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Varje år lägger processindustrin världen över 1.372*109 dollar på kostnader kopplade till korrosion. En stor del av denna summa går till korrosion under isolering (CUI). De stora utgifterna kring CUI kommer ifrån avisoleringen av för den visuella inspektionen som måste utföras inom specifika intervall enligt lag. Vid denna inspektion kläs rören av och isoleringen kasseras, vilket leder till stora materialkostnader. Då rörgatorna ofta ligger på svåråtkomliga ställen blir ställningen samt arbetartimmarna de sista stora faktorerna kring CUI hantering. Efter inspektioner uppmärksammas ofta att en stor del av rören varit opåverkade av korrosion. Ifall man kan påvisa att det inte finns någon skäl till misstanke av CUI behöver man inte alltid riva isoleringen. I detta finns det en besparingspotential som redovisas i denna rapport. Då olika anläggningar har en stor variation i sin budget redovisas besparingspotentialen för en låg budget samt en hög budget. Den låga budgeten är antagen att vara 0.35 miljoner per kilometer rör och den höga 2 miljoner per kilometer rör. Det är antaget att 10% av isoleringen kan bevaras med vissa källor säger att upp till 50% av isoleringen kan bevaras. För båda resultaten hinner CUI sensorn betala av sig själv inom de första åren. En andra del som undersöks i denna rapport har med svårigheten kring CUI sensor kontra andra metoder för att lokalisera CUI. Med en CUI sensor kam man inte få ett konkret svar på vart eller om korrosion finns. CUI sensorn mäter av omgivningstemperatur, relativ luftfuktighet alternativt närvaro av vatten men inte närvaron av korrosion. De parametrar som CUI sensorn avläser behöver tolkas om till en sannolikhet för korrosion. Denna sannolikhet representeras på en 1 - 5 skala och baseras på korrosionshastighet, tjocklek på röret samt trycket. Denna lägst nivån på denna skala är efter 0−3 år av blöta rör, den andra nivån 3−6år, den tredje 6−9år, den fjärde 9−12 och den femte allt över 12år.

The objective of this study was to investigate the stress corrosion behaviour of BioglassTM 4555 in order to predict the lifetime of the glass in use as a load-bearing prosthetic device. As part of this study, the development of BioglassTM and the medical tests conducted to assess the glass's biocompatibility are reviewed. The results of implant tests in laboratory animals which indicate that stress corrosion cracking of the glass may be a prohibitive factor to its use are presented. The theories of glass corrosion and stress corrosion cracking of silica based glasses are discussed and an extensive review of the literature presented. The corrosion behaviour of the glass was analysed and found to be similar to that obtained by previous workers. The depths of the corrosion layers were found to be smaller. This was attributed to alumina contamination of the glass. The fatigue parameters of the glass were measured by slow crack-growth studies and strength measurements in a corrosive solution simulating the physiological environment. The values of A and n in the equation relating crack velocity (v) and stress intensity (K1) v=AK1n, were found to be 1x10-173 and 30 respectively. Lifetime predictions for the glass were performed. It was determined that the glass was suitable for use as a prosthetic device if the maximum tensile stress encountered in vivo did not exceed 15MPa. / Thesis / Master of Engineering (ME)

In this study, high-fidelity conjugate heat transfer simulations are used to model a micro-channel heat exchanger (MCHE) in a crossflow to study its thermal-hydraulic performance. This study considers three different microchannels (internal flow) geometries (circular, triangular, and square) with louver-shaped fins. The local flow field showed a strong coupling between the microchannel flow, solid domain, and crossflow. The flow separation and wake regions formed near MCHE resulted in a large variation in the velocity field and temperature in the crossflow. The wake region had a significant spanwise variation due to its interaction with fins, which also causes variations in the thermal boundary layer. The heat conduction in the solid structure provided a non-uniform temperature field with a higher temperature near the microchannel and a slightly lower temperature near the surface exposed to the crossflow. The microchannel flow analysis showed that the internal geometry affects the pressure drop, which is highest for the triangular MCHE and lowest for the circular MCHE. However, the microchannel flow temperature change was relatively similar for all microchannels. Results showed that for the same volume of the microchannel, the circular shape microchannel has a higher performance index value than the triangular and square shapes. This study also considers three different fin (external flow/crossflow) geometries (louver, step, and saw) with the same tube and circular shape microchannel and identifies the corrosion hot spot. Crossflow shows higher temperatures near the boundary layer of the tube, which results in higher corrosion rates. A predicted flow field also identifies crevices between fins and tube surfaces as critical corrosion hot spots often associated with low-velocity regions. Electrochemical impedance spectroscopy (EIS) analysis was done on AA3102 (Alloy used in the circular channel and louver fin) alloy in corrosive environments containing low and high concentrations of the combination of sodium chloride and ammonium sulfate. Electrolytes used in this research have pH values ranging from 4.0 to 5.8, closer to nearly neutral environments encountered in many atmospheres. EIS results are presented, including Rsol, Rpore, and Rct of AA3102 with very thin arc evaporated porous Zinc film on AA 3102 along with their equivalent circuit.

