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Article

Microbiological Deterioration of Epoxy Coating on Carbon Steel by Pseudomonas aeruginosa

by
Shuyuan Zhang
1,2,
Huaibei Zheng
3,
Weiwei Chang
1,2,
Yuntian Lou
1,2 and
Hongchang Qian
1,2,*
1
National Materials Corrosion and Protection Data Center, Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, China
2
BRI Southeast Asia Network for Corrosion and Protection (MOE), Shunde Innovation School, University of Science and Technology Beijing, Foshan 528399, China
3
State Key Laboratory of Metal Material for Marine Equipment and Application, Anshan 114002, China
*
Author to whom correspondence should be addressed.
Coatings 2023, 13(3), 606; https://doi.org/10.3390/coatings13030606
Submission received: 8 February 2023 / Revised: 28 February 2023 / Accepted: 8 March 2023 / Published: 12 March 2023
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Abstract

:
Epoxy coating is a commonly used anticorrosive coating on metal surfaces. Pseudomonas aeruginosa has been reported to be able to accelerate the corrosion of metal materials, but its effect on the corrosion resistance of epoxy coatings is rarely reported. In this work, the accelerated deterioration of epoxy coating on carbon steel caused by marine Pseudomonas aeruginosa was investigated. The immersion tests of epoxy coatings in the sterile and P. aeruginosa-inoculated culture media with 100%, 10%, and 0% nutrients were performed. When the nutrient concentration was reduced, the number of P. aeruginosa cells attached to the coating surface was improved, and the coatings suffered more degradation under starvation conditions. The results of electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements showed that the presence of P. aeruginosa promoted the degradation of epoxy coating, and the coating had lower low frequency impedance modulus and higher corrosion current density in the inoculated medium with starvation conditions. The results of Fourier transform infrared spectroscopy (FTIR) indicated that the peak intensities of C-O-C and C-O groups of coatings decreased as nutrient concentration dropped in the inoculated medium. It indicated that P. aeruginosa accelerated the degradation of epoxy coatings through destroying the C-O-C and C-O groups.

1. Introduction

An organic coating is one of the most commonly used anticorrosion strategies. It prevents metal from directly contacting water, oxygen, and some corrosive ions through physical isolation, thus inhibiting the occurrence of corrosive electrochemical reactions [1,2,3]. During actual application in corrosive environments, organic coating can be damaged by ultraviolet radiation, water penetration, and external force, leading to a gradual decline in corrosion resistance. Many studies have elucidated the failure process of organic coatings in various service environments and proposed a variety of methods to improve their corrosion resistance [4,5,6]. Microorganisms are an important part of nature. In recent years, microbiologically influenced corrosion (MIC) has garnered extensive attention as a major problem. MIC refers to the material degradation caused by microbial activities or corrosive microbial metabolites, which accounts for 20% of global corrosion costs [7,8,9]. Numerous studies have shown that some microorganisms can accelerate the corrosion of metals [10,11,12,13,14,15,16,17]. However, the effect of microorganisms on the corrosion resistance of organic coatings is rarely reported.
Microbial communities can attach to the surface of any polymer materials by secreting extracellular polymeric substances (EPS), and their growth process and metabolic behavior often lead to the degradation of polymer materials [18,19]. The polymer is generally a large-molecular-weight polymer with long carbon chain structures and can be used as nutrient sources for microorganisms. The biodegradation process of the polymer is complex. After the extracellular enzymes secreted by microorganisms combine with the surface of the polymer, the long carbon chains are broken through hydrolysis reactions or oxidation reactions catalyzed by enzymes to generate short chain substances with small molecular weight, such as oligomers, dimers, and monomers [20,21]. These small molecules can pass through semi-permeable bacterial membranes into microbial cells, where they are oxidized to produce energy and metabolites such as carbon dioxide, water, and even methane under anaerobic conditions [22,23,24]. This biochemical degradation process is a common form of microbial degradation of coating materials, which can easily lead to large area damage of coating materials. Some fungi have been reported to be capable of destroying coating by secreting acidic metabolites, and the growth of fungi mycelia into the coating can also damage the integrity of the coating [25,26,27]. In addition, microbial degradation of additives, including plasticizers and curing agents, can also reduce the mechanical properties and corrosion resistance of coatings [23]. These additives can be selectively and preferentially degraded due to their lower molecular weight. Because of these effects, microorganisms pose a significant threat to the service performance of coatings and reduce their durability.
Epoxy coatings are widely used for corrosion protection of metals and have the characteristics of high adhesion, electrical insulation, high strength, and high corrosion resistance. Especially in the marine environment, the steel/epoxy composite coating system is one of the main anti-corrosion strategies. Hence, the failure behaviors of epoxy coatings under different marine environmental factors, including seawater, salt spray, and UV light, have been clearly elucidated, and the related failure mechanisms have also been revealed [28,29]. In addition to the above factors, microorganisms are also a major component of the marine environment. In recent years, the effect of microorganisms on the failure of epoxy coatings was a concern. Wang et al. investigated the influence of Pseudomonas putida on the deterioration of epoxy resin varnish coating in marine environments [30]. The experimental results showed that P. putida could accelerate the degradation of epoxy coating by oxidizing hydroxyl group, resulting in the decrease in corrosion resistance of coating. Deng et al. reported the degradation effect of Bacillus flexus on epoxy coating, indicating that B. flexus destroyed the aromatic rings and epoxy groups of the coating and resulted in the decrease in corrosion resistance [31]. In addition, sulfate-reducing bacteria (SRB) were also found to be capable of causing the microbial corrosion of epoxy coating [32]. Nonetheless, there are still few studies on the microbiological deterioration of epoxy coatings. Pseudomonas aeruginosa is a typical Gram-negative bacterium which widely inhabits the marine environment. The severe corrosion of carbon steels and stainless steels caused by marine P. aeruginosa in simulated marine environments has been frequently reported [33,34,35,36]. However, the effect of marine P. aeruginosa on the degradation of epoxy coatings has not been studied.
Herein, we investigated the influence of marine P. aeruginosa on the deterioration behavior of epoxy coating in the culture medium environment through 14 days of immersion tests. Moreover, nutrient starvation tests were adopted to help to study the deterioration behavior. The surface morphologies of coatings before and after removing the biofilms were observed using scanning electron microscopy (SEM). The failure process of epoxy coatings was studied by electrochemical tests, including electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves. The wettability of coating surfaces during the immersion tests was characterized by water contact angle measurements. The change in chemical composition of coating surfaces before and after the immersion tests was analyzed by Fourier transform infrared spectroscopy (FTIR).

