ANALISI CHIMICO-FISICA DEL PERGOLATO IN FERRO E GHISA DEI GIARDINI REALI DI VENEZIA

Elisa Marcoleoni1, Roberto Benvenuti2, Guido Biscontin3, Alberto Chinellato4, Zeno Morabito5

1 Università Ca’ Foscari di Venezia, elisa.marcoleoni@gmail.com

2 Comune di Venezia, Direzione Lavori Pubblici, roberto.benvenuti@comune.venezia.it

3 Università Ca’ Foscari di Venezia, bisco@unive.it

4 Comune di Venezia, Direzione Lavori Pubblici, alberto.chinellato@comune.venezia.it

5 Arcadia Ricerche Srl, Venezia, morabito@arcadiaricerche.eu

ABSTRACT

This works arises from the interest to analyze the problems related to the degradation and the conservation of cast iron works of art in Venice and it is, to the best of our knowledge, the first case of a chemical-physical study of a Venetian cast-iron artefact.

For this purpose it was decided to consider the cast iron pergola of the Royal Gardens in Venice. The aim of this study is to characterize the inorganic materials used for the construction of the pergola, namely, the alloy and the superficial treatments.

The study of the cross sections from the superficial treatments showed the use of different tones, which suggests a succession of interventions having the goal of protecting the structure from the degradation. The metallographic analysis on the alloy samples proved that it’s a grey cast iron. In several samples the cast iron structure is not visible anymore, due to the degradation of the iron (cast iron graphitization).

As a result of the chemical-phisical analysis and the in situ observation of the structure, it is possible to conclude that the level of degradation of the pergula is worrying, both because of the damages of the structure (loss of elements, cracking and corrosion of the alloy…) and because of the loss of adhesion of the surface treatments, which should protect the metal from the environment.

Eventually, the information obtained form the study of the materials and of the construction techniques allow us to conclude that the pergula was realised at the beginning of the 19th Century.

Parole chiave/Key-words:

Giardini Reali; Venezia; Ghisa; SEM; Analisi metallografiche.

Royal Gardens; Venice; Cast Iron; SEM; Metallographic analysis.