There's no single best flange sealant — there's only the sealant that matches your fluid, temperature, pressure, and joint design, and picking the wrong one from a shelf of otherwise-good products is a common, expensive mistake. Why Flange Seal Integrity Matters Flanges provide the bolted connection point for pipes, valves, pumps, and process equipment, and a compromised seal at any one of them can lead to product loss, energy waste, environmental exposure, safety hazards, and regulatory consequences. Beyond preventing leaks, a reliable flange seal maintains pressure or vacuum differentials, excludes contaminants that would compromise process purity, and keeps unplanned downtime for repairs to a minimum. Vacuum Applications Deserve Separate Consideration Vacuum systems present a subtly different challenge than pressure systems, even though both are described under the umbrella of "flange sealing." A sealant that resists a fluid being pushed out under positive pressure doesn't automatically resist atmospheric air being pulled in under vacuum, since the failure mode runs in the opposite direction. Anaerobic sealants generally perform well here because their full-contact cure eliminates the micro-channels that allow slow atmospheric ingress, but the joint's overall design — including seal geometry and any secondary O-ring backup — should be evaluated with vacuum-specific leak testing rather than assuming pressure-rated performance data translates directly to a vacuum service rating. Key Factors That Determine the Right Choice Fluid and gas compatibility. What's being transported — water, steam, oil, chemicals, or gases — and whether it's corrosive or reactive, determines which sealant chemistries are even viable candidates. Temperature range. The sealant needs to maintain flexibility or rigidity, as required, across the full operating temperature range without becoming brittle at the low end or degrading at the high end. Pressure and joint design. High-pressure applications demand sealants with strong creep resistance, and whether the joint is rigid or subject to dynamic movement changes which chemistry family is appropriate. Flange material and surface finish. Some sealants perform better on rougher surfaces, while others require a closer to pristine finish to achieve full contact. Common Sealant Chemistries and Where Each Excels Anaerobic sealants cure in the absence of air between close-fitting metal surfaces, making them well suited to rigid metal-to-metal flange joints in hydraulic systems, gearboxes, and engine assemblies where high pressure resistance and vibration resistance both matter. They require active metal surfaces and aren't suited to large gaps or non-metal flanges. RTV silicones cure via moisture in the air into a flexible, rubber-like seal, which makes them a better fit for covers, housings, and non-pressure-retaining flanges where movement, vibration, or irregular surfaces make a rigid metal-to-metal seal impractical. Gasket dressings aren't standalone sealants — they're applied to traditional compression gaskets to improve initial sealing and ease future disassembly, complementing rather than replacing the gasket. PTFE tapes and compounds offer excellent chemical inertness and low friction, but are suited primarily to threaded pipe joints rather than flat flange faces. Getting Application Details Right Regardless of chemistry, clean and dry surfaces are non-negotiable for reliable sealing, and bolt tightening should…

Apply an anaerobic sealant to a joint with too wide a gap and you won't get a weaker seal — you'll get a joint that never fully cures, because the oxygen trapped in that extra space is exactly what the chemistry needs to stay liquid. How Curing Mechanism and Gap Fill Are Linked Anaerobic sealants cure only when confined between close-fitting metal surfaces in the absence of air, with metal ions catalyzing the polymerization. That requirement is inseparable from the product's gap-filling limits: when a joint's gap is too large, residual oxygen remains trapped in the bond line and inhibits full polymerization, leaving a soft or even liquid core surrounded by a cured skin — a joint that looks sealed on the outside but isn't. Typical Maximum Gap-Filling Range For most general-purpose anaerobic sealants used in threadlocking, retaining, or flange gasketing, the typical maximum recommended gap is in the range of 0.25 mm (0.01 in.) to 0.5 mm (0.02 in.). The lower end of that range covers standard threadlockers and flange sealants formulated for precision-machined parts, where the goal is filling microscopic irregularities rather than bridging a meaningful gap. Higher-viscosity gasketing and retaining formulations can tolerate the upper end of that range, intended for joints with slightly more manufacturing tolerance built in. Exceeding a product's specified maximum consistently leads to incomplete