Selleys Marine Flex - Waterproof Adhesive Sealant product guide

AI Summary

Product: Selleys MarineFlex Flexible Waterproof Adhesive Sealant Brand: Selleys Category: Marine Adhesive Sealant Primary Use: A single-component, silane-modified polymer sealant for waterproof bonding and sealing in marine environments, both above and below the waterline.

Quick Facts

Best For: Boat owners and marine professionals sealing hull-to-deck joints, through-hull fittings, portholes, deck hardware, hatches, and keel joints
Key Benefit: Stays flexible after curing to handle joint movement while maintaining a watertight seal through continuous saltwater immersion and UV exposure
Form Factor: 410 mL cartridge (black — product code 101084; white — product code 101086)
Application Method: Cut nozzle at 45 degrees, apply via cartridge gun, tool within 10–15 minutes; cures through atmospheric moisture — no mixing required

Common Questions This Guide Answers

Can MarineFlex be used below the waterline? → Yes, it is rated for continuous below-waterline immersion including through-hull fittings, keel-to-hull joints, and rudder post seals
What PPE is required when handling MarineFlex? → Nitrile rubber gloves, protective clothing, and eye/face protection; chemical goggles are recommended for overhead work given the GHS Eye Damage/Irritation Category 2A classification (H319)
What should I do if MarineFlex contacts my eyes? → Flush continuously with running water for at least 15 minutes and get to a doctor or hospital; Australian emergency contact: 1800 220 770; New Zealand: 0800 220 770

Product Overview

Selleys MarineFlex is a flexible waterproof adhesive sealant built specifically for marine environments. It bonds and seals reliably both above and below the waterline (SELLEYS_MARINEFLEX-AUS_GHS.pdf). Available in 410 mL cartridges in black and white, this single-component sealant handles the real demands of marine life — constant water exposure, relentless movement, and harsh environmental stress.

General-purpose sealants aren't built for this. MarineFlex stays flexible after curing, moving with boat hulls, deck fittings, and underwater fixtures as they expand, contract, and flex. Its silane-modified chemistry creates a durable bond in wet environments where ordinary adhesives fail — making it the right choice for hull-to-deck joints, through-hull fittings, porthole sealing, and everything in between.

Two variants cover your project needs: product code 101084 for black and product code 101086 for white. Same performance, whichever colour suits your application (SELLEYS_MARINEFLEX-AUS_GHS.pdf).

Chemistry & Composition

MarineFlex performs because of what goes into it. Its silane-modified polymer base contains specific chemical components that deliver marine-grade results. The formulation includes 1–10% (w/w) 3-(trimethoxysilyl)-1-propanamine (CAS 13822-56-5) — the primary silane coupling agent responsible for strong adhesion to wet and porous surfaces (SELLEYS_MARINEFLEX-AUS_GHS.pdf).

Two UV stabilisers protect the sealant from sun exposure: bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate (CAS 41556-26-7) and methyl (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate (CAS 82919-37-7), each present at less than 1% (w/w) (SELLEYS_MARINEFLEX-AUS_GHS.pdf). These hindered amine light stabilisers shield the polymer matrix from photodegradation, extending service life where UV exposure is relentless.

The rest of the formulation uses non-hazardous proprietary ingredients that deliver flexibility, adhesion, and moisture-cure performance (SELLEYS_MARINEFLEX-AUS_GHS.pdf). This single-component system cures through atmospheric moisture — no mixing, no catalyst. That matters when you're working in a tight marine space or making repairs at sea.

The silane chemistry bonds well to gelcoat, fibreglass, aluminium, stainless steel, and treated timber — the core materials of boat construction. As moisture enters the uncured sealant, silanol groups form and condense into a three-dimensional polymer network that bonds chemically to substrate surfaces while keeping its elastomeric properties. The result is a seal that holds.

