when rust removers remove iron oxide from the corroded surface what are the reaction products that remain on the surface? I mean for the chelation reaction between the chelator ligand complex and the iron oxide... what are the compounds that remain on pure metal after the reaction which can be rinsed with water......Please advise...
A chelation reaction corresponds to an equilibrium (or equilibria). If the chelating agent has acidic H:
FeO(s) + n HL (chelating comp) [FeLn] + H2O + (n-2) H+
Therefore, these equilibria depend on the pH. If there are more than one stable species Fe-L, all of them could be present in solution, that is, [FeL], [FeL2], and so on. Usually, it is used an excess of the chelating agent to assure the formation of [FeLn].
Iron hydroxides are very insoluble, especially iron(III), with pKs ~10-38 for [Fe(OH)3]. The chelate species can mantain iron ions soluble, even at higher pH, depending on its formation constants. Ex.:
Fe3+ + edta4- ⇄ [Fe(edta)]- Kf = 1.3 x 1025
Fe3+ + 6 CN- ⇄ [Fe(CN)6]3- Kf = 1.0 x 1042
The chelate species (for example, [Fe(edta)]-, will be soluble, so they do not remain in the surface of iron. However, a film of iron oxide can be again formed in the surface of the metal, with time.
Thank you so much Ana Maria Da Costa Ferreira and Saeideh Hosseini.
What is the role of microorganisms in the rumen of chelating minerals?
A “rust stain removal formula” was proposed by Robert F. Crist (Iron Out, Inc.; Fort Wayne, IN), Patent US 6,297,208 B1, Oct. 2, 2001; it suggests use of hot aqueous solution of ammonium bifluoride and boric acid (which react to form fluoboric acid) complemented with added oxalic acid.
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