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WELCOME TO NANOCOATINGS WORLD

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Coating

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Pigment Pigment are used decoratively as colorant or functional as anticorrosion or magnetic pigment.Binder The binder bonds the pigment particles to each other and to the substrate.Additives - Substances added in small proportion to coating composition to modify or improved properties Fillers - Mostly used to extend the volume (low price), to confer or to improve technical properties.Solvent Liquid consists of several components and dissolved binders without chemical reaction.

Component of Coating

For corrosion-protective coatings, pigments function by providing inhibition or passivation of a metal surface, preventing corrosionThe binder, sometimes called a resin, and a suitable solvent(to make it liquid) are combined to form the vehicle.Pigment particles then are dispersed and mixed into theliquid resin, and the paint is packaged.Most fillers are inorganic substances.

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Nanocoating are coating that produced by usage of some components at nanoscale to obtain desired properties.Nanocoatings can be categorized as nanocrystalline, multilayer coatings with individual layer thickness of nanometers, and nanocomposites.Nanostructured coatings offer greatpotential for various applications due to their superiorcharacteristics that are not typically found inconventional coatings.

Nanocoating

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CO2 is an inorganic because it does not have a H atom covalently bonded to a C atom (a property of an organic).*

FUNCTIONAL COATINGThe term functional coatings describes systems which represent other than the classical properties of a coating (decoration and protection). Functional coating come up with additional functionality. This functionality depend upon the actual application of a coated substrate.

Expectations of functional coatings Examples of functional coating

Ananti-graffiticoating is a coating that prevents graffiti paint from sticking to surfaces*

Functional coatings perform by means of physical, chemical, mechanical and thermal properties.

Chemically active functional coatings perform their activities either at:

Filmsubstrate interfaces (anticorrosive coatings), In the bulk of the film (fire-retardant or intumescent coatings)Airfilm interfaces (antibacterial, self-cleaning)

Bulk film propertiesFilm/ substrate interface propertiesAir/ Film interfaces properties

Thin film intumescent coatings are manufactured from organic materials and are inert at low temperatures. They swell (or intumesce) to provide a charred layer of low conductivity foam when exposed to high temperatures. This char layer reduces the rate of temperature rise in the steel and prolongs the steels load bearing capacity.*

Permeability is the diffusion and solubility of coating with various gases, liquids, and vapours. It is very important to determine the degree of protection that the coating will impart on the substrate. The ideal coating will have both a low solubility and low diffusion.*

The use of a sacrificial anode such as zinc to protect steel is a long standing and well-known industrial practice. The zinc layer on galvanized steel degrades when exposed to an adverse environment, and this protects the underneath surface. Using a similar approach, both inorganic and organic resin based, zinc-rich coatings have been developed to protect a variety of metal substrates.1) Sacrificial

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Polymeric coatings are applied to metallic substrates to provide a barrier against corrosive species. They are not purely impermeable. Moreover, defects or damages in the coating layer provide pathways by which the corrosive species may reach the metal surface, whereupon localized corrosion can occur.

Pigments having lamellar or plate-like shapes (e.g., micaceous iron oxide and aluminum flakes) are introduced to polymeric coatings; this not only increases the length of the diffusion paths for the corrosive species but also decreases the corrosion.

The orientation of the pigments in the coating must be parallel to the surface, and they should be highly compatible with the matrix resin to provide a good barrier effect.

Layered clay platelets such as montmorillonite may also be introduced into organic resin systems to increase the barrier effect towards oxygen and water molecules, thereby enhancing the anticorrosive performance of the coating.2) Barrier effect

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Primers containing metallic phosphate, silicate, titanate or molybdate compounds are available as compounds used as corrosion inhibitors to formulate anticorrosive primers for metallic substrate. These pigments form a protective oxide layer on the metallic substrates, and often also form anticorrosive complexes with the binder. 3) Inhibition

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High thermal-resistant coatings are required for a wide variety of metallic substrates, including nonstick cookware, barbecues and boilers.

