Microscopic Defects Research Articles

Performance of Fluxgate Magnetometer with Cu-Doped CoFeSiB Amorphous Microwire Core.

In this study, we investigated the effects of Cu doping on the performance of CoFeSiB amorphous microwires as the core of a fluxgate magnetometer. The noise performance of fluxgate sensors primarily depends on the crystal structure of constituent materials. CoFeSiB amorphous microwires with varying Cu doping ratios were prepared using melt-extraction technology. The microstructure of microwire configurations was observed using transmission electron microscopy, and the growth of nanocrystalline was examined. Additionally, the magnetic performance of the microwire and the noise of the magnetic fluxgate sensors were tested to establish the relationship between Cu-doped CoFeSiB amorphous wires and sensor noise performance. The results indicated that Cu doping triggers a positive mixing enthalpy and the reduced difference in the atomic radius that enhances the degree of nanocrystalline formation within the system; differential scanning calorimetry analysis indicates that this is due to Cu doping reducing the glass formation capacity of the system. In addition, Cu doping affects the soft magnetic properties of amorphous microwires, with 1% low-doping samples exhibiting better soft magnetic properties. This phenomenon is likely the result of the interaction between nanocrystalline organization and magnetic domains. Furthermore, a Cu doping ratio of 1% yields the best noise performance, aligning with the trend observed in the material's magnetic properties. Therefore, to reduce the noise of the CoFeSiB amorphous wire sensor, the primary goal should be to reduce microscopic defects in amorphous alloys and enhance soft magnetic properties. Cu doping is a superior preparation method which facilitates control over preparation conditions, ensuring the formation of stable amorphous wires with consistent performance.

Influence of scandium interlayer on the mechanical and metallurgical characteristics of friction stir welded AA1200-H14/ Sc/AA6061-T6

The present investigation observed the friction stir welding (FSW) of joints made from the interfacial layered dissimilar AA1200-H14 and AA6061-T6 using scandium about the UTS, frictional heat, and metallurgical properties. The experimental examination is carried out utilising a three-level, three factors, Box-Behnken Design matrix (17 tests) in response surface approach, with the welding speed (WS), axial force (AF), and tool rotation speed (TRS) as the stated input parameters. Analysis of variance (ANOVA) was used to evaluate the model’s dependability. Macroscopic and microscopic joint defects, as well as the alloy intermixture, have been found using optical microscopy and SEM. The SEM microstructural study exhibited that the generated grains are fine and equiaxed. The optimal WS (50 mm min−1), A−1F−1 (10 kN) and TRS (1750 rpm) settings produced the maximum terminal tensile strength (200.182 MPa) and perfect frictional heat observations. The inclusion of scandium interlayer as well as optimised parameters improved the joint’s mechanical characteristics and produced a fine-grained microstructure.

Impact Analysis of Microscopic Defect Types on the Macroscopic Crack Propagation in Sintered Silver Nanoparticles

Impact Analysis of Microscopic Defect Types on the Macroscopic Crack Propagation in Sintered Silver Nanoparticles

Phase field simulation of intra/intergranular pore morphology evolution of neutron-irradiated austenitic stainless steel

Intergranular or intragranular anisotropic pores can be easily observed in the FCC structure of nuclear reactor core structural materials, such as austenitic stainless steel or nickel-based alloys. Austenitic stainless steel contains a certain amount of nickel(Ni), Ni undergo transmutation reaction under neutron irradiation to produce helium. Helium combines with vacancy and continuously absorbs more helium and vacancy, evolving into underpressure pores filled with a small amount of helium. The morphology of pores is influenced by both the surface anisotropy of the crystal and grain boundary characteristic because pores nucleation predominantly occurs at grain boundaries. The swelling effect caused by pores and the embrittlement effect of high temperature helium are related to the morphology, size and distribution of pores. The phase field method can couple multiple physical fields and accurately describe the effects of material microscopic defects on pores. In this study, we use establish a free energy functional coupling between crystal plane anisotropy and pore-grain boundary interactions, using phase field methods to simulate pores’ evolution and morphology. Our results demonstrate that helium gas induces pore nucleation, with higher concentrations leading to shorter incubation period, faster nucleation rate, and greater growth rate. Grain boundaries act as heterogeneous nucleation sites for helium pores, leading to the formation of pores along these boundaries and high-density diffusion pores within grains. The intragranular pores exhibit anisotropic characteristics regulated by interfacial energy's anisotropic modulus, the strength of the anisotropy, and crystal orientation. The high-density intergranular pores interact significantly and are influenced by grain boundaries, while the anisotropic morphology is negligible. Additionally, it has been observed that the pores located at the middle of grain boundaries tend to exhibit an elliptical shape. The stress inside the pores that contain a small amount of helium gas is negative, which is lower than the value in the matrix. The findings presented herein align well with experimental results and have implications for life prediction models for service components as well as core material design.

