I see that Henry Cleere has offered me up as a victim for the dreaded cast iron corrosion.....since many of these cast iron sculptures are grey cast iron with free graphite, which tends to act as a cathode with pearlite or cementite or sometimes steadite surrounding phases being severely corroded, any corrosion that has attacked the surface to any depth is going to be a severe problem, especially if "active corrosion" is taking place as you suggest....an assessment of the chloride ion problem at the surface is important, together with examination of detached flakes of corrosion, if any, to determine if grey or white cast iron. How sound is the remaining metallic surface? Any signs of corrrosion products streaking down the surface of the sculptures? I suggest a careful assessment of the extent of corrosion and the environmental parameters to which the sculptures are subjected....if a major study, it is useful to employ the categorisation of the environment into certain levels of "corrosivity" as used by the Swedish Corrosion Institute...as for coatings, as far as I know, heavily corroded cast iron has not been studied greatly, but others on the list may know of relevant work and of corrosion inhibition with impressed current or cathodic protection, although the efficacy of these is doubtful if extensive corrosion of the surface has already occurred. There are some coatings that bind very strongly to iron hydroxides and oxyhydroxides but these are untested in the conservation field, as far as I know.
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