Localized Corrosion Research Articles

Evaluation of Passive Films on 17-7PH and 410 Stainless Steel Exposed to NaCl Solution.

This work covers the formation of a passive state for two different alloys used in the aeronautical industry. The aim of this study is to investigate the effectiveness of passivation treatments on 17-7PH and 410 SS (stainless steel) samples, specifically when performed with citric and nitric acid solutions at 49 °C using an immersion time of 90 min and subsequent exposure in 3.5 wt.% NaCl solution. Employing the cyclic potentiodynamic polarization (CPP) technique, the corrosion properties of the passivated material were evaluated according to the ASTM G65-11 standard. A microstructural analysis was performed using scanning electron microscopy (SEM). The passivated layer was characterized via X-ray photoelectron spectroscopy. In the results, the CPP curves showed positive hysteresis, indicating pitting localized corrosion, and 17-7PH steel passivated at 49 °C for 90 min in citric acid exhibited lower corrosion rate values equivalent to ×10-3 mm/year.

Substantial Improvement in Mechanical Properties and Anti‐corrosion Properties of Rolled Zn–Mg–Sr Alloys as an Orthopedic Implant

This study investigates a Zn–Mg alloy, enhanced for biodegradability and biocompatibility, by introducing trace amounts of Sr and subjecting it to hot‐rolling. The resulting Zn–Mg–Sr alloy shows a reduced average grain size to 3.35 μm and a transformed Mg2Zn11 phase from lamellar to finely dispersed particles, while maintaining a uniform SrZn13 phase distribution. The as‐rolled alloy exhibits significantly improved mechanical properties, with a tensile strength of 340 MPa and 40% of elongation, attributed to grain‐boundary strengthening, reinforcement by second‐phase particles, and the presence of intragranular dislocations and nanoscale precipitates. This microstructural refinement enhances the elongation by hindering crack propagation. Corrosion resistance tests reveal the superior performance of the as‐rolled alloy, owing to the finely distributed eutectic particles, which mitigated localized corrosion and altered the corrosion morphology from localized to finer corrosion pits. In vitro biocompatibility assessments show over 80% cell viability in C3H10 cultures with 50% Zn–Mg–Sr alloy extract, indicating low cytotoxicity. Furthermore, the alloy exhibits promising bone‐promoting properties, highlighting its potential for biomedical applications.

Electrochemical Noise Analysis: An Approach to the Effectivity of Each Method in Different Materials.

Corrosion deterioration of materials is a major problem affecting economic, safety, and logistical issues, especially in the aeronautical sector. Detecting the correct corrosion type in metal alloys is very important to know how to mitigate the corrosion problem. Electrochemical noise (EN) is a corrosion technique used to characterize the behavior of different alloys and determine the type of corrosion in a system. The objective of this research is to characterize by EN technique different aeronautical alloys (Al, Ti, steels, and superalloys) using different analysis methods such as time domain (visual analysis, statistical), frequency domain (power spectral density (PSD)), and frequency-time domain (wavelet decomposition, Hilbert Huang analysis, and recurrence plots (RP)) related to the corrosion process. Optical microscopy (OM) is used to observe the surface of the tested samples. The alloys were exposed to 3.5 wt.% NaCl and H2SO4 solutions at room temperature. The results indicate that HHT and recurrence plots are the best options for determining the corrosion type compared with the other methods due to their ability to analyze dynamic and chaotic systems, such as corrosion. Corrosion processes such as passivation and localized corrosion can be differentiated when analyzed using HHT and RP methods when a passive system presents values of determinism between 0.5 and 0.8. Also, to differentiate the passive system from the localized system, it is necessary to see the recurrence plot due to the similarity of the determinism value. Noise impedance (Zn) is one of the best options for determining the corrosion kinetics of one system, showing that Ti CP2 and Ti-6Al-4V presented 742,824 and 939,575 Ω·cm2, while Rn presented 271,851 and 325,751 Ω·cm2, being the highest when exposed to H2SO4.

