hull coatings - Graphite Powder mixed with epoxy

can Graphite Powder mixed with epoxy to produce exterior coating be a long lasting and uv resistant hull coating?

 

Maybe, but it's not waterproof. It absorbs moisture and can be pulled off with your fingernail after any time underwater.

 

Graphite thickened epoxy coatings, used on boat bottoms are typically for the really anal racer, that needs to have some kind of edge. Wet sanding with 2,500 grit isn't enough so they try graphite, which does produce a smooth slippery surface, but it really doesn't matter all that much unless the boat is quite small.

As far as it being a long lasting UV inhibiting coating, well no not really. It's better then a straight epoxy coating but still exposes the epoxy to enough UV to break down the surface molecules. As these sluff off under way, new less damaged molecule segments are exposed and the story continues until surface degradation is noticeable.

 

Never paint the outside of a boat BLACK....it will attract heat...melt, deteriorate, delaminate, change shape, before your eyes. Graphite power makes a great slippery surface. Not for underwater , but for anything that must slide against itself..like a companionway hatch runner.

 

An unfilled, good quality epoxy resin will have good UV resistance, absorb much less moisture (than filled epoxy) and can be applied to form a smooth layer that can be polished further. Graphite is 'slippery' only due to its' platelike structure - the surface breaks away easilt. Adding ingredients of low surface energy e.g. PTFE. FEP etc is possible, but will add its' own problems - these ingredients will not bond into the epoxy without chemical etching & priming (which is probably not ecenomically viable), they will therefore pull out of the surface and leave pock marks. They will also probably form a rougher initial surface.

 

I thought epoxy was not UV resistant on its own.

 

Epoxy is not UV resistant. Either paint it or add a UV filter of Aluminium powder. Best to paint .