Best Sealant

Article Contents

Time makes fools of us all and rots all of our belongings. From the boat to the home, sealants keep our engines running, houses standing and electronics humming by simply blocking out the elements. There are numerous kinds of sealants and each of them does a specific job, which means you need to be diligent to avoid using the wrong one and potentially ruining something expensive.

Below you will find lists of the best sealants in each of the major categories chosen for their cost efficiency, working life and tightness of seal among other qualities. Do the research, buy the best and seal the deal.

Best All-Purpose Sealant:

Sealants are used for many different things, from auto repair to home improvement. But in pretty much all cases, the idea behind using a sealant is to prevent water or other liquids from getting into or out of something. That purpose gives them all common ground and gives us a chance to use them at least somewhat interchangeably.

To call any sealant "all-purpose" is somewhat of a misnomer. While quality sealants can be used for a variety of tasks, they won't perform equally well in all cases. Some tasks require special characteristics of the sealant, which most sealants can't accomplish. That's why we have special sealants for high temperature and for sealing automotive engines.

But there are still a lot of uses for sealants, even though it's not the stated purpose of that sealant. When sealing a structure to protect it from rainwater entering in (one of the most common uses of sealants), it doesn't matter if the structure is a car, a building, an airplane, a bridge or a boat. Nor does it matter a whole lot if the structure is made of steel, copper, aluminum, wood or concrete. In all these cases, the basic needs of the sealant are the same.

So, what are those basic needs?

Adhesion - To start with, any sealant has to be able to stick well to the surface it's being applied to.  This can vary from sealant to sealant, especially with those which have been designed to stick to specific substrates. Sometimes that makes them a poor choice when used with other substrates.v

Durability - How long will the sealant last when used in accordance with the manufacturer's instructions? This is one of the most common means of stating the life of a sealant, especially those used in architectural applications. Remember, not all materials will last the same amount of time.

Flexibility - The cured sealant usually needs to be flexible in order to withstand changes in the substrates it’s sealing. Sealants are often used in cases where it is necessary for the substrates to be able to expand and contract with the temperature while still maintaining a weatherproof surface. One of the most telling specifications for flexibility is its ability to elongate without breaking; in fact, some sealants can stretch up to 500 percent of their cured size.

Water Resistance - Since water is the main purpose of sealing any surface, it's important to know how well it resists water or steam. Believe it or not, there are some specialty sealants not intended for sealing against water, so this is something to check on. Silicone-based sealants are the best for water resistance.

Additionally, the sealant may need to have these characteristics in certain applications:

Chemical Resistance - Sealants that are used in automotive engines need to be able to withstand the attack of many automotive chemicals, especially gasoline and motor oil. This could also be true in some pieces of equipment used in heavy industry.

High Temperature Resistance - Some repair applications require the ability to withstand temperatures in excess of 500 degrees. This is common when we're talking about engine exhausts, barbecue grilles and furnaces. Special sealants need to be used in these applications.

Gap Filling - Most places requiring sealing have at least some gap between the two pieces of substrate. However, there are applications where this gap is large. In those cases, the sealant needs to have high enough solids content to form a gasket, rather than just seal the surfaces together.  

Paint Adhesion - Not all sealants are compatible with paint. For some applications (like an automotive engine) this doesn't matter but for others like the exterior of a home or a car body, this is imperative. Although silicone is one of the best sealant materials around, paint won't stick to it. To make paintable silicone, the silicone needs to be mixed with other materials that the paint will stick to.

