Nice pair of pliers there. Well saved. I've had great results with both citric and acetic acids too. They are slow but steady and don't attack the steel too much. They would also clean down to the deepest pits if allowed to soak long enough. A fairly diluted hydrochloric acid would have eaten away at least half the metal on anything.
I used citric acid solution on an Optimus hood and it made the enamel go dull. It still has its integrity but is not so shiny
