Jason Church from NCPTT presented a useful paper on commercially available rust converters. He explained that rust converters are a chemical treatment that converts iron oxide into a more stable product, though this product varies depending on the chemical composition of the rust converter. Church and his colleagues started with the 1995 Canadian Conservation Institute study of rust converters, but found most of the products to have been discontinued or available in new formulations. This led the team to perform their own experiment.
Church et al., selected four commercial products of varying chemical composition: Ospho (phosphoric acid base), Rust-oleum Rust Reformer (tannic acid base), Corroseal (gallic acid base) and RCx427 (oxalic acid base). The four commercial products were selected on the grounds that these products were readily available, were top sellers, and could be purchased in sufficiently small quantities so as to be accessible to homeowners or for small conservation projects. Church and his colleagues also tested the CCI-recommended custom formulation of tannic and phosphoric acid, which several objects conservators they polled still claim to use. NCPTT staff tested the five rust converters on new A36 carbon steel that was naturally weathered. They subjected each of the test samples to artificial weathering and measured the samples for color changes and active corrosion every 250 hours for 1000 hours total. They found that the Rust-oleum product had the least color change and most stable surface of the five products tested, though the efficacy of each product tested was quite varied. Church mentioned that their testing is not complete. They continue to push the Rust-oleum product to metal failure through extended artificial weathering, and will also test the new aerosol version of that product. They also plan to perform outdoor accelerated weathering tests on the five products.
The presentation was interesting and informative, as is characteristic of studies done by NCPTT. I like that their experiments are developed for conservators, but the results are accessible to anyone. The information presented in this talk will surely broaden the body of knowledge for architecture and objects conservators and will be useful for homeowners and maintenance workers. Following the talk, moderator Patty Miller recommended that they eventually expand their testing scope to include conservation-grade products and less readily available materials. I concur, and I would encourage Church and his colleagues to publish their findings.