions more promote the process of pitting corrosion initiation.

A peridynamic model for crevice corrosion damage

A new peridynamic (PD) model for crevice corrosion damage is introduced and cross-validated with experimental results from the literature. Electrochemical mechanisms are reduced to a simple metal-ion concentration-dependent corrosion rate. Computations over domains with extreme aspect ratios like those seen in crevices are efficiently performed by modifying the PD formulation to accommodate arbitrary-shape horizons. The model is validated against experimental results on bolted washers. Simulations predict both the location and the depth of deep corrosion trenches that form at a distance from the crevice mouth. Far-field boundary conditions are used to autonomously reproduce the experimentally observed progression of crevice corrosion. The PD model results also show that the two factors considered here (diffusion-driven transport of dissolved metal ions, and dissolution being dependent on their concentration) are sufficient to predict the evolution of crevice corrosion.

Determining the Evolution of Galvanic Corrosion in a Complex Geometry

In aerospace structures, the balance between strength and weight is vital to maintain. Dissimilar alloys are often employed to build individual components which, when put together, create a structure achieving the optimized properties. In particular, aluminum alloys have a very high strength-to-weight ratio which makes them ideal for structural components, while stainless steel is often used for hardware, such as fasteners and washers, which holds the aluminum components together [1]. On their own, both aluminum and stainless steels form a passive oxide film which increases their resistance to corrosion. However, when in the presence of an electrolyte, such as a light rain or morning dew, a possibility of galvanic corrosion between the dissimilar metals is present. In the scenario above, stainless steel would act as the cathode, consuming electrons, and the aluminum alloy would act as the anode, releasing electrons and dissolved metal ions.The surface of the aluminum alloy is generally painted with a pretreatment, primer, and topcoat to limit exposure of the bare metal to the environment, thereby decreasing the probability of corrosion. However, the layers of surface coating are often scratched off from mechanical or external damage, leaving the aluminum alloy susceptible to galvanic corrosion. Surface scratches can provide a pathway for an electrolyte into the fastener hole, if no sealant was used in installing the fasteners. Furthermore, an occluded cell is formed between the fastener and panel, which can lead to a build-up of aggressive species and further exacerbate the galvanic corrosion. Previous work has determined how severe corrosion within this occluded region can be, with intergranular corrosion sites up to 2mm in length seen after exposure of 504 hours in an accelerated salt spray environment [2].From a structural perspective, corrosion damage within the fastener hole has much larger implications for cracking than corrosion damage occurring on the surface of the panel. The geometry of the fastener hole is a stress concentrator, which localized corrosion can promote by acting as a nucleation site for cracks [3]–[5]. Conversely, the surface of the panel has no stress concentrators, and the exposed surface makes early detection of corrosion damage feasible.Determining when the fastener hole is most susceptible to corrosion damage is of upmost importance, from a practical standpoint. In this work, finite element modeling is used to determine under what scenarios will the majority of predicted damage be within the fastener hole (worst-case) or on the surface of the panel (best-case). External factors, such as the scribe dimensions, and environmental factors, such as the water layer thickness, will be investigated. In particular, the impact of water layer thicknesses beyond the natural convection boundary layer thickness are considered. Time-dependent studies shed light on a potential transition time between damage concentrating on the surface vs. concentrating within the fastener hole. The time-dependent model will include pH-dependent boundary conditions to simulate the crevice environment. The calculated pH profile along the complex geometry will be compared with experimental results via pH probes in a crevice.[1] C. A. Matzdorf, W. C. Nickerson, B. C. Rincon Tronconis, G. S. Frankel, L. Li, and R. G. Buchheit, “Galvanic test panels for accelerated corrosion testing of coated al alloys: Part 1 - Concept,” Corrosion, vol. 69, no. 12, pp. 1240–1246, 2013.[2] R. S. Marshall, R. Kelly, A. Goff, and C. Sprinkle, “Galvanic Corrosion Between Coated Al Alloy Plate and Stainless Steel Fasteners, Part 1: FEM Model Development and Validation,” Corrosion, vol. 75, no. 12, pp. 1461–1473, 2019.[3] M. D. Mcmurtrey, D. Bae, and J. T. Burns, “Fracture mechanics modelling of constant and variable amplitude fatigue behaviour of field corroded 7075-T6511 aluminium,” Fatigue Fract. Eng. Mater. Struct., 2016.[4] J. T. Burns, J. M. Larsen, and R. P. Gangloff, “Effect of initiation feature on microstructure-scale fatigue crack propagation in Al-Zn-Mg-Cu,” Int. J. Fatigue, vol. 42, pp. 104–121, 2012.[5] J. T. Burns, J. M. Larsen, and R. P. Gangloff, “Driving forces for localized corrosion‐to‐fatigue crack transition in Al–Zn–Mg–Cu,” Fatigue Fract. Eng. Mater. Struct., vol. 34, no. 10, pp. 745–773, 2011.

