Figure 1: Showing cathodoluminsence spectrum taken at 10 kV on an SEM. a) A brass sample which has been cleaned by sonication in propanol for 5 minutes and sonication in acetone for 5 minutes and then washed in deionsed water. b) A brass sample corroded in sodium chloride solution and left in air for 2 days. c) A brass sample corroded by a fingerprint and left in air for 2.5 days.