Fluorine or silicon-based products are used for the products. Fluorinated coatings are not suitable for high-temperature applications as they degrade above ~300 C and produce toxic by products. Silicon-containing polymers offer better thermal resistance due to the high energy required to cleave silicon bonds compared to carbon bonds in analogous molecules.

Phosphorus containing compounds function by forming a protective layer as a glassy surface barrier.

Expandable graphites also used as fire retardant; these contain chemical compounds, including an acid, entrapped between the carbon layers. Upon exposure to higher temperatures, exfoliation of the graphite takes place and this provides an insulating layer to the substrate.

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Figure: SEM micrograph of intumescent char obtained on an organic coating.

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Consumer prefers to retain the aesthetic appearance of coated materials and for this reason clear coats used on automobiles must have good scratch and abrasion resistance.

Scratch resistance can be obtained by incorporating a greater number of cross links in the coatings binder but highly cross linked (hard) films have poor impact resistance due to less flexibility. A less-cross linked (softer) film will show better performance with regard to other properties such as antifingerprint and impact resistance but will have less scratch and abrasion resistance. Thus, correct combination of hardness and flexibility is required.

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Self Healing/Cleaning Coatings

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(a) Scanning electron micrograph of lotus leaf. (b) Schematic depicting the relationship between surface roughness and self-cleaning. (c) Mechanism of self-cleaning action.In 1997, Barthelott and coworkers showed that the self-cleaning property of lotus leaves was due to their specialized surface morphology and hydrophobicity.

This specialized morphology prevents dirt from forming an intimate contact with the surface, while the high hydrophobicity makes the leaf water-repellent. Consequently, as the water droplets roll onto the leaf surface, they carry along the contaminants.

The initial discovery by Barthelott, many groups have attempted to mimic this activity to develop self-cleaning or lotus-effect coatings.*

a) Cracks form in the matrix wherever damage occurs.(b) The crack ruptures the microcapsules, releasing the healing agent into the crack plane through capillary action.(c) The healing agentcontacts the catalyst, triggering polymerization that bondsthe crack faces closedCrackMicrocapsuleHealing agentPolymerized healing agent

Crack forms in material.Cracks fills bursts microcapsule, releasing healing agent.Contact with catalyst cause polymerization.

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Probably the most wide-spread application ascribed to nanotechnology in the construction industry. There are already a great number of buildings worldwide which have been treated with it.

Titanium dioxide is hydrophilic due to its high surface energy, hence water does not form drops on a surface coated with it, but a sealed water film instead.

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Photocatalyst TiO2 absorbs UV radiation from sunlight/fluorescent lampsProduce pairs of electrons and holes.Electron of the valence band of titanium dioxide becomes excited when illuminated by light. The excess energy of this excited electron promoted the electron to the conduction band of titanium dioxide therefore creating the negative-electron (e-) and positive-hole (h+) pair.The positive-hole of TiO2 breaks apart the water molecule to form hydrogen gas and hydroxyl radical. The negative-electron reacts with oxygen molecule to form super oxide anion. (Both known as photo-produced radicals)These photo-produced radicals are powerfuloxidizing species and can cause the deterioration of organiccontaminants or microbials pieces on the particle surface.MECHANISM of Self-cleaning photocatalytic nanotitanium dioxide (TiO2)

When photo catalytic TiO2 particles are illuminated with an UV light source (e.g., sunlight), electrons are seen to be promoted from the valence band (VB) to the conduction band (CB) of the particle. This creates a region of positive charge (h+), holes, in the VB and a free electron in the CB. These charge carriers can either recombine or migrate to the surface, while the holes can react with the hydroxyl or adsorbed water molecules on the surface andproduce different radicals such as hydroxyl radicals (OH)and hydroperoxy radicals (HO2). By contrast, the electrons combine with the oxygen and produce super oxide radicals. These photo-produced radicals are powerfuloxidizing species and can cause the deterioration of organic contaminants or microbials pieces on the particle surface.The other beneficial effect of TiO2 is its super hydrophilicbehavior, commonly known as the water sheathing effect. This allows contaminants to be easily washed away with water or rainfall if the coatings are applied to external surfaces.*