Corrosion evolution of 2205 duplex stainless steel in hot concentrated seawater under intermittent vacuum and boiling conditions

Long-term corrosion behavior of 2205 duplex stainless steel was investigated in the hot concentrated artificial seawater under intermittent vacuum boiling and atmosphere conditions during the immersion of more than one year by using electrochemical impedance spectroscopy (EIS). Compared to the atmosphere state, the passive film formed on specimen surface is thinner and the induction time for pitting corrosion decreases notably under intermittent vacuum boiling condition. However, the pit propagation is retarded by the lower dissolved oxygen content and violent boiling of solution. The vacuum boiling of solution has opposite effect on the initiation and stable growth processes of pitting corrosion.

Corrosion evolution of Cu-Pb alloys from the Western Zhou Dynasty in simulated archaeological soil environment

• The corrosion behaviour of Cu-Pb alloy has been explained. • The Cu-13.28Pb alloy exhibited the best corrosion resistance. • The corrosion products are composed of metal oxides and metal-insoluble compounds. The corrosion behaviour study of Cu-Pb alloy in simulated archaeological soil environment were investigated using electrochemical accelerated corrosion, Field emission scanning electron microscopy/energy dispersive spectroscopy, laser scanning confocal microscope, X-ray photoelectron spectroscopy and electrochemical methods. It is crucial that the corrosion resistance of the Cu-Pb alloy was found to alter with the Pb content in the alloy. The results demonstrated that Cu-13.28Pb alloy exhibited the best corrosion resistance with the smallest corrosion current density and the lowest anodic dissolution rate. The corrosion products are mainly composed of matrix metal oxides and metal-insoluble inert compounds. The correlation between Pb content and corrosion behaviour and the corresponding corrosion mechanism were clarified.

Time-variant burst strength of pipe with corrosion defects considering mechano-electrochemical interaction

This study aims at assessing the time-variant burst strength of pipe with corrosion defects under high internal pressure. A new numerical model was developed, where the mechano-electrochemical interaction was considered in a simplified manner. The damage evolution of corrosion, which was governed by a stress corrosion model, was realized by a user defined UMESHMOTION subroutine. The time-variant corrosion morphology and burst strength can be obtained using the numerical model. The proposed method avoids the disadvantages of the conventional method, where the damage form and size at a given moment are presumed and history-independent. Based on this simplified method, the effect of a single and two adjacent local corrosion defects on the burst strength of the pipe was investigated. Moreover, a new method was proposed that can consider the time-variant reliability of the pipe along with the randomness of the corrosion rate, geometry, and material strength. The predicted value of the deterministic method was also compared with that obtained by the stochastic method. Furthermore, systematic parametric studies were also conducted.

Construction of corrosion degree model and mechanical properties random model of non-uniform corroded reinforcement under multi-factor coupling

In order to improve the prediction accuracy of the theoretical model on steel corrosion degree, the multiple correction coefficient method was used to establish a piecewise constitutive model based on electrochemical signal of stressed reinforcement. Through “micro fault microstructure” analysis, the non-uniform local corrosion surface characteristics and evolution mechanism of rapid propagation of micro cracks and “Transgranular failure” of stressed reinforcement were deeply revealed. The “external macro surface characteristics and internal micro crystal structure” of corroded reinforcement were related. Based on micromechanics theory and failure criterion of macro deformation, the micro mechanism of micro crack propagation under the coupling effect of internal and external factors (e.g. micro defects, stress state) were revealed, and the essence of macro “low stress brittle fracture” was induced. The influence factors of time-varying and material heterogeneity of the real bridge were introduced, and the “random time-varying model” of mechanical properties of corroded reinforcement under the coupling effect of stress corrosion and material heterogeneity was constructed. Combined with previous visualization method, the “electrochemical signal non-uniform corrosion characteristics mechanical property degradation” was related to form a “three-dimensional time-varying model,” which provided guidance for engineering application.

