Cast Iron Waste Overflow

[AH81]

I am installing the Kohler K-7160 waste overflow to a K-837 Bellwether cast iron tub.

I have called Kohler, but I'm curious what the folks here say here. I have read a lot on here and found you all to be very helpful.

I have attached photos.
One Home Depot photo for reference:



Two photos of my tub:




As you guys can see the inside diameter of the hole is not coated in white porcelain.

My question is, if the gasket goes on the back of the tub and the metal face plate goes on the front,



what protects the inside diameter of the hole from rusting? Has anyone seen this be an issue? Kohler stated that though the color wasn't there, it was sealed.

Thanks guys,
Adam

 

[hj]

It is cast iron, so "rusting" is not a factor. If anything it will get a brown coating, and that is all.