This work took the iron objects from the Nanhai No. 1 shipwreck in the Southern Song Dynasty of China as the sample to test and analyze the application potential of catechin, an environmentally friendly corrosion inhibitor and rust converter. The article used metallographic microscopy to clarify that the structure of the iron artifact was hypereutectic white iron. By means of micro-Raman, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), potentiodynamic polarization and electrochemical impedance spectroscopy, catechin had the ability to react with iron oxyhydroxides such as goethite, akaganeite and lepidocrocite in the rust, forming an amorphous substance with a marked signal about 1380 cm⁻¹ as phenolic-Fe in infrared properties. The new products could make the original rust layer form a laminated dense structure. After the archaeological iron was soaked in 3.0 g/L catechin, the corrosion current density decreased by 37.13% and the corrosion potential shifted positively by 32.67 mV. The anode reaction was more inhibited than the cathode in the polarization curve. The rust resistance in electrochemical impedance increased to 3.75 times and the ion diffusion resistance increased to 6.33 times. The corrosion inhibition efficiency was 21.75% and the rust conversion efficiency was 73.26%. After 36 h of accelerated corrosion, the protection effect of the newly transformed rust layer was still better than that of the original state. Catechin was a mild protection material which showed satisfactory performance for archaeological iron and has a good application prospect.

Paraloid B-72 (B72), as a transparent, colorless polymer material, has good film-forming ability when dissolved in acetone and is widely used as a sealing material for metal artifacts. In order to analyze and evaluate the preservation performance of B72 as a sealing material on the substrate of metal artifacts, a variety of electrochemical methods, mainly electrochemical noise (EN), and scanning electron microscopy (SEM) were applied to evaluate the B72 coating. The results showed that the B72 coating had a good preservation effect at the initial stage, and its poor water resistance led to the loss of its effectiveness after a few days of immersion. Compared with conventional electrochemical methods, electrochemical noise is non-destructive, which cannot cause new corrosion on the metal substrate and can well characterize the corrosion rate of the test system, and the results of its time domain and frequency domain analyses can correspond well with the polarization resistance and impedance spectra. Electrochemical noise is an effective method for evaluating the anti-corrosion performance of material preservation coatings.