Preserving Brake Discs

[WIL35]

Is there any point in trying to preserve brake discs? The front discs on my Cerb are not readily available anymore and they aren't worn much. However I can see that the metal ribs between the outer and inner disc surfaces are getting corroded and suspect this, in time, will be what makes the disc unusable.

Is it worth trying to get some paint in there and round the outer edge?