Tape Peeling Test Research Articles

Inverse infusion processed hierarchical structure towards superhydrophobic coatings with ultrahigh mechanical robustness

Poor mechanical durability still hinders artificial superhydrophobic coatings from practical application, although these coatings were created years ago and still attract wide research interest. Previous epoxy/nanoparticle works seem to encounter a dilemma: a delicate nanostructure and low surface energy without a proper and strong microstructure to provide protection and strength naturally leads to weak mechanical adhesion and poor wear robustness. Herein, we develop an inverse infusion process (IIP) to construct hierarchical structures via newly synthesized hydrophobic and tough epoxy resin as well as rationally selected alumina nanoparticles (NPs). The IIP process forms an uncured epoxy layer first on the substrate and a preliminary nanocomposite coating next using an air spraying method, after which the epoxy layer inversely infuses into the micro/nanostructure and constructs a tougher microstructure on the top as well as a continuous nanocomposite layer throughout the coating after curing. This results in superhydrophobic coatings on a substrate with excellent adhesion and mechanical robustness, and our coatings can tolerate 600 cycles of tape peeling tests (with 3 M high-tack tape), 20 m sandpaper abrasion (with a pressure of ~5 kPa and 80 grit sandpaper), 115 cycles of Taber abrasion (with 250 g load), and 600 g of sand impact from a height of 110 cm, which are the highest values achieved by superhydrophobic coatings to the best of our knowledge. Furthermore, our coatings sustained highly corrosive media, such as sodium hydroxide and hydrochloric acid solutions. A combination of the established IIP process and the rationally selected ingredients dramatically enhanced the mechanical durability of the superhydrophobic coatings, and these attractive materials may attract attention for self-cleaning, anti-icing, and anti-fouling applications in industry.

Polydopamine and Its Composite Film as an Adhesion Layer for Cu Electroless Deposition on SiO2

We explore dopamine (DA) and its mixtures with polyethylene glycol (PEG) or polyethylenimine (PEI) as an adhesion layer for bonding between Cu and SiO2. The DA is oxidized to form polydopamine (PDA) which deposits as aggregates on SiO2 surface with notable surface roughness. After mixing with PEG or PEI, the morphology of PDA aggregates is altered considerably. Electroless Cu deposition in a mild alkaline bath is employed to deposit Cu atop the adhesion layer. The Cu films reveal an fcc lattice with (111) preferred orientation and their thickness was around 650 nm. From measurements of four-point probe, breaking strength, and tape-peeling tests, the PDA/PEG mixture reveals impressive performance serving as a strong adhesive for robust Cu bonding. We attribute the unique adhesive ability of PDA/PEG to the hydrogen bonds established between the catechol and amine groups of DA with PEG that renders desirable film formation on the SiO2 surface for optimized interaction between Cu and SiO2.

Coating “nano-armor” for robust superwetting micro/nanostructure

Recently, enhancing the stability of surface microstructure becomes a research focus due to its significant effect on various interfacial properties, such as the wettability. A new strategy that can improve the stability of existing microstructure without changing its morphology is desirable since it can keep original surface functions that are dependent on the microstructure, but it is still a challenge. Herein, we report such a strategy through dip coating and heat treatment of a layer of rigid aluminum dihydrogen phosphate (ADP) on the existing fragile copper micro/nanostructure. SEM results and the mechanical wear tests including sand abrasion and tape peeling test results demonstrate that the ADP coating can act as a layer of “nano-armor” to protect the inner microstructure without changing its morphology, as a result, the stability of both surface microstructure and corresponding underwater superoleophobicity are improved remarkably. Specifically, the hardness of microstructure is improved by a factor about 10. Theoretical simulations analysis reveals that the enhanced effect results from the nanocoating, which decreases the maximum transverse deformation and stress on the microstructure. Finally, the method was also applied on some other surfaces with particular functions including anisotropic wettings and oil/water separating properties, further confirming the universality for strengthening the microstructure-dependent surface functions. This work advances a strategy through strengthening existing surface microstructure to obtain stable superwetting performance, which starts fresh ideas for the design of robust functional interfacial materials.

