Pitting Corrosion Process Research Articles

Wide temperature range corrosion mechanism of M50 bearing steel in deteriorated oil-water mixture

Bearing corrosion is one of the important causes of engine failures in shipborne aircraft, and solving the problem of bearing corrosion failure is urgent. This article uses chromatography, image analysis, and finite element simulation to study the high-temperature deterioration behavior of Mobil Jet Oil Ⅱ aviation lubricating oil, as well as the corrosion mechanism of M50 bearing steel in oil–water mixture under a wide temperature range. The results indicate that deteriorated lubricating oil without salt water doping does not have corrosiveness. Mobil Jet Oil Ⅱ aviation lubricating oil at 200 °C has obvious deterioration within 48 h, where consumption and decomposition of additives cause acidity changing from pH 8.1 to pH 2 and surface tension decreasing by 11.3 %. The crack corrosion caused by acid and the galvanic corrosion of secondary cementite accelerate the pitting corrosion process. The corrosion enhancement effect of temperature on oil–water mixture shows a parabolic trend. Corrosion can be effectively reduced by lowering the temperature of lubricating oil and quickly removing moisture.

Influence of laser power on mechanical properties and pitting corrosion behavior of additively manufactured 316L stainless steel by laser powder bed fusion (L-PBF)

316L stainless steel parts were additively manufactured via laser powder bed fusion under different laser powers. We investigated the influence of laser power on the microstructure and mechanical properties of the printed parts by conducting scanning electron microscopy, X-ray diffraction, microhardness and tensile tests. In addition, we performed electrochemical corrosion tests including cyclic potentiodynamic polarization and electrochemical impedance spectroscopy in 3.5 wt% NaCl solution to study the influence of laser power on the corrosion behavior of as-printed parts. The results indicate that as-printed parts exhibit a preferential orientation of (220) direction, and increasing the laser power results in grain refinement of the samples, but excessive laser power can lead to a re-increase in the grain size of the samples. Excessively low laser power can result in the formation of lack of fusion pores, while excessively high power can lead to the formation of keyhole pores. These defects lead to a reduction in tensile performance. Significant differences in corrosion resistance are observed for the parts printed with different laser powers, and between the building direction and normal direction. Some defects, such as micropore, MnS inclusions and boundaries of melt pools, have an impact on the pitting corrosion resistance of printed parts. However, due to low content of MnS inclusions, the presence of pore defects remains the major factor in the pitting corrosion process. Laser powers in the range of 300–375 W can effectively reduce pore defects and improve the resistance of pitting corrosion. These findings emphasize the importance of optimizing the laser power to enhance the overall performance and pitting corrosion resistance of 316L stainless steel parts.

Integrated Scanning Electrochemical Probes Assisted by ECSTM for In Situ Imaging of the Pitting Corrosion Process of Carbon Steel in SCCP Solutions

Integrated Scanning Electrochemical Probes Assisted by ECSTM for In Situ Imaging of the Pitting Corrosion Process of Carbon Steel in SCCP Solutions

Investigation on pitting corrosion mechanism of the Fe-based amorphous alloy coating by three-dimensional X-ray imaging at micro-scale

Few work have been performed regarding the quantitative characterization of three-dimensional (3D) pitting corrosion process directly, although the corrosion behaviors and the passivation film stability of metals in various solutions have been studied heavily. The reported work quantitatively characterized the 3D pitting corrosion of the Fe-based amorphous alloy coating (Fe-based AAC) via X-ray micro-computed tomography (X-ray micro-CT) and further elucidated the mechanism of its pitting corrosion. Moreover, the microstructure and electrochemical performance of the Fe-based AAC have also been explored. The results showed that the targeted thermal sprayed Fe43Cr20Mo10W4C15B6Y2 coating was prone to be corroded with the increase of the hydrogen ion concentration, i.e. higher hydrogen ion concentration leads to poorer corrosion performance of the Fe-based AAC. The X-ray micro-CT results revealed that the pits in the Fe-based AAC initially nucleated below the pitting potential, and they also generated in the over-passivation stage. Furthermore, it was found that the corrosive medium does not penetrate into the coating/substrate interface, and the deduced corrosion mechanism from the findings was also discussed.

