Marine Antifouling Applications Research Articles

NIR-Driven Self-Healing Phase-Change Solid Slippery Surface with Stability and Promising Antifouling and Anticorrosion Properties.

Slippery liquid-infused porous surfaces (SLIPSs) have great potential to replace traditional antifouling coatings due to their efficient, green, and broad-spectrum antifouling performance. However, the lubricant dissipation problem of SLIPS severely restricts its further development and application, and the robust SLIPS continues to be extremely challenging. Here, a composite phase-change lubricant layer consisting of paraffin, silicone oil, and MXene is designed to readily construct a stable and NIR-responsive self-healing phase-change solid slippery surface (PCSSS). Collective results showed that PCSSS could rapidly achieve phase-change transformation and complete self-healing under NIR irradiation and keep stable after high-speed water flushing, centrifugation, and ultrasonic treatment. The antifouling performance of PCSSS evaluated by protein, bacteria, and algae antiadhesion tests demonstrated the adhesion inhibition rate was as high as 99.99%. Moreover, the EIS and potentiodynamic polarization experiments indicated that PCSSS had stable and exceptional corrosion resistance (|Z|0.01Hz = 3.87 × 108 Ω·cm2) and could effectively inhibit microbiologically influenced corrosion. The 90 day actual marine test reveals that PCSSS has remarkable antifouling performance. Therefore, PCSSS presents a novel, facile, and effective strategy to construct a slippery surface with the prospect of facilitating its application in marine antifouling and corrosion protection.

Zwitterionic Hydrogel Coating with Antisediment Properties for Marine Antifouling Applications.

Biofouling is a serious issue affecting the marine industry because the attached micro- and macrocontaminants can increase fuel consumption and damage ship hulls. A hydrophilic hydrogel-based coating is considered a promising antifouling material because it is environmentally friendly and the dense hydration layer can protect the substrate from microbial attachment. However, sediment adsorption can be an issue for hydrogel-based coatings. Their natural soft and porous structures can trap sediment from the marine environment and weaken the antifouling capability. There is still little research on the antisediment properties of hydrogels, and none of them deal with this problem. Here, we report on optimizing zwitterionic hydrogel-based coatings to improve their antisediment properties and achieve comparable performance to commercial biocidal coatings, which are the gold standard in the antifouling coating area. After 1 week of sediment contamination and 2 weeks of diatom coculturing, this optimized zwitterionic hydrogel coating maintained its antifouling properties with a few diatoms on the surface. Its large-scale samples also achieved antifouling performance similar to that of biocidal coatings in the Atlantic Ocean for 1.5 months. More importantly, our research provides a universal strategy to improve the antisediment properties of soft hydrogel-based coatings. For the first time, we report that the introduction of interfacial electrostatic interactions enhanced the antisediment properties of hydrogels.

Molecular structure design of polybenzoxazines with low surface energy and low modulus for marine antifouling application

The antifouling mechanism of low surface energy marine antifouling coatings is fouling release, and the key to fouling release is the adhesion strength of fouling organisms on the coating surface. Herein, we report an antifouling strategy to improve the fouling release performance of antifouling coatings by control the surface free energy and elastic modulus. Natural biomass cardanol-based benzoxazine monomers with different structures were designed by molecular structure and successfully synthesized via Mannich condensation. Detailed information of the chemical structure for the benzoxazines are analyzed by nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectroscopies. In addition, the benzoxazines polymerization behavior is investigated by differential scanning calorimetry (DSC) analyses. The properties such as surface free energy and elastic modulus of polybenzoxazine were adjusted by the structure of the amine source. Notably, polybenzoxazines with octadecylamine as amine source have higher contact angle and lower surface free energy, and their elastic modulus is significantly lower than that of the octylamine benzoxazine. The elastic modulus of the octylamine benzoxazine was 732.5 MPa, while that of octadecylamine benzoxazine was only 24.0 MPa. Therefore, the polybenzoxazine coating has less fouling adhesion and exhibits better fouling release performance, and thus has better antifouling properties. This non-releasing polybenzoxazines without antifouling agent is a green, eco-friendly antifouling coating with low surface energy and low elastic modulus designed by molecular structure.

Slippery Porous-Liquid-Infused Porous Surface (SPIPS) with On-Demand Responsive Switching between "Defensive" and "Offensive" Antifouling Modes.

