Modified hydrotalcites for improved corrosion protection of reinforcing steel in concrete – preparation, characterization, and assessment in alkaline chloride solution

Abstract

Six Mg-Al hydrotalcites (Mg/Al ¼ 2 and 3) were synthesized through the modification of two carbonate hydrotalcites (i.e., Mg(2)Al-CO 3 and Mg(3)Al-CO 3 ) by two amino acids (11-aminoundecanoic acid and p-aminobenzoic acid) and sodium nitrite. They were characterized by means of XRD, FTIR, TG/DSC, and elemental analysis. The ion exchange of the modified hydrotalcites (MHTs) were investigated in alkaline chloride solution and the results showed that ion exchange occurred between free chloride ions and the intercalated inhibitive anions in MHT.The corrosion inhibition of three MHTs (Mg/Al ¼ 2) was evaluated based on the open circuit potential and linear polarization resistance evolution of steel coupons in 0.1 M NaOH solution stepwise enriched with chlorides and the results showed that MHT, in particular, Mg(2)Al-pAB exhibited an improved corrosion inhibiting effect in terms of a higher chloride threshold compared to its constituent free inhibitor ions (i.e., pAB). This study confirms the dual protection that MHT, in particular, Mg(2)Al-pAB, offers to the steel: capturing chlorides and simultaneously releasing the intercalated inhibitors to further protect the steel from corrosion.

Use of ZnAl-Layered Double Hydroxide (LDH) to Extend the Service Life of Reinforced Concrete

“…The use of LDH to control the cement hydration kinetics has been studied by several groups [18][19][20][21]. However, most of the work with LDH in concrete is dedicated to the mitigation of steel rebars corrosion, either in chloride media [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] or carbonated concrete [32,[41][42][43][44][45][46][47][48]. Many studies have been done in simulated concrete pore solution [35,38,43,46], just a few in mortar [31,43] and only one in concrete [16].…”

On-Demand Release of Protective Agents Triggered by Environmental Stimuli

“…All these molecules contain at least a carboxylic group, but they differ for the other functional groups and their steric hindrance, as shown in Figure 1, and this can have an effect on the protective performance. These inhibitors were identified based on literature data since they were recognized as effective in corrosion inhibition (Giacomelli et al, 2004;de Souza and Spinelli, 2009;Yang et al, 2016). However, the tests assessing inhibitor efficacy are usually carried out in experimental conditions that are sometimes difficult to compare.…”

“…Several approaches have been explored to prevent or slow down the corrosion processes of metals and their alloys (Bertolini et al, 2004;Rani and Basu, 2012;Yang et al, 2013;Saremi and Yeganeh, 2014;Giuliani et al, 2018;Goyal et al, 2018). Among them, the use of corrosion inhibitors is one of the most attractive since it can offer a simple and cost-effective prevention technique (Ormellese et al, 2009;Yang et al, 2016). In the last decades, organic inhibitors mainly based on mixtures of alkanolamines, amines, organic acids, or amino acids have received great interest since they represent an effective and safe alternative to common inorganic inhibitors (Jamil et al, 2003;Söylev and Richardson, 2008;Gartner et al, 2016).…”

“…A promising approach is to develop smart materials that can act as a reservoir of inhibitors and release them under external stimuli, thus prolonging their protective action. Due to their versatility, silica and layered double hydroxides (LDHs) have great potential to be used for the storage and controlled release of corrosion inhibitors (Yang et al, 2013(Yang et al, , 2016Saremi and Yeganeh, 2014;Rahsepar et al, 2017;Salzano de Luna et al, 2018). According to the literature, silica nanocontainers were studied, for example, as a host of molybdate ions or a mercaptobenzothiazole corrosion inhibitor (Saremi and Yeganeh, 2014;Rahsepar et al, 2017).…”

“…According to the literature, silica nanocontainers were studied, for example, as a host of molybdate ions or a mercaptobenzothiazole corrosion inhibitor (Saremi and Yeganeh, 2014;Rahsepar et al, 2017). Layered double hydroxides were intercalated with different inhibitor molecules, including organic acids (Yang et al, 2016). Several substances of potential interest have also been investigated for the corrosion inhibition of steel, among them organic acids and their derivatives, such as p-aminobenzoic (pAB), succinic (SA), and caffeic (CA) acids (Giacomelli et al, 2004;Amin et al, 2007;de Souza and Spinelli, 2009;Yang et al, 2016).…”