Cat urine is an especially difficult contaminant to deal with, especially if it’s a long-term problem.
While nothing may fully eliminate odors from long-term staining, there are a couple of easy things to try before resorting to some kind of coating.
A commercial pet stain and odor-removal product would be a first choice. Another worthwhile alternative would be to cover the stained areas with activated charcoal, available at pet stores and perhaps pharmacies.
This is a treated charcoal with legendary ability to absorb chemicals and odors, functioning like a chemical magnet. This should be spread on the affected areas and renewed every couple of days. Try this for a week or two.
— Alan J. Heavens