Experimental study on seismic behavior of concrete-filled steel tubular columns subjected to localized corrosion

The seismic behavior of a circular concrete-filled steel tubular (CFST) subjected to localized corrosion was investigated experimentally. The effects of localized corrosion parameters (corrosion depth ratio, circumferential corrosion ratio, longitudinal corrosion ratio, and longitudinal location of the corrosion) on the seismic behavior were analyzed. The experimental results showed that localized corrosion significantly influenced the failure mode of the CFST columns. The hysteresis curves exhibited a pinching phenomenon and were asymmetrical about the coordinate origin for the specimens under one-sided corrosion at the bottom of the column. The seismic performance deteriorated with increasing corrosion depth ratio, circumferential corrosion ratio, and longitudinal corrosion ratio for CFST columns corroded at the bottom. Corrosion at the mid-height of the CFST columns had less adverse effects on seismic performance than corrosion at the bottom. Moreover, the plastic hinge varied with the corrosion depth ratio and circumferential corrosion ratio but was minimally influenced by the longitudinal corrosion ratio. The specimen exposed to corrosion at the mid-height yielded plastic hinges at both the bottom and middle of the column.

Localized Corrosion Behavior and Corrosion Microstructure of LZ91 and LAZ931 Mg Alloys

LZ91 (Mg-9 wt%Li-1 wt%Zn) and LAZ931 (Mg-9 wt%Li-3 wt%Al-1 wt%Zn) alloys are emerging ultra-lightweight Mg alloys, which can be used in applications that require weight reduction. Although LZ91 alloy has found some success in the 3C industry, the relatively inferior mechanical strength limits its widespread application. To improve the mechanical properties, Al was added to LZ91 alloy to form LAZ931 alloy. However, both LZ91 and LAZ931 alloys are primarily composed of a dual-phase structure with α (HCP) and β (BCC) phases, which form a microgalvanic couple in the corrosion environment. Furthermore, adding Al introduces additional secondary phases, such as AlLi and MgLi2Al, which complicate the corrosion behavior and mechanism. Therefore, this study investigates the corrosion behavior and microstructure of LZ91 and LAZ931 Mg alloys in 3.5 wt% NaCl solution and the relationships to the phase distribution in the alloy substrates.By in situ optical microscope (OM) observations and open circuit potential (OCP) monitoring, localized corrosion initiates on the LAZ931 alloy earlier than on the LZ91 alloy. The early initiation and propagation of localized corrosion on the LAZ931 alloy result in worse corrosion resistances and faster corrosion rates measured by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves. By scanning Kelvin probe force microscopy (SKPFM), the Li-rich β phase is more active than the Mg-rich α phase. However, interestingly, localized corrosion was found to preferentially propagate inside the α phase, which seems to contradict the SKPFM measurements. The preferential propagation of localized corrosion in the α phase could be related to the difference in the surface corrosion film thicknesses on the α and β phases before localized corrosion propagation. The localized corrosion behavior and corrosion microstructure of the alloys will be discussed based on electrochemical measurements and site-specific microstructure characterizations. Figure 1

Prediction of Lithium Deposition By Electrochemical Noise Method in Li-Ion Batteries

Electrochemical noise measurement methods have established a significant presence in corrosion literatures and through these measurements, it becomes feasible to discern the corrosion mode and make a clear distinction between localized and uniform corrosion types, particularly when examined alongside post-mortem studies.In recent years, the increase in the use of lithium-ion batteries demands that the tests to be performed on the batteries are faster, easier, cheaper and, if possible, non-destructive and non-perturbing. While some electrochemical noise studies on batteries have commenced, the existing literature on this subject is limited and questionable. Electrochemical noise measurement, in Lithium based batteries has the potential to serve as a non-invasive diagnostic tool for assessing battery health. One of our previous studies has demonstrated an increased voltage noise in non-rechargeable batteries with Li/MnO2 chemistry upon exposure to a short circuit, indicating detectable morphological changes in metallic lithium due to non-homogenous depletion of lithium anode through electrochemical noise measurement.In Lithium-Ion batteries, lithium deposition refers to the undesired formation of metallic lithium, commonly in the form of dendrites, on the battery’s anode during charge and discharge cycles. This phenomenon is a consequence of uneven lithium-ion plating and stripping, leading to localized overplating. This growth of lithium dendrites poses significant risk, including internal short circuits, compromised battery integrity, and the potential for thermal runaway. These issues can result in reduced battery performance, safety concerns, and shortened cycle life. Effectively addressing lithium deposition is essential for enhancing the safety and reliability of lithium-ion batteries in various applications.Similarly to our previous publication, the electrochemical noise method shows promise as a non-invasive approach to investigate the understand deposition of metallic lithium by monitoring the voltage noise during charge and discharge cycling of batteries. For this purpose, NMC/Graphite pouch and coin cells are employed. In this presentation, we will delve into the details of electrochemical noise in lithium-based batteries, discussing the method’s reliability in assessing lithium deposition in NMC/Graphite lithium-ion batteries and presenting preliminary results. Figure 1

