Anti-Graffiti coatings are found in two basic categories: Permanent and Sacrificial.
Sacrificial Coatings, almost without exception, are water-based. Some cause minimal darkening of concrete, etc; as well as being able to protect – to an extent – more sensitive surfaces such as acrylic or plastic paints, sign writing, etc.
Permanent Anti-graffiti Coatings are normally two-pack polyurethane, epoxy or so-called “iso-free urethanes”.