Modeling and Quantifying Parameter Uncertainty of Co‐Seismic Non‐Classical Nonlinearity in Rocks

AbstractDynamic perturbations reveal unconventional nonlinear behavior in rocks, as evidenced by field and laboratory studies. During the passage of seismic waves, rocks exhibit a decrease in elastic moduli, slowly recovering after. Yet, comprehensive physical models describing these moduli alterations remain sparse and insufficiently validated against observations. Here, we demonstrate the applicability of two physical damage models—the internal variable model (IVM) and the continuum damage model (CDM)—to provide quantitative descriptions of nonlinear co‐seismic elastic wave propagation observations. While the IVM uses one internal variable to describe the evolution of elastic material moduli, the CDM damage variable is a mathematical representation of microscopic defects. We recast the IVM and CDM models as nonlinear hyperbolic partial differential equations and implement 1D and 2D numerical simulations using an arbitrary high‐order discontinuous Galerkin method. We verify the modeling results with co‐propagating acousto‐elastic experimental measurements. Subsequently, we infer the parameters for these nonlinear models from laboratory experiments using probabilistic Bayesian inversion and 2D simulations. By adopting the Adaptive Metropolis Markov chain Monte Carlo method, we quantify the uncertainties of inferred parameters for both physical models, investigating their interplay in 70,000 simulations. We find that the damage variables can trade off with the stress‐strain nonlinearity in discernible ways. We discuss physical interpretations of both damage models and that our CDM quantitatively captures an observed damage increase with perturbation frequency. Our results contribute to a more holistic understanding of co‐seismic damage and post‐seismic recovery after earthquakes bridging the worlds of theoretical analysis and laboratory findings.

Effect of Y3+ doping of rare earth element on microstructure and antiferromagnetism of CuFeO2 ceramics

In this work, a set of CuFe1-xYxO2 (x = 0–0.02) specimens were synthesized using the conventional high-temperature solid-state reaction method, and the impact of Y3+ doping on the microstructure and magnetic properties of CuFeO2 ceramics was investigated. The introduction of Y3+ ions in place of Fe3+ ions induced alterations in the microstructure of CuFeO2, leading to lattice distortion. X-ray diffraction analysis confirmed the presence of impurity phases in the CuFe1-xYxO2 series samples at high doping concentrations (x ≥ 0.015). In contrast, low doping concentrations (x ≤ 0.0125) exhibited a singular copper-iron ore structure. The microstructures of the ceramic samples were examined using SEM, findings suggest that the presence of high concentrations of dopants hinders the formation of ceramic samples with high density. XPS analysis reveals that the introduction of a low concentration of Y3+ dopant does not impact the oxidation state of Cu and Fe. Raman spectroscopy results indicate that the doping process weakens the vibration mode of CuFe1-xYxO2 ceramic samples. Additionally, measurements conducted using the PPMS demonstrate that the serial samples undergo two consecutive magnetic phase transitions at temperatures of 16K and 11K. The magnetization versus M − H curve of the doped sample exhibits both antiferromagnetic and ferromagnetic behavior. The increase in magnetic susceptibility can be attributed to the greater magnetic moment of doped Y3+ compared to Fe3+. Consequently, the magnetic transformation of the sample is influenced by various factors, including lattice distortion, alterations in ion valence states, variations in microscopic defect types, and modifications in magnetic interactions.

(Invited) Understanding Mg-Related Defects for Vertical GaN p-n Junction Structures Via p-Type Ion Implantation

