El Grifo,
The Olympus compressor blades were all treated with 'Rockhard' stove enamelling, to help protect against erosion and corrosion of the aluminium alloy blades.
I can't tell you exactly what it contains unfortunately, but I've found
this link which may help.
There is reference on there to the green stove enamel resin being applied to the Pegasus engine compressor blades, and given that the Olympus and Pegasus were both Bristol designs, I'd suggest it's fundamentally the same stuff.
Hope that's of some use.
