两株优势霉菌对大足千手观音金箔腐蚀的作用机制OA

In recent years,partial deterioration of the gilded layer on the Dazu Thousand-handed and Thousand-eyed Avalokitesvara has posed a serious threat to the preservation of this cultural heritage.In this study,Asper-gillus versicolor and Mucor fragilis,previously isolated from the gold foil surface,were selected as model organisms.Laboratory-simulated conditions were employed to investigate their corrosive effects on the gold foil.Corrosion behavior was monitored through pH,open circuit potential,electrochemical impedance spectrosco-py,and polarization curves.Additionally,transmission electron microscopy(TEM)and energy-dispersive X-ray spectroscopy(EDS)were utilized to characterize morphological and elemental changes.The results demonstrat-ed that both fungal strains significantly accelerated gold foil corrosion.A marked decrease in surface gold(Au)content was observed,accompanied by the enrichment of carbon(C),oxygen(O),and sulfur(S)elements.Elec-trochemical analyses revealed a negative shift in corrosion potential by 0.20-0.24 V,a nearly tenfold increase in corrosion current density,and corrosion efficiencies of 91.38% and 88.91% for Aspergillus versicolor and Mucor fragilis,respectively.The preliminary mechanistic inferences suggest that organic acids(e.g.,citric acid and oxalic acid)produced by fungal metabolism rapidly reduced the local pH to 4.5-4.8,thereby disrupting the passive layer.Moreover,extracellular polymeric substances(EPS)secreted by the fungi facilitated biofilm for-mation and likely enhanced interfacial reactions through sulfide adsorption.The flake corrosion patterns induced by Aspergillus versicolor were attributed to the increased electrolyte penetration promoted by its hydrophilic polysaccharide-rich biofilm.Conversely,the crack propagation caused by Mucor fragilis was possibly driven by micro-galvanic effects associated with its saccharification products.