No description available.

This project involved the improvement of several properties of the current “universal” primer coating sold by Kelly-Moore Paint Company. This formulation is an all purpose primer used both for interior and exterior applications. However, its corrosion resistance has room for improvement. The addition of sodium nitrite, an aminocarboxylate salt, and a zinc phosphate-based additive were all tested as corrosion inhibitors. In addition, during the project the coating binder was changed to improve adhesion. After a systematic experimental program, a new “universal” primer with increased corrosion resistance and adhesion was formulated. A direct to metal top coat formulation sold by Kelly-Moore Paint Company was reformulated in order to produce a coating with better corrosion resistance and gloss retention. Five new latexes were investigated. Each formulation was tested for several properties including adhesion to metal substrates, water immersion resistance, accelerated UV exposure resistance, and outdoor exposure resistance. This effort resulted in a formulation that showed promise as a replacement for the current product; however, its adhesion was inadequate. Further work is needed to improve this coating.

Experiments were conducted to characterize and compare the localized corrosion susceptibility of the granular microstructure of aluminum (Al) alloy AA7050 in the peak aged T6 condition cast by the novel controlled diffusion solidification (CDS) process against the conventional wrought plate counterpart. CDS is a casting technique that involves mixing two precursor melts at specific temperatures and compositions before solidification. This process avoids the problem of hot tearing by causing copious nucleation of the solid phase within the melt before solidification, reducing the amount of solute segregation and, thus dendritic growth creating a consistently equiaxed microstructure. The effect of the CDS processing route on its relative localized corrosion susceptibility was elucidated by making links between the microstructure heterogeneities and the localized corrosion susceptibility as evaluated in aqueous saline solutions. Microstructures were characterized and compared with the use of the following techniques: 1. Scanning electron microscopy (SEM) to characterize grain size, shape and distribution. 2. Electron backscattered diffraction (EBSD) in SEM mode to characterize grain misorientation and the associated distribution. 3. Auger electron spectroscopy (AES) to characterize the composition of the grain boundary region including the precipitate free zone (PFZ) and the grain boundary precipitates. 4. Atom probe tomography (APT) to define the size, distribution, and composition of the strengthening matrix precipitates along with the grain boundary region (PFZ and grain boundary precipitates). Electrochemical experiments were conducted to characterize and compare the localized corrosion susceptibility of the two materials (CDS and conventional wrought) exhibited in aqueous saline solutions. Specific techniques include the following: i. Potentiodynamic polarization measurements of mechanically-abraded surfaces to determine the corrosion potential (Ecorr) and breakdown potential (Eb). ii. Potentiostatic anodic polarization of mechanically-abraded surfaces to observe the mode and extent of localized corrosion. iii. Open-circuit potential (OCP) measurements of fracture surfaces to determine the OCP of a surface with a significantly higher grain boundary area fraction relative to the bulk material. iv. Cyclic acidified salt (sodium chloride (NaCl)) fog testing (ASTM-G85-Annex 2) to validate the relative localized corrosion susceptibility under more realistic atmospheric corrosion exposure conductions. The CDS casting technique resulted in an entirely equiaxed microstructure. The microstructure was isotropic with an average grain size of 25±1 µm and an aspect ratio of around 1. This grain structure was in stark contrast with the wrought material, which exhibited a granular structure elongated along the rolling direction. The wrought material had a cord length of 56±3.2 µm in the rolling direction, 51±3 µm in the traverse direction and 13.3±1.6 µm in the short traverse direction. The wrought material had an aspect ratio of around 4 in the longitudinal plane (LS), 2.6 in the short transverse plane (ST) and 1.2 in the rolling plane (LT). AES and APT revealed that the CDS material had a higher amount of copper (Cu) segregation into the grain boundary precipitates. Electrochemical testing showed that the wrought material had a Eb of −750 ± 3 mV while the CDS had a higher Eb of −697 ± 4 mV. The Cu segregation into the grain boundary precipitates yielded more electrochemically active grain boundaries, as revealed by the OCP measurements. Despite this fact, localized corrosion of the CDS material initiated as pitting and propagated as a mixed mode involving intergranular corrosion (IGC) and pitting. The localized corrosion mode exhibited by the wrought material was purely IGC: both in initiation and propagation. The difference in corrosion mode was found to be due to the differences in the size of the Fe-based IMPs and the distribution of the Cu secondary phase precipitates: The CDS had large Fe IMP trapped at the grain boundary triple points and clustering of Cu secondary phase precipitates. Conversely, the wrought material had finely dispersed Fe IMP of significantly smaller size than those found in the CDS, and its Cu secondary phase precipitates are evenly distributed along the grain boundaries. These differences in precipitate distribution enhanced susceptibility for pitting in the CDS and reduced the driving force for IGC. The propagation of localized corrosion was markedly reduced in the CDS material: about half of that exhibited by the wrought material (under identical exposure conditions). Cyclic acidified salt fog testing revealed industry acceptable levels of localized corrosion susceptibility in-line with the benchmark alloys that are currently used in automotive applications. / Thesis / Master of Applied Science (MASc)