Sika Corporation 106711 Self Lev Sealant

This is the sealant we used to use in the bus plant for sealing joints and fissures in the bus bodies. Made of a combination of polyurethane and silicone, it is one of the few silicone based sealers which is also paintable. Read Full Review

See it at:
    Sika Corporation 106711 Self Lev Sealant

    Loctite 1936537 2 in 1 Sealent

    Loctite has come out with a series of 2 in 1 sealants, which are also adhesives. This particular product is the top in that line, making it just about the most universal sealant I've seen. Read Full Review

    See it at:
      Loctite 1936537 2 in 1 Sealent

      Permatex 80050 Clear RTV Silicone Adhesive Sealant

      This is permatex's pure, clear silicone sealant although they also have it available in other common colors. This sealant offers high adhesion, long life, and great flexibility. Read Full Review

      See it at:
        Permatex 80050 Clear RTV Silicone Adhesive Sealant

        Red Devil 0816 100% Silicone Sealant

        A clear silicone sealant, packed in a caulking tube for those big projects where you need a lot. This sealant forms a water tight seal on a wide variety of automotive and architectural surfaces. Read Full Review

        See it at:
          Red Devil 0816 100% Silicone Sealant

          Permatex 82099 Spray Sealant

          A unique product, this sealant from Permatex is a spray. Designed specifically for sealing off leaks, it can be used on hoses, oil pans and a host of other things that shouldn't be leaking. Read Full Review

          See it at:
            Permatex 82099 Spray Sealant

            Best Silicone Sealant:

            Silicone sealants are generally considered to be the best around since they are highly water resistant and don't age like some other materials used in sealants. It's not uncommon for silicone to last 25 or 30 years without showing any signs of age other than being a little dirty.
             
            The great thing about this is that it makes sealing a "do it and forget it" type of job. If other sealants are used, such as standard acrylic latex painters caulk, you can count on needing to reseal every time you paint. Personally, I'd rather do it once and not have to worry about it, even if it does cost me more money to do it that once.
             
            One of the rubs with silicone sealants, they are more expensive than other sealants. However, over the life of the product, they are actually cheaper, due to their longevity. Basically, the trick is look at the cost as it is spread over the life of the product.
             
            The other rub with silicone sealants is that they're not paintable. Silicone, like Teflon, is a non-stick surface which just about nothing will adhere to. So, if you want a paintable sealant, you need to use a silicone mix. While these are still good and have a much longer life than standard sealants, they don't have as long a life as silicone does.
             
            Silicone sealants have extremely good adhesion to all types of substrates, as long as the surface is clean and oil-free. The cured sealant is highly flexible with the ability to stretch over 400 percent of its original size. Between these two characteristics, there is little chance of a silicone sealant failing.
             
            Although silicone is naturally water-resistant and highly resistant to many chemicals, you should not assume it's automatically resistant to all chemicals. Some types of chemicals, especially automotive chemicals, have solvents in them which would cause damage to silicone sealants with continued exposure. However, for short-term exposure there is little risk of failure.
             
            In cases where consistent exposure to chemicals is expected, specialty silicone sealants should be used and likewise for high temperature applications. While normal silicone sealant is good up to 400 or 450 degrees, special formulations should be used for temperatures higher than that.
             
            Silicone sealants come in squeeze tubes or cartridges for use with a caulking gun. Care should be taken when applying as it can be difficult to impossible to remove the sealants from surfaces which have been covered by accident.

            Permatex 82180 Ultra Black Maximum Oil Resistance RTV Silicone Gasket Maker

            This product is part of Permatex's "ultra" lineup of extreme duty sealants. Designed for engine gasket sealing and replacement, it is highly resistant to oil and other automotive chemicals. Read Full Review

            See it at:
              Permatex 82180 Ultra Black Maximum Oil Resistance RTV Silicone Gasket Maker

              Permatex Ultra Copper Maximum Temperature RTV Silicone Gasket Maker

              Part of their "Ultra" line of sealants, this pick from Permatex, is specifically designed for high temp applications in automotive engines. Not only does it resist high temperatures well, but it can also resist most automotive liquids which can wreck havoc on lesser sealants. Read Full Review

              See it at:
                Permatex Ultra Copper Maximum Temperature RTV Silicone Gasket Maker

                Sika Corporation 106711 Self Lev Sealant

                This is the sealant we used to use in the bus plant for sealing joints and fissures in the bus bodies. Made of a combination of polyurethane and silicone, it is one of the few silicone based sealers which can be painted. Read Full Review

