Nanhai No. 1, a shipwreck in the Southern Song Dynasty, China, has a history of more than 800 years. It was salvaged in 2007 and is now on display in the Guangdong Maritime Silk Road Museum. Due to the fact that the hull is a wooden cultural relic and exposed to the air, the biological corrosion and biodegradation caused by microorganisms are key problems of hull protection. At present, the antimicrobial agent Euxyl^® K100 (isothiazolinone) has a significant antimicrobial effect in the field, but it has a certain negative impact on the environment and archeologists. In order to reduce the use of chemical antimicrobial agents, we evaluated the inhibitory effects of cinnamaldehyde on the main destructive microorganisms of Nanhai No. 1. Cinnamaldehyde is the main active component of cinnamon, and has broad-spectrum antimicrobial properties. The paper diffusion method, gas diffusion method and minimum inhibitory concentration experiment were used to detect the inhibitory effects of cinnamaldehyde on the main microorganisms of Nanhai No. 1. We found that cinnamaldehyde had significant inhibitory effects on Bacillus tequilensis NK-NH5, Bacillus megaterium NK-NH10, Bacillus velezensis NK-NH11, Bacillus sp. NK-NH15, Bacillus sp. NK-NH16, Bacillus sp. NK-NH17, Fusariumsolani NK-NH1 and Scedosporiumapiospermum NK.W1-3. At the same time, cinnamaldehyde had more inhibitory effects on fungi than bacteria. Finally, we verified that cinnamaldehyde can effectively inhibit the growth of microorganisms in water, for storing the scattered wood blocks of the Nanhai No. 1 hull through laboratory simulation experiments. Cinnamaldehyde, as an environment-friendly antimicrobial agent, is of great significance to protecting water-saturated wooden relics from microbial corrosion and degradation in the future.

The Nanhai No. 1 was a wooden merchant ship of the Southern Song Dynasty, which wrecked and sank in the South China Sea, Yangjiang City, Guangdong Province, China. The Nanhai No. 1 shipwreck was salvaged as a whole in 2007 and began to be excavated in 2013. During the archaeology excavation, some of the hull wood fell off the hull. These waterlogged archaeological woods (WAW) were immersed in the buffer containing EDTA-2Na and isothiazolinone K100 for moisture stabilization, preliminary desalination, and microbial inhibition. We evaluated the properties of these WAW through testing the chemical components (including lignin, holocellulose, and ash content) of the wood, and monitoring the iron element content, anion and cation content in the buffer. At the same time, the microbial composition in the desalination buffer was also detected. The results showed that the holocellulose content in these WAW were much lower than in fresh wood. The ash content in these WAW decreased after desalination treatment. The iron element content, anion and cation content in the buffer were high and kept at a certain level after desalination treatment. At the same time, the problem of biodegradation in the buffer should be paid attention to. The comprehensive protection of WAW requires to combine wood properties and microbial problems. This study provides a reference for the protection of WAW from the Nanhai No. 1 shipwreck and other similar historical wood.

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.