2. Experimental Section

2.1. Materials and Coating Preparation

Bisphenol A diglycidyl ether (BADGE) epoxy resin and Jeffamine D230 hardener were purchased from Sigma-Aldrich (Shanghai, China). Q235 carbon steel was used for coating preparation and cut into blocks (10 mm × 10 mm × 3 mm). All specimens were encapsulated with BADGE to ensure that only one surface (10 mm × 10 mm) was exposed. The exposed surfaces were sanded until 600 grit by abrasive paper and then ultrasonically cleaned with anhydrous ethanol for 10 min.
To prepare the epoxy coating, BADGE and D230 hardener were mixed with a mass ratio of 3:1. After mechanical stirring for 10 min, the obtained mixture was evenly brushed on cleaned Q235 steel surface with a rod applicator, followed by curing first at 80 °C for 3 h and then at 125 °C for 2 h. The thickness of all epoxy coatings was controlled at ~100 μm. The coating coupons were wiped with 75% alcohol solution for 10 s and then exposed to UV light for 30 min to sterilize before immersion tests.

2.2. Bacterium and Culture Medium

Marine P. aeruginosa 1A00099 strain was purchased from the Marine Culture Collection of China (MCCC, Xiamen). Marine medium 2216E was used for bacterial incubation and subsequent immersion tests, which consisted of the compositions as follows: 5.0 g/L peptone, 1.0 g/L yeast extract, 0.1 g/L iron citrate, 19.45 g/L NaCl, 5.98 g/L MgCl2, 3.24 g/L Na2SO4, 1.8 g/L CaCl2, 0.55 g/L KCl, and 10 mL/L trace element solution. The compositions of trace element solution contained: 16 g Na2CO3, 8 g KBr, 3.4 g SrCl2, 2.2 g H3BO3, 0.4 g Na2O3Si, 0.24 g NaF, 0.16 g NH4NO3, and 0.8 g Na2HPO4 in 1000 mL deionized water [37]. Marine medium 2216E is the most commonly used medium for P. aeruginosa inoculation and has been used in many MIC studies of P. aeruginosa. The pH value of the culture medium was adjusted to 7.6 by the dilute sulfuric acid solution and NaOH solution. Before the incubation, the culture medium was autoclaved at 121 °C for 20 min (MLS-3781PC, Panasonic, Osaka, Japan). During incubation, the growth process of P. aeruginosa was measured by ultraviolet spectrophotometer (Bio Mate3S, Thermo Fisher, Waltham, MA, USA) and characterized by optical density value at 600 nm (OD600 value). OD600 value is often used to monitor the growth of P. aeruginosa in MIC studies [38,39]. The pH value was monitored by a pH meter (S220-B, Mettler Toledo, Columbus, OH, USA).

2.3. Immersion Tests

Immersion tests were carried out in sterilized conical flasks containing 50 mL culture medium; 1 mL of P. aeruginosa planktonic seed culture medium was inoculated into the conical flasks, and the initial cell concentration of P. aeruginosa was 1 × 108 cells/mL. After P. aeruginosa was precultured at 30 °C for 24 h, two identical coupons were placed at the bottom of each conical flask without touching each other. Subsequently, the conical flasks were incubated at 30 °C aerobically for 14 days, and 50 mL sterilized culture medium with carbon steel samples was used as the sterile control. The immersion tests in sterile and inoculated groups were performed to investigate the effect of P. aeruginosa on the deterioration of epoxy coating.

2.4. Surface Characterization

The distribution of biofilm on the coating surface and coating surface defects were observed by scanning electron microscopy (FEI Quanta 250, FEI, Hillsboro, OR, USA) under 20 kV acceleration voltage in high vacuum mode. After the immersion tests, the coupons were taken out from the medium and rinsed with phosphate buffer saline (PBS), followed by immersing in 2.5% (v/v) glutaraldehyde solution at 4 °C for 8 h to fix the adherent biofilms on the coating surface. The coupons were then sequentially dehydrated with a gradient of ethanol solutions (50%, 60%, 70%, 80%, 90%, and 100 vol.%) for 8 min at each concentration. For observing the defects of coating surfaces, biofilms on the coupon surface were wiped with 75% ethanol solution using a cotton swab and then rinsed with 100% ethanol solution. Before SEM observation, Au was sputtered on the coupon surface to improve the surface conductivity. The chemical composition of coupon surfaces was measured by a Fourier transform infrared spectrometer (Nicolet IS10, Thermo Fisher Scientific, Waltham, MA, USA). The spectral range was 400–4000 cm−1. The water contact angle of the coating surface was measured by a goniometer (OCA20, Dataphysics, Filderstadt, Germany). Before the FTIR and contact angle measurements, biofilms were removed from the coupon surfaces according to the above methods.