Fabrication of a Novel Nanofluidic Device Featuring ZnO Nanochannels.

We developed a novel fabrication method for nanochannels that are easily scaled up to mass production by selectively growing zinc oxide (ZnO) nanostructures and covering using a flat PDMS surface to make hollow nanochannels. Nanochannels are used in the biotechnological and environmental fields, being employed for DNA analysis and water purification, due to their unique features of capillary-induced negative pressure and an electrical double-layer overlap. However, existing nanochannel fabrication methods are complicated, costly, and not amenable to mass production. Here, we developed a novel nanochannel fabrication method. The pillar-like dense ZnO nanostructures were grown in a solution process, which is easily applicable to mass production. The size of the fabricated ZnO nanostructures has a thickness of 30–300 nm and a diameter on the order of 102 nm, which are easily adjusted by synthesis times. The ZnO nanostructures were covered by the flat polydimethylsiloxane (PDMS) surface, and then the cracks between ZnO nanostructures served as hollow nanochannels. Because the suggested fabrication process has no thermal shrinkage, the process has higher production efficiency than existing nanochannel mass production methods based on the thermal/pressure process. The mechanical strength of the fabricated ZnO nanostructures was tested with repetitive tape peeling tests. Finally, we briefly verified the nanochannel performance by applying the nanochannel to the micro/nanofluidic system, whose performance is easily evaluated and visualized by current–voltage relation.

Amorphous TaxMnyOz Layer as a Diffusion Barrier for Advanced Copper Interconnects

An amorphous TaxMnyOz layer with 1.0 nm thickness was studied as an alternative Cu diffusion barrier for advanced interconnect. The thermal and electrical stabilities of the 1.0-nm-thick TaxMnyOz barrier were evaluated by transmission electron microscopy (TEM) and current density–electric field (J–E) and capacitance–voltage (C–V) measurements after annealing at 400 °C for 10 h. X-ray photoelectron spectroscopy revealed the chemical characteristics of the TaxMnyOz layer, and a tape peeling test showed that the TaxMnyOz barrier between the Cu and SiO2 layers provided better adhesion compared to the sample without the barrier. TEM observation and line profiling measurements in energy-dispersive X-ray spectroscopy after thermal annealing revealed that Cu diffusion was prevented by the TaxMnyOz barrier. Also, the J–E and C–V measurements of the fabricated metal-oxide-semiconductor sample showed that the TaxMnyOz barrier significantly improved the electrical stability of the Cu interconnect. Our results indicate that the 1.0-nm-thick TaxMnyOz barrier efficiently prevented Cu diffusion into the SiO2 layer and enhanced the thermal and electrical stability of the Cu interconnect. The improved performance of the TaxMnyOz barrier can be attributed to the microstructural stability achieved by forming ternary Ta-Mn-O film with controlled Ta/Mn atomic ratio. The chemical composition can affect the atomic configuration and density of the Ta-Mn-O film, which are closely related to the diffusion behavior. Therefore, the 1.0-nm-thick amorphous TaxMnyOz barrier is a promising Cu diffusion barrier for advanced interconnect technology.

Hydrophilic thin films formation on AZ31 alloys by hydrothermal treatment in silicate containing solution and the evaluation of corrosion protection in phosphate buffered saline

Magnesium alloys have been widely studied as biodegradable implants for orthopedic applications due to their more suitable mechanical and biological properties. However, Mg and its alloys themselves don’t have high hydrophilicity considered to be effective in improving the osteoconductivity of implanted materials. The drastic degradation rate of Mg alloys would also cause potential harm to the human body. With the aim to promote the hydrophilicity and corrosion resistance of Mg alloys, thin film consisting of magnesium hydroxide with silicate was synthesized by hydrothermal treatment in the alkaline solution of sodium hydroxide and sodium silicate at 423 K. The physical properties of thin films were estimated by SEM, XRD, XPS, tape peeling test and water droplet contact angle (WCA), and corrosion properties were evaluated by polarization curves and impedance measurements (EIS) in PBS solution. Mg(OH)2 was found to be the main composite of the film with little of MgO coexisted. Si was detected on the surface of the film layer, based on XPS results. The addition of silicate during hydrothermal treatment would greatly improve the hydrophilicity and its stability in the air environment. The Mg(OH)2 film containing Si also indicated higher corrosion resistance.

