# In Situ Gel-Forming System for the Removal of Ferruginous Deposits on Nanhai I Shipwreck

## 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.

## Key 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 adhesion and mechanical peeling, hence promoting efficient and controllable cleaning.