2.5. Electrochemical Measurements

All electrochemical measurements were carried out using an electrochemical workstation (Reference 600 Plus, Gamry, Warminster, PA, USA). A traditional three-electrode system was adopted, which consisted of a coating coupon as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode (SCE) as the reference electrode. Copper wires were welded on the back of carbon steel of working electrode for electrode connection in electrochemical tests. Open-circuit potential (OCP) was first performed to guarantee the steadiness of the electrochemical system. After 3, 7, 10, and 14 days of immersion in different media, EIS measurements were conducted with a frequency range from 100 kHz to 10 mHz with a sinusoidal disturbance of 10 mV. Potentiodynamic polarization curves were measured from −500 mV to 500 mV vs. EOCP with the scanning rate of 1 mV/s at the end of the 14th day. Triplicate samples were used for each measurement.

2.6. Starvation Tests

To create starvation conditions for P. aeruginosa, the contents of peptone and yeast extract were reduced. Peptone and yeast extract were not added to prepare the culture medium with 0% nutrients, and 0.5 g/L of peptone and 0.1 g/L of yeast extract were added to prepare the culture medium with 10% nutrients. In starvation tests, the coating samples were immersed into the regular 2216E culture medium, the medium with 10% nutrients, and the medium with 0% nutrients for 14 days. During the 14 days, the change of biofilm morphologies and corrosion electrochemical behaviors of the coatings in different culture media were characterized using SEM and EIS. On the 14th day, potentiodynamic polarization measurements were carried out in different media, and the FTIR and water contact angle measurements of the coating surfaces from different culture media were also performed. Starvation tests were carried out to study the influence of nutrient concentration on the microbiological deterioration behavior of epoxy coatings caused by P. aeruginosa.

3. Results and Discussion

3.1. Growth of Planktonic P. aeruginosa Cells

The growth curve of P. aeruginosa and pH value of culture medium during 14 days of incubation in the culture media with various nutrient concentrations are shown in Figure 1. The growth curve of P. aeruginosa in the regular 100% nutrient medium exhibited a stage of exponential growth in the first 7 days, reaching the maximum OD600 value of approximately 1.1 (Figure 1a). Subsequently, the growth of bacteria entered a period of slow decline, which should be related to limited space and nutrients in the culture medium. Nonetheless, the OD600 value remained above 0.8. The OD600 value of P. aeruginosa in 10% nutrient medium remained at approximately 0.2 over 14 days. In 0% nutrient medium, OD600 value remained nearly 0. As the nutrient concentration decreased, the number of planktonic bacteria cells gradually decreased. The pH value in the regular inoculated medium increased at the initial stage of immersion and then remained around 8.4, which should be related to the nitrate reducing capacity of P. aeruginosa [40]. The alkaline environment has little effect on the corrosion resistance of coatings. With the decrease in nutrient concentration, the pH value of the medium decreased gradually. For the 0% nutrient medium, the pH value was maintained at 7.8 for 14 days (Figure 1b).

3.2. Biofilm Distribution

No P. aeruginosa cell was found on the coating surface after 14 days of immersion in the sterile culture medium. In contrast, bacterial attachment was already present on the coating surface after 3 days of incubation under the inoculated state. With the increase in immersion time, the number of bacteria attached to the coating surface increased (Figure 2a1–a3). The bacteria cells remained on the coating surface in a dispersed state during 14 days of immersion. Compared with the planktonic cells, the sessile P. aeruginosa cells on the coating surfaces from the media with 10% and 0% nutrients showed different conditions. With the nutrient concentration reduced to 10%, the number of adherent bacteria cells increased significantly. Most areas of the coating surfaces were covered by P. aeruginosa cells after only 3 days of immersion (Figure 2b1). Aggregation of cells with the size between 10 μm and 20 μm appeared in localized areas of coating surfaces. The lack of nutrients forced cells to find the coating surfaces as an alternative energy source, causing more cells adhere on the coating surfaces. The amount of cell adhesion increased significantly after 7 days (Figure 2b2). This suggested that with a small amount of nutrients were depleted, more cells relied on the coating for an energy source. When the nutrients were totally removed from the culture medium, aggregation of cells could still be observed on the coating surface (Figure 2c1–c3). At the same time, there were almost no planktonic cells in the culture medium. On the 14th day, the number of adherent cells decreased, probably because the limited organic molecules from the coating surface were not adequate to sustain the large number of cells. It was worth noting that the number of cells in the 10% nutrient medium was higher than that in the 0% nutrient medium. This might be because the 10% nutrients ensured rapid cell proliferation at the initial stage of immersion, which could be distinguished from the growth curves.
After removing the bacteria cells from the coating surface, the surface SEM morphologies in different inoculated media are shown in Figure 3. It was difficult to find obvious damage on the coating surface in the inoculated medium with 100% nutrients after 14 days of immersion. Nevertheless, the coating surface became rough, which should be related to the microbial degradation effects of P. aeruginosa. After 14 days of incubation in the culture medium with 10% nutrients, it was obvious that the localized area of the coating surface was severely damaged, and holes with size of approximately 20 μm and chalking phenomenon could be clearly seen (Figure 3b). The increase in the adherent amount of P. aeruginosa aggravated the damage to the epoxy coating. When the nutrients were totally removed, holes could also be observed on the coating surface, but its size was smaller than that in the inoculated medium with 10% nutrients (Figure 3c). Chalking phenomenon also appeared at the edge of holes. For the coatings in the sterile medium, the surface morphologies had little change before and after ethanol solution cleaning. The damage to the epoxy coating was more severe in nutrient-deficient environments with P. aeruginosa.

