Cause of Worn Enamel Below Bath Drain Overflow

[Radge70]

Hi,
I'm new to the forums and have a question whereby the answer is probably obvious but I thought I'd check first...….
As per the attached photo, the enamel on my bath has worn below bath drain overflow. The bath is in a property that I rent out so I am unable to monitor what's happening but there doesn't seem to be any obvious leak coming from the overflow.
Is it a case of replacing the overflow or is there a quick fix that might work? The reason I ask is because I am about to get the bath resurfaced and don't want this to happen again once that's done.
Just to complicate things a bit though, I have recently sealed and painted the bath panel so I am reluctant to take it off to replace the overflow!
Any ideas welcome.....