Forecasting the durability of public transport bus bodies depending on operating conditions

This paper addresses the issue related to forecasting the durability indicators of public transport buses under operational conditions. It has been established that when buses are operated to transport passengers the bus bodies wear at different intensities. During operation, the strength of the body frame weakens under the influence of corrosion in combination with sites of fatigue destruction. As it was established, the intensity of corrosion of the bus body depends on the number of residents in the city where the bus is operated. The earlier established dependences were taken into consideration; the current study has identified two conditional variants of corrosion evolution based on the number of inhabitants: up to 1 million and exceeding 1 million. The expediency of repairs and their impact on the bus passive safety has been analyzed. It was found that the elements of the body frame, without external characteristic damage, no longer meet the specified conditions of strength as a result of sign-alternating loads and during long-term operation. Determining the durability of the bus body was made possible through the construction of a mathematical model. The model’s adequacy was confirmed by road tests of the bus. The devised model describes the movement of the bus over a road surface with different micro profiles, with different corrosion penetration, different loading by passengers, and bus speeds. It was established that the reason for the evolution of structural corrosion is the influence of salt mixtures preventing the icing of roads, as well as ignoring the washing of buses after such trips. It is recommended to use new software for the in-depth study into this issue addressing the combination of various factors of destruction: cyclic loads at variable bus speeds and the corrosion progress. The study results could make it possible to predict a life cycle of the body frame under factors that correspond to actual operating conditions.

The PARC_CL 2.1 Crack Model for NLFEA of Reinforced Concrete Elements Subjected to Corrosion Deterioration

During their service life, existing structures may suffer a combination of ageing and reinforcement corrosion. The corrosion deterioration can significantly affect the durability of reinforced concrete (RC) elements causing premature concrete crushing, size reduction of reinforcement cross-section, degradation of mechanical properties of steel and concrete, and stirrups rupture. One of the main purposes related to durability reduction is the evaluation of the maintenance of adequate safety and residual capacity throughout the life of the structure. For this reason, a non-linear finite element approach (NLFEA), based on multi-layer shell elements and PARC_CL 2.1 crack model has been presented in this paper. The PARC_CL 2.1 model is a fixed crack model developed at the University of Parma and implemented in a subroutine UMAT for ABAQUS that incorporates cyclic constitutive laws of materials and the evolution of corrosion over time. In the present work, the crack model was improved by implementing the effects of exposure to environmental attack. Firstly, the effectiveness of the proposed model has been validated through comparison with experimental data available in literature. The residual capacity of corroded RC panels subjected to cyclic loads was then investigated over time considering different exposure classes. Based on the obtained results, the capacity reduction in terms of maximum shear stress and ductility have been estimated over time.

Monitoring of steel corrosion and cracking in cement paste exposed to combined sulfate–chloride attack with X-ray microtomography

The degradation process of reinforced cement paste exposed to cyclic wetting and drying with a designated salt solution was monitored through X-ray microtomography (μCT). Three exposure conditions (a 3 wt% NaCl solution, a 5 wt% Na2SO4 solution, or a mixed solution of 3 wt% NaCl and 5 wt% Na2SO4) were studied to investigate the potential synergistic effects between chloride and sulfate ions on the deterioration of reinforced cement-based materials. The time-dependent evolution of steel corrosion and cracking of cement paste cover were tracked and visualized, while the volumes of steel loss, corrosion products and cracks were quantified by image analysis. The results indicated that the presence of sulfate ions significantly delayed the initiation of chloride-induced corrosion, but did not seem to greatly affect the corrosion rate once the corrosion occurred. The existence of chloride ions, in turn, also mitigated the damage of cement paste cause by sulfate attack as evidenced by the reduced volumes of cracks. The conventional volume expansion coefficient of corrosion products can be measured by μCT, but this coefficient may not be applicable for modelling the corrosion-induced cracking process when sulfate ions were present. The use of μCT provides a new angle to directly measure the interfacial displacement in reinforced cement paste, which can be used as a valuable input for modelling non-uniform chloride-induced corrosion in the presence of sulfate ions.

