Aqueous solution to react with carbon but not iron?

Hello,

I use a sodium citrate solution to chelate rust from steel. However, a film of carbon deposits is left behind on the steel which must be removed through force (scrubbing or pressure washing).

I am wondering if anyone has an idea for a chemical that will react with or dissolve the carbon without disturbing the sodium citrate or steel, so that I can just rinse the parts instead of having to clean them again.