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Corrosion Inhibiting Cation -Anion exchange pigments

Corrosion Inhibiting Cation -Anion exchange pigments Relva C. Buchanan, University of Cincinnati Main Campus, DMR 0805127 . Objective: Develop non-toxic, anodic- cathodic corrosion inhibitive pigments, as replacement for the widely used (but toxic) chromate-based pigments. ICP-MS.

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Corrosion Inhibiting Cation -Anion exchange pigments

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  1. Corrosion Inhibiting Cation-Anion exchange pigments Relva C. Buchanan, University of Cincinnati Main Campus, DMR 0805127 • Objective: Develop non-toxic, anodic-cathodic corrosion inhibitive pigments, as replacement for the widely used (but toxic) chromate-based pigments. ICP-MS • Ca2+ as anodic species, and (SiO32-, PO43-) as cathodic species, were prepared by chemical synthesis methods. • Ca2+ , phosphate and silicate ions can form insoluble • precipitate products (eqns. below), that hinder the corrosion process. The key anti-corrosion pigments • release of ions as active inhibitors, such as silicate-based species, that are only soluble in water in the ppm range. Ca2+ + 2OH- → Ca(OH)2 (1) H3SiO4- +H+ → H4SiO4 or Si(OH)4 (2) Al3+ +PO43-⇌AlPO4(3) • Inductively coupled plasma mass spectrometry (ICP-MS) • method was used to compare concentrations of inhibitor • Species over time in DI water and in 1%NaCl solution. • The ICP-MS data at right for CaSiO3/PO4 system show • much higher release of calcium ions from the 1% NaCl • solution, compared to the DI water, indicative of superior • leaching protection with the CaSiO3/PO4 pigments, • In the corrosive chloride environment. • .

  2. Broader Impacts Corrosion inhibition, leaching and toxicity in Aluminum Usage Relva C. Buchanan, University of Cincinnati Main Campus DMR 0805127 Aluminum alloys are much used in food industries, due to their excellent corrosion resistance. The protective surface oxide film, is however subject to breakdown by aggressive species such as Cl­ and gluconic acid (HG), the latter a powerful aluminum chelator, which attacks the oxide film, forming Al-gluconate complexes. Gluconic acid is present in many fruits and vegetables, hence it interaction with Al utensils for culinary purposes must be controlled. The data right show electrochemical test results for aluminum alloy AA3003 interacting with gluconic acid at room temperature. The dramatic increase in polarization resistance (Fig.A) indicates excellent corrosion protection with developed zinc acetate and CaSiO3/PO4 pigments as inhibitors. The corrosion rates (Fig.B), calculated from the polarization resistance Rp and equation (2) below, show the expected reverse response, as is corrosion current density, Icorr (Fig.C), which was reduced by one order of magnitude, indicating very good inhibition to the corrosive effects of gluconic acid, through formation of non-reacting species. A Zn Acetate Zn Acetate CaSiO3/PO4 CaSiO3/PO4 HG HG HG C Zn Acetate CaSiO3/PO4 B βAβCare the Tafelslopes , can be measured experimentally, from the linear regions of polarization curve (1) The corrosion current is reversely proportional to polarization resistance Rp (2) Where C.R.=Corrosion rate, mpy=milli-inches per yearIcorr=corrosion current density(μAcm2),E.W=equivalent weight of the corrosion species D=density of the corroding species, (g/cm3)

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