Comparative study of corrosion behavior of metals in protic and aprotic ionic liquids

- Protic (PIL) and aprotic (AIL) ionic liquids with the same anion are investigated.
- PIL has a more positive cathodic stability limit potential than AIL.
- PIL is more reactive toward metals than AIL.
- PIL has lower corrosion potential and higher corrosion current density than AIL.
- Overall corrosion behavior of metals is similar in both ionic liquids.

A comparative study of metal corrosion in a protic ionic liquid (PIL) and an aprotic ionic liquid (AIL) with the same anion is reported in this paper. The stability of Ni, Cu, Al, Zn, and Mg in 1-butylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BPyr] [NTf2]) PIL and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMPyr] [NTf2]) AIL is evaluated, and the measured corrosion potential (Ecorr) and corrosion current density (icorr) of these metals in both ionic liquids are compared. Electrochemical tests show that the PIL has a narrower electrochemical stability window and is generally more reactive toward the metals than the AIL. Even though the observed corrosion behavior is more or less similar in both ionic liquids, the corrosion parameters obtained reflect the fact that the presence of a proton on the cation of an ionic liquid makes metals more susceptible to corrosion, i.e. produces a lower Ecorr and higher icorr.