Evaluation of Crocin as green corrosion inhibitor for aluminum in NaCl solution

The role of Crocin, which is a natural organic substance from the Greek plant Crocus sativus, is investigated as a green corrosion inhibitor for the AA 1050 commercial aluminum alloy in 0.01 M sodium chloride solution. Its action was assessed by Linear and Tafel Polarization, as well as by mass loss measurements and confirmed by observation and analysis of the surface morphology of the specimens by Scanning Electron Microscopy. Corrosion inhibition efficiency of Crocin improves with concentration and at 1.25 mM was estimated in the range of 90-95%, which indicates the formation of an adsorbed layer that isolates and protects the surface. Experimental results showed that Crocin acts as a mixed-type inhibitor with predominantly anodic effectiveness, also retarding pitting corrosion process. The inhibitive action of Crocin was explained by theoretical calculations employing density functional theory, semiempirical PM6 and molecular mechanics methodologies, showing good agreement with experimental results. The reactivity of Crocin is attributed to chemisorption on the Al2O3 surface through its vicinal hydroxyls of the sugar moiety. This process is assisted by the π-conjugated system of the polyene chain together with the extended electron delocalization over the oxygen atoms of the esterified carboxyl groups, as well as by the intense electrostatic potential regions located on the sugar moiety of the Crocin molecule.

Determining the role of individual and combined chemical elements in the pitting corrosion process of austenitic Fe-Cr-Ni steels

This paper reports a study into the role of individual (S, P, N, C, Si, Mn, Ni, Cr) and combined (Q1=S, Q2=S+P, Q3=S+P+N, Q4=S+P+N+C, Q5=S+P+N+C+Si, Q6=S+P+N+C+Si+Mn, Q7=S+P+N+C+Si+Mn+Ni, Q8=Q=S+P+N+C+Si+ Mn+Ni+Cr) elements in five steel AISI 304 smelting cycles. The correlation between the rate of corrosion K in chloride-containing media and the specific magnetic susceptibility c0 of austenite (matrix), the low content Рdof d-ferrite, and the percentage of elements has been established. Taking into consideration the order of arrangement and influence of other present components, a set of the different-shaped graphic models of K dependences on c0, Рd, and percentage of elements was found. However, the sum of the eight calculated individual and combined elements (Q8) of the models coincides with the sum of the same elements (Q=Q8) of steel smelting samples that were subjected to experimental measurements of c0 and Рd. The curves of the reported models were compared with experimental dependences of K on c0, Рd. The positive and negative role of individual and combined elements in the process of pitting resistance of steel smelting cycles has been identified. Given this, it is assumed that the effect exerted on K by individual and combined elements in the intervals before and after their critical content may be ambiguous. Hence, one value K can correspond to several values of the contents of elements, c0, Рd. A proof of that is the coincidence between the calculated models K of corrosion on the same total content of Q8 for steel samples determined experimentally. The positive (negative) and ambiguous role of elements in the process of corrosion and the possibility of predicting corrosion tolerance of austenitic steels are assumed. The experimental dependence K on c0 and Рd has been established; the greater c0 and Рd, the lower the corrosion rate K. The studied steels contained d-ferrite in the low limits of 0.01...0.1 %.