Comparing the Corrosion Behavior and Microstructure of a WE43 Mg Alloy in Simulated Body Fluids Under Different CO2 Conditions

With the low density and high specific strength, magnesium (Mg) alloys are lightweight alloys with various applications. In addition, combined with biocompatibility, similar mechanical properties to human bones, and unique biodegradability, Mg alloys are promising biodegradable implant materials for orthopedic surgeries. However, the degradation rates of Mg alloys are too fast in physiological environments, which limits the clinical applications of Mg implants. Therefore, understanding the corrosion behavior in physiological environments is crucial for developing biodegradable Mg alloys.During Mg alloy degradation, hydroxide (OH-) ions are generated, and the pH near the alloy surface increases. Since carbonate-bicarbonate (CO3 2--HCO3 -) is a vital pH buffer system in the human body, the corrosion behavior of Mg alloys would be affected by the CO2 concentrations of the test environments. In this study, we performed electrochemical and corrosion tests of a solution heat-treated WE43 (Mg-4 wt%Y-3 wt%Nd) alloy in Hanks’ balanced salt solutions (HBSS) at 37°C. By performing the tests in air and in an incubator maintained at 5% CO2, the effect of carbonate-bicarbonate pH buffering on the corrosion behavior and corrosion microstructure of the WE43 Mg alloy was investigated.When testing the WE43 Mg alloy in air, a general corrosion morphology was observed during the 24-hour immersion. In contrast, WE43 Mg alloy tested in the incubator shows a more active surface potential and localized corrosion initiates on the alloy surface in the early stages of immersion. Electrochemical impedance spectroscopy (EIS) analysis shows that WE43 Mg alloy tested in air has better corrosion resistance than in the incubator. Furthermore, the corrosion resistance of the alloy tested in air increases with immersion time but decreases when tested in the incubator. Potentiodynamic polarization curves after 24-hour immersion confirm that the corrosion current density (i corr) of the WE43 Mg alloy tested in the incubator is higher than that when tested in air. The difference in corrosion behavior is owing to the carbonate-bicarbonate pH buffering effect and will be discussed based on corrosion microstructure characterizations. Figure 1

Exploring the Kinetics of Oxygen Reduction Reaction in Relation to Pitting Corrosion Resistance in Fe-Cr Alloys

Pitting corrosion, a major concern in materials science and engineering, threatens critical metallic structures and components. Its implications reach across daily life and industries such as energy, transportation, and infrastructure, potentially causing environmental harm, economic losses, and even loss of life. This complex process is influenced by factors including material composition, local environment, and mechanical stresses.1 Once initiated, pit propagation rates are largely dependent on the magnitude of the supporting cathodic current available from the oxygen reduction reaction (ORR) occurring on the external passive film.2 In Fe-Cr alloys, the ORR occurs on this film, undergoing a mixed diffusion and kinetic-controlled process. The number of electrons involved and the corrosion rate are determined by the thermodynamically stable state of the passive film.This research studies the ORR kinetics on FeCr alloys fabricated by arc-melting, using both computational and experimental methods. The rotating disc electrode technique was employed across various Fe:Cr alloys in alkaline and neutral electrolytes. The Koutecky-Levich analysis showed a dominant four-electron ORR pathway in all tested Fe-Cr alloys, with the ORR significantly inhibited by higher proportions of Cr2O3 in the film, suggesting a correlation with high chromium content. Experimental ORR overpotentials, when combined with theoretical potential-pH (Pourbaix) diagrams, helped discern the likely characteristics of the passive films on the alloys. It was deduced that the catalytic properties of potential passive films increased in the order Cr2O3 < Fe3O4 < Fe2O3 < FeCr2O4. These findings, excellently aligned with density functional theory (DFT) modelling, underscore the role of increased chromium levels in slowing pitting progression by suppressing the ORR.In summary, this research offers distinctive insights into the correlation between the kinetics of the ORR and the resistance to localized corrosion in Fe-Cr alloys, which enhances our understanding of the underlying mechanisms of pitting corrosion. Keywords FeCr alloy, pitting corrosion, ORR, rotating disc electrode, DFT Reference [1] B. Zhang, J. Wang, B. Wu, X. W. Guo, Y. J. Wang, D. Chen, Y. C. Zhang, K. Du, E. E. Oguzie, and X. L. Ma, Nat. Commun. (2018) 9, 2559.[2] G. T. Burstein, P. C. Pistorius, and S. P. Mattin, Corros. Sci. (1993) 35, 57.

