Localized Corrosion Research Articles

Study of Al7075 Localized Corrosion Inhibition by a SiO2 Superhydrophobic Coating Employing an Electrochemical Noise Technique

Aluminum presents localized corrosion when exposed to marine and industrial environments. In this research, we study the pitting susceptibility of Al7075 coated by a SiO2 sol–gel coating as a corrosion inhibitor employing the electrochemical noise technique. The analysis methods were power spectral densities (PSDs) in noise impedance (Zn), complaints by wavelet transform, recurrence plots, and Hilbert–Huang study due to the chaotic behavior of the EN signal. To perform the EN, the parameters employed were 2048 data, 1 datum per second in NaCl, and H2SO4 electrolytes at 3.5 wt.% simulating marine and industrial environments. EN tests were performed following ASTM G199. The results showed an increase in the localized corrosion process when SiO2 coating was applied. This is due to the cracking morphology of the coating.

Corrosion Mechanism of Press-Hardened Steel with Aluminum-Silicon Coating in Controlled Atmospheric Conditions

The effect of various atmospheric parameters on the corrosion mechanism of press-hardened steel (PHS) coated with Al-Si (AS) was studied. Quantitative models of the composition of soluble and stable corrosion products were developed. A high chloride concentration led to a localized corrosion due to the presence of cracks in the coating. Increased corrosion resistance of silicon-rich Al8Fe2Si and AlFe at the expense of the Al5Fe2 phase with low silicon content was shown. Under low-chloride-deposition conditions, the coating exhibited good corrosion resistance and provided sufficient protection to the underlying steel. The formation of more local anodes and cathodes under conditions of lower relative humidity led to a reduction in the depth of corrosion pits in the steel substrate. Constant high relative humidity and sulphate deposits on the surface were critical for the acceleration of steel corrosion in coating cracks.

Comparative analysis of cavitation erosion behavior in wire-arc directed energy deposition and cast nickel-aluminum bronze alloys.

In this study, the cavitation erosion (CE) behavior of wire-arc directed energy deposition (DED) nickel-aluminum bronze (NAB) alloys is compared with that of cast alloys, and the synergistic effect between corrosion and CE is investigated. The CE resistance of the wire-arc DED NAB alloy is better than that of the cast alloys. The CE of NAB alloys preferentially occurs at the boundaries of the α-Cu and residual β phases, and in the matrix around the κ phase. The residual β phase exhibits greater damage than the α-Cu phase. Throughout the CE, the alloys are dominated by local corrosion characteristics (selective-phase corrosion), while the wire-arc DED NAB alloys exhibit superior uniform corrosion characteristics. Notably, the uniform corrosion characteristics of all alloys are enhanced after CE. The mass loss caused by the synergistic effect of the cast NAB alloy and wire arc DED NAB alloy accounts for 56% and 52% of the total mass loss, with the corrosion-induced CE increment exceeding that of the CE-induced corrosion increment.

A Study of the Corrosion Behavior of AHSS Complex-Phase CP 780 Employing an Electrochemical Noise Technique Analyzed by Different Methods

The automotive industry employs structural steels with E-coats to reduce weight and increase the corrosion resistance of chassis, reducing CO2 emissions. Due to their mechanical properties, part of the chassis is a composite of advanced high-strength steels (AHSS). AHSSs are coated by conversion methods such as phosphate to increase epoxy coating adherence and corrosion resistance. The main point of this research is to characterize an AHSS complex-phase (CP) 780 in blank, with a phosphate coating and an E-coat organic coating using electrochemical noise, employing time-domain, frequency-domain, time–frequency-domain, and chaotic system methods to determine the type and corrosion kinetics of each system. The electrochemical noise technique was made with a conventional three-electrode cell, using a saturated calomel as a reference electrode. Data were recorded at 1024 s, at 1 data per second in a 3.5 wt. % NaCl electrolyte, according to ASTM G199-09. The results show how AHSS CP 780 presented uniform corrosion, similarly to the phosphate sample; however, the E-coat presented a trend of a localized process when analyzed by Wavelets transform. On the other hand, corrosion resistance increased for the E-coat sample, with values of 2.58 × 106 Ω·cm2. According to the results of the research, all the samples are susceptible to present localized corrosion.