3.3. Electrochemical Analysis

EIS can characterize the corrosion electrochemical process of complex interfaces and has been frequently used to investigate the barrier properties of coatings [41,42]. The evolution of Nyquist and Bode plots of epoxy coatings under sterile and inoculated conditions during 14 days of incubation is shown in Figure 4. In the sterile culture medium, the low frequency impedance modulus (|Z|0.01Hz) in the Bode plots reached approximately 1.02 × 108 Ω·cm2 after 3 days, and two time constants could be observed from the Nyquist and phase angle plots (Figure 4a1,a2). |Z|0.01Hz is often used as a semi-quantitative indicator to characterize the corrosion resistance of coatings because it is related to the electric double layer of the electrochemical reaction at the solution/metal interface [43,44]. The time constant in the high frequency region represents the coating, while the time constant in the low frequency region represents the electric double layer on the metal surface. This indicated that corrosion reaction has occurred under the epoxy coating. The curing process of the coating might leave tiny pores, causing water to penetrate and contact with the carbon steel. With the increase in immersion time, the impedance of the coating increased gradually, and the |Z|0.01Hz reached over 1 × 109 Ω·cm2 after 14 days. This improvement might be caused by the corrosion products of the carbon steel, which blocked the pores and hindered the penetration of water [3]. In the presence of P. aeruginosa, the |Z|0.01Hz value decreased to approximately 1.70 × 107 Ω·cm2 after 3 days of incubation (Figure 4b1). This decline should be related to the adhesion of P. aeruginosa cells on the coating surface, which destroyed the surface molecular structure and increased water infiltration channels. The |Z|0.01Hz value gradually decreased to 1.26 × 107 Ω·cm2 after 14 days, which was two orders of magnitude lower than that in the sterile medium on the 14th day.
The evolution of EIS of the epoxy coatings in the inoculated culture media with 10% and 0% nutrients is presented in Figure 4c1,c2 and Figure 4d1,d2. When the nutrient concentration was reduced to 10%, the |Z|0.01Hz value was approximately 1.0 × 107 Ω·cm2, which was similar with that in the inoculated culture medium with 100% nutrients on the third day. This indicated that coating degradation was not significant during 3 days of immersion, as the 10% nutrients could still sustain the bacteria cells. There was a significant drop in |Z|0.01Hz value and the radius of capacitive arc in Nyquist plots after 7 days of immersion. After 14 days of exposure, the |Z|0.01Hz value further decreased to 7.08 × 104 Ω·cm2, nearly two orders of magnitude lower than that in the inoculated culture medium with 100% nutrients at the 14th day. After 3 days, the depletion of nutrients caused bacteria to start using the coating as a carbon source, thus accelerating the deterioration of corrosion resistance of the epoxy coating. When all nutrients were removed from the culture medium, the |Z|0.01Hz value dropped below 1 × 105 Ω·cm2 after only 3 days. This indicated that the bacteria had already caused significant damage to the coating during the 3 days, which was related to the complete deficiency of nutrients. From EIS results, it can be seen that P. aeruginosa promoted the failure of the epoxy coating, and with the reduction of nutrients, the failure rate of the epoxy coatings increased first and then decreased.
The polarization curve measurements were conducted at the end of the 14th day in the sterile and inoculated culture media, which are shown in Figure 5. The corresponding electrochemical parameters obtained from the polarization curves, including the corrosion potential (Ecorr) and the corrosion current density (Icorr), are summarized in Table 1. The Ecorr in the inoculated medium with 100% nutrients shifted to −0.82 V (vs. SCE), which was higher than that in the sterile culture medium. The presence of P. aeruginosa made the polarization curve shift to positive direction, which caused the Icorr value increase from 1.23 nA·cm−2 to 3.98 nA·cm−2. The lack of nutrients caused the curves to continue to shift to the positive direction. The Icorr values in 10% nutrients and 0% nutrients media were enhanced to 0.68 μA·cm−2 and 0.31 μA·cm−2, respectively, which were two orders of magnitude higher than that in the culture medium with 100% nutrients. The increase in Ecorr might be caused by the increase in corrosion products on the surface of exposed carbon steel. Compared with that in the sterile medium and inoculated medium with 100% nutrients, the epoxy coatings in the inoculated media with 10% and 0% nutrients had higher Icorr values and suffered more serious deterioration. The results of polarization curve measurements were consistent with the results of EIS.

3.4. Contact Angle Measurements

After 14 days of incubation, the biofilms on the coating surfaces were removed and the water contact angles of the sample surfaces were measured, as shown in Figure 6. The water contact angle of the coating surface remained above 70° after 14 days of immersion in the sterile medium. In the presence of P. aeruginosa, the water contact angle of the sample surface decreased to approximately 63° after 14 days. When the nutrient concentration decreased, the water contact angle of the sample surface decreased to approximately 56° after 14 days. This indicated that the presence of P. aeruginosa led to an increase in the hydrophilicity of the coating surface. A prerequisite for biofilm formation is to form a conditioning film, which contains some organic chemicals such as proteins [45]. The conditioning film is firmly combined with the epoxy coating surface and is difficult to completely remove. This should be the reason for the increased hydrophilicity of the coating surface. The increase in hydrophilicity aggravates the damage from water to the epoxy coating.