Corrosion behavior and mechanism of dual phase Fe1.125Ni1.06CrAl high entropy alloy

This investigation explores the corrosion behavior and mechanism of as-cast dual phase Fe1.125Ni1.06CrAl high entropy alloy with low density (6.65 g/cm3) and high hardness (460.67 kgf/mm2) in 3.5 wt% NaCl solution. The microstructure, elemental distribution and corrosion behavior of high entropy alloys before and after the corrosion process were investigated via electrochemical quantitative analysis and then the corrosion mechanism of high entropy alloys was obtained by the first principles and experimental modeling approaches. The results show that quaternary Fe1.125Ni1.06CrAl high entropy alloy display spinodal decomposition microstructure of dual BCC phase with high hardness and distinguished corrosion resistance compared with other established alloys. The self-corrosion current density of 9.262 × 10−9 A/cm2 and corrosion potential of − 0.228 V are gotten for this alloy via potentiodynamic polarization measurements and the calculated parameters of high entropy alloys were analyzed by fitting equivalent circuit. Corrosive pits emerged on the alloy surface when the Fe1.125Ni1.06CrAl and Fe1.125Ni1.125CrAl specimens have experienced preferentially localized corrosion at the areas enriched in Ni and Al characterized by scanning electronic microscope and atomic force microscope. Oxides and hydroxides films of constitutional elements on the alloy surface are formed by X-ray photoelectron spectroscopy analysis, which indicates that corrosion properties of high entropy alloys possess. Chloride anions are easier to be adsorbed and attacked on the BCC2 phase surface based on the adsorption behavior analysis, accelerating the localized pitting and micro-galvanic corrosion processes.

Surface relaxation and initial surface corrosion of strained Mo(100) surface

Metal surface corrosion is a common phenomenon under atmospheric conditions, however, the design of corrosion resistant materials at the atomistic level is hindered by the limited knowledge about the corrosion mechanism. Here, the initial surface corrosion of metallic molybdenum, an important in industrial materials, is investigated by using the density functional theory calculations. The adsorption energies of several key corrosion intermediates on Mo(100) surfaces are calculated under various strain (-5% to 5%). The concerted effect of strain and adsorbates can cause significant relaxation of surface atoms (the in-plane atom displacement is within 0.1 - 0.4 Å). The small repulsive lateral interactions among O* adsorbates allow high O coverages. The ensuing corrosion follows the uniform corrosion process rather than the pitting corrosion process. Tensile strain can accelerate the initial surface corrosion process. Further analyses indicate that higher coverage of adsorbates correlates to bigger variation of the interlayer distances, which is the consequence of the competition between the adsorption interactions and the interlayer interactions. The findings reveal the oxidation process over Mo(100) and provide a general understanding for metal corrosion.

Simulating Pitting Corrosion in AM 316L Microstructures Through Phase Field Methods and Computational Modeling

This work investigates how the crystallographic features of additive manufactured (AM) microstructures impact the pitting corrosion process through computational simulations of phase field models. Crystallographic influence is explored by introducing orientation dependencies into the corrosion potentials and elastic constants of the model through microstructural data provided from AM 316L samples. Comparisons of evolved pit morphologies and stress responses are made to a standard homogeneous, semi-circular model to better highlight how the complexity of AM microstructures affects pit evolution and stress concentrations. The results illustrate that AM-informed modeling cases produce larger, deeper pits with numerous locations of elevated stress concentrations along the pit front.

Using Multi-Physics Models to Capture the Influence of Microstructure on Pitting Corrosion Morphologies and Stress Concentrations

Pitting corrosion is of particular concern to the navy because while significant progress has been made in preventing uniform and general corrosion, the possibility of corrosion pits transitioning to crack initiation sites remains a persistent threat with potentially catastrophic consequences. Beyond considerations for the magnitude and mode of mechanical loading, the transition from pit to crack may be influenced by the prevailing electrochemical environment and the microstructural composition of the corroding material. Additionally, both the microstructure and evolving pit morphologies will directly affect local stress concentrations, potentially leading to crack initiation. Until recently, most studies of pitting corrosion, with or without the application of mechanical load, have dealt with the phenomenon from an electrochemical and compositional perspective at the macroscale and have not considered the microstructure nor changes in the evolving pit shape over time. This work presents an investigation of how underlying microstructures can influence the pitting corrosion process, and the resulting stress distributions around pits, through a multi-physics computational modeling framework that incorporates crystallographic orientation dependencies into both the corrosion potential and mechanical response. This is accomplished by importing a microstructure’s orientation data, i.e., the Euler angle information, directly into the computational modeling domain in order to provide crystallographic information.Based on this modeling paradigm, computational simulations are conducted using both experimental and synthetic microstructures for conventionally and additively manufactured stainless steel alloys. Experimental microstructures are provided from electron backscatter diffraction data, while the synthetic microstructures are generated using DREAM3D software. The computational modeling framework utilizes phase field methods to resolve the moving pit boundary while the underlying concentration and displacement gradients are solved over a finite element mesh. Over the course of the simulations, the orientation dependence of the corrosion potentials, and ensuing corrosion current densities, lead to non-uniform growth and propagation of the pit throughout the model domain as it evolves over time, producing irregular pit morphologies. Further, the microstructural influence on mechanical response is measured through differences in peak stresses and stress concentrations along the pit boundary, as well as stress intensity factors. This work highlights the significant local impact microstructure has on the pitting corrosion process and contrasts these impacts over different manufacturing processes (conventional vs. additive) for the same alloy system.

