Novel conversion coatings for magnesium alloy AZ31 using ionic liquids

Ionic liquids (ILs) are generally defined as salts which have a melting point below 100 °C. The work presented here describes an investigation of the properties of the surface film formed when a reactive metal (e.g., magnesium alloy AZ31) is exposed to an IL. Treatment of AZ31 coupons with the IL, trihexyl(tetradecyl)phosphonium bis(trifluoromethanesulfonyl)amide (P 6,6,6,14TFSA), is effective in forming a passivation film which imparts improved corrosion resistance to the alloy. Corrosion data along with spectroscopic evidence detailing the nature of the passivation film formed on the AZ31 surface is presented. In addition, preliminary results from another IL, trihexyl(tetradecyl)phosphonium bis 2,4,4-trimethylpentylpentylphosphinate (P 6,6,6,14M 3PPh), which shows promise for corrosion mitigation are presented.