CaFe-Based Layered Double Oxides With Superior Iron Alloy Corrosion Inhibition Behaviors in Aggressive Seawater Environment

Abstract

Reinforced concrete is among the most multifaceted materials used in the construction field. Maintaining the resistance of reinforced concrete to weathering, abrasion, and chemical attack, particularly in aggressive natural conditions such as seawater environments, is challenging. The main factor in the degradation of reinforced-concrete durability is chloride penetration, which accelerates iron alloy corrosion and facilitates structural degradation. In this study, calcium-iron-based layered double hydroxides (CaFe-LDHs) were fabricated at room temperature, followed by structural modulation, and their effectiveness in mitigating iron alloy corrosion due to chloride ions (in 3.5 wt% of NaCl) was investigated. The synthesized CaFe-LDHs with phase transfer notably improved the Cl− removal capacity (Qmax) to 881.83 mg/g, which is more than three times that reported based on previous studies. The novelty of this research lies in the sophisticated structural and phase transformations of the as-synthesized CaFe-LDHs, determination of crucial factors for chloride ion removal, and suggestion of calcium-iron-based layered double oxide (CaFe-LDO)-based chloride ion removal mechanisms considering chemical and ion-exchange reactions. Moreover, when the phase-transformed LDHs, C-700 LDOs, were applied to inhibit iron alloy corrosion, a noticeable inhibition efficiency of 98.87% was obtained, which was an 11-fold improvement compared to the case of iron alloys without LDOs. We believe this work can provide new insights into the design of CaFe-LDOs for the enhancement of the lifespan of reinforced concrete structures.

Mechanistic Insights on Solution-Based Green Synthesis of Phase-Pure Ca-Based Layered Double Hydroxides from Ca(OH)2

“…Ca-based LDHs, also known as hydrocalumite-like compounds (HClcs) due to their similarity to hydrocalumite (Ca 2 Al­(OH) 6 Cl·2H 2 O), are mostly being studied for applications that involve anionic exchange or selective adsorption of acidic molecules . Such is the case for some drug delivery systems, alloy corrosion inhibition, industrial waste recycling, environmental remediation, and CO 2 capture where higher purity of crystalline Ca-LDHs has been associated with increase in adsorption capacity. − Ca-LDHs are also relevant to the cement industry as they constitute the AFm phases in hydrated Portland cement. Because AFm phases do not form solid solutions, but rather stay in a heterogeneous mix in cement paste, being able to synthesize phase-pure variants of Ca-LDHs allows for a better characterization of AFm phases in Portland cement .…”