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The present work represents an attempt to study the inhibition of corrosion of mild steel in acid media by seventeen furan derivatives, at 17 to 30 different inhibitor concentrations, from 0 up to 20 mMole per liter. / One of the techniques used to correlate the inhibitive action of organic compounds is based on the Linear Free Energy Relationship (LFER). The relationship is used to elucidate the mechanism of inhibition, by studying the effects of physico-chemical characteristics of the inhibitor molecules, such as functional group, polar function electron density, steric effects, and (pi)-orbital character of the donating electrons on the corrosion inhibition of mild steel in acid solution. / The results show that furfuryl alcohol, 2,5-furan dimethanol, and 2-furonitrile act as excellent inhibitors over the entire concentration range covered in this study, whereas the remaining investigated compounds exhibit substantial fluctuations in the inhibitive action with concentration. Frequent maxima and minima of inhibitive action have been observed. This behaviour can be explained on the basis of the different reaction mechanisms of the absorbed intermediate inhibitor complex at the metal surface. / The results of the study suggest that the inhibitive action of ortho-substituted compounds is influenced by steric effect. Although LFER is a valuable tool for comparing inhibitive actions of various compounds, other criteria should be considered. These criterion or special effects include polymerization, (pi)-orbital electrondelocalization, and mesomeric effects. Such effects could cause a compound to act as a good inhibitor, irrespective of considerations relating to electron affinity.

Volcanic eruptions are powerful, uncontrollable natural events which produce a number of hazards that can impact upon all aspects of society, including critical infrastructure. The most widespread and disruptive of these hazards is volcanic ashfall. Direct ashfall impacts, even minor, can cause multiple knock on effects throughout all critical infrastructure sectors leading to disruption of these services, on which society relies. However with appropriate volcanic risk management strategies, these impacts can be lessened. Electronic equipment, including laptop computers, are a common and vital component in all critical infrastructure sectors, field based volcanic research and wider society. Therefore, it is important to understand how laptops will function in volcanic environments. This thesis assesses the vulnerability of laptop computers to volcanic ash and gas hazards through field and laboratory based experimentation and the development of quantitative risk assessments metrics. Laboratory based ash vulnerability experiments were carried out in the Volcanic Ash Testing Facility, University of Canterbury, using a mass produced basalt ‘pseudo ash’, which is physically and chemically analogous to fresh volcanic ash. Each laptop was exposed to ash for 100 160 hours at fall rates of ~500 g/m² h. None of the ten laptops used sustained any permanent damage from volcanic ash, however, three shutdown temporarily due to overheating. This was because laptops only contain a few small ventilation holes which prevent large quantities of ash from entering the laptops. However, ash contamination reduced functionality of keyboards, CD drives and some cooling fans as these are open to the environment or located close to ventilation holes. Wet ash, known to cause short circuits of electrical equipment, was not able to enter the laptops because it is less mobile than dry ash. Functionality was retained with the use of simple mitigation techniques such as placing laptops inside heavy duty polyethylene bags. Volcanic gas vulnerability experiments were undertaken at White Island, New Zealand. Three laptops were exposed to high concentrations of volcanic gases for ~5 hours. None however, sustained any permanent damage, due to the limited quantity of gas that could enter the laptop, although metal components on the outside of the laptop sustained minor corrosion.

The use of magnesium for degradable implants can fill the need for temporary, load bearing, metallic orthopaedic implants without the risks and expense of further surgeries once the bone has healed. Mg is non toxic and biocompatible, but the corrosion rate in the body is too high. The rate will need to be moderated if these implants are to be made clinically useful. A review of common orthopaedic coatings found that the biomimetic calcium phosphate coating process meets the criteria for a good coating. This process was designed for permanent implants, and its corrosion protection properties were unknown on Mg. The research presented here evaluates and optimizes aspects of the corrosion protection of biomimetic coatings in vitro. To accurately identify the corrosion mechanisms of such coatings, the in vitro behaviour of several common simulated body fluids and buffer systems was evaluated. The deposition of biomimetic coatings on Mg was compared to Ti. The effect of common surface treatments on the deposition, composition, and ultimate corrosion protection was identified in order to understand the corrosion properties of these coatings. Following the results, the biomimetic method was modified to optimize the protection by reducing the defects. The corrosion properties of these modified coatings were assessed in vitro. The limitation of the biomimetic coatings was found to be in all cases sensitive to the defects present in the coating. While these could be minimized, they were not eliminated. This led to unfavourable corrosion properties. To solve this problem, a novel treatment was developed to give the biomimetic coatings self-healing properties. This treatment promoted local repair in the coating at the defects, greatly improving the corrosion properties. The in vitro model was increased in complexity by adding first amino acids, then proteins. The corrosion behaviour of the coatings was compared in these solutions to understand the effects of these molecules. The data gathered will help to build a better model of in vivo corrosion, and allow better prediction of the performance of biomimetic coatings for corrosion resistance.

