What Is Lithium Nitrite?
Lithium nitrite is an inorganic lithium compound with the formula LiNO2. Its CAS number is 13568-33-7. This compound is a hygroscopic white crystal at room temperature, with a molecular weight of 52.947 and a melting point of 431.6 °F (222 °C). It decomposes at 365 °F (185 °C) upon heating and is classified as a deleterious substance, requiring careful disposal methods and waste liquid management.
Uses of Lithium Nitrite
Lithium nitrite is primarily used to prevent rust and salt damage in reinforced concrete, serving as a component in concrete repair admixtures. Nitrite ions are effective against corrosion as they regenerate the passive film on steel surfaces, while lithium ions repair ASR (alkali-silica reaction) deterioration by inhibiting the expansion of alkali silica gel. In application, lithium nitrite permeates the entire concrete structure.
Principle of Lithium Nitrite
The principles of lithium nitrite are explored from the perspectives of production, synthesis, and its corrosion inhibition effect on rebar, as well as its role in inhibiting concrete deterioration.
1. Production and Synthesis of Lithium Nitrite
Lithium nitrite is industrially produced from lithia pyroxene and naphtha, with other synthesis methods including the thermal decomposition of lithium nitrate (LiNO3) at about 932 °F (500 °C) and the reaction of nitrogen monoxide (NO) with lithium hydroxide (LiOH).
2. Principle of Lithium Nitrite’s Corrosion Inhibition Effect on Rebar
Lithium nitrite inhibits rebar corrosion by reacting with divalent iron ions (Fe2+) to prevent their leaching and regenerate the protective passive film (Fe2O3), thus suppressing the corrosion reaction.
3. Principle of Lithium Nitrite’s Effect on Concrete Deterioration Inhibition
Lithium ions help inhibit ASR deterioration in concrete by reacting with alkali silica gel, replacing it with non-expansive lithium monosilicate (Li2-SiO2) or lithium disilicate (Li2-2SiO2), thus preventing water absorption and expansion, and the subsequent cracking of the concrete.
Types of Lithium Nitrite
Lithium nitrite is available as chemical reagents in n-hydrate form (LiNO2-nH2O) and in industrial-grade 40% aqueous solutions for concrete repair admixtures. The reagent form is typically sold in small quantities like 5g, 25g, and 500g, while the industrial solution is often packaged in 20 kg containers.