Corrosion Inhibition Study of Mg-Nd-Y High Strength Magnesium Alloy Using Organic Inhibitor
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Corrosion Inhibition Study of Mg-Nd-Y High Strength Magnesium Alloy Using Organic Inhibitor G.R. Argade, S. Sanders, G. Mohandass, A. Alsaleh, F. DÕSouza, T.D. Golden, and R.S. Mishra (Submitted April 27, 2018; in revised form October 24, 2018) A study on corrosion inhibition mechanism has been performed on rare earth containing WE43 magnesium alloy in 3.5 wt.% NaCl containing 8-hydroxyquinoline (HQ). After an initial increase in corrosion rate due to the formation of sparingly soluble MgQ2 complex, it was found to decrease owing to inhibition effect of the complex. Scanning electrochemical microscopic analysis showed a decrease in corrosion currents and enhanced resistance to pitting corrosion was observed for WE43 samples in the presence of HQ after an exposure of 48 h. With time, the MgQ2 thus generated formed a protective layer on the Mg alloy surface to prevent further corrosion. The corrosion rate of WE43 samples decreased by 50% in HQ containing medium after a constant exposure of 28 days (from 0.22 mg/cm2 day in no HQ to 0.11 mg/cm2 day in HQ). For the WE43 samples in the presence of HQ, formation of MgO and MgQ2 was detected by x-ray photoelectron spectroscopy and x-ray diffraction. Shallower and smaller pits appeared on the magnesium alloy with HQ in the solution as compared to deeper and larger pits on the samples with no HQ in the solution. The significance of metal-complexing organic agent, hydroxyquinoline, in initial acceleration and subsequent prevention of Mg corrosion via protective MgQ2 complex layer formation is demonstrated. Keywords
corrosion inhibitor, magnesium alloy, scanning electrochemical microscopy, scanning electron microscopy, x-ray photoelectron spectroscopy
1. Introduction During the past few years, corrosion susceptibility for magnesium and its alloys has received considerable attention from researchers due to their beneficial lightweight applications in aeronautics and automotive industries (Ref 1-3). In a recent review, Esmaily et al. (Ref 4) concluded that tailoring the surface properties of magnesium alloys through coatings or inhibitors was a reliable strategy for improvement in corrosion behavior. Previous efforts in this direction include the use of inorganic as well as organic compounds as inhibitors (Ref 5-9). Most of such corrosion inhibition studies were conducted on either pure magnesium or conventional AZ series alloys (Ref 5, 10-15). Very few studies were on rare-earth (RE)-added magnesium alloys (Ref 9, 16). These studies were carried out on Mg-Gd-Y alloy in ethylene glycol after exposure to multiple inorganic and organic compounds (Ref 9) and in ASTM D1384-87 (148 g/L Na2SO4 + 138 g/L NaHCO3 + 165 g/L NaCl) corrosion water at pH of 8.2 to study synergy between organic silicates with inorganic zinc salt (Ref 16).
G.R. Argade and R.S. Mishra, Department of Materials Science and Engineering, University of North Texas, Denton, TX 76207; and Advanced Materials and Manufacturing Processes Institute, University of North Texas, De
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