8 Things That Flex Seal Tape Will Not Stick To

You've seen the infomercials: Flex Seal Tape can stick to almost anything! It even works underwater to patch up leaks and holes. But which things will Flex Tape not stick to? We have done research and put together a list for you in this post!

Flex Tape cannot stick to the surfaces of certain materials, as well as items that are subjected to high pressure and high temperatures. These include the following:

  • Radiator Hoses
  • Gas Tanks
  • Oil Tanks
  • Tires
  • Siliconized surfaces
  • Greasy surfaces
  • Water-repellent surfaces
  • Chemical surfaces

Though there can be some exceptions, test out some Flex Tape on your material to see if it will stick or not. In some cases, it might stick to the things in the list above but is not recommended for use.

For a more detailed explanation on the items mentioned in this list, check out the rest of this post! We will explain some of the basic ideas behind how Flex Tape works and why it can and cannot stick to different materials. If you want to learn more, read on!

Containers of Flex seal for sale at a store, 8 Things That Flex Seal Tape Will Not Stick To

Why Won't Flex Seal Tape Stick?

Flex Tape is meant to work right away and takes around 24 hours to completely bond. Though the adhesive on Flex Tape is strong, it is not completely compatible with every material out there.

There are only a number of conditions that adhesive can stick to. Some factors like the pressure, temperature, and type of chemical present will affect the ability of Flex Tape adhesive to bond.

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Flex Seal containers for sale at a store

Here is the list of things that Flex Tape will not stick to and why:

Radiator Hoses

You would think that Flex Tape would work just fine on radiator hoses, but this is not the case. The Flex-Seal brand even advises against using Flex Tape on radiator hoses. 

Radiator hoses connect between the engine, radiator, and water pump of your vehicle to move the engine coolant around. Naturally, this creates a lot of heat and pressure building up through the hose.

While Flex Tape may stick to the hose, it will not last for long. The pressure from the mechanism will leak out, while the constant heat will prevent the Flex Tape from completely setting.

Gas Tanks And Oil Tanks

Flex Tape can also initially stick to your gas or oil tank, which are usually made out of metal. But, similar to to hoses, it is not recommended. The pressure and heat from your gas or oil tank will prevent the tape from staying secured for long.

This can also be a safety hazard. If you try patching up a hole in the body of your tank, the gas or oil content will still be able to leak. Flex Tape is strong enough to bond but not to keep other elements from passing through.


The ridges on tires can make it difficult for your Flex Seal Tape to stick. The high pressure a tire goes through on the road will also keep Flex Seal Tape from sticking. This goes for most tires, whether it be for a car, motorcycle, or bike.

According to Flex Seal, their Flex Tape is only recommended for normal hydrostatic pressure. While it has a rubber-like backing that makes it flexible yet sturdy enough to contort onto a surface, it is not as leakproof as the infomercials make it out to be.

Flex Seal Tape can be a decent temporary fix in the case of any damage, but it is quite literally a band-aid solution. The best way to address any damaged tire would be through vulcanizing or a replacement.

Siliconized Surfaces

Flex Tape will not stick to siliconized surfaces. The adhesive will simply not bond.  Silicone is a plastic and may be considered a rubber, but it is still a different material altogether.

Flex Seal Tape can stick to some rubber materials. If you are trying to stick Flex Seal Tape onto a rubber surface but it will not stick, then you may have silicone or a silicone blend on your hands.

In the same vein, Flex Seal Tape will not stick to paint. An alternative you could go for in the case of painted surfaces would be Flex Seal Spray.

Greasy Or Oily Surfaces

Greasy or oily surfaces are not very friendly to Flex Tape. Though you can use the tape underwater, grease and oil are a completely different story. If you plan on using Flex Tape on any greasy surface that it would typically stick to, give it a clean first.

The simplest way to clean grease off a surface is with soap and water. But, this could vary depending on what you are cleaning. Your Flex Tape should be able to stick once the surface is clean, and if it is not made of anything else on this list!

Water-repellent Surfaces

Flex Seal Tape will not stick to water-repellent or hydrophobic surfaces. These types of surfaces repel water molecules, which include greasy surfaces, as we mentioned above.

Some other types of hydrophobic surfaces are made with a rough surface of water-repellent material. This makes it difficult for the adhesive on Flex Tape to lay evenly and bond to the surface.

Chemical Surfaces

Acids, mineral spirits, acetone, and the like are all harsh chemicals that will break down the adhesive on Flex Tape. If possible, you could probably clean chemicals off the surface you are going to stick the tape on to make it work.

What Will Flex Seal Tape Stick To?

A Flex seal stall at a store

While less powerful on porous surfaces, Flex Tape is still able to bond with a little heat. Try using a hair dryer when setting it on for the first time. In 24 hours, the tape should strongly adhere to the surface.

Click here to see Flex Tape on Amazon

As advertised by Flex Seal Products, their Flex Tape works on metal, steel, PVC, copper, aluminum, acrylic, glass, wood, rubber, stone, ceramics, and fabric, just to name a few. The list on the brand website is twice as long and non-exhaustive!

A key selling point for Flex Seal Tape is that it works even under water. As long as the material is compatible with the tape, it will stick no matter how wet.

Overall, just look out for the eight things we mentioned above when working with Flex Seal Tape. They are not likely to stick. But chances are, most of the things you are trying to tape will work.

Click here to see Clear Flex Tape on Amazon

Is Flex Seal Tape Removable?

Once you let your Flex Seal Tape set, it will not move from its position. Its adhesive is so strong that you will need to use an adhesive remover if you want to get rid of it. Flex Seal offers their own brand of adhesive remover

There are alternatives to the Flex Seal brand of adhesive remover on the market.

Click here to see Goo Gone Adhesive on Amazon

Do note that Flex Seal brand adhesive remover is made with Flex Seal products already in mind, so it should be guaranteed to work for Flex Tape.

The Flex Tape Adhesive Remover comes as a spray to help peel away any tape. It also works on other types of tapes. If you are worried about having to clean any adhesive residue, you can simply use the adhesive remover.

Does Flex Seal Tape Work?

A store shelf filled with lots of Flex seal containers

Flex Tape boasts superior holding and staying power, as well as water resistance. Based on the label, Flex Tape claims to bond to a large number of surfaces. However, it does not claim to be a permanent fix.

Rather, Flex Seal Tape is best as a temporary or emergency repair solution. So if you are mending anything with Flex Tape, you will still need to get it properly fixed or replaced.

Flex Tape is waterproof and can be used to patch up leaks temporarily. However, you will need to take care with its application. Some people find that Flex Tape is not as leakproof as it claims, likely due to high water pressure or improper application.

There is another variant of Flex Seal Tape called Flex Tape MAX. This version claims to cover 400% more than the classic Flex Tape. If you need more strength from a waterproof material, then it may work better for you.

A more permanent option is Flex Seal, a waterproof liquid sealant. Like Flex Tape, it will take 24 to 48 hours to completely bond, or in this case, cure.

Wrapping Things Up

Containers of Flex seal for sale at a store

While Flex Tape advertises itself as a triple-thick adhesive that virtually welds to the surface, Flex Seal Tape does not stick to every surface.

If you are planning to repair something that it does not stick to, try another one of their products, such as the Flex Seal Spray or their basic Flex Seal.

Did you find this post helpful? Check out our other articles before you go!

Can You Use Flex Seal On Shower Floor?

What's The Best Adhesive For Transition Strips?

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