Effect of air pressure and flow on steels materials in simulated wet fire drives

The corrosion behaviour of N80, 3Cr, and 5Cr steels were investigated under wet fire drive conditions using a high-temperature and high-pressure autoclave, weight-loss method, and scanning electron microscopy analysis. The findings indicated that elevated air pressure (4–6 MPa) and flow rates (0.5–1.5 m/s) significantly exacerbated corrosion, leading to both localised pitting and general corrosion on the steel samples. Predominant components of the corrosion product scales were identified as FeCO3 and Cr2O3. Notably, N80 steel exhibited higher pitting sensitivity compared to 3Cr and 5Cr steel, whereas 5Cr steel demonstrated superior corrosion resistance under the experimental conditions. Consequently, it is recommended to use cost-effective pipes with adequate corrosion resistance, such as various low-alloy pipes with differing chromium (Cr) contents, in oilfield applications. This study underscores the importance of selecting corrosion-resistant pipes as a primary means of corrosion prevention in oil and gas operations. Furthermore, it provides valuable insights into the corrosion performance of diverse steel materials in wet fire drive environments, offering pertinent implications for corrosion mitigation strategies within the industry.

The effect of phosphorous content on the microstructure and localised corrosion of electroless nickel-coated copper

A detailed microstructural and electrochemical analysis of electroless nickel phosphorous (NiP) coatings with P contents of 13.2 ± 1.2 wt%, 12.9 ± 0.7 wt%, and 8.3 ± 0.8 wt% on a copper substrate was performed to study the corrosion behaviour of electroless NiP/Cu systems. The P content of the electroless NiP coatings plays an essential role in the microstructure of the coatings in terms of crystallinity. The crystallinity variations, representing the extent of crystalline and amorphous phases within the material, with P content, affect the local electrochemical characteristics and, hence, the corrosion protection behaviour of electroless NiP coatings. The coatings with the highest P content showed the best corrosion performance in a 3.5 wt-% NaCl solution. In contrast, the surface of the electroless NiP coatings with low P content is more susceptible to corrosion due to the presence of locations with heterogeneous electronic properties that initiate localised corrosion. Microgalvanic interactions with a high cathode-to-anode surface ratio govern the localised corrosion kinetics of the low P-content samples. A high concentration of nodule boundaries and/or other existing structural defects on the surface serve as anodic sites, whereas the remainder of the surface serves as cathodic sites.

Self-healing property and corrosion resistance of MgF2/polylactic acid/amorphous calcium phosphate coating on biodegradable Mg alloy for medical implant

Self-healing coatings on the surfaces of magnesium and its alloys have garnered significant attention due to their ability to autonomously repair local corrosion. In this work, a novel F/P/ACP (fluoride/poly(lactic acid)/amorphous calcium phosphate) coating was developed on medical magnesium alloy wires using a chemical reaction deposition method. This innovative coating served not only as a physical barrier but also exhibits intrinsic self-healing capabilities. The artificial scratches in F/P/ACP coating can be efficiently sealed by anti-corrosive products in solution. The coating exploited pH fluctuations induced by magnesium and coating corrosion to trigger its self-healing mechanism. The composite coating presented as an anti-corrosion self-repairing solution that did not require additional corrosion inhibitors. It enabled the development of autonomous self-repairing coatings without embedding additional corrosion inhibitors. The composite coating demonstrated excellent corrosion resistance and durable self-repair capabilities, offering broad prospects for advancing research and applications of efficient self-repair coatings for biodegradable magnesium implants.

