Abstract
This paper presents results of treating a magnesium alloy surface using an aprotic ammonium-phosphate ionic liquid (IL) to form a conversion coating for corrosion protection. The IL, tetraoctylammonium di(2-ethylhexyl)phosphate ([N8888][DEHP]), was applied to AZ31B Mg surfaces at room temperature (RT) or 300 C with or without pretreatment. The morphology and composition of the IL-produced conversion coatings were characterized by means of scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS). The corrosion protection performance of the conversion coatings were investigated in a 1 wt.% NaCl solution saturated with Mg(OH)2 using the potentiodynamic polarization technique. Results suggested that the IL treatment at 300 C is more effective than RT in corrosion protection. This is attributed to the thermal breakdown of IL molecules and the consequent chemical reactions between the reactive IL decomposition products and the Mg alloy surface, which form a film containing metal phosphates and oxides. It was also found that an appropriate pretreatment process is essential for achieving superior corrosion inhibition.
| Original language | English |
|---|---|
| Pages (from-to) | 58-65 |
| Number of pages | 8 |
| Journal | Electrochimica Acta |
| Volume | 123 |
| DOIs | |
| State | Published - Mar 20 2014 |
Funding
This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The authors thank Drs. M.P. Brady and G.-L. Song from Oak Ridge National Laboratory (ORNL) for technical discussions. Research sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory. H.H. Elsentriecy acknowledges the postdoctoral fellowship administered jointly by ORNL and ORISE, and L. Grado acknowledges the Science Undergraduate Laboratory Internship sponsored by the DOE Office of Science.
| Funders | Funder number |
|---|---|
| U.S. Department of Energy | |
| Office of Science | |
| Oak Ridge National Laboratory | |
| Oak Ridge Institute for Science and Education |
Keywords
- Ammonium-phosphate ionic liquid
- Corrosion
- Magnesium
- Pretreatment