Corrosion Performance of Carbon Steel in Simulated Pore Solution in the Presence of Micelles

Abstract

This study presents the results on the investigation of the corrosion behavior of carbon steel in model alkaline medium in the presence of very low concentration of polymeric nanoaggregates ͓0.0024 wt % polyethylene oxide ͑PEO͒ 113 -b-PS 70 micelles͔. The steel electrodes were investigated in chloride-free and chloride-containing cement extracts. The electrochemical measurements ͑electrochemical impedance spectroscopy and potentiodynamic polarization͒ indicate that the presence of micelles alters the composition of the surface layers ͑i.e., micelles were indeed absorbed to the steel surface͒ and influences the electrochemical behavior of the steel, i.e., the micelles lead to an initially increased corrosion resistance of the steel whereas no significant improvement was observed within longer immersion periods. Surface analysis, performed by environmental scanning electronic microscopy, energy-dispersive x-ray analysis, and x-ray photoelectron spectroscopy, supports and elucidates the corrosion performance. The product layers in the micelles-containing specimens are more homogenous and compact, presenting protective ␣-Fe 2 O 3 and/or Fe 3 O 4 , whereas the product layers in the micelles-free specimens exhibit mainly FeOOH, FeO, and FeCO 3 , which are prone to chloride attack. Therefore, the increased "barrier effects" along with the layers composition and altered surface morphology denote for the initially increased corrosion resistance of the steel in chloride-containing alkaline medium in the presence of micelles. A well-known fact is that corrosion of steel reinforcement can cause reinforced concrete deterioration and thus affect civil structures durability.1,2 Logically, corrosion-related issues result in a significant economic loss. For example, in the United States, the annual direct cost of bridge infrastructure corrosion was estimated to be $8.3 billion, and the indirect cost was reported to be many times higher. 3In normal conditions, the reinforcing steel embedded in cementbased materials ͑i.e., cement paste, mortar, and concrete͒ is in a passive state because of the high alkalinity ͑pH = 12.6-13.5͒ of the pore solution and the cement paste, respectively. 4,5 However, corrosion can be initiated due to carbonation or chloride contamination. 6 Carbonation can result in a pH drop ͑to about 8-9͒ 7,8 in the pore solution of the bulk cementitious matrix, leading to a general corrosion of the reinforcing steel. In the event of chloride penetration and chloride arrival at the steel/cement paste interface, localized corrosion is initiated; the local pH can drop to even below 6, resulting in fast corrosion propagation. This will cause accelerated damage of the reinforcing steel and possible rapid failure of reinforced concrete. 9To minimize the corrosion processes, various methods and techniques are used. Among them, the polymer-based organic corrosion inhibitors are widely applied because they can provide an easy handling, cost-effective corrosion prevention, delaying corrosion initiation.10-14 The organic inh...

Corrosion performance of reinforced mortar in the presence of polymeric nano-aggregates: electrochemical behavior, surface analysis, and properties of the steel/cement paste interface

“…In cement extract [24], a very low concentration of the micelles in the corrosion medium (0.0024 wt%) is able to initially increase the corrosion resistance of the carbon steel in the presence of 1% NaCl and the pronounced effect only appeared at early stages, which was as expected to some extent, considering the very low concentration of micelles used. At early stages, the micelles adsorbed on the steel surface and altered the morphology and chemical composition of the formed products, a more uniform and compact layer, i.e., with increased barrier properties.…”

“…The expectation results from the fact that in the presence of micelles, the reduced permeability [22,25] will lead to a reduced chloride penetration and corrosion initiation, respectively, will be delayed. Further, in the event of chloride arrival at the steel/cement paste interface, the presence of micelles would even further halt corrosion propagation due to maintained superior properties of the passive layer (as this was observed for earlier stage in model liquid environment, [24]). To this end, this article reports on the integration of electrochemistry and concrete material science for a thorough evaluation of a reinforced mortar system modified with the same type of micelles (PEO 113 -b-PS 70 ) in comparison to non-modified such in control (non-corroding) and corroding conditions.…”

“…Further, within more systematic studies, involving a modified variety of the nano-aggregates (PEO 113 -b-PS 70 micelles), the corrosion performance of carbon steel in cement extract (simulated concrete pore water) and material properties of plain mortar in the presence of micelles have been recently investigated [24,25].…”

Early Age Hydration, Microstructure and Micromechanical Properties of Cement Paste Modified with Polymeric Vesicles

“…In our previous research, the influence of polymeric micelles and vesicles (with a hydrodynamic radius of 50 nm and 220 nm) respectively on the corrosion performance of reinforced concrete was investigated (Hu et al 2012b(Hu et al , 2011(Hu et al , 2012c. Micelles are polymeric, self-assembled nano-architectures with amphiphilic properties in our case, whereas vesicles are nano-sacs, that enclose a volume, containing water or chosen substances.…”

“…Initial tests in simulated pore solution (Hu et al 2011) and reinforced mortar in the presence of micelles (Hu et al 2012b) proved that corrosion initiation was delayed on one hand and chloride binding capacity of the mortar was increased on the other. Further investigations on admixed vesicles, and especially Ca-containing ones, where saturated Ca(OH) 2 solution was pre-reserved in their core, (Hu et al 2012c) indicated "self-healing" effect of the corrosion damage in the reinforcement: after corrosion initiation, the steel corrosion resistance was significantly increased and corrosion propagation on the steel reinforcement was halted.…”