Effect of interrupted aging on mechanical properties and corrosion resistance of 7A75 aluminum alloy

The effects of interrupted aging on mechanical properties and corrosion resistance of 7A75 aluminum alloy extruded bar were investigated through various analyses, including electrical conductivity, mechanical properties, local corrosion properties, and slow strain rate tensile stress corrosion tests. Microstructure characterization techniques such as metallographic microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were also employed. The results indicate that the tensile strength of the alloy produced by T6I6 aging is similar to that produced by T6I4 aging, and it even exceeds 700 MPa. Furthermore, the yield strength increases by 52.7 MPa, reaching 654.8 MPa after T6I6 aging treatment. The maximum depths of intergranular corrosion (IGC) and exfoliation corrosion (EXCO) decrease from 116.3 and 468.5 µm to 89.5 and 324.3 µm, respectively. The stress corrosion factor also decreases from 2.1% to 1.6%. These findings suggest that the alloy treated with T6I6 aging exhibits both high strength and excellent stress corrosion cracking resistance. Similarly, when the alloy is treated with T6I4, T6I6 and T6I7 aging, the sizes of grain boundary precipitates (GBPs) are found to be 5.2, 18.4, and 32.8 nm, respectively. The sizes of matrix precipitates are 4.8, 5.7 and 15.7 nm, respectively. The atomic fractions of Zn in GBPs are 9.92 at.%, 8.23 at.% and 6.87 at.%, respectively, while the atomic fractions of Mg are 12.66 at.%, 8.43 at.% and 7.00 at.%, respectively. Additionally, the atomic fractions of Cu are 1.83 at.%, 2.47 at.% and 3.41 at.%, respectively.

Influence of pulse frequency on microstructure, mechanical properties, and corrosion resistance of electrodeposited Ni-SiC composite coatings

The current study explores the effects of SiC co-deposition in Ni matrix during pulse electrodeposition (PED) at various pulse frequencies. X-Ray Diffraction (XRD) analysis indicates that at lower frequencies, the composite coating favours the (111) plane orientation, while at higher frequencies (50 and 100 Hz), it changes toward the (200) plane. Scanning Electron Microscopy (SEM) analysis shows a decrease in SiC particle content with increasing frequency. Coatings deposited at 10 Hz display a compact, uniform structure with higher SiC particle concentration, resulting in smoother surfaces compared to pure Ni coatings. This leads to higher hardness (440 HVN) compared to coatings deposited at higher frequencies (425 HVN and 410 HVN for the 50 Hz and 100 Hz, respectively). Furthermore, the composite coatings exhibit superior corrosion resistance, with reduced electrolyte penetration and localized corrosion relative to pure Ni. Notably, the 10 Hz coating demonstrates a lower corrosion rate of 0.005 mm/year and a higher corrosion protection efficiency of 88 %. Therefore, SiC co-deposition at 10 Hz acts as a protective barrier, inhibiting corrosion progression and enhancing long-term durability against corrosion.

Effects of CuO nanoparticles on SAC composite solder joints: Microstructural and DFT study

In this paper, novel application possibilities of CuO nanoparticles were investigated in SAC0307 solder alloy for composite soldering purposes. CuO nanoparticles in 0.25 and 0.5 wt% were mixed into the solder paste to produce composite solder joints. Solder joints were manufactured using standard surface mounting technology from different solder pastes. The solder joints were loaded in an 85 °C/85RH% temperature and humidity test for 4000 h. It was found that the CuO composite solder joints showed improved mechanical quality due to the microstructural refinement, which was studied using scanning electron microscopy (SEM) and focused ion beam (FIB) analysis. On the other hand, the corrosion resistance of CuO joints decreased, as they suffered localized corrosion extensively, which produced longer and more Sn whiskers on their surface than on the reference SAC0307. Density functional theory (DFT) calculations proved that CuO can bond to Sn, but CuO is not chemically inert in the solder bulk. CuO can start a cyclic reaction with the dispersed Cu6Sn5 intermetallics, which produces SnO2 in the solder bulk, ultimately enhancing corrosion. Therefore, CuO nanoparticles are suggested to be applied only in non-corrosive environments, such as space applications.

