Study on the rust products and rust layer structure of Ming and Qing iron anchors excavated offshore in Penglai,Shandong Province
Iron anchors of the Ming and Qing Dynasties excavated offshore in Penglai have been affected by the marine environment,showing serious surface corrosion and obvious shedding of the rust layer.This deterioration has not only impacted their aesthetic appearance but also compromised the structural integrity of the anchors.To assess corrosion levels and evaluate preservation strategies,we employed ultra depth-of-field 3 D microscopy,scanning electron microscopy with energy-dispersive spectrometry(SEM-EDS),laser confocal micro-Raman spectrometry(Raman),and X-ray diffraction(XRD)in this study.The results show that the primary rust components on the anchor surfaces were iron hydroxides and oxides.The rust layers displayed clear stratification:the compact inner black rust layer consisted mainly of Fe3O4 and goethite(α-FeOOH),while the outer porous rust layer was comprised of α-FeOOH,β-FeOOH,and hematite(α-Fe2O3).Also seen was the presence of poorly stabilized uneven rust γ-FeOOH on the peeling surface of the rust layer and the substrate.Elemental chlorine was detected in all the iron anchor rust samples.The distribution of soluble chlorine ranged from 0.66 to 35.46 mg/g,with large differences in soluble chlorine content among the different samples.The soluble chlorine content of the rusted iron anchors preserved in the museum was higher than that of the rusted iron anchors in the open environment.The iron anchors exhibited pitting attack index(PAI)values ranging from 1.16 to 13.34,with consistently lower PAI values observed in the inner rust layers compared with the outer layers,indicating lower stability in the inner rust layers.In order to better conserve these iron anchors as cultural relics,targeted dechlorination of chlorine-containing iron anchors will be needed in the subsequent conservation.Monitoring and regulating the preservation of iron anchors and controlling the temperature and humidity of the environment should be conducted in the daily work in order to avoid further corrosion of iron anchors.This study contributes valuable scientific insights into the preservation and restoration of Penglai iron anchors,and has significant implications for safeguarding marine-recovered iron artifacts,in general.
Iron cultural relicsCorrosion productRust layer structurePAI valuePreservation assessment
国家科技期刊平台
NSTL
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