DURABLE HYDROPHOBIC COATINGS FOR METAL CORROSION PROTECTION & EASY CLEANING

Functional Surface Design Super- Hydrophobic Paints Self-Decon Surfaces DARPA Corrosion Resistance Air Force Super- Hydrophobic NASA Water Shedding Transparent Coatings Periscope Windows, NavSea Rain Repellent Canopies, NavAir Corrosion Resistance AF, Navy Hydrophilic Anti-fog Respiratory Masks, Army Antifouling ONR Textiles Chem/Bio Protection Army Parachutes Army Anti-Ice Coatings Bridge Windows, NavSea Wind Turbine, DOE

KEY ATTRIBUTES Hydrophobicity and watershedding Coating exhibits > 110° contact angle and <5° watershed angle. Corrosion protection Dense network provides a high physical barrier to electrolytes that cause corrosion; insulating for electronic barrier for galvanic corrosion Adhesion The coating has robust adhesion to glass, plastic (acrylic, polycarbonate), paint (polyurethane, latex, acrylic), and metallic (aluminum, steel, etc.) substrates. Flexibility, abrasion resistance The polymer coating exhibits excellent flexibility and abrasion/wear resistance via a tough crosslinked polymer matrix. Thickness and Weight The coating is very thin (4-6 µm) and lightweight Environmental Durability Coating shows excellent resistance to degradation from salt spray and UV exposure. Facile synthesis and ease of application The coating is readily prepared from commercially precursors. It is applied in a single coat using spray, flow or brush methods with minimal surface preparation.

COATING AIRCRAFT CANOPIES Goal: Produce durable transparent coatings with very low surface energy and excellent abrasion resistance Approach: -Tailored self assembled surface morphology -Surface active components impart low surface energy -Tough, flexible, transparent sol gel binder Advantages - Simple coating application - Excellent transparency, low haze - Excellent abrasion resistance and weatherability - Long lasting durable coatings with little to no maintenance - High hardness and toughness for high speed rain and hail erosion resistance

AIR FORCE LANDING GEAR Motivation: Landing gear is prone to corrosion when the surface is damaged by impact or wear Gentoo Solution: Apply coating over existing surface treatments/coatings to provide extended service

PROPERTIES: HYDROPHOBIC Control Gentoo Contact angleWatershedding (120 µl) Watershedding (50µl) Steel 63  >45  Aluminum 60  >45  Polyurethane (MIL PRF 85285) 95  15  30  Gentoo  3-5  7-11  Gentoo leaves little to no trail of water, whereas all uncoated substrates leave a significant trail

PROPERTIES: FLEXIBILITY Coating on Al Panel - bends around 1/8” mandrel without cracking or delamination Coating on MIL PRF Polyurethane treated Al Panel - bends around 1/8” mandrel Gentoo only ½” mandrel at 52 o C Gentoo only ½” mandrel at -51 o C

PROPERTIES: TRANSPARENCY/HAZE Control Gentoo TransparencyHaze Bare acrylic Gentoo coating on acrylic Bare glass Gentoo coating on glass Minimal change in transparency or haze on different substrates

F-16 CANOPIES Two F-16 canopies

STABILITY WITH UV EXPOSURE - QUV testing – 500 hour exposure Bare acrylic Gentoo coating on acrylic

APPEARANCE AFTER ABRASION (GLASS) Abraded with 150 cycles with 316 Steel wool compared with commercial superhydrophobic Bare Glass Gentoo As cast Abraded Commercial 1 As cast Abraded Commercial 2 As cast Abraded Gentoo is virtually unaltered by abrasion, whereas commercial coatings flake off and turn opaque

APPEARANCE AFTER ABRASION (STAINLESS STEEL) Abraded with 150 cycles with 316 Steel wool compared with commercial superhydrophobic

WATER SHEDDING

WATER REPELLENCY AFTER ABRASION Stainless steel coupons abraded with Scotch Brite compared with commercial Superhydrophobic Gentoo Ultra-Ever Dry

FLUID IMMERSION Gentoo coating on MIL PRF Wet tape adhesion – 5B rating 23 o C (186 h); 49 o C (96 h), 65 o C (168 h) Fluid Resistance/ Immersion - excellent – Lubricating oil 121 o C (24 h) – Hydraulic fluid 66 o C (24 h) – JP-8 Ambient (168 h) Fluid Corrosion Resistance Test o C (168 h) – Deicing/ Anti-Icing fluid: SAE AMS 1424 – Degrease Compound: MIL-PRF Gentoo Commercial superhydrophobic

FLUID IMMERSION 48 hour exposure to fluids Hydrophobicity is maintained for most solvents Solvent Mild soap Salt water IPA Naptha Heptane Jet fuel Deicing fluid Hydraulic fluid Lubricant Polyalphaolefin coolant Navy plastic polish Airplane wash cleaner fluid Alodine 1201 wash and rinse Uncoated Gentoo

ICE ADHESION TESTING: -15°C Gentoo coating significantly decreases ice adhesion, lowering time/cost of de-icing operations SurfaceIce Adhesion (KPa) MIL PRF on steel641 Gentoo coating on MIL PRF Gentoo coating on steel130

CORROSION – ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY The initial (dry) sample shows that Gentoo is not significantly better then the current polyurethane coating (likely because it is much thinner it does not impact electrical penetration). However, after it is wet (immersed or salt fog) the impedance (related to electrical resistance) is much higher, showing the rate of corrosion is expected to be better for Gentoo then for regular paints. PU Topcoat + Gentoo (dry) PU Topcoat + Gentoo (336 hrs) PU Topcoat (dry) PU Top coat (336 hrs)

CORROSION – ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY EIS – used to evaluate the barrier properties of the coatings Substrate - Aluminum alloy 2024-T4 treated with MIL PRF polyurethane (1 mil) Tested initially and after 336 hours immersion in salt fog PU Topcoat + Gentoo (dry) PU Topcoat + Gentoo (336 hrs) PU Topcoat (dry) PU Top coat (336 hrs)

CORROSION – ASTM G48-11 CREVICE CORROSION Stainless steel coupons with and without the hydrophobic polymer/inorganic hybrid coating. Two PTFE crevice washers against each face of a 1”x2”x0.050” stainless steel coupon Cut scribes into the coated surfaces corresponding to each crevice location on the washers to represent heavy damage from over torqued fasteners

CORROSION – ASTM G48-11 CREVICE CORROSION The samples were then immersed in an acidified ferric chloride solution and allowed to sit for five days at ambient temperature Bare uncoatedGentoo Coated coupons showed significantly lower mass loss after exposure for 5 days

CORROSION – GALVANIC FASTENER Salt fog for 1340 hours Applying Gentoo on top of traditional anti-corrosion surfaces further enhances the corrosion resistance of the material.

GENTOO – EXCELLENCE IN CORROSION PROTECTION & EASY CLEANING Hydrophobic – sheds water and fluids well Excellent adhesion, environmental stability Improved abrasion resistance Excellent barrier for improved corrosion resistance

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