cure, reduced ultimate strength, poor sealing under pressure, and cure times that stretch out far longer than the technical data sheet suggests. Factors That Affect Real-World Gap Performance Viscosity: thicker formulations resist running out of a wider joint before curing, while thinner, low-viscosity products are better suited to wicking into already-assembled, tight-tolerance threads. Active versus passive metals: cure speed is faster on active metals like steel and copper; passive metals such as stainless steel or plated surfaces often need an activator to cure reliably, even within the product's rated gap range. Temperature: cold slows the cure reaction, making it harder to fully polymerize in a larger gap; elevated temperatures accelerate it. Surface finish: rough or irregular surfaces effectively create local gaps larger than the nominal clearance, which can push a marginal joint past a product's limit. When to Choose a Different Sealing Approach If your joint consistently presents a gap wider than roughly 0.5 mm, or involves a non-metal substrate, an anaerobic sealant is generally the wrong tool regardless of formulation. RTV silicone sealants handle larger, more dynamic gaps and a wider range of substrates; two-part epoxy or acrylic systems offer structural bonding for larger gaps without depending on oxygen exclusion to cure; and in some cases a traditional pre-cut gasket remains the right choice when compression resistance matters more than gap-filling precision. If you're not sure which category your joint falls into, Email Us and our technical team can help you evaluate the gap and recommend the right sealing approach before you commit to a production process. Why a Radiused or Chamfered Edge Changes the Picture Gap-fill specifications assume a relatively uniform clearance across the bonded area, but…

Mechanical fasteners and compression gaskets have held industrial assemblies together for a century, but neither one was designed to eliminate the microscopic gaps that eventually turn into leaks, corrosion, or a bolt that backs itself loose under vibration. The Curing Mechanism That Sets Anaerobics Apart Anaerobic sealants stay liquid on exposure to air and only cure once confined between close-fitting metal surfaces in the absence of oxygen, where metal ions catalyze a rapid polymerization into a tough thermoset plastic. That mechanism is the foundation for everything these products do well: because the sealant is liquid until confinement, it flows into every microscopic gap on the mating surfaces before it locks in place, rather than bridging the high points the way a compressed gasket or a dry mechanical fit does. The Practical Advantages That Follow From That Chemistry Superior sealing and leak prevention. Traditional joints, even well-torqued ones, leave microscopic gaps that become leak paths for fluids, gases, or contaminants over time. An anaerobic sealant fills those gaps completely, creating full surface-to-surface contact and eliminating the leak paths a compression-only joint can't avoid. Enhanced joint strength and durability. Mechanical fasteners concentrate stress at discrete points, which makes them susceptible to loosening under vibration or thermal cycling. Anaerobic threadlockers and retaining compounds unitize the assembly instead, distributing stress evenly across the entire bonded surface and improving fatigue resistance. Corrosion and fretting prevention. By excluding air and moisture from the joint, anaerobic sealants remove the conditions that drive galvanic corrosion and fretting wear between mating metal parts. Simplified assembly and reduced inventory. A liquid gasket formulation can replace a shelf full of pre-cut gasket sizes, and an anaerobic threadlocker can eliminate the need for lock washers or cotter pins entirely — fewer parts to stock, fewer steps in the assembly process. Where the Cost Savings Actually Show Up Leaks, loosened fasteners, and fretting corrosion all translate directly into warranty claims, unplanned maintenance, and production downtime. Preventing those failure modes at the design stage is consistently less expensive than repairing them after the fact, and the rapid handling strength of anaerobic chemistry also speeds up assembly-line throughput compared to methods that require extended clamping or curing time. Documenting Formulation Choices for Future Maintenance Teams A detail that's easy to overlook at the design stage: whatever anaerobic sealant, threadlocker, or retaining compound strength grade goes into an assembly should be documented somewhere a maintenance technician will actually see it years later. A joint assembled with a specific strength grade in mind — say, medium-strength for periodic servicing — loses that intent entirely if the next person to open the assembly has no record of what was used and defaults to whatever is on hand, potentially over-bonding a joint that was meant to stay serviceable or under-securing one that needed permanent strength. Recording formulation and strength grade in assembly documentation, service manuals, or even a simple part tag closes a gap that otherwise resurfaces as an avoidable maintenance problem down the line. Why Full Cure Time…