Hydride corrosion kinetics on metallic surface: a multiphase-field modeling

The hydride growth on metallic surface can cause material failure, which is a significant form of pitting corrosion. A new multiphase-field model is constructed to study the hydride corrosion kinetics, in which three order parameters are introduced to represent the passive film, hydride and metal phase, respectively. Coupling with hydrogen concentration field and elastic strain field, this model not only presents the growth of hydride and the rupture of passive film, but also reveals the hydrogen diffusion mechanism and the effect of strain energy on pitting corrosion process. The simulation shows the semi-ellipsoidal cerium hydride forms and grows near the passive film/cerium interface. During this process, the passive film on the upper side of the hydride is also hydrogenated or peeled off, resulting in faster hydrogen transport, which in turn promotes the growth of hydride. The formation of cerium hydride causes volume expansion, and the strain energy is mainly distributed around the hydride, which inhibits its growth. The present study contributes to understanding the formation mechanism of hydride corrosion at mesoscale, especially the pitting corrosion kinetics of rare earth metals.

A hybrid population-based degradation model for pipeline pitting corrosion

This paper presents a novel algorithm to develop a population-based pitting corrosion degradation model for piggable oil and gas pipelines. The algorithm is designed to estimate and predict the distribution of actual depth of existing pits on a pipeline segment, given two or more sets of in-line inspection data that have uncertainty in size and number of the detected pits. This algorithm eliminates the need for a defect-matching procedure for those pits that are not critical, that is required in developing defect-based pitting corrosion degradation models. A hierarchical Bayesian model based on a non-homogeneous gamma process is developed to fuse the uncertain in-line inspection data and physics of failure knowledge of pitting corrosion process. Measurement error (ME), probability of detection (POD), and probability of false call (POFC) are addressed in the developed algorithm. The application of the developed algorithm is demonstrated by implementing it on a simulated case study and the results are compared with the simulated data from a generic degradation model that is available in the literature. Results indicate that this algorithm can predict the degradation level of the pipeline with a high accuracy.

One-step rapid synthesis of a 3D porous surface on Zr-based bulk metallic glass

In this study, a nanoscale 3D porous structure is rapidly synthesized on the surface of a Zr-based BMG by dealloying in solutions containing Cl − and F − . The influence of the porous surface structure the electrolyte on the preparation of the porous surface structure is studied. The Zr-based BMG is more likely to be passivated when F − is added to the HCl solution. The corrosion potential gap between the five components in the alloy increases after the addition of F − . The phase transformation and structure formation of a Zr-based BMG during dealloying are studied. The main dissolved elements in the dealloying process are Zr, Ti, and Al. Cu 10 Zr 7 , Zr 2 Ni 7 and AlTi 3 are the main crystal phases after dealloying, but the Zr-based BMG remains dominated by amorphous phases. The formation of the porous structure can be divided into two stages, the pitting corrosion process and the dealloying process, and these two processes are dominated by Cl − and F − , respectively. A porous surface structure is beneficial to improve the biomineralization activity of Zr-based BMGs. • A method for quickly synthesizing porous structure on the Zr-based BMGs surface has been developed. • The main process of the porous structure formation is the pitting corrosion and the dealloying. • The porous structure is beneficial to improve the biomineralization activity of Zr-based BMGs.