Aniline oligomers have become a very interesting topic for research because of their potential application not only in organic electronics but also in smart coatings for corrosion treatment of iron and steel. A majority of the studies in the literature are focussed on the bulk or direct interaction between the organic molecules with metal substrates, without considering the native oxide film. In order to develop smart coatings (has redox activity and self-healing ability) for iron and steel, one must first understand how these oligomers interact with the native iron oxide film. In this thesis, we develop new knowledge from our fundamental understanding of the interactions of redox-active aniline oligomers with the iron oxide surface. Phenyl capped aniline dimer with two oxidation states [fully reduced (DPPD) and fully oxidized (B2Q1)] and phenyl-capped aniline tetramer (PCAT) with three oxidation states [fully reduced (B5), half-oxidized (B4Q1), fully oxidized (B3Q2)] were chosen for investigation. The former is the smallest redox active aniline oligomer but with one fewer oxidation states than polyaniline whereas the latter mimics the redox system as well as corrosion inhibition properties of polyaniline. Moreover, the phenyl-caps help both of these molecules to resist polymerization on the surface. Raman spectroscopy, mid-IR spectroscopy, atomic force microscopy (AFM), temperature programmed desorption (TPD) and electrochemical impedance spectroscopy (EIS) were used to study interactions. We demonstrate that charge transfer and interconversion to different oxidation states take place during interactions between each of these molecules with iron (III) oxides surfaces. During interaction with the surface, all three tetramer molecules and DPPD prefer standing on their edge orientation, whereas B2Q1 molecules tend to orient in lying down direction on the same surface. Having amino groups in the chain helps reduced and half oxidized molecules to strongly hydrogen bond with the surface and make them static on the surface. On the other hand, a lack of amino groups makes oxidized molecules mobile and loosely bound to the surface. Interactions and change of oxidation states impact the corrosion inhibition properties of PCAT. Strong ability of sticking to the surface and not fully oxidizing (B3Q2) during interactions makes B5 molecules superior corrosion inhibitors than B4Q1 and B3Q2 molecules. Transformation into B3Q2 form at the beginning of interaction allows B4Q1 to moderately inhibit corrosion but as it transforms back to its original form with time it becomes the 2nd best corrosion protector of iron oxide surface after B5. The study of all oxidation states and their surface interactions with iron oxide surface will open up pathways towards of designing smart coatings using aniline oligomers and other redox-active molecules. / Thesis / Doctor of Philosophy (PhD) / Aniline oligomers have become a very interesting topic for research because of their potential application not only in organic electronics but also in smart coatings for corrosion treatment of iron and steel. A majority of the studies in the literature are focussed on the bulk or direct interaction between the organic molecules with metal substrates, without considering the native oxide film. In order to develop smart coatings (has redox activity and self-healing ability) for iron and steel, one must first understand how these oligomers interact with the native iron oxide film. In this thesis, we develop new knowledge from our fundamental understanding of the interactions of redox-active aniline oligomers with the iron oxide surface. Phenyl capped aniline dimer with two oxidation states [fully reduced (DPPD) and fully oxidized (B2Q1)] and phenyl-capped aniline tetramer (PCAT) with three oxidation states [fully reduced (B5), half-oxidized (B4Q1), fully oxidized (B3Q2)] were chosen for investigation. The former is the smallest redox active aniline oligomer but with one fewer oxidation states than polyaniline whereas the latter mimics the redox system as well as corrosion inhibition properties of polyaniline. Moreover, the phenyl-caps help both of these molecules to resist polymerization on the surface. Raman spectroscopy, mid-IR spectroscopy, atomic force microscopy (AFM), temperature programmed desorption (TPD) and electrochemical impedance spectroscopy (EIS) were used to study interactions. We demonstrate that charge transfer and interconversion to different oxidation states take place during interactions between each of these molecules with iron (III) oxides surfaces. During interaction with the surface, all three tetramer molecules and DPPD prefer standing on their edge orientation, whereas B2Q1 molecules tend to orient in lying down direction on the same surface. Having amino groups in the chain helps reduced and half oxidized molecules to strongly hydrogen bond with the surface and make them static on the surface. On the other hand, a lack of amino groups makes oxidized molecules mobile and loosely bound to the surface. Interactions and change of oxidation states impact the corrosion inhibition properties of PCAT. Strong ability of sticking to the surface and not fully oxidizing (B3Q2) during interactions makes B5 molecules superior corrosion inhibitors than B4Q1 and B3Q2 molecules. Transformation into B3Q2 form at the beginning of interaction allows B4Q1 to moderately inhibit corrosion but as it transforms back to its original form with time it becomes the 2nd best corrosion protector of iron oxide surface after B5. The study of all oxidation states and their surface interactions with iron oxide surface will open up pathways towards of designing smart coatings using aniline oligomers and other redox-active molecules.

