Molten NaOH will oxidize many metals, including nickel and iron, so maybe cathodic protection?

Yes, that's what it looks like: https://www.freepatentsonline.com/y2020/0105424.html

It seems unfortunate that it's possible to patent something so well documented:

https://en.wikipedia.org/wiki/Cathodic_protection

https://en.wikipedia.org/wiki/Galvanic_anode

It’s a well documented problem that many groups have tried various technical approaches to mitigate over 100,000 hour operating windows.

It’s not too surprising that a particular implementation that has various benefits compared to the existing state of the art would be patentable.

Isn't the point that a patented process is documented as part of the patent application? Industrial processes and materials seem like a great use of patents from my POV. Psychology and biology I'm more concerned with.

Well it says that's the company's core IP, so...

Presumably the fundamentals are patented and not a trade secret. I could see parts of the manufacturing process being a trade secret.