Layered double hydroxides intercalated with methyl orange as a controlled-release corrosion inhibitor for iron in chloride media

In this study, the corrosion inhibition properties of nanocontainer-type layered double hydroxide (LDH) are evaluated on iron that is immersed in a 3.5% NaCl aqueous solution. LDH ZnAl-NO3 was synthesized via coprecipitation. The material presents satisfactory crystallinity with a Zn/Al ratio of 2:1. Methyl orange (MO) has been added into the synthesis process by exchange with nitrate ions and/or by adsorption of MO onto LDH surfaces (LDH-MO). Iron was immersed in solutions with various concentrations of LDH and LDH-MO ranged 1–6 gl−1, and the corrosion inhibition properties were investigated using linear sweep votammetry, electrochemical impedance spectroscopy (EIS), and SEM. Based on pitting potential studies, LDH has demonstrated inhibition of the pitting corrosion process, and the optimal concentration was identified as 2 gl−1. The presence of MO in LDH provides excellent anticorrosive properties with a mixed inhibition mechanism. The corrosion potential of LDH-MO presents more noble values and exchange current densities that are one order of magnitude less than those of the bare iron after 72 h of immersion in a 3.5% NaCl aqueous solution. EIS results corroborated that the corrosion resistance increased when 2 gl−1 of LDH-MO was in solution. SEM images support the anticorrosive behaviour of the LDH-MO.

Analysis of the pitting corrosion process of nickel-plated metal using the phase-field method

Analysis of the pitting corrosion process of nickel-plated metal using the phase-field method

Cellular Automata Simulations of Random Pitting Process on Steel Reinforcement Surface

The corrosion of reinforcement in the concrete will cause the effective cross-sectional area of reinforcement to be weakened and the performance of reinforcement to change and lead to the degradation of the bond behavior between reinforcement and concrete, which can seriously affect the mechanical properties of the structural elements. Therefore, it is of great practical significance to accurately simulate the corrosion morphology and the corrosion products of reinforcement. This paper improves the previous cellular automata models and establishes a new cellular automata model framework for simulating the random pitting corrosion process of reinforcement in concrete. This model defines the detailed local evolution laws of material transformation, penetration and diffusion processes during the corrosion. Meanwhile, based on the spatial inhomogeneity of corrosion, three parameters are introduced into the model: The dissolution probability parameter p, the local corrosion space parameter <i>λ</i> and the local corrosion probability parameter <i>ɛ</i>, which establishes a parameterized model of corrosion probability. The research results show that the common steel reinforcement corrosion morphology can be obtained by adjusting the parameters. The volume expansion rate of the corrosion products is about 2, which is consistent with the relevant experimental research results. The cellular automata model in this paper can simulate the common steel reinforcement corrosion morphology and corrosion products in engineering.

Effects of Sodium Phosphate and Sodium Nitrite on the Pitting Corrosion Process of X70 Carbon Steel in Sodium Chloride Solution

In this paper, effects of sodium phosphate (Na3PO4) and sodium nitrite (NaNO2) on the pitting corrosion of X70 carbon steel in 0.10 mol/L NaCl solution were investigated by potentiodynamic polarization technique, electrochemical impedance spectroscopy (EIS) method, scanning electron microscope (SEM) and scanning electrochemical microscope (SECM). The SECM equipment was used to observe the dynamic processes of the pitting corrosion in situ. Na3PO4 or NaNO2 in the sodium chloride solution decreased the local anodic dissolution and increased the pitting resistance of the specimen. By analysis and comparison, it can be concluded that the inhibition effect of Na3PO4 is mainly due to the formation of a salt film, while the corrosion inhibition of NaNO2 is principally attributed to a protective oxide film on the electrode surface.