Key Features & Marine-Specific Benefits

MarineFlex accommodates joint movement without losing adhesion or letting water through (SELLEYS_MARINEFLEX-AUS_GHS.pdf). Thermal cycling puts real stress on marine joints — aluminium fittings move differently than fibreglass decks, and wood transoms respond differently than acrylic hatches. A rigid sealant cracks under this stress. MarineFlex stretches and compresses while holding a watertight seal, year after year.

Below-waterline performance is where MarineFlex separates itself from standard construction sealants. Continuous saltwater immersion attacks sealants at every level — osmotic pressure forces water into polymer matrices, salt crystals expand within microscopic voids, and biological fouling targets any vulnerable surface. MarineFlex's silane-modified polymer resists water penetration at the molecular level, preventing the swelling and softening that undermine ordinary products.

UV stability, provided by the hindered amine stabilisers at less than 1% each, prevents the chalking, cracking, and discoloration that hit marine sealants under intense sunlight reflected off water (SELLEYS_MARINEFLEX-AUS_GHS.pdf). Above-waterline applications on deck hardware, hatches, and portlights need this protection — cosmetic deterioration often signals that functional breakdown isn't far behind.

The single-component moisture-cure system removes mix-ratio errors and pot-life pressure from the equation. In marine environments — at a dock, on a mooring, or during an emergency repair — accurate two-part mixing is often impractical. MarineFlex delivers consistent results straight from the cartridge. Ambient humidity does the work.

Applications in Marine Environments

The "above and below waterline" rating covers a wide range of critical sealing tasks in boat construction and repair (SELLEYS_MARINEFLEX-AUS_GHS.pdf). Below-waterline applications include through-hull fittings for transducers, depth sounders, and raw water intakes; keel-to-hull joints; and rudder post seals. These locations demand absolute reliability — water ingress here isn't an inconvenience, it's a vessel-threatening event.

Above-waterline applications include hull-to-deck joints, one of the most common leak sources in production boats, where differential movement between hull and deck requires a flexible bond that stays watertight through years of flexing. Porthole and hatch installations benefit from MarineFlex's ability to seal against fibreglass and acrylic or polycarbonate glazing simultaneously, handling thermal expansion differences between these dissimilar materials without issue.

Deck hardware installations — cleats, winches, stanchion bases, rail fittings, and bow rollers — need sealing that keeps water from penetrating mounting holes and causing core rot in sandwich-construction decks. MarineFlex's flexibility maintains the seal even as hardware loads flex the deck under stress.

Cabin and cockpit applications include windows, overhead hatches, and ventilator installations where water intrusion damages interiors and electrical systems. The white formulation matches gelcoat and painted surfaces in visible locations. The black version blends with rubber hatch seals and dark hardware.

MarineFlex bonds to the full range of materials in marine construction: hand-laid and moulded fibreglass, gelcoat, marine-grade plywood and treated timber, anodised and painted aluminium, stainless steel, brass, bronze, and rigid PVC used in plumbing systems.

Surface Preparation & Application

Surface preparation determines whether MarineFlex achieves its full adhesive potential. Marine surfaces carry contamination that's invisible to casual inspection — mould release agents on new fibreglass, wax from polishing compounds, salt residue, fuel and oil films, and silicone from previous repairs. These contaminants block chemical bonding and cause premature adhesion failure.

Clean all surfaces with a suitable solvent — acetone or isopropyl alcohol for most marine surfaces — and allow complete evaporation before application. For porous surfaces like timber or delaminated fibreglass, ensure substrates are dry. While the product cures with moisture, excess water on the surface prevents initial adhesion. For repairs below the waterline, dry-docking or hauling is necessary to achieve dry surfaces. Applying sealant to wet substrates underwater won't deliver the result you need.

Cut the cartridge nozzle at a 45-degree angle to the desired bead diameter. For structural joints like hull-to-deck bonds, use a larger bead (8–12 mm) to ensure the material fills the joint gap completely. For hardware bedding, a 3–5 mm bead provides solid sealing without excessive squeeze-out. Apply steady pressure to the cartridge gun to maintain a consistent bead, moving the tip along the joint at a uniform speed.