Titanium dioxide to reduce pollution and clean the air

Happy Watching photocatalytic nanotitanium dioxide (TiO2) video!!! *

Microorganisms represent potential threats for our modern hygienic lifestyle.VirusesFungiBacteriaProblems of aesthetics (discoloration of the coating), Risks to health and hygiene,Biofilm development or microbial corrosion in the case of metallic substrates.

The classical biocides function is to either by inhibit the growth of bacteria (biostatic) or by kill them (biocidal). New legislations and the possibility of bacterial mutation have forced coating manufacturers to seek new alternatives. Today, more emphasis is placed on the development of bio-repulsive (without killing) antibacterial coatings. A wide variety of organic or inorganic biocides are available commercially and these demonstrate a wide variety of biocidal and biostatic mechanisms.

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Schematic of biofilm formation by microorganisms.Nitric oxide (NO)-releasing solgels as potential antibacterial coatings for orthopedic devices. Bacterial infection due to an implanted medical device is a potentially serious complication, typically leading to premature implant removal.

These coatings are intended for application onto biomedical devices to prevent device-related infections caused by bacterial biofilms.

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Antifouling CoatingsProblem:The microorganisms cause inconsistencies in the coating surface and create friction with the water. This friction decreases the speed of the vessel and adds weight to the hull. Both of these factors increase fuel consumption and inflate the cost of maintaining the vessel. The ideal antifouling coating would prevent marine growth as well as maintain a long performance life while keeping within strict environmental regulations.

Fouling is generally more prominent in coastal waters where ships or boats are either docked or travel at slow speed. Depending upon the types of marine organism involved, fouling is of two main types, namely micro fouling and macro fouling by marine animals (barnacles, tubeworms) and plants (algae).*

There are two main types of underwater antifouling coatings. Chemical release coatings use biocides, or chemical toxins that are released into the seawater and prevent marine organisms from attaching to the surface. The toxins create a barrier that prevents the marine growth. In the past these coatings were typically copper oxide. Some of the chemicals that give these products their toxic properties include; cuprous oxide, mercury, copper, arsenic and tributyltin oxide (TBT). Any combination of these chemicals provides a harmful biocide to the aquatic environment.

Another type of underwater hull coating is an ablative, self-polishing coating system. Ablative systems prevent marine sea life from attaching sufficiently to the coating surface. The initial coating surface steadily dissolves in the seawater. As the top layer dissolves, a new smooth layer is left behind to repeat the process. The rate of replenishment is controlled and constant allowing a uniform transition through each layer of the coating. Schematic of critical biofouling stages

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Auckland University have discovered that the fouling of vessels by marine creatures is greatly increased by the underwater sounds generated by the vessels themselves.Fouling of hulls is a major problem for world shipping.Application of antifouling paint to a ship hull

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Conducting Polymer

A conductive polymer is an organic polymer semiconductor. They provide pathways for electronic conduction by doping. Common classes of organic conductive polymers include: Poly(acetylene)s, Poly(pyrrole)s, Poly (thiophene)s, Poly(aniline)s etc.

Biosensor- Biosensor is an analytical device which converts a biological response into readable signal. Bio sensor comprises of three components: bioreceptor, transducer and detector.

Polypyrrole nanocomposites with oxides, especially with Fe3O4 have prospects for usein corrosion protection of iron.Nanopolymer Coatings

Organic or inorganic particles can be mixed with or incorporated in the conducting polymers to modify their morphology, conductivity and different physical properties depending upon the application, such as corrosion protection.