                See it at:
                  Sika Corporation 106711 Self Lev Sealant

                  Star brite Silicone Adhesive Marine Sealant

                  This ideal silicone sealant can be used for just about any application you can find on a boat as it works well above and below the waterline. It is not affected by sunlight, weathering, most chemicals or solvents. Read Full Review

                  See it at:
                    Star brite Silicone Adhesive Marine Sealant

                    3M Marine Adhesive/Sealant 5200

                    3M provides an excellent quality adhesive sealant for marine applications. A gap-filling sealant, this can be used both above and below the waterline to provide a watertight bond which isn't affected by harsh weather or the effects of salt water. Read Full Review

                    See it at:
                      3M Marine Adhesive/Sealant 5200

                      Best Hi Temp Sealant:

                      While sealants all perform the same purpose, not all are created equal. Some applications require special sealants and if ordinary options are used in those cases, they will not last; such is the case of high temperature applications.
                       
                      Most sealants are not designed for use in high temperature applications because most will never see a situation where they are subject to temperatures over 200oF. However, that means when these situations are encountered, using standard sealants only guarantees their failure. One must seek out sealants which are formulated to withstand those high temperatures without failing.

                      More than anything, high temperature sealants are used in automotive applications. Gasoline ignites at 260oC or 500oF. However, parts of the flame can reach over 2000oF. This is why a car's engine needs a cooling system to suck off the heat and dissipate it into the air.
                       
                      While a typical car's engine is not exposed to temperatures in excess of 195oF, the exhaust is regularly exposed to temperatures much higher than that. Therefore, any sealant used on the exhaust, including connecting the exhaust to the engine, must be a high temperature sealant. Otherwise, it will burn up after a while.
                       
                      Typically, there is no sealant used for the exhaust manifold gasket, or the exhaust manifold to exhaust pipe gaskets, so this isn't much of an issue. However, there are times when an exhaust manifold might be warped or damaged and a sealant is required. You might also need a high temperature sealant for a temporary repair to an exhaust pipe, catalytic converter or muffler. Once again, this can't be done without a high temperature sealant.
                       
                      There are a few other applications which require high temperature sealants, either in their normal use or in the process of performing repairs. Repairing a damaged barbecue grille or wood-burning stove would necessitate use of high temperature sealants, as would sealing a piece of glass into a smoker you're building. Charcoal burns at 2,700oF, creating an amazing amount of heat. A problem with a gas-burning furnace can often be handled with a high temperature sealant, eliminating the need to buy high dollar, hard to find parts.
                       
                      Pretty much all high temperature sealants are made of silicone, so they can't be painted. They often have fillers added, in order to assist in withstanding the high temperatures. Some are actually made so as to be food safe, which is what you want to use for repairing that barbecue grille. Others are designed for superior bonding, allowing the sealant to be an adhesive as well.

                      Blue Magic 8024 ThermoSteel High-Temp Metal Repair

                      If you need extreme heat resistance, this is the sealant for you. Able to withstand 2400 degrees, this one beats anyone else out there. This manufacturer also produces other high temp sealants, which aren't quite as extreme. Read Full Review

                      See it at:
                        Blue Magic 8024 ThermoSteel High-Temp Metal Repair

                        Permatex Ultra Copper Maximum Temperature RTV Silicone Gasket Maker

                        Part of their 'Ultra' line of sealants, this one, from Permatex, is specifically designed for high temp applications in automotive engines. Not only does it resist high temperatures well, but also all automotive liquids, which can wreck havoc on lesser sealants. Read Full Review

                        See it at:
                          Permatex Ultra Copper Maximum Temperature RTV Silicone Gasket Maker

                          Deacon Crow-Seal #4402 High Temp Sealant

                          Primarily an industrial hi temp sealant, this one from Deacon withstands temperatures up to 200 degrees. It provides a sure seal between any metal surfaces, but is not recommended for use around water or steam. Read Full Review

                          Deacon Crow-Seal #4402 High Temp Sealant

                          Permatex 81160 High-Temp Red RTV Silicone Gasket

                          Probably the most common hi temp sealant around; this red RTV silicone gasket maker from Permatex will meet pretty much any automotive need. It can be used as a gasket sealer or in place of the gasket, forming and filling gaps to make its own gasket. Read Full Review