For underwater applications, apply the sealant generously and ensure complete coverage — any gaps or voids create leak paths. Press hardware or fittings firmly into the wet sealant to achieve full contact, then install fasteners while the sealant remains workable. Squeeze-out confirms complete bedding. Remove excess with a disposable tool before skin formation begins.

Tool the sealant within 10–15 minutes of application if a smooth finish is the goal. For underwater applications, complete coverage matters more than tooling. For visible joints, use a plastic tool or gloved finger wetted with soapy water to create a concave profile that sheds water away from the joint.

Handling, Storage & Shelf Life

Store MarineFlex cartridges in a cool, dry, well-ventilated location away from direct sunlight (SELLEYS_MARINEFLEX-AUS_GHS.pdf). Temperature extremes affect both the uncured product and empty cartridges. Storage above 30°C can accelerate the moisture-cure reaction inside the cartridge, causing the sealant to skin over or partially cure before use. Below 5°C, viscosity increases, making dispensing harder and affecting bead flow.

Keep containers standing upright and check regularly for leaks (SELLEYS_MARINEFLEX-AUS_GHS.pdf). Seal or cap partial cartridges immediately after use to prevent moisture ingress. Once exposed to atmospheric humidity, the product begins curing from the surface inward — an unsealed nozzle lets this process work back into the cartridge.

Store away from foodstuffs and incompatible materials (SELLEYS_MARINEFLEX-AUS_GHS.pdf). Keep uncured material away from food storage areas on boats or in workshops, and keep containers closed when not in use to prevent contamination and moisture exposure.

The product is classified as combustible, though not as a dangerous good for transport purposes (SELLEYS_MARINEFLEX-AUS_GHS.pdf). Store away from ignition sources, open flames, and heat-generating equipment. In marine applications, this means keeping spare cartridges away from engine compartments, battery boxes, and electrical panels.

During application, avoid inhaling vapours and prevent repeated or prolonged skin contact (SELLEYS_MARINEFLEX-AUS_GHS.pdf). Work in well-ventilated areas — especially important in boat interiors where air circulation is limited. When working in bilges, lockers, or confined spaces, ensure adequate ventilation through hatches or forced-air circulation.

Safety Considerations & Personal Protection

MarineFlex is classified as hazardous under Safe Work Australia GHS 7 criteria, specifically Eye Damage/Irritation Category 2A with hazard statement H319: "Causes serious eye irritation" (SELLEYS_MARINEFLEX-AUS_GHS.pdf). This classification requires specific precautions during handling and application — particularly relevant in marine environments where wind, spray, and confined working spaces increase exposure risks.

Wear protective gloves, protective clothing, and eye/face protection during all handling operations (SELLEYS_MARINEFLEX-AUS_GHS.pdf). For marine applications, this means chemical-resistant gloves — nitrile rubber is suggested for intermittent contact, though users should verify compatibility based on specific glove construction (SELLEYS_MARINEFLEX-AUS_GHS.pdf). Standard work gloves provide no protection against chemical irritation.

Eye protection is non-negotiable when working overhead or in tight spaces where accidental contact is likely. When bedding deck hardware or sealing overhead hatches, chemical goggles provide better protection than safety glasses — they seal around the eyes and stop sealant squeeze-out or drips from reaching sensitive tissue.

Wash hands, face, and all exposed skin thoroughly after handling (SELLEYS_MARINEFLEX-AUS_GHS.pdf). Marine work often involves sequential tasks where sealant residue on hands transfers to tools, rigging, and then to faces and eyes during normal work movements. Wash before breaks, meals, and at the end of each work session.

If eye contact occurs, hold eyelids apart and flush continuously with running water for at least 15 minutes, then get to a doctor or hospital (SELLEYS_MARINEFLEX-AUS_GHS.pdf). If irritation persists after flushing, seek medical attention immediately (SELLEYS_MARINEFLEX-AUS_GHS.pdf). On boats, this means having access to copious water for emergency eyewash. A portable eyewash station or dedicated water supply belongs in any marine work setup where sealants are being applied.