Fabrication of multifunctional closed-surface SiO2-TiO2 antireflective thin films

Multifunctional thin films with superhydrophilicity, broadband antireflective performance, humidity resistance and outstanding mechanical robustness are essential as for their wide applications. However, so far, it remains a big challenge to take into consideration all these properties simultaneously due to the structural contradiction. Herein, we develop an effective dip-coating process to prepare hybrid thin films with mechanical robustness, high transmittance, super-durable moisture resistance, excellent photocatalytic activity and durable superhydrophilicity. Three different nanoparticles were deposited sequentially to construct the above thin film and the maximum transmittance of this particular thin film reached ∼96.0%. The film surface showed an excellent superhydrophilicity (water contact angle ≈3.0°), and antifogging property. The superhydrophilic thin film could keep its property for more than 20 days. The transformation from hydrophilicity to superhydrophilicity of the thin film could be readily realized by UV irradiation. Moreover, its self-cleaning property could be retained after reduplicative storage and UV illumination cycles. Sponge washing test, water drop impact, pencil hardness test and tape peeling test revealed that the thin film possessed outstanding mechanical robustness. Methylene blue photodegradation was chose to weigh the photocatalytic activity of the hybrid thin film. In addition, the thin film shows excellent humidity-resistance at high temperature, and the excellent performance is due to its closed-surface structure. The closed-surface multifunctional thin films pave way toward use in solar cells, high-rise architecture windows under severe climate conditions.

Catalyst-Free and Rapid Chemical Approach for in Situ Growth of "Chemically Reactive" and Porous Polymeric Coating.

Design of "chemically reactive" coating with a tailored topography is a simple basis for optimizing various physical and chemical parameters, which is essential for achieving different biomimicked liquid wettability. In general, the essential topography and appropriate chemistry in the superhydrophobic coating is optimized following various top-down and bottom-up approaches, where various hydrophilic building blocks are associated using electrostatic interaction, hydrogen bonding, and other weak bonding (e.g., metal-thiol etc.), for both developing the desired hierarchical features and optimizing the appropriate chemistry on top of this featured interface. Such designs are inappropriate to sustain practically relentlessly harsh settings. So, further development for the synthesis of a durable and substrate-independent superhydrophobic coating is essential for various prospective applications in "real-world" scenarios. However, the design of highly abrasion-tolerant and "absolutely" substrate-independent artificial superhydrophobicity following a simple and scalable synthesis procedure is rare in literature. In this current work, a catalyst-free and facile chemical approach is adopted for an in situ and rapid deposition of a "chemically reactive" nanocomplex for decorating a wide range of substrates, including water-soluble, water-sensitive, highly flexible, rigid, and fibrous substrates with a highly tolerant biomimicked superhydrophobicity property. Branched poly(ethylenimine) (BPEI) and dipentaerythritol pentaacrylate (5Acl) mutually react through 1,4-conjugate addition reaction, and a hierarchically featured "chemically reactive" dip-coating is synthesized by the appropriate selection of the alcoholic solvent that is 1-heptanol. Furthermore, the choice of small alkylamines for post-covalent modifications of the "chemically reactive" dip-coating provided superhydrophobicity with a tailored water adhesion. A gradual increase in both roll-off angles, and the contact angle hysteresis (from 5° to 30°) was noted with a decrease in the hydrocarbon tail of selected alkylamines. The synthesized biomimicked interfaces are capable of performing under various practically relevant, severe physical and chemical challenges including bending, creasing, twisting, different physical abrasions (i.e., adhesive tape peeling test, abrasive sand paper test, etc.), high compressive strain, highly acidic and alkaline aqueous phases, artificial sea water, river water, etc. Moreover, this current approach was extended in developing various relevant functional materials, including superhydrophilic/superhydrophobic physical patterns on flexible papers and highly compressible super-oil-absorbent, etc.