The effect of nonstirred aqueous Portland cement solution on the corrosion rates of zinc and cadmium metal using Tafel extrapolation and linear polarization measurements has been investigated. Results indicate that for the corrosion systems under investigation, zinc metal has a higher corrosion potential and lower corrosion rate than cadmium metal.

Corrosion in reinforced concrete bridge decks has always been a concern amongst engineers. However, as structures continue to increase in size and in the amount of reinforcement present, consideration must be given to parameters such as the clear spacing arrangements between bars, the presence and absence of stay-in-place (SIP) forms, and differences in the cathode bar to anode bar ratios. Limited research has been performed to determine the effects of the parameters (Shiessel, P. 1986). Research has been conducted on the effects of macrocell corrosion compared to microcell corrosion. Previous studies have shown that the measured microcell corrosion is not augmented greatly by the macrocell current (Andrade et al. 1991). In this study, twenty-seven specimens were cast with reinforcing steel to represent reinforcing mats at the top and bottom of each specimen. Top and bottom spacing arrangements were approximately 51, 76, 102 mm (2, 3, and 4-inches), cathode-to-anode bar (C/A) ratios were 2 and 1, and the presence and absence of SIP were considered. Macrocell currents, resistivity measurements, half-cell potential measurements, and corrosion current densities were recorded over a 273 day time period to compare the differences that existed amongst the three different parameters. Based upon the data that was collected, no significant differences were recorded when comparisons were made between the spacing arrangements, the absence and presence of SIP, and differences in C/A ratios. The formation of the passive layer was confirmed by the corrosion current densities and half-cell potentials. The rate of the formation of the passive layer occurred in two distinct periods, a rapid rate from casting to about 105 days and a significantly slower rate beyond 105 days after casting. There was no detected influence of the macrocell activity on the formation of the passive layer throughout the 273 day study period. / Master of Science

Call number: LD2668 .T4 1965 W122 / Master of Science

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Dentistry / Master / Master of Dental Surgery

No description available.