The influence of alloying elements segregation on heterogeneous nucleation of TiN on Al2O3 and its local corrosion resistance

A comprehensive study utilizing first-principles calculations has examined the heterogeneous nucleation of TiN on Al2O3 in steel and the impact of alloying elements on this process. Additionally, the study delved into how this nucleation affects local corrosion activity. The findings indicate that alloying elements such as Cr, Mn, Mo, and V tend to concentrate at the Al2O3 (0001)/TiN (001) interface, enhancing the interface's stability, thereby favoring the heterogeneous nucleation of TiN on Al2O3. Consequently, the nucleation leads to the formation of interfaces, namely Al2O3 (0001)/TiN (001) and TiN (100)/bcc-Fe (100), which are less prone to adsorbing chloride ions, replacing the Al2O3(0001)/bcc-Fe (110) interface that can stably adsorb chloride ions, consequently reducing the adsorption of chloride ions at grain boundaries. Moreover, it is difficult for Cr atoms to incorporate into the TiN structure, while Ti atoms readily replace Cr in CrN. TiN exhibits a lower formation energy compared to CrN, and the precipitation of TiN mitigates the formation of Cr-depleted zones, thereby inhibiting local corrosion.

Light-driven extracellular electron transfer accelerates microbiologically influenced corrosion by Rhodopseudomonas palustris TIE-1

This study investigates the microbiologically influenced corrosion (MIC) of X80 steel accelerated by the phototrophic bacterium Rhodopseudomonas palustris TIE-1. The photorespiration plays a key role in promoting extracellular electron transfer (EET)-induced MIC. In the early corrosion stage, unstable localized corrosion dominated in the dark, while intense diffusion-controlled corrosion occurs in light. Compared to the sterile anaerobic medium, R. palustris TIE-1 accelerated corrosion of X80 steel, with a significantly higher corrosion rate under light conditions, approximately three times that of dark conditions. Inhibition of photosynthetic electron transfer or cessation of photostimulation resulted in pronounced reduction in the corrosion rate.

Development of a two‐dimensional bipolar electrochemistry technique for high throughput corrosion screening

AbstractBipolar electrochemistry allows testing and analysing the crevice corrosion, pitting corrosion, passivation, general corrosion, and cathodic deposition reactions on one sample after a single experiment. A novel two‐dimensional bipolar electrochemistry setup is designed using two orthogonal feeder electrode arrangements, allowing corrosion screening tests across a far wider potential range with a smooth potential gradient to be assessed. This two‐dimensional bipolar electrochemistry setup was applied here to simultaneously measure for the simultaneous measurement of the nucleation and propagation of pitting and crevice corrosion under a broad range of applied potential on type 420 stainless steel, which has a very short localised corrosion induction time. It reduces the error from corrosion induction to corrosion competition, and all pits and crevice corrosion have no lacy cover. Results show crevice corrosion can gain current density and easier to support its nucleation and propagation at different potential regions more easily than pitting corrosion.

Study on microstructure and electrochemical corrosion behavior of ζ-FeZn13 phase layer in hot-dip galvanized coating

In this study, the electrochemical corrosion behavior of outburst and flat ζ-FeZn13 phase layers was investigated using scanning electron microscopy, field emission scanning electron microscopy, electrochemical workstation, and Raman spectroscopy instrument. The ζ phase layer is composed of the η phase, coarse ζ phase, and fine ζ phase. Their corrosion potential is Eη-Zn=-1.140±0.003 V, Efine-ζ=-1.052±0.003 V, and Ecoarse-ζ=-1.036±0.002 V. The presence of fine ζ phases can form a thick passivation film on the surface of the coating. The thickness of the passivation film for the outburst and flat ζ phase layers is 5.31 nm and 6.47 nm, respectively. The more uniform the distribution of fine ζ phases, the thicker the passivation film. The corrosion types of the outburst phase layer are mainly local corrosion and pitting corrosion, and the flat phase layer is mainly uniform corrosion. The corrosion products of η phase are ε-Zn(OH)2, 4Zn(OH)2.ZnCl2, Zn5(CO3)2(OH)6, and Zn5(Cl2)(OH)8.H2O. The corrosion products of ζ phase are Fe2O3, ZnO, and Zn(OH)2.