Optical microscopic study of the stress induced corrosion of brass and aluminium in dilute electrolyte, and the inhibition effect of Cedrus Atantica and Ocimum Basilicum

Optical microscopic analysis of the stress induced (85% calculated stress) corrosion of brass in 1M ammonium sulfate [(NH4)2SO4] + 1M copper (II) sulfate (CuSO4) solution, and aluminium in 0.5M, 1M and 2M sulfuric (H2SO4) solution at 10% and 20% addition of Cedrus Atlantica and Ocimum basilicum Linn. essential oil extracts were documented. The optical images obtained showed the effect of both extracts on the alloys. Optical images of aluminium in the presence of Cedrus Atlantica showed increased susceptibility of the alloy to localized and general corrosion compared to Ocimum basilicum Linn which enhanced the corrosion resistance of aluminium. Cedrus Atlantica increased the susceptibility of alpha brass to corrosion compared to the solution without it. In the absence of Cedrus Atlantica, general surface deterioration was observed without any localized corrosion. However, at 10% Cedrus Atlantica concentration superficial crack was observed. The crack further increased to visible intergranular crack (fracture) at 20% Cedrus Atlantica concentration. Ocimum basilicum Linn performed effectively at 10% concentration, sustaining the corrosion resistance of brass in 1M (NH4)2SO4 + 1M CuSO4 solution. At 20% Ocimum basilicum Linn concentration superficial cracking appeared.

CORROSÃO LOCALIZADA DO ALUMÍNIO EM MEIOS AERADOS E EM MEIOS COM BAIXO TEOR OXIGÊNIO: ESTUDO E COMPARAÇÃO POR MEIO DE CURVAS DE POLARIZAÇÃO

LOCALIZED CORROSION OF ALUMINUM IN AERATED ENVIRONMENTS AND IN ENVIRONMENTS WITH LOW OXYGEN CONTENT: STUDY AND COMPARISON THROUGH POLARIZATION CURVES. In this study, the influence of deaeration on the electrochemical behavior of aluminum was studied by polarization techniques. The advantages of deaeration for the evaluation of localized corrosion on aluminum are discussed. The influence of the corrosive environment with low oxygen contents on the electrochemical response of aluminum was evaluated by anodic and cathodic potentiodynamic polarization curves. The polarization tests were carried out in chloride solutions followed by optical and scanning electron microscopy characterization. It was observed that deaeration of the solution significantly influences the electrochemical behavior of aluminum, as predicted by corrosion kinetics theories. For the cathodic curves, a decrease in the limiting current density for the oxygen reduction reaction (ORR) was observed for low oxygen solutions, while the “apparent” initiation of the hydrogen evolution reaction (HER) was shifted to higher potentials. In the anodic curves, a common passive behavior was not observed in aerated conditions, however, at the corrosion potential, localized pitting was observed indicating that the material was already above the breakdown potential (Ebr). In the low oxygen content solution, however, a passive region with a breakdown potential, was observed on the anodic curves.

Insights into the localized corrosion initiation mechanisms of alloy 718

Insights into the localized corrosion initiation mechanisms of alloy 718

Flexible, self-healing and portable supramolecular visualization smart sensors for monitoring and quantifying structural damage.

Visually monitoring micro-crack initiation and corrosion failure evolution is crucial for early diagnosis of structural health and ensuring safe operation of infrastructures. However, existing damage detecting approaches are subject to the limited-detection of heterogeneous structures, intolerance of harsh environments, and challenge of quantitative analysis, impeding applications in structural health monitoring (SHM). Herein, we present a stretchable, semi-quantitative, instrument-free, supramolecular SHM sensor by integrating a polyurea elastomer with sensitive corrosion-probes, enabling localized corrosion monitoring and quantification of failure dynamics. Initially, a correlation between visual monitoring signals and structural health status is proposed, and sensor-based image processing software that accurately quantifies structural failure indicators (crack scale, corrosion reactivity and deterioration status) is proposed. Moreover, this sensor can be fabricated as multiple derivatives: a coating or patch covered on metallic substrates and an ionic-responsive test strip, ensuring real-time detection of the initiation of pitting, degradation events of metallic components and convenient monitoring of ion concentrations in corrosive media. Furthermore, the inherent geometric plasticity and dynamic hydrogen-bonded network validates the reliability for heterogeneous components and stability under extreme environments of sensors. This portable, smart SHM strategy established the channel-transformation model from corrosion dynamics to visual signals, exhibiting prospects for structural monitoring in offshore energy-harvesting equipment.

