My boat has been attacked by a coral infestation which looks like lots of little vines on the hull. The majority comes off with the power wash but the shapes are still stuck to the hull. If I sand it then the Coppercoat will also be removed. Does anyone know of a way to remove the residue?

Acid wash, you can try industrial vinegar or ascetic acid.

Thanks, I'll try

Don't use acetone

forums.ybw.com/threads/coppercoat-advice.187844/page-2#:~:text=A%20couple%20of%20contributors%20mention,off%20with%20some%20general%20advice.

For acid wash or industrial vinegar suggest as mandatory to check with Coppercoat directly before you do anything.

forums.ybw.com/threads/coppercoat-cleaning.604105/

Scotchbright with Metal Gleam. Don't waste time with vinegar. Life is too short.

I was under the impression that copper coat needed to be sanded occasionally to expose fresh copper, but I have been wrong before

Please communicate with Coppercoat

coppercoat.com/

Thanks for the replies everyone. yes Coppercoat does have to be abraded from time to time. I didn't do it last time out but should have!
I have contacted Coppercoat in England and they have given advice.