Analysis of Corrosion Evolution in Carbon Steel in the Subtropical Atmospheric Environment of Sichuan

Analysis of Corrosion Evolution in Carbon Steel in the Subtropical Atmospheric Environment of Sichuan

Corrosion rates of reabsorbable Mg-based materials coated with phytic acid

ABSTRACT The development of temporary protective coatings on magnesium implants is a priority in the biomedical field. In the present study, corrosion rates were determined by various techniques for powder metallurgy Mg and AZ31 magnesium alloy uncoated and coated with phytic acid (PA). Weight loss measurements, potentiodynamic polarisation, and electrochemical impedance spectroscopy were performed to monitor the corrosion evolution in a phosphate-buffered saline solution at 37°C. The corrosion rates of all samples determined from weight losses were higher than those obtained by electrochemical techniques. According to electrochemical data, the initial corrosion current density of the coated samples decreased by three orders of magnitude as compared with that of the bare substrates. However, the protective effect weakened with the testing time due to the presence of microcracks in the PA conversion coating, which indicated the potential applicability of the coated AZ31 alloy as a biodegradable and resorbable temporary implant material for bone repair.

Designing in-house cathodic protection system to assess the long-term integrity of natural gas pipelines

The sustainability of energy supplies depends highly on the integrity of natural gas pipelines that often compromised by corrosion deleterious effects. The integrity commitment to safety is intuitively achieved by establishing robust protection systems, such as coating and cathodic protection (CP). The objective of this study is to predict failure indicators by identifying parameters that may adversely impact the pipeline protection.In this study, an in-house CP system and pipes network were designed to track the corrosion evolution. Pipe-to soil potential (P/S) measurement was proposed in this research as a monitoring strategy for judging whether a pipe is adequately protected. One of the National Association of Corrosion Engineers (NACE) International acceptance criteria recommending −0.850 V as a minimum instant-off potential for a pipeline to be considered protected was chosen as a baseline. The parameters evaluated in this study were the effect of the coating and the number of anodes of the ground bed. P/S of coated and bare pipes that have been installed since 1995 were measured at different conditions.Surprisingly, the comparative analysis conducted to assess the protection level of coated and uncoated pipes revealed that P/S potentials for both pipes were close and above −0.850 V. This indicates that the pipes were cathodically protected. The similarities in potential readings could be referred to the rust layer that accumulated on the bare pipes’ surfaces and acts as a passive barrier similar to coating. Another interesting observation is that the P/S potentials increase gradually as the numbers of the anodes decreases. The results showed that decreasing the anodes numbers by 25–50% has little to no impact on the P/S potentials change, as the reading in the range of −1.473 to −1.666 V. However the P/S potentials reading abrupt to the range of −2.217 to −2.695 V when the number of anodes reduced by 75%. Although the increase in the P/S potentials appears to be beneficial, in fact, this increase can be considered as a negative indicator since the elevated potential implies that the anode discharges a high electrons influx which in turn shortens its lifetime.

The Influence of Archaeometallurgical Copper Alloy Castings Microstructure towards Corrosion Evolution in Various Corrosive Media

The local patterns at the interfaces of corrosion stratification, developed on two archaeometallurgical bronzes (a Cu-Sn-Pb and a Cu-Zn-Sn-Pb alloy), in the as-cast condition, were assessed by OM and SEM-EDS systematic elemental chemical analyses. Previously, the alloys—whose metallurgical features and electrochemical behaviour were already well studied—have been subjected to laboratory corrosion experiments. The corrosion procedures involved electrochemical anodic polarization experiments in various chloride media: 0.1 mol/L NaCl, 0.6 mol/L NaCl and two other synthetic chloride-containing solutions, representing electrolytes present in marine urban atmosphere and in the soil of coastal sites. The characterization of the Cu-Sn-Pb alloy electrochemical patinas after anodic sweep (OCP+ 0.6 V) revealed that the metal in all electrolytes undergoes extensive chloride attack and selective dissolution of copper which initiates from the dendritic areas acting as anodic sites. The most abundant corrosion products identified by FTIR in all electrochemical patinas were Cu2(OH)3Cl), Cu2(OH)2CO3 and amorphous Cu and Sn oxides. The characterization of the Cu-Sn-Pb alloy electrochemical patina after slow anodic sweep (OCP+ 1.5 V) in 0.1 mol/L NaCl reveals selective oxidation of dendrites and higher decuprification rate in these areas. Corrosion products of Sn-rich interdendritic areas are dominated by oxygen species (oxides, hydroxides, hydroxyoxides) and Cu-rich dendrites by chlorides. In the case of Cu-Zn-Sn-Pb, Zn in dendritic areas is preferentially attacked. The alloy undergoes simultaneous dezincification and decuprification, with the former progressing faster, especially in dendritic areas. The two processes at the alloy/patina interface leave behind a metal surface where α-dendrites are enriched in Sn compared to the alloy matrix. The results of this study highlight the dynamic profile of corrosion layer build-up in bronze and brass. Moreover, the perception of the dealloying mechanisms progression on casting features, at mid-term corrosion stages, is extended.