Fabrication of durability superhydrophobic LDH coating on zinc sheet surface via NH4F-assisted in-situ growth and post-modification for enhancing anti-corrosion and anti-icing

In this work, a superhydrophobic layered double hydroxide (LDH) coating was fabricated on zinc sheet surface by in-situ growth and post-modification technology. The obtained zinc sheet exhibited excellent superhydrophobicity with a water contact angle (WCA) of 160° and a water sliding angle (WSA) of 5o. To determine the mechanical stability, chemical stability, storage stability of the superhydrophobic LDH coating on zinc surface, sandpaper abrasion test, tape-peeling test, immersion test and long-term exposure to the outdoors were employed. The results of stability test suggested that the LDH coating on zinc surface possessed excellent superhydrophobic stability (WCA > 150°, WSA < 10°) during all kinds of harsh conditions except pH = 1, indicating the superior adaptability to outdoor environment. More importantly, the superhydrophobic LDH coating on zinc surface exhibited excellent anti-corrosion efficiency (η = 99.99%) and delay icing ability (t = 75 min), which was beneficial to the application of zinc in a variety of practical fields.

Robust, self-cleaning, anti-fouling, superamphiphobic soy protein isolate composite films using spray-coating technique with fluorinated HNTs/SiO2

The practical applications of protein-based materials have so far been limited due to their natural hydrophilicity and high sensitivity to moisture. In this study, we developed a facile surface coating technique to prepare superamphiphobic soy protein isolate (SSPI) films materials. First, fluorinated superamphiphobic HNTs/SiO2 particles (HS-SH-F) were prepared through simple and efficient thiol-ene click reaction. Then, HS-SH-F particles were sprayed onto SPI films while Polydimethylsiloxane (PDMS) as a medium adhesive layer. The as-prepared SSPI films exhibited excellent repellent liquid (both water and oil) ability. To the best of our knowledge, this is the first time for exploring and achieving superamphiphobic property on protein-based films materials. The as-prepared superamphiphobic protein films can repel various liquids even with low surface tension (the n-heptane contact angle is 154.2°, and the slide angle is 9.5°). Moreover, the SSPI films retained great superamphiphobic performance after various harsh conditions tests, such as 20 times tape-peeling test, blade-scratch, strong acid/basic and organic solvents immersion, etc., indicating excellent mechanical robust and chemical durability. Such surface coating deservedly exhibits outstanding self-cleaning property and antifouling function. Therefore, it can be applied in various harsh environments, such as outdoor service and underwater materials. More importantly, this is a scalable approach for a wider range of materials other than protein-based materials.

A Facile Approach to Fabricate the Durable and Buoyant Superhydrophobic Fabric for Efficient Oil/Water Separation

In recent years, the superhydrophobic fabrics with specific wetting property had attracted extensive attention of the researcher and industry for their extraordinary performance. In this report, a robust superhydrophobic fabric with oil/water separation property and load carrying capacity had been successfully prepared by introducing the modified magnesium oxide (MgO) and aluminate. It has proved that the modified fabric has excellent stability through tape peeling test, folding test, washing experiment and pH test. In particular, the fabric weight of 200 g could be moved by 22 m on 600 # sandpaper without losing superhydrophobic property. Besides, the fabric can separate oil and water from different oil-water mixtures with a separation efficiency of over 90%, using superhydrophilic-superoleophobic properties. Otherwise, it is 66.8 N/m2 that loadable pressure of the fabric in water. The superhydrophobic fabric has tremendously wide applications in the field of oil-containing wastewater and diving equipment.