Vertical GaN power devices have emerged to become promising candidates for next-generation high power applications due to superior material properties such as high breakdown voltage, low on-resistance, and high mobility compared to devices based on Si and SiC. GaN-based p-n junction switching devices enable higher voltage power with significantly higher efficiencies with added advantages of systems with reduced size and weight. A technological limitation of GaN, however, has been the inability to achieve high p-type doping in a planar, vertical device. Here, we will focus on recent developments to achieve high p-type efficiency though ion implantation, novel high temperature annealing schemes, and the importance of defects and morphology in native substrates and epitaxial layers.Mg-implanted homoepitaxial GaN annealed at temperatures at or above 1400 °C eliminates the formation of inversion domains and leads to improved dopant activation efficiency. Extended defects in the form of inversion domains contain electrically inactive Mg after post-implantation annealing at temperatures as high as 1300 °C (one GPa N2 overpressure), which results in a low dopant activation efficiency. While residual defects, such as dislocation loops, still exist after annealing at and above 1400 °C, chemical analysis at multiple dislocation loops shows no sign of Mg segregation. Meanwhile, an overall decreasing trend in the dislocation loop size and density is observed after annealing at the higher temperatures and longer times. Earlier work addressing electrical measurements of these types of samples showed that annealing at ~1400 °C leads to a dopant activation efficiency that is an order of magnitude higher than that observed at 1300 °C. This work complements the earlier work by identifying the microscopic defects (inversion domains) which incorporate Mg, and points to the benefits, in terms of defect density and p-type dopant activation, of using higher temperature (1400 °C) annealing cycles to activate Mg in GaN.

Multi scale simulation of crack propagation in polycrystalline SiC

Silicon carbide (SiC) is considered one of the most promising emerging materials in the fields of refractory materials and semiconductors. In this paper, a multi-scale numerical simulation method is proposed to investigate crack propagation in SiC at different scales, using a combination of cohesive zone model and molecular dynamics (MD). The microstructure of the material is represented by Voronoi subdivision, and bilinear treatment is applied at the grain boundaries. Firstly, MD models with different microscopic defects were established to obtain the corresponding traction separation curves. Then, the element parameters, obtained by fitting the traction separation law, were inserted into the cohesive elements located at the grain boundary and within the grain. Finally, the finite element models were simulated by the failure criterion. The fracture toughness of the material is predicted, and the influence of microscopic defects and grain distribution on macroscopic fracture toughness is explored. The results indicate that the grain distribution and the type of micro defect have an impact on the crack growth path and macro fracture toughness. The simulation results are consistent with published experimental results, which demonstrates the viability of employing this multi-scale analysis method for examining and replicating the micro-, meso-, and macro-scale crack propagation characteristics of SiC.

Microstructure and mechanical properties of T2 copper /316L stainless steel explosive welding composite with small size wavy interface

Copper/stainless steel composite is often used for preparation of superconducting busbar “double box” lap joints. However, it is a challenge for the large thickness T2 copper/316L stainless steel composite is fabricated by explosive welding, because of the bonding interface is always present many problems such as large ripple size, many microscopic defects, low bonding strength and poor sealing etc. In this paper, the big-thickness T2 copper/316L stainless steel composite with small size wavy interface was successfully fabricated by explosive welding. Microstructure of bonding interface indicated that the welding process could be divided into three stages: detonation growth stage, detonation stabilization stage, detonation descent stage. The morphology of bonding interface presented a regular wavy interface and no defects such as cracks, voids and intermetallic compound were formed in the stable stage, which was consistent with the results of ultrasonic and permeability quality inspection. The hardness of copper side and stainless steel side close to the bonding interface reached 131HV and 432HV, respectively. Dynamic recrystallization and fine grain generated in the bonding interface. The mechanical properties of tensile strength, pull-off strength and shear strength in the stable detonation stage is greater than 110 MPa, which is meeting the requirements of preparation of superconducting busbar “double box” lap joints. The deformation failure mainly occurred in the copper side near the bonding interface, which presented a higher bonding strength than copper. Some dimples and tearing edges with different sizes on the fracture surfaces, indicating that the fracture was a typical ductile fracture.

Improving vertical GaN p–n diode performance with room temperature defect mitigation

Defect mitigation of electronic devices is conventionally achieved using thermal annealing. To mobilize the defects, very high temperatures are necessary. Since thermal diffusion is random in nature, the process may take a prolonged period of time. In contrast, we demonstrate a room temperature annealing technique that takes only a few seconds. The fundamental mechanism is defect mobilization by atomic scale mechanical force originating from very high current density but low duty cycle electrical pulses. The high-energy electrons lose their momentum upon collision with the defects, yet the low duty cycle suppresses any heat accumulation to keep the temperature ambient. For a 7 × 105 A cm−2 pulsed current, we report an approximately 26% reduction in specific on-resistance, a 50% increase of the rectification ratio with a lower ideality factor, and reverse leakage current for as-fabricated vertical geometry GaN p–n diodes. We characterize the microscopic defect density of the devices before and after the room temperature processing to explain the improvement in the electrical characteristics. Raman analysis reveals an improvement in the crystallinity of the GaN layer and an approximately 40% relaxation of any post-fabrication residual strain compared to the as-received sample. Cross-sectional transmission electron microscopy (TEM) images and geometric phase analysis results of high-resolution TEM images further confirm the effectiveness of the proposed room temperature annealing technique to mitigate defects in the device. No detrimental effect, such as diffusion and/or segregation of elements, is observed as a result of applying a high-density pulsed current, as confirmed by energy dispersive x-ray spectroscopy mapping.