"Do you put gasket sealer on both sides of a gasket?" is a common question on the assembly floor, and it has no single answer. The right practice depends on the gasket type, the sealer, the condition of the flange faces, and the application. For most traditional gaskets, a single-sided application is the safer default. Why Gasket Sealers Are Used A gasket fills imperfections between two mating surfaces to prevent leakage of fluids or gases. Gasket sealers, also called dressings or compounds, are applied with solid gaskets to serve several purposes: Fill minor scratches, pits, and surface imperfections a dry gasket cannot perfectly conform to. Hold and position the gasket during assembly, preventing slippage or damage. Add a layer of chemical resistance in some cases. Either ease future disassembly, if the sealer acts as a release layer, or make the joint more permanent, depending on the product. When to Apply Sealer to One Side For most compressible gaskets, such as paper, cork, rubber, or soft non-asbestos fiber, applying sealer to one side only is the recommended practice. Prevents over-compression and squeeze-out: coating both sides makes the gasket slippery and prone to squishing out when the bolts are torqued. That reduces effective gasket thickness, weakens the seal, and can foul internal components. Aids disassembly: leaving one side dry keeps the gasket from bonding hard to both flanges, so it comes off in one piece and cleanup is faster. This matters on components serviced regularly. Provides sufficient sealing: on well-machined flanges with the correct gasket, a thin even coat on one side fills microscopic voids; the gasket's compression does the primary sealing. Simplifies positioning: the sealer tacks the gasket to one flange, making alignment easier during assembly. A common approach is a thin, even layer of a non-hardening or semi-hardening sealer on the face that will sit against the less critical or easier-to-clean flange. Getting this detail right avoids both leaks and unnecessary rework at the next service. Email Us to review your gasket type and flange condition with Incure's technical team. When Both Sides Might Be Considered A thin application of a suitable sealer on both sides is occasionally warranted: Severely pitted or scratched flanges that cannot be resurfaced, where a very thin non-hardening layer on both faces bridges larger imperfections. This is a last resort. Highly porous gasket materials that might wick fluid, where a thin coat on both sides forms a better barrier. This is less common with modern materials. Specific manufacturer instructions that explicitly call for a dual-sided dressing on a particular design. Difficult alignment on large or complex gaskets, where a minimal tack coat on both sides holds position, applied with care to avoid over-application. This guidance applies to gasket dressings used with solid gaskets. It does not apply to anaerobic flange sealants, which replace the gasket entirely and are applied as a continuous bead on one clean, dry metal face. Choosing a Dressing Type Gasket dressings fall into three broad categories, and the choice affects both…

Ensuring a leak-proof flange connection is a constant priority in manufacturing and maintenance. Pre-cut gaskets have long been the standard. Anaerobic flange sealants offer a different approach, and the common question is whether they supplement a gasket or replace it. In practice they replace it. The Anaerobic Cure Principle Anaerobic sealants cure under two conditions that must both be present: Absence of oxygen: the sealant must be confined between mating surfaces. Contact with active metal: metal ions catalyze the curing reaction. This mechanism is the reason anaerobic sealants and traditional gaskets do not work together. Why You Should Not Combine Them Anaerobic sealants are generally not designed for use with pre-cut gaskets made of cork, paper, rubber, or most semi-metallic materials. Combining them tends to produce a worse seal, for several reasons: Oxygen exclusion is defeated: a fibrous or porous gasket traps air in the joint, so the anaerobic sealant stays liquid or forms a weak partial gel. Metal contact is blocked: the gasket sits between the flange faces, keeping the sealant from touching metal, so the catalytic reaction never fully initiates. Gap mismatch: anaerobic flange sealants are formulated for tight, rigid, machined joints up to about 0.5 mm. A gasket creates a larger, compressible gap the sealant cannot cure across. Material incompatibility: some gasket rubbers and plastics are