I've played with acids (weak and strong) and didn't like the post flash rust or constant checking of the surface. "..Unlike most acids, Evapo-Rust will not damage the underlying iron or steel if the object is left soaking too long..."
I don’t know about that. I let a set of pushrods soak in Evapo-Rust, with about an inch of the pushrods protruding from the liquid and there was a definite mark at the liquid line where metal had gone away. They say probably 4 days or so.