Antisolvent-Free Heterogenous Nucleation Enabled by Employing 4-Tert-Butyl Pyridine Additive and Two-Step Annealing for Efficient CsPbI2Br Perovskite Solar Cells.

All inorganic perovskite based on CsPbI2Br has attracted significant attention due to its relatively thermal stable structure compare to its hybrid counterparts. With a wide bandgap of 1.9eV and excellent light absorption capability, it has been extensively explored for applications in indoor photovoltaics and as a front absorber in tandem devices. However, the uncontrollable crystallization process during solvent evaporation and thermal annealing leads to both macroscopic defects like cracks and microscopic defects such as voids. In this study, a metastable adduct with lead (II) halides by incorporating 4-tert-butyl pyridine as a volatile Lewis base monodentate ligand in the precursor solution is formed. The strategic preferential decomposition of the adduct during the early-stage low-temperature annealing facilitated the desorption of lead (II) halides, inducing antisolvent-free heterogenous nucleation. This, in turn, promoted crystal growth during subsequent high-temperature annealing, resulting in dense films with low defect density. As a result, a maximum open-circuit voltage of 1.30V is achieved with the champion power conversion efficiency of 16.5% in CsPbI2Br-based perovskite solar cell. The work reveals a new mechanism of using Lewis acid-base adduct to obtain high quality perovskite films other than hindering crystallization in traditional way.

Non-resonant absorption of the X-band electromagnetic wave power in a narrow-gap PbS semiconductor at temperatures of 2.6–8 K in the range of magnetic fields 0–100 mT

Studies of magnetically dependent effects of nonresonant absorption of electromagnetic wave energy in the resonator of the X-band EPR spectrometer related to the superconductivity of metallic lead inclusions and microscopic structural defects in crystals of narrow-band semiconductors PbS1 – x and PbS1 – x:Mn have been performed. It is shown that nanoscale lead particles present in polycrystalline material PbS0.96 with a high content of sulfur vacancies at temperatures of 2.6–8 K manifest themselves as superconductors of the 2nd kind and demonstrate high thermomagnetic stability. It was found that in a single-crystal sample PbS0.996 with a significantly lower concentration of sulfur vacancies under the influence of the electric component of the microwave field in the resonator of the ESR spectrometer, non-periodic bursts of microwave power absorption associated with avalanches of Abrikosov vortices and demonstrating the absence of thermomagnetic stability of superconducting regions associated with defects in the crystal structure of the sample PbS0.996 are observed.

Experimental investigation of axial tensile and fatigue behaviors of HTS round strands

For the development of high-temperature superconducting (HTS) magnet systems of future fusion devices, a novel HTS round strand based on a stacking structure was designed and manufactured using second generation (2G) HTS tapes. Different mechanical loads during operation can result in irreversible degradation of the strand. The axial tension and fatigue loads need particular attention. Therefore, it is important to investigate the electromechanical behavior of the round strand under various axial tension and cyclic loads. In this paper, the axial tensile and fatigue tests were conducted at 77 K, self-field. Taking 95% critical current (Ic) retention as the criterion, the results of the tensile tests revealed that the average tensile stress and strain were as high as 344 MPa and 0.47%, respectively. Fatigue characteristics were also investigated as a function of axial tensile stress. No significant performance degradation was observed up to 100,000 loading cycles with stress amplitudes ranging from 20 MPa to 200 MPa. Ic degradation occurs after 16,000 loading cycles with 380 MPa as the maximum stress. Furthermore, the microscopic defects of the round strand samples due to fabrication imperfections and mechanical loading were investigated using metallographic microscope and scanning electron microscope. These results presented in this paper are useful for comprehending and improving the mechanical behaviors of the strand in high-field and large-scale fusion magnet systems.