Slippery liquid-infused porous surfaces (SLIPS) have received widespread attention in the antifouling field. However, the reduction in antifouling performance caused by lubricant loss limits their application in marine antifouling. Herein, inspired by the skin of a poison dart frog which contains venom glands and mucus, a porous liquid (PL) based on ZIF-8 is prepared as a lubricant and injected into a silicone polyurethane (SPU) matrix to construct a new type of SLIPS for marine antifouling applications: the slippery porous-liquid-infused porous surface (SPIPS). The SPIPS consists of a responsive antifoulant-releasing switch between "defensive" and "offensive" antifouling modes to intelligently enhance the antifouling effect after lubricant loss. The SPIPS can adjust antifouling performance to meet the antifouling requirements under different light conditions. The wastage of antifoulants is reduced, thereby effectively maintaining the durability and service life of SLIPS materials. The SPIPS exhibits efficient lubricant self-replenishment, self-cleaning, anti-protein, anti-bacterial, anti-algal, and self-healing (97.48%) properties. Furthermore, it shows satisfactory 360-day antifouling performance in actual marine fields during boom seasons, demonstrating the longest antifouling lifespan in the field tests of reported SLIPS coatings. Hence, the SPIPS can effectively promote the development of SLIPS for neritic antifouling.

Nanomaterials and Nanotechnologies for Marine and Membrane Antifouling Applications

The major responsibility of the marine industry includes the global transportation of goods, materials, and people. To cater the longstanding challenges like degradation of materials and biofouling, it has embraced nanotechnology solutions. Nano-technology offered numerous products such as nano-ZnO, nano alumina, and nano silica, etc. to deal with corrosion in a cost-effective manner. Similarly, to address the biofouling in the aquatic environment, hybrid nanocomposites of organic-inorganic materials, photocatalytic nanomaterials, metal and metal oxide nanomaterials (nanoparticles, nanowires, nanorods), etc. are employed as viable agents to create non-toxic or low-toxic antifouling coatings. On the other hand, membrane separation technology plays a significant role in various industries including water treatment plants, food, medicine, pharmacy, biotechnology, etc. in addition to the domestic arena for the purification of drinking water. Such a wonderful technology is being totally disturbed by a troublesome problem and a predominant barrier called membrane fouling, which drastically limits the commercialization of the membranes and the whole membrane industrial technology as well. Hence, this review exclusively throws light on the role of nanomaterials and nanotechnologies developed for the prevention of fouling that occurs on submerged structures and membranes as well and to give possible solutions with increased resilience against challenges to come.

Design and synthesis of novel Pt/Fe3O4@SiO2@WO3 magnetic core/shell microspheres for solar light driven photocatalytic production of hypochlorous acid

Visible light catalysis technology is a potential environment-friendly marine antifouling technology. However, most photocatalytic antifouling agents are based on a free radical mechanism and are difficult to recycle. To address this problem, we reported the design and assembly of Pt/Fe3O4@SiO2@WO3 with a novel core@double shell structure. Pt/WO3 is the outermost shell layer used for photocatalytic reactions. Benefiting from the existence of the most central Fe3O4 core, the magnetic recovery can be easily achieved. As an intermediate layer, SiO2 can effectively block the electron transfer between WO3 and Fe3O4, avoiding loss of photocatalytic activity. Pt/Fe3O4@SiO2@WO3 can produce 6.31 μM HClO in a simulated seawater medium under visible light irradiation for 2 h and achieves efficient recovery under an applied magnetic field. This strategy shows us a new idea for the construction of photocatalytic antifouling materials and has an important guiding role for the marine antifouling application of photocatalytic technology.

