Microstructural damage induced by sulfate attack in concrete is a cause of primary concern in building foundations and other structures. Most research focuses on prevention. In contrast, the concept of damage recovery has not received significant attention. Studies were conducted using alumina-coated-silica nanoparticles to facilitate an electrochemical recovery of strength. Treatments were applied to extract sulfates while the nanoparticles were being injected. Initial sodium sulfate exposure on cylindrical concrete specimens was conducted for a period of 30 days. This exposure induced body cracking and microstructural damage. The specimens were subjected to electrokinetic treatment using a constant current density of 1 A/m2 for 7 days. Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) analysis revealed significant sulfate content in the sulfate-exposed specimens that was not detected in the treated cases. Raman spectroscopy also indicated a higher C-S-H among the treated specimens, ...

Electrokinetic nanoparticle (EN) treatments were employed to mitigate corrosion in reinforced concrete. In this approach an electric field was used to drive pozzolanic nanoparticles through the capillary pores of concrete and directly to the reinforcement. The intent was to use the nanoparticles as pore-blocking agents to prevent the ingress of chlorides. Treatment effectiveness was examined for both freshly batched and relatively mature concrete. Cylindrical reinforced concrete specimens were subjected to EN treatment immediately after batching and then exposed to chlorides for a period of two years. The EN-treated specimens exhibited a reduction in corrosion rates by a factor of 74 as compared to the untreated controls. Another set of specimens was subjected to chlorides for a period of two years prior to EN treatment application. Electrochemical chloride extraction and EN treatments were performed on these mature specimens for one week. These specimens were placed back into saltwater exposure for an additional year. The mature controls exhibited severe corrosion cracking as compared with the mature treated specimens after 1 year of saltwater exposure. The corrosion rates were 8 times that of the treated specimens. Microstructural and chemical analysis was conducted using scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. This study demonstrated that microstructural changes attributable to treatment were effective in mitigating reinforcement corrosion in both young and mature concrete.

Electrokinetic nanoparticle treatments have been demonstrated to reduce the permeability of hardened cement paste by orders of magnitude. The origin of this approach stems from the tendency of particles to flocculate and precipitate when they make contact with pore fluid. The feasibility of a given treatment application is dependent upon the transport properties of the particle and of the cement paste. It is theorized that this process causes particles to fill the initial sections of pores to a large extent before further penetration is achieved. In this work a model was developed to predict the rate of penetration of a given nanoparticle treatment using the principle of superposition to combine the influence of electrophoresis, electroosmosis, and hydraulic flow. The model finds the penetration depth by dividing the net transport rate by the effective number of degrees of freedom in the pore system and multiplying by the treatment time. The model was found to compare well with experimental results, both for predicting if a penetration is possible and for predicting the extent of penetration.

Iron and iron-nickel alloy electrodeposits synthesized from sulfate-based electroplating baths were applied to a mild carbon steel substrate. Coated specimens were immersed in an oxygen-saturated, weak ammonium hydroxide solution (pH 9.5–10.0), and their corrosion performance was evaluated using electrochemical techniques. Galvanic and general corrosion behaviors were analyzed to assess the sacrificial protection provided by Fe and Fe-Ni coatings relative to uncoated steel. The influence of anode-to-cathode (A/C) surface area ratios (1:1, 10:1, and 100:1) on the occurrence of plating-induced surface cracks was also examined. Surface morphology and elemental composition of the deposits were characterized. Results of the study indicated that increasing the Ni²⁺/Fe²⁺ molar ratio of the electroplating bath from 0 to 0.167 led to (1) reduced surface porosity and cracking, (2) decreased galvanic corrosion rates between the electrodeposit and substrate, and (3) a progressive increase in the temperature dependence of the general corrosion rate between 20 °C and 60 °C. The development of Fe and Fe-Ni alloy electrodeposits as protective coatings is of particular interest in water-tube power boiler applications, where production of corrosion products must be controlled. Further research is needed to develop coatings that perform predictably under elevated pressures and temperatures typical of operating boiler environments.

The galvanic and general corrosion characteristics of plated iron were evaluated for consideration as a fatigue crack treatment for ASTM A36 steel. The general corrosion rate of the plated iron in a 3.5 wt-% NaCl solution ranged from 2-5 mpy. SEM examination revealed mud cracking as well as pitting of the plated metal. Galvanic corrosion assessment showed that the steel was generally cathodic to the plated iron. The anode/cathode ratio exhibited by the mud cracking morphology projected to a galvanic corrosion rate of 1-2 mpy. Fatigue crack treatments conducted with electroplated nickel exhibited galvanic corrosion that was expected to harm the steel substrate via galvanically assisted crevicing. In contrast, this study showed that the corrosion characteristics of electroplated iron in this application would tend to render the A36 steel galvanically protected.