Evaluation of localized corrosion resistance in wireless anodic protection of PANI-304SS galvanic couple in the presence of gabapentin inhibitor: Molecular dynamics, Monte Carlo and electrochemical noise measurements

Evaluation of localized corrosion resistance in wireless anodic protection of PANI-304SS galvanic couple in the presence of gabapentin inhibitor: Molecular dynamics, Monte Carlo and electrochemical noise measurements

Corrosion Behaviour of Cu-Plate Current Collector under Ex-situ Cyclic Stability Testing for Energy Storage Application

This study compares the corrosion behaviour of a copper plate current collector subjected to an ex-situ cyclic stability test in a 6M KOH and a 6M Na2SO4 electrolyte solution for an electrochemical supercapacitor cell. Through experimental analysis, the change in microstructures resulting from the corrosion behaviour of the copper plate current collector samples are examined by employing various analytical techniques, including microscopy, spectroscopy, and surface roughness analyzer. The corrosion behaviour was studied by employing potentiodynamic polarization and electrochemical impedance spectroscopy analyses. The copper plate current collector samples analysed in 6M KOH and 6M Na2SO4 electrolyte solution showed uniform and localized corrosion product formation, respectively. The CU-72HRS sample recorded a corrosion potential of -608.6mV, -628.87mV, and -89.5mV, -87.588mV using both Tafel and resistance polarization data fitting analysis, respectively, for both 6M KOH and 6M Na2SO4 electrolyte solution using a scan rate of 5mV/s at a voltage window of -1 to 1V. Comparing the microstructural changes under various cyclic conditions provides valuable insights into the durability and reliability of copper plates as current collectors in energy storage systems. The results of this study help improve our understanding of the supercapacitor cell performance in ex-situ cyclic stability tests, assisting in the development of more efficient and durable energy storage technologies.

Mathematical modelling of sensitization and desensitization in austenitic alloys using Gaussian-based peak models

Abstract This study presents four Gaussian-based mathematical models for accurately simulating the sensitization and desensitization processes in austenitic alloys. By incorporating temperature and time as variables, these models aim to predict the Degree of Sensitization (DOS) and generate Time-Temperature-Sensitization (TTS) diagrams. Validation using experimental datasets shows that the models perform well across various datasets, minimizing over-fitting when peak sensitization data is adequately provided. The models also
introduce a statistical index to assess accuracy, combining fitting parameters systematically. This work offers a comprehensive tool for investigating localized corrosion phenomena and supports the development of strategies to control chromium depletion during heat treatments, relevant for stainless steel and nickel-based alloys.

Test and Theoretical Investigations on Flexural Behavior of High‐Performance H‐Shaped Steel Beam with Local Corrosion in Pure Bending Zone

This article undertakes the tested and theoretical investigations on the flexural behaviors of high‐performance steel (HPS) beams subjected to local corrosion in pure bending zone. Four H‐type HPS beams are designed, then the flexural bearing capacity test is carried out. Mechanical behaviors, including load‐deflection response, strain development, and failure modes are investigated in detail. A simple theoretical model of flexural strength is proposed. The tested and theoretical results show that: with the increase of corrosion rate, the random distribution of the residual section of HPS beam tends to be stable, the corrosion position also plays an important role in the random distribution of the residual area. The corrosion position has a greater influence on the residual flexural strength of corroded HPS beam than the corrosion degree. The theoretical flexural strength model can slight accurately predict the flexural strength of corroded H‐type HPS beam, the error is less than 5%. The corrosion of compressive flange has the most serious effect on the flexural strength degradation of HPS beams, followed by the corrosion of tensile flange and web corrosion. The influence of corrosion in the web height direction on the flexural strength of corroded HPS beam is extremely limited.

A Review of Additive Manufacturing of Biodegradable Fe and Zn Alloys for Medical Implants Using Laser Powder Bed Fusion (LPBF).

