Greg, please reread the article, you missed the last paragraphs, apparently:
"In an article published in Nature Communications this week, the University of Manchester team shows that it is possible to tightly close those nanocapillaries using simple chemical treatments, which makes graphene films even stronger mechanically as well as completely impermeable to everything: gases, liquids or strong chemicals. For example, the researchers demonstrate that glassware or copper plates covered with graphene paint can be used as containers for strongly corrosive acids.
The exceptional barrier properties of graphene paint have already attracted interest from many companies who now collaborate with The University of Manchester on development of new protective and anticorrosion coatings.
Dr Nair said “Graphene paint has a good chance to become a truly revolutionary product for industries that deal with any kind of protection either from air, weather elements or corrosive chemicals. Those include, for example, medical, electronics and nuclear industry or even shipbuilding, to name but the few.”"
Nevertheless, out of curiosity, I look in Calder's 'Boatowners Electrical and Mechanical Manual,' 3d edition, page 199, Table 5-1 Galvanic Series of Metals in Seawater, and note that the most noble/passive listed is.... graphite.
BTW, and what about the copper in your bottom paint right now?