Testing of the siderophore deferoxamine amended in hydrogels for the cleaning of iron corrosion

Abstract

Bioderived alternatives to commonly used complexing agents for the cleaning of iron artworks are sought for their natural origin and better biodegradability. Indeed, complexing agents currently used for the removal of undesired corrosion products from iron artworks can be difficult to control and their environmental impact is often overlooked. This paper studies the use of siderophores, focusing on the ability of one of them, deferoxamine, to be employed as an active agent loaded in polysaccharides hydrogels, on corrosion phases. Preliminary tests were conducted on artificially aged steel samples and further studies were performed on naturally corroded steel to assess the most performing application parameters. Long-term behavior of cleaned surface was assessed. Cleaning outcomes were compared with those obtainable with disodium ethylenediaminetetraacetic acid using optical microscopy, colorimetry and atomic absorption spectroscopy as well as Infrared and Raman micro-spectroscopies. Among the different gelling agents evaluated, agar applied when hot and gellan gum prepared at room temperature were the most effective gel formulations and agar left few residues over the treated surfaces. The protocol was then tested on altered steel artifacts belonging to heritage institutions in France. Encouraging outcomes in the removal of iron corrosion phases with green approaches are here presented. Graphical abstract

Innovative perspective for the cleaning of historical iron heritage: novel bio-organogel for the combined removal of undesired organic coatings and corrosion

“…5a). Indeed, the formulation changed from whitish to bright red coloured indicating the possible formation of iron-DFO complexes, as reported in the literature [51] (Fig. 5b).…”

“…The polymer poly-3-hydroxybutyrate (PHB) was then added at 7% w/v concentration. The final concentration of the DFO solution was 4 × 10 -2 M, which is a value in the range of other exploitations of this ligand in art conservation [24,51,52]. The mixture was stirred in a glass petri dish at about 110 °C until the gel was formed and let cool down to room temperature before application (Fig.…”

“…Specifically, the removal of an acrylic varnish (i.e., Paraloid ® B72) and the underlying corrosion, generally composed of iron oxyhydroxides (i.e., lepidocrocite, goethite), was studied as representative for protective coatings and alterations often present on indoor historical iron alloys. These targets were selected in accordance with the replies obtained through a survey addressed to metal conservator-restorers (CRs) and spread worldwide by authors in 2020 [36].…”

Agar and Chitosan Hydrogels’ Design for Metal-Uptaking Treatments

“…It is bioderived as it is extracted from red seaweed membranes [16]. It is appreciated by conservators thanks to good mechanical and retention properties [11,17]. Moreover, it is easily accessible, affordable, and peelable, implying an ease of removal.…”

“…In a second step, this article examines gel-chelator interactions, focusing on agar and chitosan with the addition of a selected chelating agent, a microbial siderophore called deferoxamine (DFO). This active agent was selected as its metal uptake properties have been praised in the cultural heritage field on several substrates (e.g., paper, wood, metal, textiles) [17,43,44], and allows for the achievement of bio-based formulations. In addition, this chelator shows high biodegradability in the environment, which means it has a reduced ecological impact compared to EDTA, a chelator commonly used in the heritage conservation field [45].…”