not chemically compatible with anaerobic formulations and can degrade. If you use an anaerobic liquid gasket, sometimes called a formed-in-place gasket, you are replacing the pre-cut gasket, not adding to it. When Anaerobic Sealants Replace Gaskets Anaerobic flange sealants are engineered to take the place of cut gaskets on rigid metal flanges, and offer real advantages there: Full-contact sealing: they fill every microscopic void between machined faces, giving a continuous seal that resists leaks better than many gaskets. No relaxation or creep: the cured thermoset holds clamp load, unlike compressible gaskets that lose bolt tension over time. Unitized assembly: the joint resists vibration and shock that loosen gasketed joints and fasteners. Corrosion protection: sealing out moisture limits fretting and galvanic corrosion. Simplified inventory: one product covers many flange sizes. Ideal applications include gearbox housings, engine sumps with rigid machined flanges, pump housings, compressor casings, and rigid hydraulic and pneumatic connections. Choosing between a formed-in-place sealant and a gasket is a decision about flange rigidity, gap, and materials. Email Us to review your joint with Incure's technical team. When Gaskets or Other Sealants Remain Right Traditional gaskets, or an RTV silicone, stay appropriate when: Flanges are flexible or stamped rather than rigid machined castings, so the faces move or are uneven. Gaps are large or irregular, where a flexible RTV silicone that cures with atmospheric moisture is more suitable. Surfaces are dissimilar, such as plastic to metal, where an anaerobic sealant will not cure. Frequent, easy disassembly is required, favoring a reusable gasket or a non-hardening paste. The equipment maker specifies a gasket or a particular RTV for warranty or performance reasons. Cost and Lifecycle Comparison The purchase price of a tube…

"How long until it dries?" is the wrong question for an anaerobic sealant. These materials do not dry; they cure through a chemical reaction that starts only when specific conditions are met. Understanding the timeline, and what shifts it, is essential for predictable assembly and reliable joints. No Drying Step Solvent- and water-based products dry as their carrier evaporates. Anaerobic sealants stay liquid while exposed to air and begin to cure rapidly only when: Confined between close-fitting metal surfaces, which excludes oxygen. In contact with active metal ions, which catalyze the reaction. Any sealant squeezed out of the joint and left exposed to air stays liquid and wipes off cleanly, with no residue. Handling Strength Versus Full Cure Two stages matter on a production line. Handling strength, also called fixture time, is when the sealant has developed enough strength to let you move the assembly without disturbing the joint. On active metals such as steel, brass, and copper, this is typically 10 minutes to 1 hour. On passive metals such as stainless steel, aluminum, or plated surfaces, it takes longer unless an activator is used. This fast initial set is a key advantage in high-volume work, letting parts progress to the next station quickly. Full cure, also called functional cure, is when the sealant reaches maximum strength, chemical resistance, and pressure capability. This usually takes 24 hours at room temperature, around 20 to 25 degrees C. Assemblies can often go into light service after handling strength, but for high pressure, high temperature, or dynamic loads, wait for full cure as specified on the technical data sheet. Factors That Change Cure Time Metal activity: steel, iron, copper, and brass carry ions that catalyze cure quickly. Stainless steel, aluminum, zinc, and plated surfaces are far slower and often need an activator. Temperature: higher temperatures speed cure; lower temperatures slow it. Below about 5 degrees C, cure can be very slow or stall without an activator or applied heat. If you work cold, preheat parts or use a heated cure station. Gap size: anaerobic sealants cure best in gaps up to roughly 0.5 mm. In larger gaps, trapped oxygen can leave the center of the joint uncured. Select a grade rated for your gap, or switch technologies for wide gaps. Contaminants: oil, grease, dirt, and some cleaner residues interfere with the metal's catalytic action. Thorough degreasing with a residue-free solvent is essential. Activators and primers: these deposit catalytic species, often a copper salt, on one surface to accelerate cure on passive metals or in the cold. Cure time is a controllable process variable, not a fixed property. Email Us to review your metals, gap, and shop temperature with Incure's technical team. Planning Around Cure Time Set line takt so the joint reaches at least handling strength before the assembly is stressed or handled roughly. Add a hold or buffer station before any pressure test or heavy service load, sized to the full cure time. If incoming part passivation varies, standardize with an activator…

