The ability of sodium linear-saturated carboxylates to protect magnesium alloys against aqueous corrosion was characterized. Electrochemical measurements of polarization resistance (Rp) and corrosion current (Icorr) showed the inhibition efficiency of these compounds is a function of their concentration and of the length of the aliphatic chain. In every case studied, the efficiency increased with immersion time. At pH 8, the best inhibiting behavior was observed with 0.05 M sodium undecanoate. The potential-pH diagram of magnesium in an aqueous solution containing undecanoate anions was generated based upon the solubility determined for magnesium undecanoate (Mg[CH3(CH2)9COO]2). According to this diagram, the very low corrosion rate was suspected to result from formation of Mg(CH3[CH2]9COO)2. Infrared spectrometry carried out on both the synthesized magnesium carboxylate and the product from the magnesium alloy surface after inhibitive treatment confirmed this hypothesis.

Subject
Water, Spectroscopy, Magnesium alloys, Solubility, Aqueous solutions, Sodium, Carboxylates, Corrosion inhibitors, Magnesium, Immersion, Aluminum alloys, Alloys, Anodic inhibitors
Keywords:
electrochemical testing, infrared spectroscopy, inhibition, magnesium, polarization, potential-pH diagrams, rapid solidification, sodium carboxylates
NACE International
1998
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