3.5. FTIR Analysis

To analyze the effect of P. aeruginosa on the chemical composition of the epoxy coating surface, FTIR of coating surfaces after 14 days of immersion in the sterile and inoculated culture media with different nutrient concentrations was carried out (Figure 7). Before the measurements, the biofilms were removed from the coating surfaces. The absorption bands between 2700 cm−1 and 3000 cm−1 were associated with the hydrocarbon groups (-CH) [46]. The peaks at 1607 cm−1 and 1507 cm−1 were characteristic absorption peaks of the vibrations of the aromatic ring in epoxy resin [47]. The peaks at 1243 cm−1 and 1033 cm−1 were assigned to the C-O-C groups [48,49]. The peaks at approximately 1100 cm−1 were related to the C-O groups [50]. The intensities of C-O-C groups and C-O groups in the inoculated culture medium with 100% nutrients were lower than those without immersion treatment. Furthermore, the peak intensities of these two groups continued to decrease as nutrient concentration decreased. This indicates that adherent P. aeruginosa mainly destroyed C-O-C groups and C-O groups to degrade the epoxy coating and obtain small molecular chains as energy sources. The degradation of the epoxy resin led to an increase and expansion of defects, which made water penetration easier and aggravated the corrosion of the carbon steel substrates.

4. Conclusions

In this work, the effect of P. aeruginosa on the failure process of epoxy coating was studied. The surface condition, electrochemical behavior, surface wettability, and chemical composition of epoxy coatings during 14 days of immersion in the sterile and inoculated media were compared. Starvation experiments were used to further investigate the degradation behavior of the epoxy coating. After immersion in the inoculated media with 10% and 0% nutrients, obvious holes and chalking phenomenon appeared on the coating surfaces. Electrochemical results showed that the corrosion resistance of the epoxy coating decreased due to the presence of P. aeruginosa. The nutrient starvation environments in the medium led to the further decrease in corrosion resistance of the coatings, and the coatings in the inoculated medium under starvation conditions exhibited lower |Z|0.01Hz values and higher Icorr values than those in the medium with 100% nutrients after 14 days. The results of contact angle tests showed that the adhesion of P. aeruginosa increased the hydrophilicity of the coating surface. FTIR results showed that the adherent P. aeruginosa destroyed the C-O-C and C-O groups in the molecular chains of epoxy coatings, which accelerated the degradation of the coatings.

Author Contributions

Conceptualization, S.Z.; Investigation, S.Z.; Methodology, H.Z.; Visualization, W.C. and Y.L.; Writing, S.Z.; Review & editing, H.Q. All authors have read and agreed to the published version of the manuscript.

