Expert Tips: What Not to Use Flex Seal On

As an expert in the field, I have seen many people use Flex Seal for various purposes. While it is a versatile product with many uses, there are certain things that you should not use it on. In this article, I will share my knowledge and experience to help you make informed decisions when using Flex Seal.

Do Not Use on Foam

One of the most common mistakes people make is using Flex Seal on foam. This is not recommended as some foams may react poorly with the product, causing them to deform or dissolve.

It is always best to test a small area first before applying Flex Seal on foam surfaces.

Avoid High Temperatures and Pressures

Flex Seal is not suitable for use in situations where it is subject to high temperatures or pressures. This includes areas such as engine radiators or fuel tanks. The extreme heat or pressure can cause the product to break down and lose its effectiveness.

Stay Away from Vinyl

Another surface that you should avoid using Flex Seal on is vinyl. The chemicals in the product can cause damage to vinyl surfaces, leading to discoloration or even deterioration.

If you need to seal something made of vinyl, it is best to use a product specifically designed for that material.

Other Surfaces to Avoid

In addition to foam and vinyl, there are a few other surfaces that are not suitable for Flex Seal. These include rubber, plastic, and polystyrene. Again, it is important to test a small area first before applying the product to these surfaces.


In conclusion, while Flex Seal is a great product for many purposes, there are certain surfaces that you should avoid using it on. These include foam, high-temperature or high-pressure areas, vinyl, rubber, plastic, and polystyrene.

By following these tips, you can ensure that you are using Flex Seal effectively and safely.