The effect of , , and inhibitor ions on the oxygen reduction reaction (ORR) was experimentally investigated on AA2024-T3 and selected castings containing intermetallic phases (i.e., Al–Cu–Mg and Al–Cu–Mn–Fe). All the inhibitors were found to reduce both the activation-controlled and mass-transfer-limited current densities associated with ORR. Molybdate ions were found to be the most effective cathodic inhibitors, followed by the cerium ions. Cobalt(II) ions were found to be effective, as well. The effect of inhibitors was modeled by considering three possible cases using a heterogeneous electrode model including an array of active electrodes embedded in an inactive matrix: (i) reduction of the size of electrochemically active sites, (ii) reduction of the spatial density or increase in the spacing between active sites, and (iii) formation of permeation barrier to diffusion. These models were found to be consistent with the experimental findings.
not Available.
No abstract is provided for this article.
This brief study aims at providing a model to predict the time of service of a cracked bar in corrosive environment, in view of both the fracture mechanics and elastic failure criteria. Dolinskii's assumption on the relationship between stress and the corrosion rate is adopted. It is superimposed with fracture mechanics consideration. A comparison between the time of service of a cracked bar and that of a uniform bar is provided.
Reproducible measurements of magnetic susceptibility χ m of laboratory and field extracted concrete core samples were achieved with simple instrumentation. There was a nearly linear relationship between χ m and the mass of fly ash per unit volume, or its volume fraction. The magnetic response of a given FA was not significantly affected by the process of curing and subsequent evolution of the concrete over two years, or by carbonation of the concrete. Field extracted concrete cores exhibited a wide range of χ m values. The group of specimens with the highest values of χ m also had the lowest chloride ion diffusivity, consistent with the presence of admixed FA. Conversely, specimens with nil magnetic response included those from concrete with the highest chloride diffusivity. The magnetic measurements provided reasonable order-of-magnitude indications of FA presence in field extracted cores. However, precise determination of FA content from magnetic measurements of field cores does not appear feasible in the absence of additional information.
First Name is required invalid characters Last Name is required invalid characters Email Address is required Invalid Email Address Invalid Email Address
No abstract is provided for this article.
The determination of concrete resistivity via the Wenner probe has become an established non-destructive technique either as to verify performance based concrete quality or to assess the chloride diffusivity of existing concrete structures. However, various factors can result in misinterpretations when taking the resistivity measurement. In this study, the finite element method (FEM) is employed to assess the effects of specimen geometry, specimen size, rebar presence, cover depth, multi-layered resistivity, and the combined effects of these factors. The findings confirm that the influence can be quantified by FEM computations to obtain normalization parameters (i.e. cell constants) or to better interpret field resistivity measurements.
No abstract is provided for this article.
No abstract is provided for this article.
A variety of approaches enable deposition of metallic coatings containing rare earth (RE) elements for corrosion protection. Al-TM-RE amorphous and amorphous nanocrystalline alloys are one type of multifunctional material for protection of Al alloys. Ce and Al-Ce coatings have also been deposited. Results for high density, low porosity multifunctional Al-Co-Ce metallic coatings applied to an AA-2024-T351 substrate using a pulsed thermal spray (PTS) are discussed in detail. Three proposed modes of corrosion protection are provided by the coating (i.e. a localized corrosion barrier, a sacrificial anode to supply cathodic protection of any exposed AA 2024-T351, and active inhibitor release) to protect AA 2024-T351. Chemical protection is afforded by either Ce(OH)2 2+ or Ce3+ release.
The resistivity evolution vs. time of concrete prepared with three different compositions and subjected to various curing regimes for an extended period of time was studied. Two of the curing regimes consisted of immersing the specimens in either tap water or 3.5% NaCl solution. The other three curing regimes consisted of exposure to: fog room, high humidity and laboratory humidity. The measured resistivity values were then used to estimate the aging factor. It is found that the aging factor is time dependant for concrete with mineral admixtures. The curing exposure affects the magnitude of the aging factor.
First Name is required invalid characters Last Name is required invalid characters Email Address is required Invalid Email Address Invalid Email Address
Most corrosion experiments conducted on reinforced concrete are terminated upon corrosion initiation. This paper presents preliminary results on corrosion initiation and propagation on three corrosion resistant alloys (CRAs). Two types of experiments were conducted: CRAs exposed to simulated pore solution (with chloride concentration gradually increased), CRAs embedded in mortar specimens (most with 0.5 w/c ratio) with a reduced cover (~10 mm) exposed to 15% (m/m%) NaCl (initially permanent ponding and later alternate ponding). Three surface conditions were tested on each CRA type: as received, with mill scale, with mill scale then sandblasted. The open circuit potential was monitored over time. Linear polarization resistance and solution resistance were measured periodically. In this research the experiments were not terminated upon corrosion initiation, rather exposure continued to gain a better understand how corrosion propagates. No cracks have appeared on the mortar specimens with the CRA actively corroding.