Nanoparticulate dispersions of organic metal polyanilines invarious paints at low concentrations can cause tremendouseffects in corrosion protection*

Pregnancy test- Detects the hCG protein in urine.Glucose monitoring device (for diabetes patients)- Monitors the glucose level in the blood.

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Self-assembled nanophase (SNAP) Coating

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SNAP - potential replacement for chromate-based surface treatments on aircraft aluminum alloys.

This Self-assembled Nanophase Particle (SNAP) process can be used to form thin, dense protective organic surface treatment coatings on Al aerospace alloys. The ability to design coating components from the molecular level upward offers tremendous potential for creating multifunctional coatings.

The SNAP coating mostly be used as part of a complete aircraft coating system designed to protect the aircrafts aluminum alloy from corrosion. The coating steps include, in order of application, surface preparation, surface treatment (SNAP), primer and topcoat.

Conventional chromate conversion coatings (CCC) work well for iron and aluminum alloys in terms of their corrosion protection performance. However, the strong oxidation properties of chromates make them a potential lung carcinogen responsible for the DNA damage.

For primer coating applied solgel derived thin lms. Solgel lms have good adhesion to both metallic substrates and organic top coats.

However, they result voids throughout the solid gel after the drying procedure (Evaporation process). Besides, they cannot provide any active corrosion protection or stop the propagation of corrosion once corrosion is initiated (Highly crack-forming potential).BEFOREAFTER

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Conventional Coating System

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SNAP Coating System

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Nanoparticle/Fillers For CoatingA microscopic particle with at least one dimension less than 100nm.

What is nanoparticle??

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TiO2 nanoparticles dispersion in an epoxy resin matrixTiO2 nanoparticles dispersed when sliding against a smooth steel counterpartThe friction and wear behavior of nanocomposits sensitive to the dispersion states of the nanoparticlesThe wear resistance could be increased if the micro structural homogeneity was improved 1. TiO2 Nanoparticle Dispersed In An Epoxy Resin (Min Zhi Rong et al, 2001 )

Method for Coating

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The desired amount of resin and nanoclay was mixed together and performed in an oil bath (50-70 degree)The mixture was subjected to sonication for 8-12hAddition of some additives to epoxy clay mixtureThe stoichiometric amount of the hardener was added to mixture3 samples containing different amount of clay (1.3 and 5%) were preparedThe clay loading increases the barrier and anti-corrosive properties increasesThe best anti-corrosive performance of coatings was obtained at 3 and 5 wt % clay concentrations2. Epoxy-clay nanocomposite coating TiO2 Nanoparticle Dispersed In An Epoxy Resin (M.R.Bagherzadeh et al, 2007)

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Nanoparticles/Fillers For CoatingsPrepared nanosilica containing coatings by UV curing of an epoxy system. They found that, surface properties were modified with an increase on hardness in the presence of filler.

Finally the strong decrease on water uptake in the presence of SiO2 was noticed. These nanocomposite materials can be a good choice for gas barrier coatings applications.

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3. Nano-CaCO3 Powder Coatings Using Epoxy Resin/NanoCaCO3 (H.J.Yu et al, 2006 )Nano-CaCO3 modified powder coatings was prepared using epoxy resin/NanoCaCO3 composite by in situ and inclusion polymerizationCompared with unmodified powder coatingsThe dispersion of nanoparticles in the films effects on the properties of resultant powder coatings was greatlyThis method can be a reference to make other kinds of nanoparticle modified powder coatings The tensile properties and neutral salt spray corrosion resistance of the modified coating was improvedMethod of in situ and inclusion polymerization is effective way to disperse nano-caco3 in the powder coatings

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Conclusion Protective coatings perform important functions based on types of coatings. The application of nanotechnology in the corrosion protection of metal has recently gained momentum as nanoscale materials have unique physical, chemical and physicochemical properties, which may improve the corrosion protection in comparison to bulk size materials. Significant work on nanoscale coatings is underway globally in the area of the area of nanocoating in the way of incorporating nanoparticles in coating formulation that enhance specific features.

