i once had a bag of coins that i inherited, and like a bad apple the whole lot had become covered in the stuff. If they are making physical contact then yes definately. Not touching but in a close environment, then the infected coin will continue to corrode, but this might alter the chemical makeup of the entire micro environment, and thus potentially affect the others near by, kinda like a chemical experiment. Not sure how minute those chances are... but i should imagine it's a possibility. Anyhow the verdigris is the least of the problems, tin corrodes much faster and has progressive corrosion (like iron does). Unlike aluminium which has protective corrosion.