LiNO3 addition to prevent hydrogen gas generation from cement-solidified aluminum wastes

LiNO3 addition to the cement solidified miscellaneous wastes has been proposed for preventing hydrogen gas generation caused by the corrosion of aluminum materials contained in the wastes. To determine an additive among alkaline metal ions, galvanic current was measured in 0.1 M alkaline metal hydroxide solution between aluminum and platinum electrodes. The volume of hydrogen gas generated from an aluminum specimen was measured in a KOH solution with LiNO3, LiCl, LiBr, Li2CO3 or Li2SO4 to decide the best additive. Applicability of the chosen additive to cement was confirmed by hydrogen gas generation measurement from an aluminum specimen in cement paste. The prevention mechanism was analyzed by X-ray diffraction, SEM and SIMS. The current measured in LiOH solution decreased with time, then reached 0 μA/mm2, while the current was detected in other alkaline metal hydroxide solutions. The least volume of hydrogen gas generation was measured in a KOH solution with LiNO3. The volume of generated hydrogen gas in cement paste with LiNO3 was less than 10% of that without LiNO3. The results of analyses showed that an insoluble film of LiH(AlO2)25H2O was formed on the aluminum surface. These results suggested that LiNO3 addition to cement is effective to prevent hydrogen gas generation by formation of the insoluble film on aluminum. (author)