Evaluated Alternative FR CROS – Halogen free flame retardant for coating systems The FR CROS® Series provides halogen-free ammonium polyphosphates for intumescent coating systems. FR CROS® specialties are key ingredients in intumescent paints and coatings influencing the performance and stability of the finished coating. They ensure the long-term bearing capacity of the steel beam in case of fire. FR CROS improves the fire resistance of steel.