Rust on outdoor steel sculpture

This is a follow up on Graham Sussex's question about what is in ZUD
(TM). ZUD contains oxalic acid (H2C204?) which, in addition to its
bleaching properties, is also used as a rust and scale remover.

I suppose that oxalic acid does not "convert" rust into an inert
substance like phosphoric acid does. Is there a chemist out there
who can explain the chemical reaction of oxalic acid on iron oxide?

John Horton, Restoration Specialist
NC State Historic Preservation Office

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                  Conservation DistList Instance 11:20
                 Distributed: Thursday, August 28, 1997
                       Message Id: cdl-11-20-004
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