Superhydrophobic and highly oleophobic coatings based on litchi-like FDA-SiO2-PS nanocomposite with excellent self-cleaning and anti-bioadhesion performances

The development of superhydrophobic and highly oleophobic nanocomposites that are highly adhesive to substrates is a major challenge in surface-related technologies. In this study, litchi-like polystyrene (PS) particles were prepared by soap-free emulsion polymerization with styrene (St) as monomer, KH-570 as crosslinking agent and KPS as initiator. Dual-sized litchi-like 1H,1H,2H,2H-perfluorodecyltriethoxy silane-SiO2-PS (PFDTES-SiO2-PS) particles was sol–gel synthesized using TEOS, PS, and PFDTES. Special superhydrophobic, highly oleophobic, and highly adhesive FDA-SiO2-PS (fluoride hdroxyl acrylate-resin-SiO2-PS copolymer) coatings were fabricated by embedding fluorosilane-modified litchi-like SiO2 particles in fluoride hdroxyl acrylate-resin (FHA resin) followed by curing through cross-linking using free radical polymerization. The structure, surface morphology, and properties of the coatings were examined by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle measurements, and chemical analysis. The measured Ra roughness value was 181 nm for FDA-SiO2-PS coating. The fluorine-containing groups have a strong tendency to direct themselves to the coating surface, resulting in a superhydrophobic and highly oleophobic coating (water and CH2I2 contact angles of 169.61° and 137.04°, respectively, and a water rolling angle of 4.35°) that is also highly adhesive to substrates (adhesion 5B). Exposing to air for 24 months, the coating possessed long air-stability with contact angles of 159.31° and 135.04° for water and CH2I2, independently. Furthermore, the FDA-SiO2-PS coating endows it with excellent antifouling and self-cleaning abilities, and resistance to E. coli and platelet adhesion; hence, FDA-SiO2-PS is a promising coating for use in biomedical and marine antifouling applications.

Construction of robust slippery lubricant-infused epoxy-nanocomposite coatings for marine antifouling application

From an environmental perspective, slippery liquid-infused porous surface (SLIPS) have great potential to substitute for traditional antifouling coatings due to their green and broad-spectrum antifouling properties. However, the complicated strategy curbs its forward application. In this study, the superhydrophobic surfaces (SHS) was constructed by an air spraying method via solution blending, with epoxy resin and hydroxyl-terminated polydimethylsiloxane as the matrix and nano titanium dioxide particles as the filler. Then, silicone oil with different viscosities were infused into the SHS to form SLIPS. Experiments of simulated fluid erosion in a marine environment showed that silicone oil with 500 mPa·s maintained a contact angle hysteresis (CAH) of 6.9° with good liquid-repellency performance after 12 h of scouring，while the silicone oil with lower viscosity loosed the liquid-repellency performance. Antifouling test results showed that SLIPS had excellent antifouling performance, and the antifouling rates of against Phaeodactylum tricornutum and Bacillus sp. were 90.8 % and 93.6 %, respectively. Thermodynamic analysis showed that the air layer of SHS coating and the liquid layer of SLIPS played a vital role in antifouling performance, which coincided with antifouling experimental results. The efficient and environment-friendly coating preparation method was used in this study will provide reference value and theoretical basis for the application of SLIPS in the field of marine antifouling.

Cu@C core-shell nanoparticles modified polydimethylsiloxane -based coatings with improved static antifouling performance

PDMS-based fouling release coatings have promising applications in the fields of marine fouling control. However, development of silicone-based coatings with good antifouling / fouling-release property under relative static conditions remains challenging. In this work, a new PDMS-based nanocomposite coating consisting of PDMS matrix and nanofiller of copper@carbon core-shell nanoparticles was developed. Uniformly dispersed Cu@C core-shell in the PDMS matrix enhance the antifouling ability. The PDMS with low surface energy endows the composite coatings with hydrophobicity thus fouling release property. The introduction of Cu@C core-shell/PDMS improves both the Young's modulus, tensile strength and the elongation at break. Furthermore, laboratory bioassay against diatom adhesion and field tests indicated that the PDMS-based nanocomposite coatings with Cu@C core-shell exhibited outstanding antifouling / fouling-release property even under static conditions, showing promising application in marine antifouling.

Hydrophilic tyrosine-based phenolic resin with micro-ripples morphology for marine antifouling application

Since biofouling challenges negatively influence the marine and transportation industries, developing effective antifouling materials have attracted extensive concern. A tyrosine-based antifouling phenolic resin (TPP resin) was synthesized using tyrosine as a natural phenol source. TPP exhibited shell-like surface morphology with micro-ripples and excellent anti-adhesion properties against bacteria and diatom. The micro-ripples surface might be caused by the strong hydrogen bonding or ionic interaction among tyrosine units resulting in microphase separation during the curing process. Tyrosine content in TPP resin has a great influence on the surface properties, morphology and antifouling characteristics. The higher the tyrosine content, the higher is the surface hydrophilicity, the denser and more regular is the micro-ripples morphology, and the stronger is the antifouling performance. TPP-60 % exhibited the best antifouling performance. Combination of the surface hydrophilicity and regular micro-ripples surface morphology afford TPP excellent antifouling performance. TPP resins offer a broad prospect for developing phenolic resin in the antifouling field.