Improved adhesion of polyurethane-based coatings to tin surface

Polyurethane (PU)—based conformal coatings which protect electronic components and boards from harsh environmental exposures were further developed to mitigate the tin (Sn) whisker growth in lead (Pb)—free electronics. As a means of achieving this goal, the adhesion mechanics of PU-based conformal coating on tin surfaces was investigated. We attempted to improve the interfacial adhesion between PU-based conformal coatings and tin (Sn) as it slows down the formation of tin whisker growth. A multi-layer sandwiched specimen made between two Si beams was employed to create an interface between PU coating and Sn for four-point bending testing (4PBT). The result shows that PU has strong adhesion to Sn while polyurethane acrylate (PUA) has much weaker adhesion to Sn. The PUA adhesion, however, increased by introducing a silane agent ((3-Aminopropyl)triethoxysilane) on the tin surface, which is covalently bonded to PUA. The adhesion improvement of a modified tin surface was also confirmed by a simple cross-cut tape peeling test. Post fracture analysis suggested that blocking the reaction between bare Sn surface and the acrylate component contribute to improved adhesion.

Large Area Graphene Deposition on Hydrophobic Surfaces, Flexible Textiles, Glass Fibers and 3D Structures

Graphene and its derivatives have many superior electrical, thermal, mechanical, chemical, and structural properties, and promise for many applications. One of the issues for scalable applications is the lack of a simple, reliable method that allows the deposit of a well-ordered monolayer using low-cost graphene flakes onto target substrates with different surface properties. Another issue is the adhesion of the deposited graphene thin film, which has not been well investigated yet. Following our former finding of a double self-assembly (DSA) process for efficient deposition of a monolayer of graphene flakes (MGFs), in this work we demonstrate that the DSA process can be applied even on very challenging samples including highly hydrophobic polytetrafluoroethylene (PTFE), flexible textiles, complex 3D objects, and thin glass fibers. Additionally, we tested adhesion of the graphene flakes on the flat glass substrate by scotch tape peel test of the MGFs. The results show that the graphene flakes adhere quite well on the flat glass substrate and most of the graphene flakes stay on the glass. These findings may trigger many large-scale applications of low-cost graphene feedstocks and other 2D materials.

Robust Fluorine-Free and Self-Healing Superhydrophobic Coatings by H3BO3 Incorporation with SiO2-Alkyl-Silane@PDMS on Cotton Fabric.

Limited robustness is a serious drawback for superhydrophobic coatings and degrades the performance of superhydrophobic surfaces in practical applications. Although fluororeagents have excellent durability for superhydrophobicity, their use has been restricted due to various health and environmental concerns. In this work, we describe a facile and efficient fabrication strategy for creating robust fluorine-free superhydrophobic composite coatings that are prepared by a simple dip-dry method, in which the H3BO3-incorporated SiO2-alkyl-silane coatings are deposited on woven cotton fabric surfaces followed by polydimethylsiloxane modification. The coated surface shows a large water contact angle of 157.95 ± 2° and a small sliding hysteresis angle (SHA) of 3.8 ± 0.6°, demonstrating excellent superhydrophobicity. The coated fabric surface also exhibited robustness and durability, withstanding a tape-peeling test (under 48.05 kPa) for around 80 repetitions and sandpaper rubbing (loaded 100 g) for 40 cycles. Furthermore, the coated fabric surface displayed self-healing and oil-water separation capacities. The developed superhydrophobic coatings in this study are robust, environmentally benign, and easy to fabricate, showing promising applications in textile industries.