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Q & A

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Answer Question 1: Conventional Coating Vs Nanocoating

Conventional coatingNanocoating

Micron scale structureNanostructured materials

High contact tension between water drop of and coating layerContact tension reduced (water repellence)

Moisture can penetrate housingMoisture penetration is minimized

Surface roughness is 5 m due to larger particle sizeSurface roughness reduce to 1 nm for better dirt repellence

Physical, chemical, mechanical and thermal propertiesImproved the properties of conventional coating

Properties of nanomaterials are different from conventional materials since the majority of atoms are in different environment.Nanomaterials represent increasing surface area and chemically active because the number of surface atom is very large.*

Nanostructured helps to maintain important surface and to accelerate drying.Nanoparticles helps increased hydrophobicity and alter the wetting properties.On a surface treating with nanoparticles water cannot adhere and at the molecular level is not in contact with the surface at all. This molecular force pushes water and anything in it away.*

Answer Question 2: Preparation of SNAP (Self-Assembled Nanophase Protection)

Particles (SNAP) process is a new method of forming functionalized silica nanoparticles in-situ from hydrolyzed tetramethoxysilane (TMOS) and glycidoxypropyltrimethoxysilane (GPTMS) in an aqueous solgel process, and then cross-linking the nanoparticles to form a thin, fully dense, protective film on Al aerospace alloys.The SNAP coating process consists of three stages: (1) solgel processing; (2) SNAP solution mixing; (3) SNAP coating application and cure. *

SNAP solutions were prepared by drop-wise addition of 42.8 glycidoxypropyltrimethoxysilane (GPTMS) and 8.9 ml tetramethoxysilane (TMOS) to 64.8 ml solution of 0.05 M acetic acid in doubly distilled deionized (DDI) water. The application solutions were prepared by diluting the aged SNAP solution with water and subsequent addition of a crosslinking agent (DETA) and surfactant.The final mixture was vigorously stirred and applied to the cleaned aluminum alloy panels by dip-coating.

SNAP Procedures

surfactant (3M FC-430, 0.04 wt./v % and FC-171, 0.01 wt./v %). The coatings were made within a time frame of 10-30 min, from the addition of the crosslinking agent. The coated panels were allowed to dry overnight under room conditions.*

2.0 Coating technique

2.1 Processing or coating for organic coatingSpray coating

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Dip coating

Stages of the dip coating process: dipping of the substrate into the coating solution, coating of substrate (wet layer ) by solvent evaporationPlastic dip coatingDippingWet layer formation Solvent evaporation

Applying a thermoplastic to the surface of metal items to provide long-term corrosion, impact and chemical resistance whilst offering an attractive decorative finish.*

Conductive nanocoating on textiles

atomic layer deposition(VCD)2.2 Processing for inorganic and hard coating

ALD utilizes sequential precursor gas pulses to deposit a film one layer at a time. The first precursor gas is introduced into the process chamber and produces a monolayer of gas on the substrate. A second precursor gas is then introduced into the chamber and reacts with the monolayer produced from the first gas. Since each pair of gas pulses (which is one cycle) produces exactly one monolayer of the desired film, the thickness of the final film is precisely controlled by the number of deposition cycles.*

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*For corrosion-protective coatings, pigments function by providing inhibition or passivation of a metal surface, preventing corrosionThe binder, sometimes called a resin, and a suitable solvent(to make it liquid) are combined to form the vehicle.Pigment particles then are dispersed and mixed into theliquid resin, and the paint is packaged.Most fillers are inorganic substances.

