Just to clear up a couple points. None of the reactions of acids with iron or rust (iron oxide) generate any oxygen.
Because the density of hydrogen is so much less than air, it will rise so rapidly you are very unlikely to accumulate enough in open air to ignite it when cleaning small parts.
Just because phosphoric (or any acid) is added to Coke doesn't mean it's harmless. It's the final pH and concentration that's important.
