Will this be a problem?

[1Clown]

Noticed my Kessil mount's black paint or whatever it is has erroded away and the bare metal is now exposed to the water.

 

[WIReefer]

If it’s sitting in the water then yes I would think it will be an issue.

 

[...]

Yes, it can release harmful toxins and heavy metals into the water column.

 

[1Clown]

Well that sucks, really don't want to spend £130 just to get 2 mounts for those specific parts.

 

[vetteguy53081]

You can coat it with clear aquarium sealant to waterproof it