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*CO2 is an inorganic because it does not have a H atom covalently bonded to a C atom (a property of an organic).*Ananti-graffiticoating is a coating that prevents graffiti paint from sticking to surfaces*Thin film intumescent coatings are manufactured from organic materials and are inert at low temperatures. They swell (or intumesce) to provide a charred layer of low conductivity foam when exposed to high temperatures. This char layer reduces the rate of temperature rise in the steel and prolongs the steels load bearing capacity.*Permeability is the diffusion and solubility of coating with various gases, liquids, and vapours. It is very important to determine the degree of protection that the coating will impart on the substrate. The ideal coating will have both a low solubility and low diffusion.*

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*The initial discovery by Barthelott, many groups have attempted to mimic this activity to develop self-cleaning or lotus-effect coatings.*Crack forms in material.Cracks fills bursts microcapsule, releasing healing agent.Contact with catalyst cause polymerization.

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*When photo catalytic TiO2 particles are illuminated with an UV light source (e.g., sunlight), electrons are seen to be promoted from the valence band (VB) to the conduction band (CB) of the particle. This creates a region of positive charge (h+), holes, in the VB and a free electron in the CB. These charge carriers can either recombine or migrate to the surface, while the holes can react with the hydroxyl or adsorbed water molecules on the surface andproduce different radicals such as hydroxyl radicals (OH)and hydroperoxy radicals (HO2). By contrast, the electrons combine with the oxygen and produce super oxide radicals. These photo-produced radicals are powerfuloxidizing species and can cause the deterioration of organic contaminants or microbials pieces on the particle surface.The other beneficial effect of TiO2 is its super hydrophilicbehavior, commonly known as the water sheathing effect. This allows contaminants to be easily washed away with water or rainfall if the coatings are applied to external surfaces.*Happy Watching photocatalytic nanotitanium dioxide (TiO2) video!!! *

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*Fouling is generally more prominent in coastal waters where ships or boats are either docked or travel at slow speed. Depending upon the types of marine organism involved, fouling is of two main types, namely micro fouling and macro fouling by marine animals (barnacles, tubeworms) and plants (algae).*

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*Organic or inorganic particles can be mixed with or incorporated in the conducting polymers to modify their morphology, conductivity and different physical properties depending upon the application, such as corrosion protection.

Nanoparticulate dispersions of organic metal polyanilines invarious paints at low concentrations can cause tremendouseffects in corrosion protection*

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*Properties of nanomaterials are different from conventional materials since the majority of atoms are in different environment.Nanomaterials represent increasing surface area and chemically active because the number of surface atom is very large.*Nanostructured helps to maintain important surface and to accelerate drying.Nanoparticles helps increased hydrophobicity and alter the wetting properties.On a surface treating with nanoparticles water cannot adhere and at the molecular level is not in contact with the surface at all. This molecular force pushes water and anything in it away.*Particles (SNAP) process is a new method of forming functionalized silica nanoparticles in-situ from hydrolyzed tetramethoxysilane (TMOS) and glycidoxypropyltrimethoxysilane (GPTMS) in an aqueous solgel process, and then cross-linking the nanoparticles to form a thin, fully dense, protective film on Al aerospace alloys.The SNAP coating process consists of three stages: (1) solgel processing; (2) SNAP solution mixing; (3) SNAP coating application and cure. *surfactant (3M FC-430, 0.04 wt./v % and FC-171, 0.01 wt./v %). The coatings were made within a time frame of 10-30 min, from the addition of the crosslinking agent. The coated panels were allowed to dry overnight under room conditions.*

*Applying a thermoplastic to the surface of metal items to provide long-term corrosion, impact and chemical resistance whilst offering an attractive decorative finish.*ALD utilizes sequential precursor gas pulses to deposit a film one layer at a time. The first precursor gas is introduced into the process chamber and produces a monolayer of gas on the substrate. A second precursor gas is then introduced into the chamber and reacts with the monolayer produced from the first gas. Since each pair of gas pulses (which is one cycle) produces exactly one monolayer of the desired film, the thickness of the final film is precisely controlled by the number of deposition cycles.*

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