Figure 1: Showing the C 1s peaks for a) a brass disc (BS002) which has been cleaned (sonicated in micro 90 and water for 10 minutes), b) A brass disc (BS004) which had been corroded by fingerprint sweat for 24 hours anthen cleaned, c) the same disc as in b) which was left in air for another 15.5 hours d) the same disc in b) after being left in air for a further 60.5 hours. Data normalised so the C 1S peaks are the same height.