For skin contact, remove contaminated clothing and flush skin and hair with running water. Seek medical assistance if swelling, redness, blistering, or irritation occurs (SELLEYS_MARINEFLEX-AUS_GHS.pdf). If swallowed, do not induce vomiting — rinse mouth with water, give water to drink, and seek medical advice (SELLEYS_MARINEFLEX-AUS_GHS.pdf).

Keep the product out of reach of children and read all instructions before use (SELLEYS_MARINEFLEX-AUS_GHS.pdf). In marine contexts, this extends to crew members and dock workers who access storage areas — ensure cartridges are secured and clearly labelled.

For emergency response, contact the Australian emergency number 1800 220 770 or New Zealand emergency number 0800 220 770 (SELLEYS_MARINEFLEX-AUS_GHS.pdf). Keep product containers or labels available when seeking medical advice (SELLEYS_MARINEFLEX-AUS_GHS.pdf).

Fire Safety & Emergency Response

MarineFlex is classified as combustible but is not classified as dangerous goods under Australian or New Zealand transport regulations (SELLEYS_MARINEFLEX-AUS_GHS.pdf). If the material becomes involved in a fire, use water fog (or fine water spray if fog is unavailable), alcohol-resistant foam, standard foam, dry chemical powder, or carbon dioxide (SELLEYS_MARINEFLEX-AUS_GHS.pdf).

The combustible classification means the product can burn under sufficient heat — relevant when stored in engine rooms, near fuel tanks, or in areas with fire risk. During combustion or decomposition, toxic fumes may be emitted (SELLEYS_MARINEFLEX-AUS_GHS.pdf). Firefighters should wear self-contained breathing apparatus and suitable protective clothing if exposure to vapours or combustion products is possible (SELLEYS_MARINEFLEX-AUS_GHS.pdf).

On boats, this guides storage decisions directly. Keep sealant cartridges away from engine compartments where fuel fires could occur, and store them somewhere that won't contribute to fire spread if other ignition sources trigger a marine fire incident.

Spill Management

Small spills require wearing protective equipment to prevent skin and eye contact while avoiding vapour inhalation (SELLEYS_MARINEFLEX-AUS_GHS.pdf). Wipe up material with absorbent rags or paper towels, then collect and seal in properly labelled containers for disposal (SELLEYS_MARINEFLEX-AUS_GHS.pdf). On boats, contain spills immediately before the sealant contacts water or spreads across deck surfaces.

Large spills require clearing the area of all unprotected personnel — the material becomes slippery when spilled (SELLEYS_MARINEFLEX-AUS_GHS.pdf). Work upwind or increase ventilation, cover with damp absorbent material (inert material, sand, or soil), and sweep or vacuum up while avoiding dust generation (SELLEYS_MARINEFLEX-AUS_GHS.pdf). If contamination of waterways has occurred — a real concern in marina environments — advise local emergency services immediately (SELLEYS_MARINEFLEX-AUS_GHS.pdf).

Spilled sealant creates a slip hazard on boat decks where secure footing is already challenged by movement and wet surfaces. Clean up spills immediately (SELLEYS_MARINEFLEX-AUS_GHS.pdf).

Troubleshooting Common Issues

Poor adhesion almost always traces back to surface preparation rather than the product. When seals break down prematurely, check whether surfaces were properly cleaned and dried. Salt deposits, wax residue, and remnants of previous sealant are the most common culprits in marine applications. Re-cleaning with appropriate solvents and allowing complete dry time resolves these issues.

Slow or incomplete curing can occur in low-humidity environments. The moisture-cure mechanism needs atmospheric water vapour to initiate crosslinking. In arid climates or during winter storage in dehumidified spaces, cure may be significantly delayed. Lightly misting the applied sealant with water from a spray bottle accelerates surface cure — do this sparingly to avoid disrupting adhesion at the substrate interface.

Discoloration or chalking despite the UV stabilisers (SELLEYS_MARINEFLEX-AUS_GHS.pdf) may point to chemical exposure beyond normal marine service. Petroleum products, strong solvents, and chlorinated cleaning agents can degrade the surface of cured sealant. The bulk material often remains functional, but cosmetic appearance suffers. For visible applications, keep harsh chemicals away from sealed joints during boat cleaning.

