Graphite corrosion rates due to Cl2 at high temperatures have been shown to be very low; please see reference below:

Article Chlorine corrosion of graphites and technical carbons - I. R...

However, graphites are porous to varying degrees, and you would need to consider diffusion through the graphite, sorption, etc. as well as structural considerations (due to e.g. pressure, and fittings needed for connection) as it can be fragile/brittle.

Dear Lukas,

thanks for your helpful answer.