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.

Ceramic artifacts excavated from the Nanhai No. 1 shipwreck exhibit dense iron sediments that are mechanically interlocked with the glaze, posing significant challenges for traditional corrosive chemical cleaning. Here, we engineered a near-neutral physicochemical synergistic cleaning system utilizing Micro-Nano Bubbles (MNBs) water and monoethanolamine (MEA)-activated thiourea dioxide (TDO). This work enables near-neutral TDO activation to circumvent alkaline-induced glaze corrosion, while broadening the utility of MNBs from conventional desalination to the physicochemical removal of recalcitrant iron sediments. Multi-scale characterizations, including NTA, EPR, XRD, ICP-OES, and SEM-EDS, were employed to optimize formulations, elucidate mechanisms, and validate efficacy on authentic shards. Results indicated that the optimal formulation (2 wt% TDO/0.1 wt% MEA) maintained safe operating range pH (6.0–8.0) over 3 h. Mechanistically, MEA activated TDO to generate reactive radicals, driving the efficient reductive dissolution of Fe(III) oxides. Crucially, MNBs collapse-induced micro-turbulence significantly enhanced mass transfer into rust fissures, increasing total iron dissolution by 19.7% compared to conventional aqueous solutions. Application on authentic artifacts successfully eradicated Iron Sediments with the glaze integrity well preserved. Ultimately, this facile and highly effective strategy provides a minimally destructive technological framework for the broad conservation and subsequent utilization of underwater cultural heritage.