Surface-functionalization of isotactic polypropylene via dip-coating with a methacrylate-based terpolymer containing perfluoroalkyl groups and poly(ethylene glycol)

Isotactic polypropylene (PP) is one of the most popular plastics. However, the remarkably low surface energy of PP prevents the surface functionalization of PP. We studied the surface functionalization of PP by dip-coating with a maleic anhydride-grafted chlorinated polypropylene (MPO)/methacrylate-based terpolymer mixture. A methacrylate-based terpolymer (PMFP) was synthesized, which contained perfluoroalkyl (Rf)-conjugated monomers and poly(ethylene glycol)-conjugated monomers. Tape-peeling tests revealed that MPO successfully immobilized PMFP on a PP surface, although PMFP was less adhesive to PP. X-ray photoelectron spectroscopy (XPS), contact angle, and protein adsorption measurements revealed that the Rf groups and PEG chains in PMFP were segregated to the outermost surface of the dip-coated layer. The surface segregation of these moieties produced a low-fouling surface on the PP substrate. In addition, we synthesized a terpolymer that contained Rf groups and PEG chains with carboxy groups at their termini (PMFB) and used it to dip-coat a PP substrate. The surface segregation of side chains in PMFB induced the presentation of carboxy groups at the outermost surface, which were used as reactive sites for enzyme immobilization. We studied the surface functionalization of PP by dip-coating with a maleic anhydride-grafted chlorinated polypropylene (MPO) /methacrylate-based terpolymer mixture. A methacrylate-based terpolymer (PMFP) was synthesized, which contained perfluoroalkyl (Rf)-conjugated monomers and poly(ethylene glycol)-conjugated monomers. We found that the presence of MPO aided the adhesion of the terpolymer to the PP surface and that the coated PP surface exhibited low protein-fouling properties. In addition, the dip-coating of a terpolymer containing reactive groups (–COOH) with MPO caused the reactive groups to be presented at an outermost surface.

Effect of H2 SO4 Solution Treatment on Adhesion, Charge Transfer, and Catalytic Performance of Screen-Printed PEDOT:PSS.

Post-treatment was performed for poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films screen-printed on fluorine-doped tin oxide (FTO) substrates, to improve their charge transfer efficiency. Different H2 SO4 solutions, including concentrated H2 SO4 and H2 SO4 diluted with H2 O or dimethyl sulfoxide (DMSO), were adopted during the post-treatment. The adhesion of the as-treated films was evaluated by adhesive tape peeling tests, the surface morphology and vertical charge transfer from the films to the substrates were investigated by current-sensing atomic force microscopy, and the catalytic activities toward I3- reduction of PEDOT:PSS films were characterized by electrochemical measurements. It is discovered that selecting proper H2 SO4 solutions is crucial to improve the charge transfer efficiency and catalytic performance while maintaining reliable adhesion of the film on the substrates, with H2 SO4 /DMSO performing best as the solution for post-treatment. A mechanistic explanationis proposed based on different interactions among solution, PEDOT:PSS, and the substrate for various post-treatment solutions.

Separation of oil-water via porous PMMA/SiO2 nanoparticles superhydrophobic surface

A porous superhydrophobic coating on filter paper is developed by employing solution-casting technique using polymethyl methacrylate-co-ethyl acrylate polymer (PMMA) and silica nanoparticles (SiO2). The wettability, surface topography and chemical composition of coating were examined. The coated filter paper shows a static water contact angle of 170° ± 2° and sliding angle of 8° ± 1°. Additionally, thermal stability by annealing at different temperature ranging 40–280 °C, UV stability, chemical stability by immersing in different solutions of pH range of 2–13, and mechanical durability by performing adhesive tape peeling, sand abrasion, and washing tests of coatings were evaluated. Petroleum ether – water mixture and emulsion were successfully separated via a simple filtering method by using coated filter paper with high separation efficiency. Furthermore, coating also exhibits the excellent self-cleaning property. This coating can apply for any size and shape of the filter papers and has tremendous industrial applications.