Effect of temperature on the electrochemical pitting corrosion behavior of 316L stainless steel in chloride-containing MDEA solution

Here, the effect of temperature on the electrochemical corrosion of 316L stainless steel (SS) in methyl diethanolamine (MDEA) solution with/without 1.0 wt% NaCl in the presence/absence of CO2 was investigated using potentiostatic polarization, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). The electrochemical measurements showed that although the MDEA solution was highly basic, both chloride and temperature played greater roles in the pitting corrosion of 316L SS, similar to plain NaCl solution. The critical pitting temperature (CPT) of 316L SS in MDEA solution with 1.0 wt% NaCl decreased from 67.2 °C to 59.6 °C, and the breakdown potential underwent a negative shift of approximately 400 mV, and the EIS Bode impedance decreased. Furthermore, the breakdown potential shifted negatively with increasing temperature when the temperature was lower than CPT in the MDEA solution containing Cl−; however, the breakdown potential decreased slowly, and its temperature dependence was unclear when the temperature was higher than the CPT. In addition, the passive film resistance of 316L SS in all MDEA solutions decreased as the temperature increased. Particularly for the MDEA solution containing Cl−, the passive film resistance decreased by one order of magnitude when the temperature increased from 50 °C to 60 °C. Although the presence of CO2 in the MDEA solution decreased the passive film resistance, it seemed to reduce the individual corrosion contribution of Cl−. The pitting corrosion process of 316L SS in MDEA solution containing chloride ions was discussed by combining these results with classical pitting mechanisms of stainless steel.

Microelectrochemical Smart Needle for Real Time Minimally Invasive Oximetry.

A variety of brain disorders such as neural injury, brain dysfunction, vascular malformation, and neurodegenerative diseases are associated with abnormal levels of oxygen. Current methods to directly monitor tissue oxygenation in the brain are expensive and invasive, suffering from a lack of accuracy. Electrochemical detection has been used as an invasiveness and cost-effectiveness method, minimizing pain, discomfort, and injury to the patient. In this work, we developed a minimally invasive needle-sensor with a high surface area to monitor O2 levels in the brain using acupuncture needles. The approach was to directly etch the iron from stainless steel acupuncture needles via a controlled pitting corrosion process, obtaining a high microporous surface area. In order to increase the conductivity and selectivity, we designed and applied for the first time a low-cost coating process using non-toxic chemicals to deposit high surface area carbon nanoparticle, catalytically active laccase, and biocompatible polypyrrole. The physicochemical properties of the materials were characterized as well as their efficacy and viability as probes for the electrochemical detection of PO2. Our modified needles exhibited efficient electrocatalysis and high selectivity toward O2, with excellent repeatability. We well engineered a small diagnostic tool to monitor PO2, minimally invasive, able to monitor real-time O2 in vivo complex environments.

Direct and Indirect Evidence of the Microbially Induced Pitting Corrosion of Steel Structures in Humid Environments

Corrosion is a severe problem for steel structures in humid environments. In particular, humidity usually triggers the surface adhesion of microorganisms, leading to microbiologically induced corrosion. This study aims to explore the effect of bacterial biofilm formation on the pitting corrosion of stainless steel. This research uses electrochemical methods to obtain indirect evidence of the pitting corrosion of steel. In addition, in order to obtain direct evidence of the pitting corrosion of stainless steel, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) were used to characterize the dimensional morphology of the stainless steel after pitting. It was shown that the bacterial adhesion increased with the pH and temperature, which significantly increased the surface roughness of the stainless steel. Electrochemical analysis revealed that the formation of biofilm greatly destroyed the oxide film of 304 SS and accelerated the corrosion of stainless steel by forming an oxygen concentration battery. SEM and AFM analyses showed cracks and dislocations on the surface of stainless steel underneath the attached bacteria, which suggested a direct role of biofilm in corrosion induction. The results presented here show that the bacterial biofilm formation on the steel surfaces significantly accelerated the corrosion and affected the pitting corrosion process of the steel structure.