Decay induced by manufacture and environment: Synchrotron revelations on the Hartog (1616) plate.

To mark the 400^th anniversary of its placement on Dirk Hartog Island, the Hartog plate was brought from its home in the Rijksmuseum in Amsterdam to Australia for a series of exhibitions. As the oldest record of European visitation, the plate has great significance to The Netherlands and Australia. Following its exhibition tour, the extremely delicate and damaged pewter plate was examined at the XFM beamline facility at the Australian Synchrotron. The object's historic significance and fragility precluded any form of destructive analysis. The XFM data has revealed previously undetected touch marks and "lost" lettering, as well as features relating to the plate's manufacture and subsequent corrosion. A combination of mechanical damage from cyclonic winds at Cape Inscription and the fully oxygenated salt saturated solutions have caused two decay mechanisms to create the existing patina. Differential corrosion of the tin and the lead rich phases in the eutectoid changed in accordance with periodic flushing from rain. Analysis of iron, arsenic, copper and germanium impurities has helped to understand the decay mechanisms and the residual microstructure, which will inform future conservation management plans.