Bead sagging or slumping during application indicates either an oversized bead for the joint geometry or application to vertical and overhead surfaces without proper support. For large gaps, apply the sealant in multiple passes, allowing partial cure between applications to build thickness without sagging. For overhead work, temporary backing with release tape supports the sealant until it develops sufficient green strength.

Nozzle clogging from partial cure in the tip is easy to manage — cut away the cured portion and resume application. For extended projects, seal the nozzle between work sessions or replace it with a fresh cut. Proper storage and prompt nozzle sealing after each use prevents waste.

Expert Application Techniques

For hull-to-deck joints, apply a generous bead to both mating surfaces before assembly. This "buttering" technique ensures complete void filling even when joint gaps are irregular. As fasteners draw the joint together, sealant should squeeze out uniformly along the entire seam. Any section without squeeze-out signals an insufficiently filled void — address it before moving on.

When bedding through-hull fittings below the waterline, apply sealant to all threaded connections in addition to the flange-to-hull interface. This creates multiple seal barriers. Tighten mounting hardware while the sealant remains workable so it flows into threads and fills every potential leak path.

For porthole and hatch installations, create a dam of sealant around the perimeter of the opening before setting the unit. This prevents squeeze-out from dripping into the cabin while ensuring complete sealing. Work the hatch or porthole in a slight circular motion as you press it into position — this distributes the sealant evenly and eliminates air pockets.

When sealing deck hardware, apply enough sealant that cleanup becomes necessary but not so much that fastener engagement is compromised. The goal is a small, uniform bead of squeeze-out around each fastener hole — confirmation that sealant has filled the gap between hardware and deck.

For repairs to existing installations, complete removal of old sealant is essential. Silicone, polyurethane, and polysulfide remnants block adhesion of fresh MarineFlex. Use mechanical removal — scrapers and wire brushes — followed by solvent cleaning to reach bare substrate. The extra preparation time here is the investment that prevents future issues.

Plan application around temperature and humidity. The product performs across a range of conditions, but moderate temperatures (15–25°C) and moderate humidity (40–70% RH) deliver the best working time and cure characteristics. Hot conditions accelerate cure and shorten tooling time. Cold conditions extend cure and may require additional time before joints face stress or water exposure.

Professional Maintenance Practices

Inspect sealed joints annually as part of routine boat maintenance. Look for separation at substrate interfaces, cracks in the sealant bead, or discoloration indicating UV degradation or chemical exposure. Catching seal deterioration early means small repairs before water intrusion causes structural damage.

For underwater applications, haul-out inspections are the only opportunity to assess seal integrity. Pay close attention to through-hull fittings and keel joints — these are the locations where breakdown carries the most serious consequences. When sealant shows cracking, hardening, or separation, schedule re-sealing during the same haul-out.

Re-bed deck hardware on a regular schedule rather than waiting for leaks to develop. Many marine professionals re-bed every 5–7 years as preventive maintenance. The cost of sealant and labour is minimal compared to repairing core damage from undetected leaks.

When removing hardware for re-bedding, document the original sealant's condition. If adhesion to one substrate appears weaker than the other, adjust surface preparation for that material on the next application. Some gelcoats, for instance, benefit from light abrasion to improve mechanical keying.

Maintain records of sealant applications — product type, date, and conditions during application. If premature issues arise, this documentation helps identify whether cure conditions, surface preparation, or product selection played a role. For professional yards, this record-keeping supports warranty claims and drives continuous improvement in sealing protocols.

