Old cast iron plumbing stack question

[papakevin]

I’m in the process of remodeling a home with big issues and need some guidance. The house was build in the mid 40’s and had some significant water damage. While removing the damaged flooring and wall, I exposed the old cast iron plumbing stack which appears to have some growth on it. As far as I can tell the stack feels solid. So my question, do I leave it as-is, try to spray it with something to clean it, spray it with a rubber sealer to encapsulate the rust/nasty, something else? Picture of all the fun included.

 

[Snoonyb]

M0ost of what you see is probably as a result of the, other, water damage, so, if it doesn't leak, don't fix it.