Common Reasons for Sealant Failure

Summary: Sealants can fail due to product incompatibility, poor surface preparation, improper maintenance, or clogging—understanding these causes helps ensure better durability and performance.

1) Product Incompatibility

Some sealants and some paints just don’t work with each other. It’s not something you can really control — it’s just bad luck. Every product out there has a few “nemesis” paints on which it simply does not work.

2) Improper Surface Preparation

Especially oily substances can form a layer on the paint that prevents proper adhesion, as it doesn’t allow the sealant to make contact with the paint. These substances can only be removed with a panel prep or tar remover (but be careful — tar remover can and will damage your rubber and plastic trim if you’re not careful).

Old sealants can sometimes also prevent proper adhesion, but more often than not this is a non-issue. That’s why my personal opinion is: slap it on, see if it works, and if not — eh, you’ll need to do a strip wash. This is of course mandatory for actual coatings, never apply a real coating over old sealant residue!

3) Improper Maintenance

Neglect

Not washing the car at all, or washing it too rarely, will cause the sealant or coating to become overly stressed and worn. A sealant or coating is a tool to make washing easier — not a permission to neglect the car.

Chemical degradation

Using cleaners that are too strong for the sealant, and doing so too frequently, can lead to premature failure. For most coatings (YMMV — check with your manufacturer!), the “safe zone” is between pH 2 and pH 12.

HOWEVER, just being within that range does not automatically mean a product is safe for coatings or sealants. Other strong cleaners — especially iron removers, tar removers, waterspot removers, and alkaline cleaners — can still cause damage. Not every sealant is as chemically resistant as a coating. For example, a carnauba wax–based product needs far more gentle care.

4) Clogging

Clogging means the sealant isn’t dead, but something is sitting on top of it that disturbs or masks its properties.

The most common case is clogged coatings that have a layer of mineral contamination and just need an “unclog” wash.

Improper washing chemicals can also cause this. There are several shampoos known to clog coatings because they contain gloss additives that mask the coating’s true behavior. Weaker sealants that are chemically incompatible can also clog stronger sealants or coatings. This is especially problematic with drying aids.