Iron particle surface chemistry and corrosion protection by amine-quinone polyurethanes

The ability of amine-quinone polyurethanes to protect iron particles from corrosion was shown to depend on the polymer composition and on the particle surface chemistry. The amine-quinone polyurethanes were prepared from 2,5-bis(N-2-hydroxyethyl-N-methylamino)-1,4-benzoquinone (AQM-1), tolylene diisocyante and polytetrahydrofuran diol (average molecular weight 650). The AQM-1 content was varied from 20 to 40 wt % (AQPU-15); the polymer with 40 wt % AQM-1 had the highest affinity for the iron surface and showed the best corrosion protection. AQPU-15 had a higher affinity for the commercial iron particle having a aluminum-rich surface, than for a commercial particle having a silicon-rich surface. Tape samples containing AQPU-15 and the particles having the Al-rich surface showed excellent corrosion resistance, maintaining 98% of the initial saturation magnetization after 48 h exposure to pH 2 aqueous buffer. Samples containing AQPU-15 and the particles having the Si-rich surface completely corroded after 2 h exposure. The presence of aluminum on the iron surface served to enhance the adsorption of AQPU-15 and improve the corrosion resistance. (C) 1996 American Institute of Physics.