From the FAQ:
"Can you use Ultra-Ever Dry where it is continuously submerged in water or liquid, like the inside of a pipe with constantly flowing liquid?
No, this is not a good application. The reason is the nano-coating relies on a barrier of oxygen/air to form the bar- rier on the surface of the material it is coating. Unless the coating can become exposed to air every now and then, it cannot “recharge”. So coating the inside of continuously flowing pipes is not a prime application. If it is intermittent usage, it may work well. Steel coated with Ultra-Ever Dry has been immersed in salt water for 30 days without any effect."