Funding

This work is supported by National Natural Science Foundation of China (52161160308, 52001021), Joint Fund of Basic and Applied Basic Research Fund of Guangdong Province (2021B1515130009), and the Open Fund from State Key Laboratory of Metal Material for Marine Equipment and Application (SKLMEA-K202006).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Lyon, S.B.; Bingham, R.; Mills, D.J. Advances in corrosion protection by organic coatings: What we know and what we would like to know. Prog. Org. Coat. 2017, 102, 2–7. [Google Scholar] [CrossRef] [Green Version]
  2. Nazari, M.H.; Zhang, Y.; Mahmoodi, A.; Xu, G.; Yu, J.; Wu, J.; Shi, X. Nanocomposite organic coatings for corrosion protection of metals: A review of recent advances. Prog. Org. Coat. 2022, 162, 106573. [Google Scholar] [CrossRef]
  3. Zhang, D.; Qian, H.; Wang, L.; Li, X. Comparison of barrier properties for a superhydrophobic epoxy coating under different simulated corrosion environments. Corros. Sci. 2016, 103, 230–241. [Google Scholar] [CrossRef]
  4. Rammelt, U.; Reinhard, G. Application of electrochemical impedance spectroscopy (EIS) for characterizing the corrosion-protective performance of organic coatings on metals. Prog. Org. Coat. 1992, 21, 205–226. [Google Scholar] [CrossRef]
  5. Zhao, X.; Wang, J.; Wang, Y.; Kong, T.; Zhong, L.; Zhang, W. Analysis of deterioration process of organic protective coating using EIS assisted by SOM network. Electrochem. Commun. 2007, 9, 1394–1399. [Google Scholar] [CrossRef]
  6. Qian, H.; Xu, D.; Du, C.; Zhang, D.; Li, X.; Huang, L.; Deng, L.; Tu, Y.; Mol, J.M.C.; Terryn, H.A. Dual-action smart coatings with a self-healing superhydrophobic surface and anti-corrosion properties. J. Mater. Chem. A 2017, 5, 2355–2364. [Google Scholar] [CrossRef] [Green Version]
  7. Gu, T.; Jia, R.; Unsal, T.; Xu, D. Toward a better understanding of microbiologically influenced corrosion caused by sulfate reducing bacteria. J. Mater. Sci. Technol. 2019, 35, 631–636. [Google Scholar] [CrossRef]
  8. Hou, B.; Li, X.; Ma, X.; Du, C.; Zhang, D.; Zheng, M.; Xu, W.; Lu, D.; Ma, F. The cost of corrosion in China. Npj Mat. Degrad. 2017, 1, 4. [Google Scholar] [CrossRef]
  9. Qian, H.C.; Chang, W.W.; Cui, T.Y.; Li, Z.; Guo, D.W.; Kwok, C.T.; Tam, L.M.; Zhang, D.W. Multi-mode scanning electrochemical microscopic study of microbiologically influenced corrosion mechanism of 304 stainless steel by thermoacidophilic archaea. Corros. Sci. 2021, 191, 109751. [Google Scholar] [CrossRef]
  10. Jia, R.; Unsal, T.; Xu, D.; Lekbach, Y.; Gu, T. Microbiologically influenced corrosion and current mitigation strategies: A state of the art review. Int. Biodeter. Biodegr. 2019, 137, 42–58. [Google Scholar] [CrossRef]
  11. Wakai, S.; Eno, N.; Mizukami, H.; Sunaba, T.; Miyanaga, K.; Miyano, Y. Microbiologically influenced corrosion of stainless steel independent of sulfate-reducing bacteria. Front. Microbiol. 2022, 13, 982047. [Google Scholar] [CrossRef]
  12. Lekbach, Y.; Liu, T.; Li, Y.; Moradi, M.; Dou, W.; Xu, D.; Smith, J.A.; Lovley, D.R. Microbial corrosion of metals: The corrosion microbiome. Adv. Microb. Physiol. 2021, 78, 317–390. [Google Scholar] [PubMed]
  13. Liu, T.; Pan, S.; Wang, Y.; Guo, Z.; Wang, W.; Zhao, Q.; Zeng, Z.; Guo, N. Pseudoalteromonas lipolytica accelerated corrosion of low alloy steel by the endogenous electron mediator pyomelanin. Corros. Sci. 2020, 162, 108215. [Google Scholar] [CrossRef]
  14. Wu, J.; Zhang, W.; Chai, K.; Yu, A. Corrosion Behavior of AISI 1045 Steel in Seawater in the Presence of Flavobacterium sp. Front. Microbiol. 2020, 11, 303. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  15. Dou, W.; Liu, J.; Cai, W.; Wang, D.; Jia, R.; Chen, S.; Gu, T. Electrochemical investigation of increased carbon steel corrosion via extracellular electron transfer by a sulfate reducing bacterium under carbon source starvation. Corros. Sci. 2019, 150, 258–267. [Google Scholar] [CrossRef]
  16. Liu, H.; Chen, C.; Yuan, X.; Tan, Y.; Meng, G.; Liu, H.; Cheng, Y.F. Corrosion inhibition behavior of X80 pipeline steel by imidazoline derivative in the CO2-saturated seawater containing sulfate-reducing bacteria with organic carbon starvation. Corros. Sci. 2022, 203, 110345. [Google Scholar] [CrossRef]
  17. Yang, J.; Zhang, Y.; Chang, W.; Lou, Y.; Qian, H. Microbiologically influenced corrosion of FeCoNiCrMn high-entropy alloys by Pseudomonas aeruginosa biofilm. Front. Microbiol. 2022, 13, 1009310. [Google Scholar] [CrossRef] [PubMed]
  18. Gu, J.D. Microbial biofilms, fouling, corrosion, and biodeterioration of materials. In Handbook of Environmental Degradation of Materials; William Andrew Publishing: Oxford, UK, 2018; pp. 273–298. [Google Scholar]
  19. Al Hosni, A.S.; Pittman, J.K.; Robson, G.D. Microbial degradation of four biodegradable polymers in soil and compost demonstrating polycaprolactone as an ideal compostable plastic. Waste Manag. 2019, 97, 105–114. [Google Scholar] [CrossRef]
  20. Mohanan, N.; Montazer, Z.; Sharma, P.K.; Levin, D.B. Microbial and enzymatic degradation of synthetic plastics. Front. Microbiol. 2020, 11, 580709. [Google Scholar] [CrossRef]
  21. Amobonye, A.; Bhagwat, P.; Singh, S.; Pillai, S. Plastic biodegradation: Frontline microbes and their enzymes. Sci. Total Environ. 2021, 759, 143536. [Google Scholar] [CrossRef]
  22. Pathak, V.M. Review on the current status of polymer degradation: A microbial approach. Bioresour. Bioprocess. 2017, 4, 1–31. [Google Scholar] [CrossRef] [Green Version]
  23. Mohan, K. Microbial deterioration and degradation of polymeric materials. J. Biochemical. Technol. 2011, 2, 210–215. [Google Scholar]
