David, Its the epoxy word thats significant. Coal Tar Epoxy is used to coat
steel pipes and equipment in sewage treatment plants so you may gather it
can withstand all sorts of acidic substances and has a long life. However, I
don't know how it withstands the wear caused by rushing through water.
I have no experience of that.
Wilf

Here in Thailand it is widely used on steel boats and boats with cast
iron keels ( our 42' ketch) lasts for many years especially when
overcoated with anti-foul. Coal Tar Epoxy is as the name suggests - an
epoxy.

Tony
S/V Ambrosia