Fluorinated-Triazole-Modified ZnO and Its Application in Marine Antifouling

The accumulation of marine biological growth has irreversible negative effects on shipping and coastal fisheries. In this paper, a new antibacterial nanofiller—triazole fluoroaromatic hydrocarbon−modified nano−zinc oxide (ZnO−APTES−TRF)—was prepared by a Cu(I)−catalyzed azide–alkyne click chemical reaction. The modification of nano−ZnO with triazole ring fluoroaromatic hydrocarbons were testified by FT−IR, XPS, and EDS. The grafting rate of ZnO−APTES−TRF can reach 32.38%, which was verified by the TGA test. The ZnO−APTES−TRF was mixed with zinc acrylate resin to produce a low surface energy antifouling coating with a surface water contact angle of 106°. The bactericidal rate of ZnO−APTES−TRF against Escherichia coli, Staphylococcus aureus, and Pseudoalteromonas sp. can reach more than 98% due to the synergistic effect of triazole and fluorine. The 120−day marine experiment shows that the low surface energy antifouling coating of ZnO−APTES−TRF/ZA is expected to be widely used in the field of marine antifouling.

Hydrogel Antifouling Coating with Highly Adhesive Ability via Lipophilic Monomer

AbstractThe poor adhesion of hydrogel antifouling materials on substrates limits their application in marine antifouling. From the perspective of practical application, a lipophilic monomer tackifying strategy is proposed, in which hydrogel coatings can be firmly adhered to substrates very simply. Hydrogel prepolymers containing lipophilic monomers are adhered to the substrate surface after crosslinking, and hydrogel coatings are obtained after drying and absorbing water. The experimental results show that the molar content of lipophilic monomers in the hydrogel reached 42% and can significantly improve its adhesion on the organic substrate. The highly adhesive ability of the hydrogel manifest as its long‐term no‐shedding ability in the experimental results of static seawater immersion panels, dynamic rotating seawater environments (80 revolutions min−1), and testing‐panels in real marine (150 days‐no‐shedding). A powerful supplement for understanding the direct adhesion of hydrogel coatings to the substrate is provided by this strategy. These hydrogels have a good effect on inhibiting the adhesion of proteins and microalgae and show significant antifouling performance in testing‐panels in real marine environments, with great potential for marine antifouling applications.

A facile hydrophilic modification strategy initiated by flame treatment of silicone coatings for marine antifouling application

Non-toxic poly(dimethylsiloxane) (PDMS) elastomer antifouling coatings are used to protect marine equipment from biofouling; however, the coatings cannot resist all fouling organisms. Hydrophilic modification is an effective way to enhance antifouling performances in PDMS but most modification methods are complex and inconvenient. In this work, flame treatment was used to replace other complex surface activation techniques, such as plasmas. The sulfobetaine silane and polyvinyl alcohol (PVA) modifications were developed for flame treatment. The sulfobetaine silane-modified flame-treated PDMS reduced diatom adhesion by 99.0% compared to untreated PDMS. The PVA modification involves a two-step spray process and is simpler than sulfobetaine silane modification. This strategy coats PVA on flame-treated PDMS through the crosslinking effect of boric acid on PVA, which reduced diatom adhesion by 86.6% in the lab and gave better antifouling performances in field tests compare to bare PDMS.

Spray Coating of 2‐ and 3‐D Solid Substrates Using a Sulfated Polysaccharide for Marine Antifouling Applications

AbstractMarine antifouling coating using functional polymers has emerged as an important tool to combat marine fouling. Owing to their natural abundance, polysaccharides represent a more sustainable option than synthetic polymers and carrageenan, a sulfated polysaccharide, is identified as a promising candidate for further research based on its excellent marine antifouling properties. However, existing research has only explored the application of carrageenan‐based coatings for 2D objects, using techniques such as spin‐coating. Here, a spray‐coating method is proposed to apply carrageenan‐based coatings to the surfaces of 2‐ and 3‐D objects. The coated surfaces exhibit high stability under various chemical/physical stresses and high resistance to protein adsorption and marine diatom adhesion.