This review explores the advancements in additive manufacturing (AM) of biodegradable iron (Fe) and zinc (Zn) alloys, focusing on their potential for medical implants, particularly in vascular and bone applications. Fe alloys are noted for their superior mechanical properties and biocompatibility but exhibit a slow corrosion rate, limiting their biodegradability. Strategies such as alloying with manganese (Mn) and optimizing microstructure via laser powder bed fusion (LPBF) have been employed to increase Fe's corrosion rate and mechanical performance. Zn alloys, characterized by moderate biodegradation rates and biocompatible corrosion products, address the limitations of Fe, though their mechanical properties require improvement through alloying and microstructural refinement. LPBF has enabled the fabrication of dense and porous structures for both materials, with energy density optimization playing a critical role in achieving defect-free parts. Fe alloys exhibit higher strength and hardness, while Zn alloys offer better corrosion control and biocompatibility. In vitro and in vivo studies demonstrate promising outcomes for both materials, with Fe alloys excelling in load-bearing applications and Zn alloys in controlled degradation and vascular applications. Despite these advancements, challenges such as localized corrosion, cytotoxicity, and long-term performance require further investigation to fully harness the potential of AM-fabricated Fe and Zn biodegradable implants.

Biodegradable zinc alloys with high strength and suitable mechanical integrity as bone repair metals

Mechanical properties and integrity of biodegradable Zn alloys during degradation holds significant importance. In this study, a Zn-Mg-Mn alloy with tensile strength of 414 MPa and an elongation of 26% was developed. The strength contributions of as-extruded Zn alloy from grain boundary strengthening, precipitation strengthening, and second phase strengthening. Degradation of the Zn alloy in Hank’s solution exhibited a decreasing trend with prolonged immersion, eventually stabilizing at 16 μm/year. Corrosion morphology analysis revealed that the corrosion modes transformed from pitting corrosion to severely localized corrosion with prolonged immersion time, eventually lead to formation of large holes. Although the tensile strength of the Zn alloys remained relatively unchanged following varied immersion time, a substantial decrease in elongation was observed. The decreased elongation primarily attributed to the formation of surface corrosion pits or holes, exacerbating crack propagation during tension. Biocompatibility assessments of Zn alloys demonstrated that a 50% concentration of Zn alloy leach solution cultured with C3H10 and RMSC cells yielded cellular activity exceeding 80%, indicating excellent cytocompatibility. Alkaline phosphatase (ALP) and alizarin red staining results further underscored the remarkable early and late osteogenic properties exhibited by Zn-Mg-Mn alloy.

Bottom of Line Corrosion Mechanism in Marginal Sour Environment Wet Gas Pipelines

Internal pipeline corrosion is a well-recognized issue in the oil and gas industry, especially in multiphase flow systems, such as wet gas transportation pipelines that contain mixed phases. Internal corrosion typically manifests as either top-of-the-line corrosion (TLC) or bottom-of-the-line corrosion (BLC). While corrosion mechanisms in sweet environments (dominated by CO₂) are relatively well-understood, those in sour environments (dominated by H₂S) remain less thoroughly examined. In sour environments, the primary corrosion product is iron sulfide (FeS), while in sweet environments, iron carbonate (FeCO₃) tends to form. In marginally sour conditions, FeS layers are often non-uniform, promoting localized corrosion and pitting because low concentration of H2S. It is hypothesizes that higher concentrations of H₂S reduce both the pitting rate and depth.The objective of this research is to investigate the corrosion rate, surface profile, and morphology in a marginal sour environment, using profilometry analysis (ASTM G46) to assess pitting. The experiments were conducted in a glass cell setup simulating pipeline conditions with 3 wt% brine solution and 1000 ppm acetic acid. Corrosion behavior was assessed at H₂S concentrations of 0 ppm, 30 ppm, and 80 ppm using weight loss analysis, surface morphology, and profilometry measurements. Results indicate that increasing H₂S concentration decreases the pitting rate, supporting the study’s hypothesis.

Experimental and Numerical Investigation on the Ultimate Bearing Capacity of Axially Compressed Steel Tube Columns with Local Corrosion

Experimental and Numerical Investigation on the Ultimate Bearing Capacity of Axially Compressed Steel Tube Columns with Local Corrosion

Robust Damage-Sensing and Corrosion-Warning Polymeric Coatings: a New Approach to Visually Monitor the Degradation Dynamics of Coated Mg-Alloys.