Modified cellulose membrane with good durability for effective oil-in-water emulsion treatment

Industrial spilled oil and oily wastewater have caused serious environmental pollution and energy dissipation. Hence, a robust cellulose-based filter paper-polyvinyl alcohol (cellulose-PVA) membrane for efficient oil-in-water emulsion separation was fabricated by a universal method of hydroxyl oxidation for any substrate containing hydroxyl groups that was cost-effective and easy to scale up. The resulting membrane exhibited superhydrophilicity, superoleophilicity in air, and stable superoleophobicity under various pH value solutions with contact angles exceeding 150°. The cellulose-PVA membrane can dispose of many types of surfactant-stabilized and different oil droplet sized oil-in-water emulsions with 98.75 % efficiency driven only by gravity without consideration the secondary processing problem. Furthermore, sand paper abrasion tests, tape peeling tests and chemical corrosion resistance tests were executed, indicating the excellent mechanical stability and superior durability of the cellulose-PVA membrane. These results suggest that it is a prospective and competitive candidate for industrial oil-in-water emulsion treatment.

Facile one-step fabrication of highly hydrophobic medium density fiberboard (MDF) surfaces via spray coating

We proposed a simple and useful one-step spray coating method to protect MDF panels against physical and mechanical damages commonly presented in indoor real-life conditions. Highly hydrophobic surfaces were designed by TMCS (trimethylchlorosilane)-SiO2 nanoparticles deposition on MDF panels as a function of concentration of solution (0.1 and 0.3%) and number of cycles (10, 20 and 30 times). The formation of TMCS-SiO2 coating on MDF surface was investigated by scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), X-ray photoelectron spectroscopy (XPS), attenuated total reflectance with Fourier transform infrared spectroscopy (ATR-FTIR) and time-dependent apparent contact angle (WCA). Water drop impacting, dust impacting, and tape-peeling tests were conducted to simulate real-condition damages on MDF surfaces and to investigate the durability of highly hydrophobic coating. The coated MDF panels showed apparent water contact angle exceeding 140° with an interesting time-dependent stability and ability to roll-off, especially because the hydrophobicity of TMCS and hierarchical structure self-organized by spherical SiO2 nanoparticles. This rougher surface and presence of alkyl groups provide physical and mechanical durability of MDF panels even after water drop and dust impact tests, and tape-peeling up to five cycles. Therefore, this facile one-step MDF coating can be an effective, stable and mechanically durable alternative to protect MDF in undesirable real-life conditions.

Evalution of Corrosion Performance of Coated Steels Using Surface Potential Measurement

Coated steels have been widely used for structures and industrial products, but the coating film deteriorates due to environmental factors such as suneshine and rain, and eventually under-film corrosion occurs. Conventional methods such as tape peeling test for evaluating corrosion deterioration of coated steels are destructive and also the quantitativeness is not high. On the other hand, non-contact type surface potential measurement was proposed for degradation evaluation of coated steels. The masurement method gave the information on the position and size of the deteriorated region. However, the method is applied just for the coated steel with the coating film of under 20 цm, and it is unknown whether it is applicapable for the coated steel with thick coating film which is practically used. The principle of surface potential measurement used in this study is almost the same as that of the Kelvin method. The contact potential difference between the measurement probe and the sample corresponding to the work function occurs by electrical connection of the both. An AC signal proportional to the charge amount is obtained by opening / closing the shutter attached between the sample and the detection electrode, and the surface potential of the sample is measured using that signal.Carbon steels of 4 cm × 4 cm was used as a steel substrate, and coated steels with a variety of coating thicknesses were prepared by spraying transparent acrylic lacquer. Corrosion test was conducted by alternating of wet and drying using 100 μL droplet of NaCl solution. After washing away of NaCl precipitated on the surface, the surface potential distribution was measured and the surface was observed by a digital microscope. The potential of 100 µm coated steel went down to 0.1 from 0.2 V after 38 cycles. The potential became further lower with an increase of the number of cycles, and the potential change region also expanded. This means that the deteriorated position and size of the coated steels can be detected by measurement of surface potential distribution. The surface potential measurement is a powerful tool as a deterioration evaluation method of coated steels.