Urethane resin conformal coatings are very resistant to chemical solvents. They are second only to parylene conformal coating in their resistance. Applications that require any prolonged exposure to harsh chemical solvents should consider urethane resins.
Tin Whisker Mitigation
Long term NASA studies have shown that urethane conformal coatings are one of the few ways to successfully mitigate tin whisker growth. Since there is no known way to completely eliminate tin whisker growth, you have to select a proper tin whisker mitigation strategy. Urethane conformal coatings are a great place to start.
For applications that can see any direct mechanical wear against the coating should consider urethane conformal coatings. Urethane resins are very hard and resistant to mechanical wear. Their hardness is second only to epoxy conformal coating, but urethanes are much easier to be reworked than an epoxy.