Urushiol-based benzoxazine copper polymer with low surface energy, strong substrate adhesion and antibacterial for marine antifouling application

Biofouling is a common problem, has serious impact on the biomedical applications and maritime activities by human beings, and developing eco-friendly antifouling coatings is the key to the prevention of biofouling. Traditional low surface energy antifouling coatings, such as silicones and fluororesins, have the inherent defects of weak substrate adhesion and poor static antifouling performance. Herein, a low surface energy marine antifouling coating, urushiol-based benzoxazine copper polymer (UBCP), was synthesized using natural product urushiol and n-octylamine, paraformaldehyde as the reactants, and then CuCl2 as the catalyst for further reaction. UBCP can be cured into films at room temperature, which have strong substrate adhesion, smooth and dense surface, and controllable release of effective copper ion at minimized concentrations. Moreover, UBCP exhibits excellent antifouling performance, with both fouling release and antifoulant release characteristics. The antibacterial performance of UBCP towards typical Gram-negative bacteria (E. coli) and Gram-positive bacteria (S. aureus) both reach almost 100%, while its ability to inhibit algal activity is above 99%, and the surface of UBCP can effectively prevent microbial adhesion. In summary, UBCP is a highly effective and eco-friendly coating material and provides a promising approach to address the economic and operational issues caused by marine biofouling.

Flavonoid Glycosides with a Triazole Moiety for Marine Antifouling Applications: Synthesis and Biological Activity Evaluation.

Over the last decades, antifouling coatings containing biocidal compounds as active ingredients were used to prevent biofouling, and eco-friendly alternatives are needed. Previous research from our group showed that polymethoxylated chalcones and glycosylated flavones obtained by synthesis displayed antifouling activity with low toxicity. In this work, ten new polymethoxylated flavones and chalcones were synthesized for the first time, including eight with a triazole moiety. Eight known flavones and chalcones were also synthesized and tested in order to construct a quantitative structure-activity relationship (QSAR) model for these compounds. Three different antifouling profiles were found: three compounds (1b, 11a and 11b) exhibited anti-settlement activity against a macrofouling species (Mytilus galloprovincialis), two compounds (6a and 6b) exhibited inhibitory activity against the biofilm-forming marine bacteria Roseobacter litoralis and one compound (7b) exhibited activity against both mussel larvae and microalgae Navicula sp. Hydrogen bonding acceptor ability of the molecule was the most significant descriptor contributing positively to the mussel larvae anti-settlement activity and, in fact, the triazolyl glycosylated chalcone 7b was the most potent compound against this species. The most promising compounds were not toxic to Artemia salina, highlighting the importance of pursuing the development of new synthetic antifouling agents as an ecofriendly and sustainable alternative for the marine industry.

Durable self-polishing antifouling Cu-Ti coating by a micron-scale Cu/Ti laminated microstructure design

Marine biofouling is a major issue deteriorating the service performance and lifespan of marine infrastructures. The development of a durable, long-term, and environment-friendly antifouling coating is therefore of significant importance but still a critical challenge in maritime engineering. Herein, we developed a Cu-Ti composite antifouling coating with micron-sized alternating laminated-structure of Cu/Ti by plasma spraying of mechanically mixed Cu/Ti powders. The coating was designed to enable controlled release of Cu ions through galvanic dissolution of Cu laminates from the Cu/Ti micro-galvanic cell in aqueous solution. Results showed that remarkable antifouling efficiency against bacterial survival and adhesion up to ∼100 % was achieved for the Cu-Ti coating. Cu/Ti micro-galvanic cell was in-situ formed within Cu-Ti coating and responsible for its Cu ions release. The successive dissolution of Cu laminates resulted in the formation of micro-channels under Ti laminates near surface, which contributed to controlled slow Cu ions release and self-polishing effect. Thus, environment-friendly antifouling capability and ∼200 % longer antifouling lifetime than that of the conventional organic antifouling coatings can be achieved for the Cu-Ti coating. On the other hand, as compared to the conventional organic antifouling coatings, the Cu-Ti composite coating presented much higher mechanical durability due to its strong adhesion strength, excellent mechanical properties, and two orders lower wear rate. The present laminated Cu-Ti coating exhibits combination of outstanding antifouling performance and high mechanical durability, which makes this coating very potentially candidates in marine antifouling application.