References

Source PDF: SELLEYS_MARINEFLEX-AUS_GHS.pdf (canonical)

Frequently Asked Questions

What is Selleys MarineFlex: A flexible waterproof adhesive sealant for marine environments

Is MarineFlex suitable for below-waterline use: Yes

Is MarineFlex suitable for above-waterline use: Yes

What sizes does MarineFlex come in: 410 mL cartridges

What colours is MarineFlex available in: Black and white

What is the product code for black MarineFlex: 101084

What is the product code for white MarineFlex: 101086

How many components does MarineFlex have: One — single-component system

How does MarineFlex cure: Through atmospheric moisture

Does MarineFlex require mixing: No

Does MarineFlex require a catalyst: No

What is the primary chemistry of MarineFlex: Silane-modified polymer

What is the main silane coupling agent in MarineFlex: 3-(trimethoxysilyl)-1-propanamine (CAS 13822-56-5)

What percentage of silane coupling agent does MarineFlex contain: 1–10% (w/w)

Does MarineFlex contain UV stabilisers: Yes

What are the UV stabilisers used in MarineFlex: Hindered amine light stabilisers (HALS)

What percentage of UV stabilisers does MarineFlex contain: Less than 1% each

Does MarineFlex stay flexible after curing: Yes

Will MarineFlex crack under joint movement: No, it stretches and compresses

Is MarineFlex resistant to saltwater: Yes

Does MarineFlex resist UV degradation: Yes

What materials does MarineFlex bond to: Fibreglass, gelcoat, aluminium, stainless steel, and treated timber

Does MarineFlex bond to gelcoat: Yes

Does MarineFlex bond to fibreglass: Yes

Does MarineFlex bond to aluminium: Yes

Does MarineFlex bond to stainless steel: Yes

Does MarineFlex bond to treated timber: Yes

Does MarineFlex bond to rigid PVC: Yes

Does MarineFlex bond to brass and bronze: Yes

Can MarineFlex seal hull-to-deck joints: Yes

Can MarineFlex seal through-hull fittings: Yes

Can MarineFlex seal porthole installations: Yes

Can MarineFlex seal deck hardware: Yes

Can MarineFlex seal hatch installations: Yes

Can MarineFlex seal keel-to-hull joints: Yes

Can MarineFlex seal rudder post seals: Yes

Which colour suits visible interior applications: White

Which colour suits dark hardware and rubber seals: Black

What solvent should be used to clean surfaces before applying MarineFlex: Acetone or isopropyl alcohol

Must surfaces be dry before applying MarineFlex: Yes

Can MarineFlex be applied to wet underwater surfaces: No

When should MarineFlex be tooled after application: Within 10–15 minutes of application

What tool can be used to smooth MarineFlex: A plastic tool or gloved finger wetted with soapy water

What bead size is recommended for structural joints: 8–12 mm

What bead size is recommended for hardware bedding: 3–5 mm

At what angle should the cartridge nozzle be cut: 45 degrees

What storage temperature should be avoided (high): Above 30°C

What storage temperature should be avoided (low): Below 5°C

Should MarineFlex cartridges be stored upright: Yes

Should partial cartridges be sealed after use: Yes, immediately

Is MarineFlex classified as dangerous goods for transport: No

Is MarineFlex classified as combustible: Yes

Is MarineFlex classified as hazardous under GHS 7: Yes

What is the specific GHS hazard classification for MarineFlex: Eye Damage/Irritation Category 2A

What is the GHS hazard statement for MarineFlex: H319 — Causes serious eye irritation

What PPE gloves are recommended for handling MarineFlex: Nitrile rubber gloves

Is eye protection required when handling MarineFlex: Yes

What type of eye protection is recommended for overhead work: Chemical goggles

How long should eyes be flushed if MarineFlex contacts them: At least 15 minutes

Should a doctor be seen after eye contact with MarineFlex: Yes

Should vomiting be induced if MarineFlex is swallowed: No

What should be done if MarineFlex is swallowed: Rinse mouth, give water, seek medical advice

What is the Australian emergency contact number for MarineFlex incidents: 1800 220 770

What is the New Zealand emergency contact number for MarineFlex incidents: 0800 220 770

What extinguishing media can be used on a MarineFlex fire: Water fog, foam, dry chemical, or carbon dioxide