                          See it at:
                            Permatex 81160 High-Temp Red RTV Silicone Gasket

                            Sil-Bond RTV 6500 Food Grade Silicone Sealant Adhesive Red Hi-Temp 2.8oz

                            Another industrial sealant, this high temp product comes in caulking tubes for high volume use. It has superior adhesion on all types of metals, as well as ceramic, tile and glass. Read Full Review

                            Sil-Bond RTV 6500 Food Grade Silicone Sealant Adhesive Red Hi-Temp 2.8oz

                            Best Auto Sealant:

                            Cars and trucks have a lot of sealants in them; sealants for the engine, sealants for the floor, sealants for the windows and sealants for the doors. There really is no one sealant that's used throughout a car. I remember when I was engineering in the bus plant and we measured the sealant we used in the buses by the pounds.
                             
                            Each application requires a sealant that works for that particular need. But overall, there are three major qualifications for automotive sealants; the ability to withstand heat, automotive chemicals and vibration; if it can accomplish all three, it's pretty good.
                             
                            Typically, you'll find sealants that can withstand two out of the three qualifications mentioned above. That's not a problem if the sealant is used in an area where it doesn't need to deal with the third one. For example, a sealant that can't handle automotive chemicals, but can handle vibration and heat can be used anywhere but in the engine. One that can handle the chemicals but isn't good with vibration can still work in the engine, but not for the body.
                             
                            Silicone is one of the best materials for use in sealants, because of its ability to withstand all three of those issues. The problem with silicone is that nothing sticks to it so it can't be used in areas where the vehicle has to be painted, regardless of the type of paint being applied. The solution to this problem is to make a sealant that combines silicone with other materials which paint can bond to.
                             
                            Sealants used in the engine compartment need to be able to withstand oil and anti-freeze, both of which are rather harsh on sealants but fortunately silicone is good at this, as well as a few other materials. It's not uncommon for the seals and gaskets in an engine to dry out, especially if it's not used much. In these cases, applying a sealant may be a means of stopping the leak without having to take the engine apart. However, the right way is to take the engine apart.
                             
                            If the engine is taken apart, then there are automotive sealants which will act as gasket makers, replacing the original gaskets. This is especially useful for older vehicles, where the original gaskets may no longer be available. Silicone gasket sealer actually makes a better gasket than the original in many of these cases.
                             
                            I've selected some of the finest automotive sealants here, giving you a good selection to choose from, for a variety of automotive applications.

                            Permatex 82180 Ultra Black Maximum Oil Resistance RTV Silicone Gasket Maker

                            This product is part of Permatex's 'ultra' lineup of extreme duty sealants. Designed for engine gasket sealing and replacement, it's highly resistant to oil and other automotive chemicals. Read Full Review

                            See it at:
                              Permatex 82180 Ultra Black Maximum Oil Resistance RTV Silicone Gasket Maker

                              Sika Corporation 106711 Self Lev Sealant

                              This is the sealant we used to use in the bus plant for sealing joints and fissures in the bus bodies. Made of a combination of polyurethane and silicone, it is one of the few silicone based sealers which is also paintable. Read Full Review

                              See it at:
                                Sika Corporation 106711 Self Lev Sealant

                                3M 08008 Black Super Weatherstrip Adhesive

                                An adhesive specifically designed for use with automotive weather-stripping, able to adhere well to both metal and rubber. That makes this sealant from 3M one that everyone needs in their toolbox. Read Full Review

                                See it at:
                                  3M 08008 Black Super Weatherstrip Adhesive

                                  DAP Auto/Marine 100% RTV Silicone Sealant

                                  This clear silicone sealant is rated for use in both automotive and marine applications. The cured sealant is highly waterproof and weather resistant. Read Full Review

                                  See it at:
                                    DAP Auto/Marine 100% RTV Silicone Sealant