Uniform nucleation enabled by confinement effect for dendrite-free Zn anode

The severe dendrites have been considered longstanding plaguing to the high energy density batteries using Zn metal anode. Here, the Zn foil treated by rapid cooling in water after annealing can promote uniform Zn nucleation on its surface which can alleviate the formation of Zn dendrites is discovered. Especially, the point that microscopic morphology and defect cluster caused by the quenching in the Zn metal anode can restrain the surface diffusion of the adsorbed-state Zn atoms which is beneficial to uniform Zn nucleation is proposed. Therefore, the resultant Zn anode achieves sustained ultra-stability in cycling performance (over 1700 h) at 2 mA cm−2 for 1 mAh cm−2 in the symmetric cell and the long-term cycling performance with a discharge capacity of 126.2 mAh g−1 after 1100 cycles at 1 A g−1 in the MnO2 full cell. Our work merges the traditional preparation technology of metal to provide a general pathway toward energy-dense metal batteries.

Tuning defect chemistry of vertical graphene arrays toward highly stable and dendrite-free sodium metal anodes

Vertical graphene (VG) arrays, characteristic of particularly porous microscopic structures, are one promising host to accommodate Na deposition, relieve the formidable volume change and eliminate uncontrolled dendrite growth, by decreasing the local current density. However, in practice, the prepared VG arrays possess superabundant defect sites in the local tip positions, which would guide the accumulation of rampant Na-ion flux concentration on these tip defect sites, and thus result in strong local electric field distribution and the divisional dendritic growth. Herein, a novel reconstruction strategy is proposed to re-build the edges and stacking of VG, by removing some unstable carbon defects and changing turbostratic stacking structure of VG to a Bernal stacking mode of the graphited VG, which enables to guide the comparatively smaller and stable interface with Na. Benefiting from the synergistic effect of microscopic structure and defect chemistry design, the re-build VG achieves a long-term reversible Na plating/stripping over 6400 h at an areal capacity of 8 mAh cm−2 in half cell, as well as a long cycle life of up to 3300 h at 1 mA cm−2 with a plating capacity of 4 mAh cm−2 in symmetric cells. Concomitantly, the density functional theory calculations demonstrate that Na atoms tend to nucleate and grow into lateral Na plating on the re-build VG arrays at an atomic level. As a result, the full cell coupled with a P2-Na2/3Ni1/3Mn1/3Ti1/3O2 cathode has a predominant improved cycling stability. This microscopic structure/defect chemistry engineering strategy provides new insight into guiding the uniform deposition of Na metal for high-performance sodium metal battery.

Research on Representative Volume Element Fex-Cy High-Temperature Mechanical Model Based on Response Surface Analysis

In this research, a multi-scale representative volume element method is introduced that combines the temperature and stress fields to analyze the force field distribution around microcracks in low-carbon steel using a combination of molecular dynamics and finite element analysis. Initially, an orthogonal experimental design was used to design the molecular dynamics simulation experiments. Next, a nano-level uniaxial tensile test model for mild steel was established based on the experimental design, and the uniaxial tensile behavior of low-carbon steel was investigated using molecular dynamics. Lastly, mathematical models of the modulus of elasticity E and yield strength Q of mild steel at a high temperature were obtained statistically using the response surface methodology. Meanwhile, a finite element model with a coupled temperature–stress field was established to investigate the force field distribution around the microscopic defects, and the microscopic crack stress concentration coefficient K was revised. The results indicate that regardless of the location of microcracks within the structure, the stress distribution due to size effects should be considered under high-temperature loading.

Study on creep-fatigue interaction mechanism and life prediction of aero-engine turbine blade

Aiming at the creep-fatigue interaction damage failure problem of turbine blades in aeronautical engineering, firstly, based on the modified Kachanov-Rabotnov-Chaboche (MKRC) damage mechanics theory, the creep-fatigue life prediction model of turbine blade material was constructed with the experimental verification completion of nickel-based superalloy DZ125. Meanwhile, the creep-fatigue interaction behavior was investigated with the mechanism revelation. Then, considering the shape, size and microscopic defect difference effect from the material to the structure, the creep-fatigue life prediction model of turbine blade structure is proposed by introducing the comprehensive correction factor with experimental verification. Finally, the research results show that there are a large number of interwoven tear edges, micro-cracks and micro-pores in the fracture morphology, and creep and fatigue interact with each other in the form of effective stress. Simultaneously, the creep-fatigue life prediction model has a high life prediction ability with an error of 3%, which can provide a theoretical reference for the damage tolerance design of the turbine blade.

