Some Good Studies Of Rust Conversion Products

Here’s one from Canada:

https://archive.is/Jpquf

Here is one from National Park Service that is supposed to have results comeback some in 2017.

One from 2013 found tannic acid Rust Oleum product did best:

Rust-oleum® Rust Reformer® is a tannic acid based rust converting product. It also has an acrylic vinylidene chloride copolymer additive. Tannic acid acts as a chelating agent while the copolymer creates a protective coating. The product has a pH of 2.13, falling in the mid-range pH of this study’s converters. Rust Reformer® has a relatively thick consistency, and is blue-ish white in appearance.

OSPHO®, manufactured by the Skybryte Company, is a phosphoric acid based rust converting product balanced with dichromate and wetting agents. OSPHO® is by far the most acidic rust converter of those tested. The product’s pH is 0.08, and is a thin, translucent green liquid.

Corroseal® is a rust converting product based in gallic acid. This converter is composed of gallic acid, ethylene glycol and acetate. It is relatively acidic, both generally and in comparison to other tested converters, with a pH of 1.50. Corroseal® is creamy white and has a thick consistency

RCx427 is a product of Enviro-Safe Services, Inc. that uses oxalic acid as the rust converting compound. Like Corroseal®, it also incorporates ethylene glycol in the chemical composition. Oxalic acid as an active ingredient—a compound that exhibits different physical properties after conversion. Instead of causing the iron oxide layer to darken, it instead turns a light gray. Of the tested rust converters, this product is the least acidic with a pH of 3.11. RCx427 has a thick consistency and is a blue-gray color.

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After each of the tests were performed and the 1032 hours of accelerated weathering completed, many questions were answered and many were raised. Overall, the Rustoleum® Rust Reformer® performed the best, with no active corrosion evident and a nice even surface nish intact. The main active ingredient in the Rust Reformer® is tannic acid. However, the additive acrylic vinylidene chloride copolymer may have been just as important in sealing the metal’s surface. The combination of the two outlasted all other converters in this study. This product is readily available online and in most large hardware stores.