                                    Amazing Goop Automotive Contact Adhesive and Sealant

                                    A very unique product, designed specifically for automotive repair. While it can be used as a gasket adhesive and sealer, it's true value comes out when used for repairs of everything from upholstery to vinyl tops. Read Full Review

                                    See it at:
                                      Amazing Goop Automotive Contact Adhesive and Sealant

                                      Best Marine Sealant:

                                      Marine applications are a special challenge for sealants, as they’re often immersed in or surrounded by water. Even in cases where the sealant is not immersed, it’s constantly being splashed by water, so the sealant needs to be especially resistant.
                                       
                                      In many cases, different sealants are used for applications above the waterline than those used for applications below the waterline. Sealants which contain water-absorbing materials, such as talc, can fail if left submerged for too long. Older silicone sealants had this problem as well, but modern ones can be immersed without problem.
                                       
                                      The problem usually isn't the ability of the sealant itself being able to withstand the water, but the sealant to substrate bond being able to withstand it. That's the weakest point in any place where sealants are used. To combat this, marine sealants need to feature especially strong adhesion with the ability to flow into irregularities in the surface of the substrate.
                                       
                                      In most cases, marine sealants are not painted, so it's possible to use silicone for the sealant. Silicone has excellent adhesion and water resistance, but paints cannot bond to it. However, this means that the sealant needs to be applied carefully so as to avoid a messy seam which will never go away.
                                       
                                      The two main issues with these sealants are flexibility and strength. Marine hulls are flexible so as to withstand the strain of constant pounding they receive in the water. The sealants used for them must be flexible as well in order to maintain contact with the hull as it moves. But some sealant applications are more than just sealing as they are functioning as adhesives as well. In those cases, strength is extremely important since flexing won't help if the sealant itself tears under the strain.
                                       
                                      Finally, the sealant used must be compatible with the substrate. Chemicals used in the manufacture of some sealants can act as solvents for some of the materials used in boat manufacture. If the wrong combination is used, it can end up weakening the hull, rather than strengthening it.

                                      Star brite Silicone Adhesive Marine Sealant

                                      This ideal silicone sealant can be used for just about any application you can find on a boat as it works well both above and below the waterline. It's not affected by sunlight, weathering, or the corrosive effects of most chemicals or solvents. Read Full Review

                                      See it at:
                                        Star brite Silicone Adhesive Marine Sealant

                                        3M Marine Adhesive/Sealant 5200

                                        3M provides an excellent quality adhesive sealant for marine applications. A gap-filling sealant, this can be used both above and below the waterline, it provides a watertight bond which isn't affected by weather or salt water. Read Full Review

                                        See it at:
                                          3M Marine Adhesive/Sealant 5200

                                          DAP Auto/Marine 100% RTV Silicone Sealant

                                          A clear silicone sealant, this product by Dap can be used in locations where the visibility of the sealant is not desirable. It stays flexible when cured, despite exposure to extreme weather conditions. Read Full Review

                                          See it at:
                                            DAP Auto/Marine 100% RTV Silicone Sealant

                                            Eclectic Amazing Goop Marine

                                            Amazing Goop is truly amazing as this sealant works in all outdoor applications, not just marine conditions. Formulated to be UV resistant, it isn't affected by exposure to sunlight or even extreme weather conditions. Read Full Review

                                            See it at:
                                              Eclectic Amazing Goop Marine

                                              Travaco Gluvit Epoxy Waterproof Sealer

                                              This product is a bit different than the others, being a two-part epoxy. It excels in applications which require gap filling, strengthening, and sealing surface irregularities. Read Full Review

                                              See it at:
                                                Travaco Gluvit Epoxy Waterproof Sealer

                                                Best Foam Sealant:

                                                Foam sealants are purely an architectural sealant, used for sealing the exterior of buildings. They are unique in this category, both in the way that they work and their purpose. Unlike other sealants, these are porous and expand once sprayed in place so that they can fill cracks and holes in the exterior walls of homes. As such, they are predominantly used as gap filling sealants, rather than to seal two adjacent or overlapping surfaces together.
                                                 