A leak at a flange connection is more than a nuisance. It drives downtime, wasted fluid, safety exposure, and quality escapes. Flange joints in fluid and gas systems need dependable sealing, and modern anaerobic flange sealants offer a durable alternative to cut gaskets when the flanges are rigid and machined. Anaerobic Flange Sealants Versus Cut Gaskets Cut gaskets seal by compressing between two flange faces. Over time they relax, can extrude under pressure, and often fail to fill fine surface imperfections, which leads to slow leaks under thermal cycling or vibration. Anaerobic flange sealants behave differently: Formed-in-place sealing: they fill every microscopic void between rigid metal flanges, giving full surface-to-surface contact and closing leak paths a gasket leaves open. No relaxation or shrinkage: once cured to a thermoset plastic, they hold clamp load without creep. Added joint strength: they resist vibration, shock, and thermal movement. Corrosion control: by displacing air and moisture, they limit fretting and galvanic corrosion at the interface. Simplified inventory: one product replaces many pre-cut gasket sizes. Serviceability: many grades still allow disassembly with standard tools. Step 1: Surface Preparation This step decides the outcome. Anaerobic adhesives need clean, active metal. Remove all old gasket material, previous sealant including RTV silicone, paint, oil, grease, dirt, and rust with a residue-free solvent cleaner. Avoid razor blades and aggressive wire wheels that gouge the flange face and create new leak paths. Use plastic scrapers or dedicated gasket removers. Inspect for nicks, burrs, and warping. Anaerobic sealants bridge minor imperfections; severe damage needs machining. Typical gap-filling capability is up to 0.5 mm. Larger or irregular gaps call for an RTV silicone instead. Confirm both faces are fully dry before application. Step 2: Activate If Needed Anaerobic sealants cure readily on active metals such as steel, brass, and copper. On passive metals such as aluminum, stainless steel, or plated surfaces, or in a cold shop, apply a thin, even coat of activator to one flange face and let the solvent flash off completely before sealing. Good surface preparation and activation choices are where most flange leaks are won or lost. Email Us to review your substrates and shop conditions with Incure's technical team. Step 3: Apply the Sealant Dispense a continuous bead onto one prepared flange face, placed near the inner rim and encircling every bolt hole. On large flanges or automated lines, a dispensing head or roller gives a consistent bead. Apply enough to fill surface imperfections without heavy excess, which only squeezes out and has to be wiped away. Step 4: Assemble Promptly Bring the flanges together as soon as possible so the sealant is confined and the cure begins. Avoid lateral sliding, which smears the bead. Torque the bolts to specification in a cross pattern for even pressure. Some grades give an instant low-pressure seal, but full strength follows the specified cure, typically 24 hours at room temperature. Step 5: Cure and Test Allow the full data sheet cure before putting the joint into service. Wipe away uncured…

Anaerobic sealants stay stable as liquids in the bottle, then turn into durable, leak-proof solids once applied and assembled. That change is a precisely engineered chemical reaction, not a drying step, and understanding it helps you control quality and cycle time. Two Conditions Drive the Cure The word anaerobic means without air, and oxygen exclusion is the defining trait of these sealants. Unlike adhesives that cure by reacting with oxygen or evaporating solvent, anaerobic sealants are formulated to stay liquid while oxygen is present. Two conditions must both be met for cure to start: Absence of oxygen: once the sealant is confined between mating surfaces, dissolved oxygen is consumed or displaced, removing the inhibitor that keeps it liquid. Contact with active metal ions: active metals such as iron, copper, brass, and steel carry trace surface ions that act as catalysts, initiating the reaction that converts the liquid resin into a solid polymer. The Chain Reaction, Step by Step The cure is a free-radical polymerization: Initiation: the sealant contains methacrylate monomers, initiators such as peroxides, and accelerators. With metal ions present and oxygen absent, the initiators break down into reactive free radicals. Propagation: those free radicals attack the monomers, linking them into long chains that branch and cross-link into a dense polymer network. Termination: the reaction continues until the free radicals are consumed or the entire confined volume has polymerized. Any sealant that squeezes out of the joint and stays exposed to air remains liquid and