Catechol‐conjugated Dextran for Marine Antifouling Applications: The Adverse Effects of High Catechol Content

Marine antifouling property of dextran coating was investigated. Catechol‐conjugated dextrans (Dex‐C) with different grafting densities were synthesized and used for surface coating. The coating efficacy was analyzed by spectroscopic ellipsometry and water contact angle goniometry, and as a result, coating thickness was shown to increase with increasing catechol content in Dex‐C. Marine antifouling property of Dex‐C coating was then investigated via marine diatom adhesion assays. Unlike the coating thickness, marine antifouling performance of Dex‐C coating was found to be not proportional to the catechol content in Dex‐C. We expect that this study will provide an important factor to consider in designing catechol‐conjugated antifouling materials.

Multifunctional ZnWO4 nanoparticles for photocatalytic removal of pollutants and disinfection of bacteria

Herein, ZnWO4 nanoparticles (NPS) with controllable size were synthesized by a facile solvothermal method via changing EG concentration in the solvent. The physicochemical properties of ZnWO4 NPS were characterized by XRD, TEM, EDS, BET, XPS, UV–vis DRS, PL and photocurrent. The results shown that the EG concentration has a great influence on the morphology, size and crystallinity of ZnWO4 NPS. On the one hand, the photocatalytic activity of ZnWO4-EG62.5 was obviously better than that of ZnWO4-EG0 in the removal of hazardous pollutants including Cr6+, MB, RhB and MO by 71.4, 33.3, 13.5 and 21.3 %, respectively. Moreover, ZnWO4-EG62.5 displayed excellent photocatalytic stability for Cr6+ reduction. The ZnWO4-EG75, on the other hand, exhibited the best antibacterial activity to Bacillus subtilis and Vibrio alginolyticus, and the maximal inhibition zone area of Bacillus subtilis and Vibrio alginolyticus over ZnWO4-EG75 was 3.4 and 6.8 times than that of ZnWO4-EG0, respectively. Our work indicated that ZnWO4 NPS presented potential future application in water treatment and marine antifouling, and it is a feasible approach to enhance the photocatalytic and antibacterial performance of semiconductor NPs by controlling its size and crystallinity.

Electrodeposition of capsaicin-induced ZnO/Zn nanopillar films for marine antifouling and antimicrobial corrosion

Zinc oxide with the morphology of nanopillar is promising marine antifouling materials as they can kill adhered bacteria and fungi. The zinc oxide with the morphology of nanopillar has shown super-antibacterial properties on galvanized steel, which makes ZnO/Zn nanopillar films promising in marine antifouling and antimicrobial corrosion. Thus, an efficient approach to coat ZnO/Zn nanopillar films on steel is of great significance. The electrodeposition method is a universal method for both ZnO crystals and galvanized coatings, and it can control the morphologies and structures of the resultant films. Therefore, in this study, capsaicin was added into an alkaline electrolyte to induce the formation of ZnO nanopillars. Due to capsaicin addition to the electrolyte, ZnO/Zn nanopillar films were obtained in a single cathodic electrodeposition. The added capsaicin in the electrolyte was absorbed on the electrodepositing surface by the functional –NH– groups in amide bond. The Zn(OH)42− diffusion was promoted by negatively shifted electrodepositing potential. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) results illustrate that regular ZnO nanopillars were obtained when the capsaicin concentration was 0.6 g L−1 in the electrolyte. The resultant ZnO/Zn nanopillar films showed high antibacterial properties in Escherichia coli suspended solutions and relatively low living bacterial coverage, indicating promising application in marine antifouling. Electrochemical evaluation revealed that the obtained capsaicin-induced ZnO/Zn nanopillar films exhibited significantly enhanced corrosion resistance in a sulfate-reducing bacteria (SRB) medium. Moreover, the results illustrate that adding 0.6 g L−1 concentration of capsaicin in the electrolyte yielded the best films, which featured the lowest bacterial coverage and highest corrosion resistance.