  24. Gu, J.D. Microbial colonization of polymeric materials for space applications and mechanisms of biodeterioration: A review. Int. Biodeter. Biodegr. 2007, 59, 170–179. [Google Scholar] [CrossRef]
  25. Flemming, H.C. Relevance of biofilms for the biodeterioration of surfaces of polymeric materials. Polym. Degrad. Stabil. 1998, 59, 309–315. [Google Scholar] [CrossRef]
  26. Kopteva, Z.P.; Zanina, V.V.; Kozlova, I.A. Microbial corrosion of protective coatings. Surf. Eng. 2004, 20, 275–280. [Google Scholar] [CrossRef]
  27. Little, B.; Ray, R. A review of fungal influenced corrosion. Corros. Rev. 2001, 19, 401–418. [Google Scholar] [CrossRef]
  28. Ghasemi-Kahrizsangi, A.; Shariatpanahi, H.; Neshati, J.; Akbarinezhad, E. Degradation of modified carbon black/epoxy nanocomposite coatings under ultraviolet exposure. Appl. Surf. Sci. 2015, 353, 530–539. [Google Scholar] [CrossRef]
  29. Qian, H.; Zhang, D.; Deng, L.; Huang, L.; Xu, D.; Du, C.; Li, X. The role of surface morphology in the barrier properties of epoxy coatings in different corrosion environments. Prog. Org. Coat. 2017, 104, 199–209. [Google Scholar] [CrossRef]
  30. Wang, G.; Chai, K.; Wu, J.; Liu, F. Effect of Pseudomonas putida on the degradation of epoxy resin varnish coating in seawater. Int. Biodeter. Biodegr. 2016, 115, 156–163. [Google Scholar] [CrossRef]
  31. Deng, S.; Wu, J.; Li, Y.; Wang, G.; Chai, K.; Yu, A.; Liu, F. Effect of Bacillus flexus on the degradation of epoxy resin varnish coating in seawater. Int. J. Electrochem. Sci. 2019, 14, 315–328. [Google Scholar] [CrossRef]
  32. Tambe, S.P.; Jagtap, S.D.; Chaurasiya, A.K.; Joshi, K.K. Evaluation of microbial corrosion of epoxy coating by using sulphate reducing bacteria. Prog. Org. Coat. 2016, 94, 49–55. [Google Scholar] [CrossRef]
  33. Jia, R.; Yang, D.; Xu, J.; Xu, D.; Gu, T. Microbiologically influenced corrosion of C1018 carbon steel by nitrate reducing Pseudomonas aeruginosa biofilm under organic carbon starvation. Corros. Sci. 2017, 127, 1–9. [Google Scholar] [CrossRef]
  34. Huang, L.; Chang, W.; Zhang, D.; Huang, Y.; Li, Z.; Lou, Y.; Qian, H.; Jiang, C.; Li, X.; Mol, A. Acceleration of corrosion of 304 stainless steel by outward extracellular electron transfer of Pseudomonas aeruginosa biofilm. Corros. Sci. 2022, 199, 110159. [Google Scholar] [CrossRef]
  35. Qian, H.C.; Chang, W.W.; Liu, W.L.; Cui, T.Y.; Li, Z.; Guo, D.W.; Kwok, C.T.; Tam, L.M.; Zhang, D.W. Investigation of microbiologically influenced corrosion inhibition of 304 stainless steel by D-cysteine in the presence of Pseudomonas aeruginosa. Bioelectrochemistry 2022, 143, 107953. [Google Scholar] [CrossRef]
  36. Li, Z.; Huang, L.; Hao, W.; Yang, J.; Qian, H.; Zhang, D. Accelerating effect of pyocyanin on microbiologically influenced corrosion of 304 stainless steel by the Pseudomonas aeruginosa biofilm. Bioelectrochemistry 2022, 146, 108130. [Google Scholar] [CrossRef]
  37. Liu, D.; Yang, H.; Li, J.; Li, J.; Dong, Y.; Yang, C.; Jin, Y.; Yassir, L.; Li, Z.; Hernandez, D.; et al. Electron transfer mediator PCN secreted by aerobic marine Pseudomonas aeruginosa accelerates microbiologically influenced corrosion of TC4 titanium alloy. J. Mater. Sci. Technol. 2021, 79, 101–108. [Google Scholar] [CrossRef]
  38. San, N.O.; Nazır, H.; Dönmez, G. Microbially influenced corrosion and inhibition of nickel–zinc and nickel–copper coatings by Pseudomonas aeruginosa. Corros. Sci. 2014, 79, 177–183. [Google Scholar] [CrossRef]
  39. Huang, L.Y.; Huang, Y.; Lou, Y.; Qian, H.; Xu, D.; Ma, L.; Jiang, C.; Zhang, D. Pyocyanin-modifying genes phzM and phzS regulated the extracellular electron transfer in microbiologically-influenced corrosion of X80 carbon steel by Pseudomonas aeruginosa. Corros. Sci. 2020, 164, 108355. [Google Scholar] [CrossRef]
  40. Sias, S.R.; Ingraham, J.L. Isolation and analysis of mutants of Pseudomonas aeruginosa unable to assimilate nitrate. Arch. Microbiol. 1979, 122, 263–270. [Google Scholar] [CrossRef] [PubMed]
  41. Liu, X.; Xiong, J.; Lv, Y.; Zuo, Y. Study on corrosion electrochemical behavior of several different coating systems by EIS. Prog. Org. Coat. 2009, 64, 497–503. [Google Scholar] [CrossRef]
  42. Wang, L.; Deng, L.; Zhang, D.; Qian, H.; Du, C.; Li, X.; Mol, J.M.C.; Terryn, H.A. Shape memory composite (SMC) self-healing coatings for corrosion protection. Prog. Org. Coat. 2016, 97, 261–268. [Google Scholar] [CrossRef]
  43. Qian, H.; Ma, L.; Zhang, D.; Li, Z.; Huang, L.; Lou, Y.; Du, C. Microbiologically influenced corrosion of 304 stainless steel by halophilic archaea Natronorubrum tibetense. J. Mater. Sci. Technol. 2020, 46, 12–20. [Google Scholar] [CrossRef]
  44. Chang, W.; Li, Y.; Li, Z.; Lou, Y.; Cui, T.; Qian, H.; Mol, A.; Zhang, D. The effect of riboflavin on the microbiologically influenced corrosion of pure iron by Shewanella oneidensis MR-1. Bioelectrochemistry 2022, 147, 108173. [Google Scholar] [CrossRef]
  45. Lou, Y.; Dai, C.; Chang, W.; Qian, H.; Huang, L.; Du, C.; Zhang, D. Microbiologically influenced corrosion of FeCoCrNiMo0. 1 high-entropy alloys by marine Pseudomonas aeruginosa. Corros. Sci. 2020, 165, 108390. [Google Scholar] [CrossRef]
  46. Golru, S.S.; Attar, M.M.; Ramezanzadeh, B. Studying the influence of nano-Al2O3 particles on the corrosion performance and hydrolytic degradation resistance of an epoxy/polyamide coating on AA-1050. Prog. Org. Coat. 2014, 77, 1391–1399. [Google Scholar] [CrossRef]
  47. Feng, T.; Wu, J.; Chai, K.; Liu, F. Effect of Pseudomonas sp. on the degradation of aluminum/epoxy coating in seawater. J. Mol. Liq. 2018, 263, 248–254. [Google Scholar] [CrossRef]
  48. Ramezanzadeh, B.; Attar, M.M. Studying the corrosion resistance and hydrolytic degradation of an epoxy coating containing ZnO nanoparticles. Mater. Chem. Phys. 2011, 130, 1208–1219. [Google Scholar] [CrossRef]