Corrosion and degradation of magnesium (Mg)alloy result in serious damage and limit its application in new-energy automobile industry. Considerable protective coating is proposed, yet it is hindered by the difficulties in avoiding and visually monitoring coating micro-damage and localized metal corrosion. Herein, a novel anticorrosion coating system with autonomously monitoring multiple levels of damages in coated Mg-alloy system, is proposed. In this design, the top layer of coating consists of polymethyl methacrylate (PMMA) microcapsules containing crystal violet lactone (CVL) and polyurethane resin dispersed with SiO2 nanoparticles. Upon surface damage, the presence of SiO2 triggers the chromogenic reaction of CVL liberated from ruptured microcapsules, resulting in an immediate blue coloration to highlight coating damage. Meanwhile, the primer coating incorporates PMMA microcapsules with a phenolphthalein (PHP) core, which timely reveals alkaline corrosion pits at Mg alloy/coating interface by generating pink coloration. Furthermore, the microcapsules-embedded coating exhibits superior corrosion resistance. The failure evolution dynamics of coating-Mg system, including both the external coating damage and internal localized corrosion, can be visually indicated. This work provides an innovative strategy to tailor and monitor the degradation of coated Mg alloys, thereby presenting promising prospects for application in automotive anticorrosion engineering.

Corrosion Inspection for Hard Disk Media with Carbon-Based Overcoats by In-Liquid Open-Loop Electric Potential Microscopy.

The hard disk medium (HDM) with a carbon overcoat (COC) is a fundamental component of a hard disk drive. The conventional test for its corrosion durability, known as the "HOT/WET test," requires considerable time and effort and does not provide any local information about the corrosion. Here, we address this issue by employing open-loop electric potential microscopy (OL-EPM), a potential measurement technique based on atomic force microscopy (AFM), for corrosion inspection. To explore the applicability of OL-EPM, we observed the surface of the HDMs with different COC thicknesses in a dilute HNO3 solution. Through time-dependent and high-resolution OL-EPM observations, we found that this technique can be used for detecting nanoscale COC defects. This is because the HDM surface under a COC defect is exposed to the solution and undergoes anodic dissolution, increasing the local potential around the defect. This is readily detected by OL-EPM even before corrosion product formation around the defects induces the topographic change. This work demonstrates that OL-EPM is useful not only for understanding the local corrosion mechanisms but also for detecting the COC defects in a much shorter time (∼3 h) than the HOT/WET test (3-4 days).

Understanding Electrochemical Behavior and Localized Corrosion Susceptibility in Cold Sprayed Al-Mg Binary Deposits with Varying Mg Contents

This paper elucidates electrochemical behavior and localized corrosion susceptibility in cold sprayed Al-Mg binary deposits with varying Mg content. Cold spray (CS) deposition is a solid-state deposition process, being investigated as protective layers and repair applications. Nevertheless, a lack of understanding of corrosion mechanisms in CS deposits is prevalent due to its complex microstructure-driven mechanisms different from wrought counterparts. Analytical electrochemistry techniques, including potentiodynamic polarization and Mott-Schottky testing showed that corrosion resistance increased with increased Mg content in CS Al-Mg binary deposits. However, immersion tests (50 h) demonstrated that the effect of Mg content on localized corrosion damage was insignificant compared to that of prior particle boundaries that primarily governed localized corrosion initiation and propagation.

`Evaluation of the antimicrobial corrosion properties of electropolymerized poly(aniline-co-o-toluidine) films on carbon steel surfaces

Microbiologically influenced corrosion (MIC) can lead to structural weakening and shortened service life of carbon steel, resulting in serious economic losses and safety hazards. In particular, sulfate-reducing bacteria (SRB) produce hydrogen sulfide and sulfide during their growth and metabolism, which accelerates the corrosion of carbon steel. Thin films of poly(aniline-co-o-toluidine) (PA-co-POT) were electrodeposited on the surface of carbon steel using cyclic voltammetry in an electrolyte consisting of oxalic acid, aniline and o-toluidine monomers. The mechanical properties of the polymer films were analyzed by a micro-Vickers hardness tester. The corrosion resistance of the polymer films was evaluated by an electrochemical corrosion test and immersion test of the polymer films in a solution containing SRB and 3.5% NaCl. The results showed that PA-co-POT films have superior SRB corrosion resistance than single polymer films. The corrosion rate of PA-co-POT film was 0.0171mm/year, and the protection efficiency was 83% after 14 days of immersion in solution. In addition, due to the antibacterial properties of the PA-co-POT film, the adhesion of bacteria on its surface is significantly reduced, and local corrosion is also effectively inhibited. This study demonstrates the potential of electropolymerized aniline derivative copolymer films in preventing MIC of carbon steel and provides valuable insights for the development of new corrosion protection materials.