Inhibitive Characteristics of Cefalexin Drug Addition on Corrosion Evolution of Mild Steel in Chloride Medium

The inhibition effect of Cefalexin on the corrosion of mild steel in sodium chloride has been examined with the use of weight loss and potentiodynamic polarization methods at ambient temperature. Cefalexin showed good protection ability by adsorbing on the mild steel surface. The mixed inhibition characteristics of Cefalexin were revealed by the Potentiodynamic polarization results. The inhibitor efficiency was found to be above 65% obeying the Langmuir and Freundlich isotherm law with correlation regression coefficients of R2 = 0.9984 and R2 = 0.9488, respectively. The closeness of these R2 values to unity established the reliability of Cefalexin as an inhibitor.

Study on the corrosion behaviors of high-silicon chromium iron in acidic and alkaline soil solutions

Purpose High-silicon chromium iron (HSCI) has been used in ground grids in southern China, while there was a lack of study on its corrosion behavior in this soil environment. The purpose of this paper is to discover the corrosion of HSCI in acidic and alkaline soil solutions. Design/methodology/approach The original defects on the HSCI surface were observed using optical microscopy, and the corrosion behavior of the HSCI in the acidic and alkaline soil solutions were jointly detected using electrochemical measurements and scanning electron microscopy/energy dispersive spectrometer. Findings The results showed the corrosion rates of the HSCI in the acidic and alkaline soil solutions were limited, and the high contents of Cr and Si in matrix was responsible for its high corrosion resistance. The HSCI showed a similar corrosion tendency in the two solutions, while its corrosion rate in the acid soil solution was higher than that in the alkaline soil solution. The corrosion pits on the specimen surface were originated from the original defects in matrix, and the edges of the corrosion pits were more rounded than the original defects after 720 h immersion in the two solutions. The original defects in the HSCI matrix played a significant role in the corrosion process. Originality/value The paper discovered the corrosion evolution of HSCI in the acidic and alkaline soil solutions. What is more, the acceleration role of the original defects on the corrosion of the HSCI in the acidic and alkaline soil solutions was discovered in the paper. The results are beneficial for the material selection of ground grid equipment in engineering.

Evolution of microstructure, mechanical properties and corrosion behavior of Al-4Mg-2Zn-0.3Ag (wt.%) alloy processed by T6 or thermomechanical treatment

The evolution of microstructure, mechanical properties and intergranular corrosion (IGC) resistance of the heat-treatable Al-Mg-Zn-Ag alloy processed by T6 or thermomechanical treatment (TMT) technologies are systematically investigated. The mechanical properties and IGC resistance are both improved by the TMT technology. The combination of pre-deformation with aging promotes the dynamic precipitation of nanoparticles and the formation of substructure. Consequently, the hardening effect of the alloy is improved. The intergranular microstructure of grain boundary precipitates and precipitate free zone can be ameliorated by optimizing of processing parameter of TMT technology, which greatly improve the resistance of IGC of the alloy.

Preparation and Characterization of a Silane Sealed PEO Coating on Aluminum Alloy

A dense alumina ceramic coating was formed on UNS A97075 Al alloy by plasma electrolytic oxidation (PEO). An efficient and environmentally friendly silane layer was prepared to seal the PEO coating. The scanning electron microscopy (SEM) results showed that the PEO coating was completely sealed by the silane layer. The electrochemical corrosion evolution of the silane sealed PEO composite coating was studied by electrochemical impedance spectroscopy (EIS). Based on the EIS data, the corrosion evolution of the silane sealed composite coating could be divided to three stages during 576 h of immersion test, and the silane coating acted as a good physical barrier in the immersion test, effectively delayed the corrosion process and improved the corrosion resistance.