  49. Doblies, A.; Boll, B.; Fiedler, B. Prediction of thermal exposure and mechanical behavior of epoxy resin using artificial neural networks and Fourier transform infrared spectroscopy. Polymers 2019, 11, 363. [Google Scholar] [CrossRef] [Green Version]
  50. Ghasemi-Kahrizsangi, A.; Neshati, J.; Shariatpanahi, H.; Akbarinezhad, E. Improving the UV degradation resistance of epoxy coatings using modified carbon black nanoparticles. Prog. Org. Coat. 2015, 85, 199–207. [Google Scholar] [CrossRef]
Coatings 13 00606 g001 550
Figure 1. Change of (a) OD600 value and (b) pH value with time in the P. aeruginosa−inoculated culture media with 100%, 10%, and 0% nutrients.
Figure 1. Change of (a) OD600 value and (b) pH value with time in the P. aeruginosa−inoculated culture media with 100%, 10%, and 0% nutrients.
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Figure 2. SEM morphologies of the coating surfaces after (a1) 3 days, (a2) 7 days, and (a3) 14 days of immersion in the 100% nutrient medium. SEM morphologies of the coating surfaces after (b1) 3 days, (b2) 7 days, and (b3) 14 days of immersion in the 10% nutrient medium. SEM morphologies of the coating surfaces after (c1) 3 days, (c2) 7 days, and (c3) 14 days of immersion in the 0% nutrient medium.
Figure 2. SEM morphologies of the coating surfaces after (a1) 3 days, (a2) 7 days, and (a3) 14 days of immersion in the 100% nutrient medium. SEM morphologies of the coating surfaces after (b1) 3 days, (b2) 7 days, and (b3) 14 days of immersion in the 10% nutrient medium. SEM morphologies of the coating surfaces after (c1) 3 days, (c2) 7 days, and (c3) 14 days of immersion in the 0% nutrient medium.
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Figure 3. SEM morphologies of the coating surfaces after removing the adherent cells from the inoculated media with (a) 100% nutrients, (b) 10% nutrients, and (c) 0% nutrients.
Figure 3. SEM morphologies of the coating surfaces after removing the adherent cells from the inoculated media with (a) 100% nutrients, (b) 10% nutrients, and (c) 0% nutrients.
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Figure 4. Nyquist and Bode plots of the samples from (a1,a2) the sterile medium; (b1,b2) the P. aeruginosa−inoculated medium with 100% nutrients; (c1,c2) the P. aeruginosa−inoculated medium with 10% nutrients, and the inset is the Nyquist plot in the high frequency region; (d1,d2) the P. aeruginosa−inoculated medium without nutrients after 3, 7, 10, and 14 days of immersion.
Figure 4. Nyquist and Bode plots of the samples from (a1,a2) the sterile medium; (b1,b2) the P. aeruginosa−inoculated medium with 100% nutrients; (c1,c2) the P. aeruginosa−inoculated medium with 10% nutrients, and the inset is the Nyquist plot in the high frequency region; (d1,d2) the P. aeruginosa−inoculated medium without nutrients after 3, 7, 10, and 14 days of immersion.
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Figure 5. Polarization curves of the samples after 14 days of immersion in the sterile culture medium and the P. aeruginosa−inoculated culture media with 100%, 10%, and 0% nutrients.
Figure 5. Polarization curves of the samples after 14 days of immersion in the sterile culture medium and the P. aeruginosa−inoculated culture media with 100%, 10%, and 0% nutrients.
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Figure 6. Water contact angle values of the coating surfaces after 3, 7, and 14 days of immersion in the sterile culture medium and inoculated culture media with 100%, 10%, and 0% nutrients. The insets are the morphologies of water droplets on coating surfaces after 14 days of immersion.
Figure 6. Water contact angle values of the coating surfaces after 3, 7, and 14 days of immersion in the sterile culture medium and inoculated culture media with 100%, 10%, and 0% nutrients. The insets are the morphologies of water droplets on coating surfaces after 14 days of immersion.
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Figure 7. FTIR spectra of the samples after 14 days of immersion in the sterile and inoculated culture media with 100%, 10%, and 0% nutrients.
Figure 7. FTIR spectra of the samples after 14 days of immersion in the sterile and inoculated culture media with 100%, 10%, and 0% nutrients.
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Table
Table 1. Electrochemical corrosion parameters determined from the EIS and polarization curves after 14 days of immersion.
Table 1. Electrochemical corrosion parameters determined from the EIS and polarization curves after 14 days of immersion.
MediumSterileP. aeruginosa
+ 100% Nutrients		P. aeruginosa
+ 10% Nutrients		P. aeruginosa
+ 0% Nutrients
|Z|0.01Hz (Ω·cm2)1.02 × 108 1.26 × 1077.08 × 1048.13 × 104
Ecorr (V)−0.85−0.82−0.78−0.75
Icorr (A·cm−2)1.23 × 10−93.98 × 10−96.84 × 10−73.11 × 10−7
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Zhang, S.; Zheng, H.; Chang, W.; Lou, Y.; Qian, H. Microbiological Deterioration of Epoxy Coating on Carbon Steel by Pseudomonas aeruginosa. Coatings 2023, 13, 606. https://doi.org/10.3390/coatings13030606

AMA Style

Zhang S, Zheng H, Chang W, Lou Y, Qian H. Microbiological Deterioration of Epoxy Coating on Carbon Steel by Pseudomonas aeruginosa. Coatings. 2023; 13(3):606. https://doi.org/10.3390/coatings13030606

Chicago/Turabian Style

Zhang, Shuyuan, Huaibei Zheng, Weiwei Chang, Yuntian Lou, and Hongchang Qian. 2023. "Microbiological Deterioration of Epoxy Coating on Carbon Steel by Pseudomonas aeruginosa" Coatings 13, no. 3: 606. https://doi.org/10.3390/coatings13030606

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