                                                More than simply providing a waterproof seal, these sealants provide an insulating seal. Yes, they are waterproof, but not in the same sense that silicone sealant is. Left to soak in water, these sealants probably wouldn't fare all that well. But to have water hit them (such as rain falling on the side of a house) they can more than withstand that.
                                                 
                                                To use these sealants, a short tube is attached to the nozzle which is inserted into the crack to be sealed, allowing the foam sealant to be applied directly where needed. The foam starts expanding even before leaving the hose and fills the gaps it is squirted into.
                                                 
                                                The expanding action of the foam comes about because of a chemical reaction in the foam itself when it mixes and hits air. Air bubbles form in the sealant which is what causes it to expand. Those air bubbles are what gives it the ability to work as insulation as well, as any good insulation needs thousands of small air pockets in it.
                                                 
                                                Once expanded, the sealant hardens and fills the crack or opening with rigid plastic foam, similar to Styrofoam. This can be shaped by cutting and sanding to make the foam sealant conform to the surrounding surfaces. However, cutting leaves a porous surface exposed rather than a smooth one. Therefore, once cut, the surface should be painted to retain a waterproof surface.
                                                 
                                                This type of sealant has a very high adhesion, especially when working with uneven surfaces. The expansion of the foam causes it to conform very well to those surface irregularities. Once hardened, it puts constant pressure on those surfaces, locking the sealant in place. The sealant itself is more likely to break, than it is to break contact with the surface.
                                                 
                                                Old sealant can be removed for replacement or remodeling, but it won't clean off the surfaces well. Rather, the sealant itself is cut, leaving a rough film on the surface. This residue can be sanded smooth, essentially returning the substrate surface to a like-new condition.

                                                The one drawback to this type of sealant is that the container is rarely reusable. Once the sealant has been opened and sprayed, it's necessary to use the whole container. If the sealant isn't used all at once, it probably won't come out the second time someone tries to use it since sealant stuck in the nozzle and tube cannot be removed like caulking in a nozzle can. Even if it were removed from the outer part of the nozzle and tube, the mixing chamber in the nozzle is not accessible for cleaning.

                                                Great Stuff Pro Gaps & Cracks 24oz Gun Foam

                                                Using a 'pro' version of these sealants eliminates their biggest problem, that of having to throw away an open can. This sealant uses a separate gun, which is cleanable for use time and time again. Read Full Review

                                                See it at:
                                                  Great Stuff Pro Gaps & Cracks 24oz Gun Foam

                                                  GREAT STUFF Big Gap Filler Insulating Foam Sealant

                                                  The consumer packaged Great Stuff Big Gap Filler allows you to seal and insulate gaps up to three inches wide. One 20 ounce can fills the equivalent space of 30 tubes of caulking. Read Full Review

                                                  See it at:
                                                    GREAT STUFF Big Gap Filler Insulating Foam Sealant

                                                    Owens-Corning 627720 Insulating Foam Sealant for Gaps and Cracks

                                                    Designed to go with their Owens-Corning insulation line, this foam sealant provides excellent expansion and insulation. The nozzle provides a one inch bead, which can be layered to give you three inches. Read Full Review

                                                    See it at:
                                                      Owens-Corning 627720 Insulating Foam Sealant for Gaps and Cracks

                                                      Touch 'n Foam 4001031212 MaxFill Maximum Expanding Sealant

                                                      Designed for maximum expansion, this foam sealant focuses on providing insulation, more than weatherproofing. That doesn't mean that it isn't a good weatherproofer though. It's ideal for use around pipes that pierce your walls, sealing that gap from the weather and from insects. Read Full Review

                                                      See it at:
                                                        Touch 'n Foam 4001031212 MaxFill Maximum Expanding Sealant

                                                        CRC Minimal Expansion Foam Sealant

                                                        This product actually comes from an automotive products manufacturer. As such, they've formulated it for minimal expansion, wanting a stronger sealant, when cured. Works great for crack filling, both in homes and autos. Read Full Review

                                                        See it at:
                                                          CRC Minimal Expansion Foam Sealant
                                                          Leave a Question or Comment