can simply be wiped away. Factors That Change Cure Speed and Quality Metal activity: copper and brass promote a fast cure, steel is moderate, and passive metals such as stainless steel, aluminum, and plated surfaces are slow and often need an activator. Bondline gap: anaerobic sealants are built for tight tolerances, typically up to 0.5 mm. Larger gaps leave trapped oxygen that inhibits cure in the center of the joint. Temperature: higher temperatures speed the reaction; cold parts and surroundings slow it, and below about 5 degrees C cure can stall without an activator or applied heat. Surface cleanliness: oil, grease, dirt, and some cleaner residues interfere with the metal's catalytic action and cause slow or incomplete cure. Activator use: for passive metals, cold conditions, or fast fixture requirements, an activator applied to one surface adds catalytic components and secures a reliable cure. Cure control is a process-engineering problem as much as a chemistry one. Email Us to review your metals, gap, and line conditions with Incure's technical team. Why the Cure Stays Stable in the Bottle Anaerobic sealants are shipped in permeable containers that are deliberately underfilled, because dissolved and headspace oxygen is what keeps the product liquid during storage. The polyethylene bottle wall lets oxygen diffuse in slowly to replace what is consumed by trace side reactions. This is why decanting anaerobic sealant into a sealed glass jar or a full, airtight container shortens its shelf life: the oxygen supply is cut off and slow gelling begins. It also explains why the nozzle…

Anaerobic sealants seal rigid metal-to-metal flanges. Gaskets bridge larger gaps and dissimilar materials. That raises a practical question in assembly planning: can you use an anaerobic sealant together with a conventional gasket? In most cases the two are alternatives, not partners, and combining them creates problems. What Each Method Is Designed to Do Anaerobic sealants: liquid or gel adhesives that cure in the absence of air and the presence of metal ions, forming a rigid thermoset seal that fills microscopic imperfections between close-fitting metal surfaces. They act as a formed-in-place gasket and add structural stiffness to the joint. They suit precision-machined, metal-to-metal flanges. Traditional gaskets: pre-formed compressible materials such as fiber, rubber, or cork that fill larger, less precise gaps by compressing under bolt load and conforming to surface irregularities. They suit dissimilar materials, wider clearances, and joints that are opened frequently. The General Rule: Anaerobics Replace Gaskets On rigid machined metal flanges, anaerobic flange sealants are used instead of cut gaskets. As a gasket eliminator they: Prevent the relaxation and re-torquing that compressible gaskets need over time. Improve joint rigidity by filling the entire void between flanges. Reduce inventory, since one product replaces many pre-cut gasket sizes. Seal microscopic leak paths that a solid gasket can miss. Why Combining Them Usually Fails Putting an anaerobic sealant and a compressible gasket in the same joint is generally counterproductive: Inhibited cure: the anaerobic sealant needs metal-to-metal contact and oxygen exclusion. A non-metallic gasket between the flanges blocks the metal ion contact and can trap air, leaving the sealant partly or fully uncured. Compromised gasket function: a rigid cured film interferes with the designed compressibility of the gasket, so the gasket cannot seat and seal as intended. Disassembly damage: uneven partial adhesion can tear the gasket and mar the mating faces during future service. Redundancy: you spend on two solutions for a job one is designed to do, adding cost and assembly steps with no benefit. If you are using an anaerobic liquid gasket, you are replacing the pre-cut gasket, not supplementing it. What Happens Inside a Combined Joint Picture a compressible fiber gasket coated on both faces with anaerobic liquid, then bolted between two cast flanges. The gasket holds the flange faces roughly a millimeter apart, so almost none of the anaerobic material sees metal contact. Air trapped in the fiber keeps the inhibitor active. When the joint is torqued, the gasket compresses unevenly because pockets of gelled adhesive resist where the material happened to touch metal at a bolt boss. The finished joint has neither the full clamp stability of a formed-in-place seal nor the even compression the gasket was designed for. Under thermal cycling it tends to weep at the low-contact zones first. The Rare Exception A very thin, non-curing anaerobic liquid used as a gasket dressing is occasionally applied with a rigid, non-compressible gasket in specialized static applications where fluid resistance on the gasket surface is critical. This is outside standard practice and requires material compatibility checks and…