depends what you want to achieve.
Removing rust without damage to the file is, I presume, the aim of
Super Iron Out is sodium metabisulphite, citric acid and sodium
bicarbonate. I am guessing but I suspect it works by some
combination of the chelating action of the Citric Acid, the reduction
action of sulphite and the bicarb acting as a buffer to manage the
pH. It should be effective at removing the rust without attacking the
oxalic acid (toxic) also works, as does tartaric and citric, but of
these citric is cheaper and non-toxic.
phosphoric acid attacks both the rust and the steel, creating a
stable phosphate/oxide coating that passivates the steel from further
if you don’t care about the rust, and want to prevent further rust,
any oil or anti rust treatment should work OK.
I’d find a file I didn’t want and experiment first…