Microstructure evolution and mechanical properties of AA2195-T8 Al-Li alloy back gas-shielded VPPA weld

Variable polarity plasma arc welding (VPPA) is an adaptable and efficient method for welding large Al-Li alloy components like rocket fuel tanks. This work investigated the microstructure and properties of AA2195-T8 Al-Li alloy weld using the back gas-shielded VPPA method. The process of microstructure evolution is established to reveal the softening mechanism of the weld. The results show that the mechanical properties of the weld are significantly reduced without back gas shielding, the back of the weld oxidizes to form Li2O with MgO, resulting in back hollows and pores. The addition of back gas shielding during welding solves the above problem. With the addition of back gas shielding, the increase of the strength and elongation for the weld with reinforcement is 33.6 % and 96.7 %, and for the weld without reinforcement is 6.9 % and 28.9 %. There is no significant effect on the microstructure of the weld. The second phases in the weld are mainly Al-Cu and Al-Cu-Mg-Ag eutectic, with a small amount of Al7Cu2Fe and separated eutectic θ phase. The matrix phase in the weld is mainly the composite phase composed of θ and Ω phases. The dissolution of the nanoscale precipitated phase, severe grain boundary segregation, burnout of alloying components, and microscopic defects are the main causes of the reduction in weld properties. In summary, this work provides practical suggestions for optimizing the VPPA welding process to improve the mechanical properties of Al-Li alloy welded joints.

Microscopic defect dynamics during a brittle-to-ductile transition

Deformation of all materials necessitates the collective propagation of various microscopic defects. On Earth, fracturing gives way to crystal-plastic deformation with increasing depth resulting in a "brittle-to-ductile" transition (BDT) region that is key for estimating the integrated strength of tectonic plates, constraining the earthquake cycle, and utilizing deep geothermal resources. Here, we show that the crossing of a BDT in marble during deformation experiments in the laboratory is accompanied by systematic increase in the frequency of acoustic emissions suggesting a profound change in the mean size and propagation velocity of the active defects. We further identify dominant classes of emitted waveforms using unsupervised learning methods and show that their relative activity systematically changes as the rocks cross the brittle-ductile transition. As pressure increases, long-period signals are suppressed and short-period signals become dominant. At higher pressures, signals frequently come in avalanche-like patterns. We propose that these classes of waveforms correlate with individual dominant defect types. Complex mixed-mode events indicate that interactions between the defects are common over the whole pressure range, in agreement with postmortem microstructural observations. Our measurements provide unique, real-time data of microscale dynamics over a broad range of pressures (10 to 200 MPa) and can inform micromechanical models for semi-brittle deformation.

Accelerated degradation of cathodic protected epoxy coating by Pseudomonas aeruginosa in seawater

The combination of coatings and cathodic protection (CP) is one of the most commonly used methods for corrosion protection of metal materials. However, the protection life of this method is difficult to match the original design, which mechanism is still not well known. Previous work reports that coatings experience degradation mainly due to cathodic disbondment and microbial factors in marine environments. To further explore the possible reason for this question, we studied the degradation behavior of epoxy coatings in the co-existence of CP and Pseudomonas aeruginosa in seawater using Electrochemical impedance spectroscopy (EIS), Confocal laser scanning microscope (CLSM), Scanning electron microscope (SEM), 3D microscopy, Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analyzer (TGA), and Energy disperse spectrometer (EDS). The EIS results indicate that coating resistance drops bellows 106 Ω cm2 after 35 d of immersion under the effect of P. aeruginosa alone, but the degradation rate of coatings increases in the co-existence of CP and P. aeruginosa. The coating resistance drops bellows 106 Ω cm2 after 7 d of immersion in the P. aeruginosa containing seawater at − 1.05 VCSE. This may be due to P. aeruginosa can cause benzene ring removal from the epoxy coating, and the presence of CP promotes biofilm formation on the coating surface. The thickness of biofilm is about 33.3 μm at − 1.05 VCSE, which is about 1.5 times larger than at OCP, and the diameter of microscopic defects is about 9 times larger than in sterile seawater at the same CP potential. The presence of P. aeruginosa accelerate Cl− penetrating through the coating causing pitting corrosion of the substrate steel. This study revealed that the shorter protection life of organic coating can be attributed to the combined effect of CP and microorganisms in marine environments. The findings of this study can be referenced for better understanding of the coating failure mechanism in marine environments, and provide guidance for selecting appropriate organic coatings with anti-fouling and anti-corrosive properties.