My brain went temporarily on vacation regarding the phosphoric acid connection.
James, it might be cheaper to use Coca-Cola.
::) ::)
Using Naval Jelly (which no longer works the way it used to... I don't bother buying it anymore..) could get pricey... and I prefer not to use it on my Cast Iron. (and no Coca-Cola either,,,, way too many $$$ so I never experimented with it...)
The good old 50/50 Vinegar bath is a cheap, effective, better choice in my book.
(with careful monitoring, as any Acid requires, when using with CI).
But, the electrolysis is my go to de-ruster always.