The aluminum-cast Madonna statue of “Tempio Votivo”, Lido di Venezia (Italy): Identification of degradation factors and assessment of a cleaning procedure

An aluminum-cast statue, representing an open-armed Madonna, was positioned in 1938 on the memorial for the victims of World War I built in Lido di Venezia (Italy). Due to the severe exposure conditions (marine industrial atmosphere), the statue suffered extensive deterioration and fell down in summer 2003. In 2009, a restoration project started, with the aim of repairing and conserving the statue, at the time badly fragmented. In the present work, the results of investigations on (i) degradation factors and (ii) potential conservation strategies, are presented. In particular, in the first part of the study composition and microstructure of the cast alloy were determined, pointing out the influence of casting defects on the intrinsic brittleness of the statue. The corrosion products on the exposed surface were also identified and related to the exposure conditions, in order to identify the main corrosion factors. In the second part of the work, a cleaning procedure aimed at removing the active corrosive ions (namely chlorides), was setup and the Ion Chromatography (IC) method was used for monitoring its effectiveness. The results showed that water leaching requires a high number of rinsing cycles in order to obtain a significant decrease of Cl− concentration.

► Investigations on aluminum-cast Madonna statue in Lido di Venezia (Italy).
► Al4Cu alloy with casting defects and intermetallic compounds (brittle fracture).
► Corrosion products: gibbsite and amorphous sulphates, with significant amounts of chlorides.
► Water leaching: high number of rinsing cycles for a significant decrease of Cl− from surface salts.