In Situ Gel-Forming System for the Removal of Ferruginous Deposits on Nanhai I Shipwreck
Jianrui Zha, Ruyi Wang, Jing Du, Naisheng Li, Xiangna Han

TL;DR
A new gel-based method was developed to efficiently remove iron deposits from the Nanhai I shipwreck, reducing labor and improving cleaning results.
Contribution
The study introduces an in situ gel-forming system using CMCS and TA for efficient and controlled removal of ferruginous deposits.
Findings
The CMTA-2 sample achieved a sprayable viscosity of 263 mPa/s and removed up to 1.01 mm of deposit thickness.
Field testing showed a 14.37% reduction in iron concentration and a significant decrease in red coloration (Δa* = 4.36).
TA chelates Fe2+/Fe3+ ions, while CMCS enhances adhesion and mechanical peeling for efficient cleaning.
Abstract
The removal of iron deposits on shipwreck surfaces by mechanical cleaning is labour-intensive work. This study develops an in situ gel and peeling cleaning method, utilising a carboxymethyl chitosan/tannic acid (CMCS/TA) colloidal solution spray on the surface of ferruginous deposits, promoting their removal by adhesion, chelation, and electrostatic bonding processes. The investigation confirmed that the CMTA-2 sample exhibited a sprayable viscosity of 263 mPa/s, the largest single removal thickness of 1.01 mm, a significant reduction in the fe/s atomic ratio by 2.53 units, and enhanced the deposit removal homogeneity. The field testing of the Nanhai I cultural relic showed a 14.37% reduction in iron concentration and a significant decrease in red colour (Δa* = 4.36). The synergistic mechanism involves TA chelating Fe2+/Fe3+ ions, while the CMCS gel network facilitates interfacial…
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Taxonomy
TopicsBuilding materials and conservation · Cultural Heritage Materials Analysis · Maritime and Coastal Archaeology
