What will Flex Seal not stick to?

Author: Mr. Marc Lockman  |  Last update: Saturday, May 23, 2026

What Does Flex Seal Spray Not Work On? We do not recommend using Flex Seal on foam. Some foams may react poorly with Flex Seal, and may warp or dissolve. We also do not recommend using it in situations where it is subjected to high heat or pressure (such as engine radiators) or gas tanks.

What does Flex tape not stick to?

Flex Tape may not work on some siliconized surfaces, greasy surfaces, water-repellent surfaces, or surfaces with harsh chemicals present (acids, mineral spirits, acetone, etc.) Please note that Flex Tape is only recommended for normal hydrostatic pressure.

What will Flex Seal bond to?

A: Yes, Flex Glue is designed to be super thick. It bonds to porous substrates such as brick, concrete, mortar and so much more.

What will Flex Seal not stick to on concrete?

I have used Flex Seal to close up cracks in concrete. However if the surface you apply the Flex Seal to is "granular" and flaking off, the Flex Seal will not stick to it. Keep in mind that Flex Seal is a coating, not a bonding agent.

Does Flex Seal stick to metal?

Flex Seal can be used on almost every surface: wood, metal, tile, concrete, masonry, fabric, glass, plastic, aluminum, porcelain, drywall, rubber, cement, and vinyl. Plus, it won't sag or drip in the summer heat, and it won't crack or peel in the winter cold. It even prevents corrosion.

EVERYTHING you NEED to Know About FLEX SEAL *How to apply*

Where should you not use Flex Seal?

We do not recommend using Flex Seal on foam. Some foams may react poorly with Flex Seal, and may warp or dissolve. We also do not recommend using it in situations where it is subjected to high heat or pressure (such as engine radiators) or gas tanks. We do not recommend the use of Flex Seal spray on vinyl.

Will Flex Seal stick to stainless steel?

A: It should work in a stainless steal sink that holds water. Keep in mind, you may need to apply several coats in order for it to fully seal the seem. I used this product on the water tank of my daughter's free-standing basketball unit.

How long does Flex Seal last?

Depending on the environment, coats added, and maintenance, many people have found Flex Seal will last for years without cracking, peeling, or losing any of its strength or sealing properties.

What materials dont stick to cement?

Molds: Most concrete molds are made from urethane rubbers that resist concrete bonding. Paint: There are no natural bonding agents in paint. Oil: Oil or oiled surfaces create a film that prevents concrete from sticking.

Will Flex Seal seal a crack in concrete?

Yes, you can use Flex Seal Spray on concrete. Flex Seal seeps into cracks and holes and dries to a watertight, flexible rubberized coating.

What happens if Flex Seal gets wet?

Once dry, Flex Seal's watertight, rubberized coating can withstand water, heavy rains, snow, and more. Flex Seal can be applied to a wet surface or moist environment in the event of an emergency. However, it will always adhere better to a clean, dry surface.

Is Flex Seal really waterproof?

Flex Seal floated our boat, and Teddy stayed dry. But with other uses, we hit rough seas. It took three coats of Flex Seal to plug the pipe holes, and larger holes blew out under water pressure. Even three coats didn't seal vertical sections of our gutter's end caps and joints: The product dripped down.

Is Flex Seal rubber or silicone?

Flex Seal is liquid rubber in a can.

How permanent is Flex Tape?

While Flex Tape can last for years without cracking, peeling, or losing its sealing abilities, it is intended as a temporary fix until a more permanent solution can be achieved. The length of time Flex Tape will last depends on factors such as the application type and environment.

What surfaces does tape not stick to?

Some surfaces like polyethylene or PVC or concrete are especially hard to adhere. A tacky tape will help, but if not, try a different roll and see if the trouble persists. Or as described above, try the tape on a flat, clean glass or metal surface.

Will Flex Seal stick to polypropylene?

Flex Seal Spray is great at sealing out water, air and moisture by providing a strong, flexible and watertight seal. Polypropylene is a type of plastic that might resist adhesion depending on the amount of olefins it contains.

Does silicone stick to concrete?

Neutral curing silicones are therefore suitable for metallic surfaces such as copper, brass, bronze, zinc, and iron. It is also compatible with alkaline surfaces such as concrete, plaster and brick.

Does concrete stick to aluminum foil?

…”Concrete shall not come in contact with any aluminum during conveying and placing operations.” Different forms and shapes of metals: Conduit, pipe, sheet and forming shapes. Fresh concrete corrodes aluminum with subsequent release of hydrogen.

Is Flex Seal a permanent fix?

Flex Tape is a temporary, emergency repair and is not meant to be a permanent fix.

Can Flex Seal be removed after it dries?

If the Flex Seal is still wet, it can be removed with a dry cloth or paper towel. If the Flex Seal is cured/dry, it can be removed with acetone, denatured alcohol, or mineral spirits. When using solvents to remove Flex Seal, make sure to read the instructions and follow all safety precautions.

What is similar to Flex Seal?

Flex Seal's top competitors include 58 Foundations & Waterproofing, Menkol, and Applied Adhesives. 58 Foundations & Waterproofing provides home repair and improvement services focused on foundation, basement, and crawl space areas.

Does Flex Seal work as waterproofing?

Flex Seal Liquid is thicker than paint and dries into a strong, rubberized coating. It can also help seal out air, water, and moisture and is chemical and mildew resistant - making it a great choice for your basement walls. Start by taping off the walls you will be waterproofing with blue painter's tape.

Can Flex Seal go over rust?

Flex Seal Liquid is an excellent option for resealing an RV roof. Also, if you notice rust spots on the roof of your car or truck, a layer of Flex Seal Liquid can help to protect it from any further deterioration.

Will Flex Seal stick to concrete?

Flex Seal Liquid is optimal for sealing, repairing, and weatherizing concrete. It works by sealing out air, water, and moisture and is mildew, chemical, and UV resistant. You can either brush, roll, dip or pour the liquid directly onto the concrete surface.

Previous article
Can I use 10^3 wire for an air conditioner?
Next article
What contains boric acid?