Purpose – The purpose of this paper is to determine if a type of cactus mucilage, Opuntia ficus-indica (OFI), may act as a corrosion inhibitor for carbon steel in cement-based materials (mortar) exposed to chloride-laden environment. Design/methodology/approach – Mortar prisms, reinforced with carbon steel rods, were immersed in sodium chloride (NaCl) solution for five wet – dry cycles. The experimentation included electrochemical monitoring (corrosion potential, Ecorr, and polarization resistance, Rp) of carbon steel during the time of exposure until corrosion-induced cracking appeared at the mortar surface. Crack survey on the mortar prisms was performed. Carbon steel rods were retrieved from the mortar after crack survey and steel mass loss at the end of the experimental period was estimated. A comparison between the different mixtures was also performed. Findings – OFI mucilage did perform as a corrosion inhibitor of steel in chloride contaminated mortar. Research limitations/implications – The experimental program needs to be corroborated in concrete specimens with typical dimensions. The surface oxide/hydroxide formation of the carbon steel in contact with the OFI mucilage is still unknown; thus, electrochemical impedance spectroscopy (EIS) and X-ray diffraction (XRD) analyses are needed. Practical implications – OFI mucilage is a suitable natural product that can be used to increase durability of concrete structures not only in countries where OFI cactus is produced, but also in many other countries where this plant is considered a plague. Originality/value – The new information obtained from this paper is the innovative use of a by-product of this cactus plant for construction industry applications.

This research includes results on the corrosion performance of reinforcing steel in cementbased mortar (pH ~ 13) when cactus (Opuntia Ficus Indica -Nopal) slime was used as an addition. The cactus slime addition was mixed at different concentrations by mixing water mass (0%, 1.5%, 4%, 8%, 42%, and 95%). Half-cell potentials and LPR measurements were performed at different time periods to characterize the possible corrosion inhibiting effect of the cactus additions tested. Results showed good corrosion inhibiting effect of Nopal slime on reinforcing steel, in all tested solutions, when chloride ions were present. The addition of such cactus led to an apparent formation of a denser and more packed oxide/hydroxide surface layer on the steel surface that decreased corrosion activity. This oxide/hydroxide layer growth was confirmed from microscopic evaluation of the metal surface layer performed at the end of the research program. The preliminary findings suggest that adding Nopal slime in concentrations between 4% and 8%, by water mass, might be suitable for durability enhancing applications in cement-based mortar.

In this study, an evaluation of the corrosion susceptibility of concrete reinforcement steel welded to stainless steel is reported, which is proposed as a potential solution to the repair and rehabilitate structures. An evaluation was conducted over 390 days by measuring the corrosion potential and current density levels by electrochemical impedance spectroscopy applied to a solution that simulated a marine environment. The welded carbon-stainless steel samples were found to be more resistant to corrosion than the carbon steel samples. These results were confirmed by visual inspection, scanning electron microscopy and energy dispersive spectroscopy of the welded zone. These findings support the concept of rehabilitating structures by replacing damaged carbon steel with stainless steel welded to the remaining structures.

This work presents a mechanistic study of the electrochemical synthesis of magnetite nanoparticles (NPs) based on the analysis of the electrochemical impedance spectroscopy (EIS) technique. After a discussion of the mechanisms reported in the literature, three models are devised and a prediction of their EIS spectra is presented. The approach consisted of the simulation of EIS spectra as a tool for assessing model validity, as EIS allows to characterize the relaxation of adsorbed intermediates. The comparison between the simulated impedance spectra and the experimental results shows that the mechanisms proposed to date do not explain all of the experimental results. Thus, a new model is proposed, in which up to three adsorbed intermediate species are involved. This model accounts for the number of loops found in experimental impedance data. The closest approximation of the features found in the experimental spectra by this proposed model suggests a better representation of the reaction mechanism within the evaluated potential range.