SIMS for investigating copper migration through aged acrylic coatings on bronze

摘要

The Stark collection at the J. Paul Getty Museum, which includes works by Barbara Hepworth and Henry Moore, is undergoing conservation for the first time since acquisition. This has prompted a scientific examination of the chemistry and microstructure of acrylic coatings within the Getty Conservation Institute in an effort to understand existing protective coatings for outdoor bronze statuary and the mechanisms by which they fail. Using spin coated statuary bronze samples the concentration of bronze constituent ions was measured in nanometer increments from the coating surface to the metal-coating using DSIMS. Samples were aged naturally and artificially. DSIMS measurements taken at various stages of ageing may show the migration of ions into the coating over time. The SIMS study was carried out in parallel with FTIR which can provide bulk organometallic bonding information. Organometallic bonding (such as copper carboxylate formation) may be the cause of the irreversibility of some of these coatings over time. In addition SIMS can be used to study pore structure if attention is focussed on the signal from the matrix, in this case a MS fingerprint from an acrylic resin. Therefore ToF-SIMS will be used to observe evolution of corrosion-inducing pores i.e. gaps in the acrylic signal. EIS results gathered from aged samples can be used to correlate pore evolution observed with ToF-SIMS with corrosion resistance and water uptake into the coating.