Implementation of a control and monitoring system for a cathodic protection cell to mitigate localized corrosion in fixed and mobile steel structures

The current study introduces a novel technique to handle electrochemical localized corrosion in certain limited regions rather than applying comprehensive cathodic protection (CP) treatment. An impressed current cathodic protection cell (ICCPC) was fabricated and firmly installed on the middle of a steel structure surface to deter localized corrosion in fixed or mobile steel structures. The designed ICCPC comprises three essential parts: an anode, a cathode, and an artificial electrolyte. The latter was developed to mimic the function of the natural electrolyte in CP. A proportional-integrated-derivative (PID) controller was designed to stabilize this potential below the ICCPC at a cathodic potential of −850 mV, which is crucial for protection efficacy. The controller of the protection system was designed to automatically activate the ICCPC when the environment of the steel structure is exposed to humidity. At a temperature range from 27 °C to 35 °C, the protection potential, current, and power showed an increase in percentage by 411 %, 688.74 %, and 2842.3 %, respectively when the humidity level rose from 10 % to 100 %. The intended spraying of sodium chloride (NaCl) solution on the structure at different concentrations from 1.5 % to 5 % showed excellent protection against corrosion, notable improvements in electrical conductivity, and reduction in resistance between the anode and cathode. The energy dispersive spectroscopy and scanning electron microscopy (SEM-EDS) analyses confirm effective corrosion inhibition under ICCPC coverage compared to unprotected areas. These tests revealed an absence of oxidation beneath the ICCPC compared with areas outside of its coverage. The areas outside of ICCPC protection showed a reduction in iron and carbon contents from 57.1 % to 47.0 % and 41.4 %–22.4 %, respectively, and an increase in oxygen from 1.6 % to 30.6 %.

Improvement in inhibition performance of anti-corrosion coatings using polyolefin matrix embedded with modified TiO2 nanoparticles

Corrosion remains a critical issue for steel structures, leading to costly repairs and potential failures in industrial sectors. This study presents the development and characterization of polyolefin coatings for enhanced corrosion protection. Initially, the porous TiO2 nanoparticles were synthesized using the sol-gel method, followed by their modification through the encapsulation of sodium benzoate (SB) as a corrosion inhibitor. Modified Polyolefin coatings were prepared by incorporating modified nanoparticles (TiO2 loaded with sodium benzoate) into the polyolefin matrix, and an unmodified/blank polyolefin coating was prepared without any additive in the polyolefin matrix. The loading of the inhibitor into porous TiO2 was 10 % analyzed using thermogravimetric analysis. Furthermore, the electrochemical analysis revealed significant improvements in the corrosion resistance and barrier properties of the modified coatings compared to the unmodified blank coatings. Specifically, after 7 days in a corrosive environment, the blank coating pore resistance dropped from 1 × 1010 Ω·cm2 to 5 × 108 Ω·cm2, while the modified coating maintained a high pore resistance of 5 × 1011 Ω·cm2. A localized corrosion study for scratched blank polyolefin coatings showed growing corrosion activity from 5 h of immersion, while modified coatings ceased the detectable activity before 4 h of immersion, which evidenced the improved corrosion inhibition efficiency of the modified coating. This stability in corrosive environments was attributed to the successful loading of modified nanoparticles (TiO2/SB), where SB served as an active agent by forming a protective film on the steel substrate. Which inhibits the corrosion processes along with Ti-based compounds and prevents corrosion propagation under the damaged coating. The enhanced hydrophobic nature of 99° and electrochemical properties support the suitability of these coatings for corrosion protection of steel in various industries.