Corrosion of steel reinforcement in Ontario bridges is causing severe soffit spalling in many situations. These spalled areas are often located within the lap splices and curtailment zones of the primary reinforcement. This can lead to inadequate bar development lengths and the possibility of failures. In order to better predict the residual strength of these deteriorated bridges, a test program was designed, which involved mid-sized concrete beam specimens, with partially de-bonded reinforcement. The de-bonding was simulated in various beam locations, with various de-bonding patterns. The test program consisted of thirteen beams; ten under-reinforced and three over-reinforced. All beams had dimensions of 2100×150×100 mm. The span between simple supports was 1900 mm with a single point load applied at the midspan. Rebar strains and displacement at the midspan were recorded. The goal of this experimental study was to determine the correlation between the spatial location and surface area of de-bonding with the strength of the beams. This was achieved by testing beam specimens with different combinations of de-bonding patterns with respect to location and area. Four beams had de-bonded reinforcement in the flexural zones, seven were de-bonded in the anchorage and flexural zones, and two were fully bonded. In a previous study, a so-called “modified area concept” was developed for rapid assessment of the remaining capacity of heavily spalled girders. This concept was integrated in a computer program, which assesses girder capacity, given a graphical spalling survey and a structural drawing of the girder. The developed program can be easily adapted for full bridge analysis, and to evaluate the effects of reinforcement cross section loss and bond deterioration. The research presented in the current thesis investigates several of the assumptions made in this previous study. The current thesis includes the rationale for the design of the experimental program. In addition, the test results are presented and analyzed. By analyzing the failure modes, failure loads, and crack patterns, along with the load-displacement, load-stiffness, and load-strain behaviour of the various beams, it is concluded that: 1) reinforced concrete beams can carry a significant portion of their original capacity after losing cover over a significant portion of their flexural reinforcement, 2) predictions of the beam capacities and failure modes using the modified area concept are reasonably accurate and conservative in most cases, and 3) the flexural stiffness of the beams was seen to decrease with an increase in the length of the exposed area, in most cases. Recommended areas of future research are identified, including: 1) tests of beams with splices in the flexural reinforcing along the span, 2) field investigation of the concrete strength in regions of the soffit immediately adjacent to the spalled regions, and 3) the development of a correction factor to account for the effects of violating the plane sections assumption.

This thesis presents a finite element (FE) modelling approach investigating the effects of corroded shear reinforcement on the capacity and behaviour of shear critical reinforced concrete (RC) beams. Shear reinforcement was modelled using a “locally smeared” approach, wherein the shear reinforcement is smeared within a series of plane-stress concrete elements at the specific stirrup location. This was done with the objective of incorporating both the reduction in cross-sectional area due to corrosion and the corresponding expansion of corrosion products build up. Corrosion damage was incorporated through equivalent straining induced by the corrosion build up on the affected surrounding concrete where the concrete cover was treated as a thick-wall cylinder subjected to internal pressure. Strains were introduced in the FE model using fictitious smeared horizontal pre-stressing steel, with a compressive pre-straining level related to the degree of corrosion penetration of the reinforcement. The FE modelling approach was first validated against published test data of shear critical RC beams with and without stirrup corrosion. The proposed modelling approach successfully reproduces the load deformation response as well as the failure mode and cracking patterns of the published experimental tests. Upon validation of the FE model, the work was extended to a parametric analysis of important shear design variables, such as the shear span-to-depth ratio, beam width and stirrup spacing The FE analyses were carried out for three increasing levels of corrosion (low, moderate and high) applied to affected stirrups within the critical section of the beams and based on steel mass loss (10%, 30% and 50%, respectively). In general, the results show a reduction in load carrying capacity accompanied by a softening of the load-deformation curves with each increasing level of corrosion. In most of the cases, a reduction in deflection associated to peak loads was also observed for moderate and high levels of corrosion. The impact of the various parameters was studied with respect to strength and deformation, as well as crack angle and mid-height horizontal strain. This was done in an effort to compare FE values to those provided by the CSA A23.3 design equations. The CSA A23.3 shear design equations were compared against FE analysis data in terms of residual shear strength estimation and individual component contributions to shear resistance (i.e., concrete and steel). The comparisons revealed an over conservative estimation for both strength and concrete contributions and an overestimation of the steel contribution. This divergence was attributed to a transition in shear behaviour within the critical section. Based on the progression of the concrete compressive struts with increasing corrosion and predicted crack angle, it was found that stresses in affected sections are redistributed towards adjacent undamaged material. The shear resistance mechanism generally transitioned from typical beam behaviour towards an arching-dominated one. Finally, based on important findings from the literature and the work conducted within this research, important considerations for assessment practice are suggested.