Do toxic fumes emit when MarineFlex burns: Yes

Should MarineFlex be stored near engine compartments: No

Is MarineFlex a slip hazard when spilled: Yes

How should small MarineFlex spills be cleaned: Wipe with absorbent rags or paper towels

How should large MarineFlex spills be managed: Cover with damp absorbent material, sweep or vacuum up

Should authorities be notified if MarineFlex enters waterways: Yes, advise local emergency services immediately

What causes poor adhesion with MarineFlex: Inadequate surface preparation

What causes slow curing of MarineFlex: Low ambient humidity

How can slow curing be accelerated: Lightly mist applied sealant with water

What causes bead sagging during MarineFlex application: Oversized bead or application to unsupported vertical surfaces

How is a clogged MarineFlex nozzle resolved: Cut away the cured portion and resume application

How often should sealed marine joints be inspected: Annually

How often should deck hardware be re-bedded as preventive maintenance: Every 5–7 years

Must old sealant be fully removed before applying MarineFlex: Yes

What is the ideal temperature range for applying MarineFlex: 15–25°C

What is the ideal humidity range for applying MarineFlex: 40–70% relative humidity

Does high temperature shorten MarineFlex tooling time: Yes

Does cold temperature extend MarineFlex cure time: Yes

Label Facts Summary

Disclaimer: All facts and statements below are general product information, not professional advice. Consult relevant experts for specific guidance.

Verified Label Facts

Product name: Selleys MarineFlex
Product type: Flexible waterproof adhesive sealant
Available sizes: 410 mL cartridges
Available colours: Black, White
Product code (black): 101084
Product code (white): 101086
Number of components: Single-component system
Cure mechanism: Atmospheric moisture cure
Mixing required: No
Catalyst required: No
Primary chemistry: Silane-modified polymer
Silane coupling agent: 3-(trimethoxysilyl)-1-propanamine (CAS 13822-56-5) at 1–10% (w/w)
UV stabiliser 1: Bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate (CAS 41556-26-7) at <1% (w/w)
UV stabiliser 2: Methyl (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate (CAS 82919-37-7) at <1% (w/w)
Remaining formulation: Non-hazardous proprietary ingredients
GHS hazard classification: Hazardous under Safe Work Australia GHS 7
Specific hazard category: Eye Damage/Irritation Category 2A
GHS hazard statement: H319 — Causes serious eye irritation
Dangerous goods (transport): Not classified as dangerous goods under Australian or New Zealand transport regulations
Combustibility classification: Classified as combustible material
Toxic fumes on combustion: Yes — toxic fumes may be emitted during combustion or decomposition
Recommended PPE — gloves: Nitrile rubber (suggested for intermittent contact; verify compatibility based on glove construction)
Recommended PPE — eye/face: Protective eye/face protection required; chemical goggles recommended for overhead work
Recommended PPE — clothing: Protective clothing required
Eye contact first aid: Flush continuously with running water for at least 15 minutes; transport to doctor or hospital
Skin contact first aid: Remove contaminated clothing; flush skin and hair with running water; seek medical assistance if irritation, swelling, redness, or blistering occurs
Ingestion first aid: Do not induce vomiting; rinse mouth with water; give water to drink; seek medical advice
Australian emergency contact: 1800 220 770
New Zealand emergency contact: 0800 220 770
Approved extinguishing media: Water fog (or fine water spray), alcohol-resistant foam, standard foam, dry chemical powder, carbon dioxide
Firefighter PPE requirement: Self-contained breathing apparatus and suitable protective clothing if exposure to vapours or combustion products is possible
Storage — temperature (high): Avoid above 30°C
Storage — temperature (low): Avoid below 5°C
Storage — orientation: Store cartridges upright
Storage — partial cartridges: Seal or cap immediately after use
Storage — location: Cool, dry, well-ventilated area away from direct sunlight, ignition sources, open flames, foodstuffs, and incompatible materials
Slip hazard (spilled): Yes — material becomes slippery when spilled
Small spill procedure: Wear PPE; wipe with absorbent rags or paper towels; collect and seal in labelled containers for disposal
Large spill procedure: Clear unprotected personnel; work upwind or increase ventilation; cover with damp absorbent material (inert material, sand, or soil); sweep or vacuum avoiding dust generation
Waterway contamination: Advise local emergency services immediately if contamination of waterways occurs
Suitable for above-waterline use: Yes
Suitable for below-waterline use: Yes
Nozzle cut angle: 45 degrees
Recommended bead size — structural joints: 8–12 mm
Recommended bead size — hardware bedding: 3–5 mm
Tooling window: Within 10–15 minutes of application
Ideal application temperature: 15–25°C
Ideal application humidity: 40–70% relative humidity
Source document: SELLEYS_MARINEFLEX-AUS_GHS.pdf

