Once the plating is corroded away, there's nothing really you can do to get it back to the original condition. I usually take a very fine sand paper and remove the corrosion. If it's really bad, I remove the metal contact, clean it, then clean the surrounding with whatever is available, including clean water or small amount of alcohol. If not too bad, I use tooth pick and pick the solidified liquid away the use cottom swab. There is no need for strong acid.