General Product Claims

MarineFlex is built specifically for marine environments and outperforms general-purpose sealants
Stays flexible after curing, moving with boat hulls, deck fittings, and underwater fixtures as they expand, contract, and flex
Silane-modified chemistry creates a durable bond in wet environments where ordinary adhesives fail
Suitable for hull-to-deck joints, through-hull fittings, porthole sealing, keel-to-hull joints, and rudder post seals
Bonds to fibreglass, gelcoat, aluminium, stainless steel, treated timber, rigid PVC, brass, and bronze
Resists saltwater immersion at the molecular level, preventing swelling and softening
UV stabilisers prevent chalking, cracking, and discoloration under intense marine sunlight
Single-component system eliminates mix-ratio errors and pot-life pressure
Slow curing in low-humidity conditions can be accelerated by lightly misting applied sealant with water
Bead sagging can be managed by applying in multiple passes with partial cure between applications
Clogged nozzles resolved by cutting away the cured tip portion
Old sealant must be fully removed before applying MarineFlex for reliable adhesion
Deck hardware should be re-bedded every 5–7 years as preventive maintenance
Annual inspection of sealed joints is recommended
High temperatures shorten tooling time; cold temperatures extend cure time
White formulation suits visible interior and gelcoat-matched applications; black suits dark hardware and rubber seals

Selleys Marine Flex - Waterproof Adhesive Sealant sits within the Selleys brand, an Australian adhesive and sealant manufacturer whose range spans general-purpose, construction, and specialist applications. Within that range, Marine Flex belongs to the specialist glue segment — products engineered for demanding conditions rather than everyday household tasks. Selleys positions this product on its own dedicated product page under the "Glues & Adhesives > Specialist Glue" category, reflecting how it is differentiated from standard sealants by its ability to perform both above and below the waterline.

Within the Marine Flex line itself, the product is available in two variants: Selleys MarineFlex Black 410mL (product code 101084) and Selleys MarineFlex White 410mL (product code 101086). Both are supplied in the same 410mL size; the choice between them is primarily aesthetic — white suits lighter-coloured hulls, fibreglass, and deck fittings, while black is better matched to dark rubbers, fenders, and similar surfaces. Beyond colour, the formulation and performance specification are consistent across both variants.

From a use-case perspective, a buyer working with Selleys MarineFlex is typically sealing joints, gaps, or penetrations on a boat hull, deck, or fitting. That kind of project commonly calls for companion products: a caulking gun (Replace 'sausage-style cartridge' with 'barrel cartridge' or simply 'cartridge'. A 410 mL cartridge is a standard barrel format requiring a standard caulking/cartridge gun, not a sausage gun.), surface cleaning or degreasing products to prepare bonding surfaces, and potentially masking tape to achieve clean sealant lines. Although no specific companion products from the Selleys range are detailed in the available knowledge graph data, these adjacencies are worth keeping in mind when planning a marine sealing project.

In terms of category position, Selleys Marine Flex occupies a narrow, specialist niche within the broader Home & Garden > Adhesives & Sealants category. What sets it apart from general sealants is its combined resistance to UV exposure, saltwater, chlorinated water, and freshwater immersion, along with flexibility sufficient to absorb the shock and vibration typical of a working boat. That combination of properties — rather than raw bonding strength alone — defines where it sits relative to more general-purpose adhesives in the Selleys catalogue.