The application of a mineral admixture, or a corrosion inhibitor, or a combination of both are methods used for the corrosion protection for reinforced concrete bridges. The results of a study on evaluation of corrosion inhibitors from three different manufacturers and of concretes with fly ash, slag cement, and silica fume and a concrete with silica fume and a corrosion inhibitor are presented. The specimens were built to simulate four exposure conditions typical for concrete bridges located in the coastal region or inland where deicing salts are used. The exposure conditions were horizontal, vertical, tidal, and immersed zones. The specimens were kept inside the laboratory and were exposed to weekly ponding cycles of 6% (w/w) sodium chloride solution. In addition, cover depth measurements from 21 bridge decks and chloride data from 3 bridge decks were used, together with laboratory data, in modeling the service lives of the investigated corrosion protection methods. The methods used to assess the condition of the specimens included chloride concentration measurements, corrosion potentials, and corrosion rates (3LP). Additionally, visual observations were performed for identification of rust stains and cracking on concrete surfaces. Modeling the time as a function of probability of the end of functional service life (EFSL) is presented. It has been shown that the distributions of surface chloride concentration, C0, and diffusion coefficient, Dc, are key elements in the model. Model predictions show that the concretes with mineral admixtures provide much better level of protection against moisture and chlorides than the ordinary portland cement concrete alone. Application of a corrosion inhibitor causes an elevation of the chloride threshold resulting in an additional increase in time to EFSL. More field studies are needed to better estimate distributions of surface chloride concentration and diffusion coefficient of Virginia bridge decks, and to confirm predicted times to EFSL for low permeable (LP) concretes. / Ph. D.

Corrosion is one of the most complicated and costly problems facing drinking water utilities. Corrosion of iron pipes can lead to economic losses and customer complaints, while lead corrosion poses a serious health risk. This work first synthesizes nearly 100 years of iron corrosion research to provide the water industry with an updated understanding of factors that influence iron pipe corrosion including water quality and composition, flow conditions, biological activity, and corrosion inhibitors. Potential impacts of upcoming regulations on iron corrosion are also considered. Next, a four-year study is presented that evaluated the effect of water quality and phosphate inhibitors on the corrosion of iron pipes under extended stagnant water conditions. Surprisingly, many of the water quality parameters traditionally thought to influence iron corrosion were not controlling under these "worst case" stagnant conditions. Moreover, addition of phosphate inhibitors often had either no statistically significant effect or actually increased iron concentration, scale build-up and overall weight loss. Temperature is often overlooked when corrosion of distribution systems pipes is considered. Temperature impacts many parameters that are critical to pipe corrosion including physical properties of the solution, thermodynamic and physical properties of corrosion scale, chemical rates, and biological activity. Moreover, variations in temperature and temperature gradients may give rise to new corrosion phenomena worthy of consideration by water treatment personnel. In laboratory experiments, cast iron samples at 5°C had 23% more weight loss, ten times higher iron release to water, and twice as much tuberculation compared to samples at 25°C. For lead corrosion, hexametaphosphate inhibitors were proven to increase release of both particulate and soluble lead to drinking water by 200 - 3500% over a wide range of water qualities when compared to orthophosphate, effectively ending a long term debate as to their impacts. Utilities should consider these adverse effects whenever polyphosphate is used to prevent scaling or iron precipitation. / Ph. D.

The purpose of this research was to investigate the potential application of additive friction stir deposition (AFSD) to repair corroded steel bridge members. AFSD is an emerging solid-state additive manufacturing (AM) technology with many advantageous qualities such as low porosity, low residual stresses, flexibility in material, and a high build rate allowing for large-scale deposits. Two parameters were studied to understand the quality of AFSD on corroded steel: surface roughness and surface cleanliness. Three rounds of depositions were done: AerMet100, a high-strength corrosion-resistant steel, deposited onto AISI 1018 plates, with varying degrees of section loss, sectioned from a bridge taken out-of-service; AISI 1018 steel deposited onto an A572 Gr. 50 plate with 12 holes of varying diameters and depths drilled into the plate to simulate surface roughness; and AISI 1018 steel deposited onto an A572 Gr. 50 plate with mill scale, corrosion, and an industrial three-coat bridge paint system. The repair quality of each deposition was studied using scanning electron microscopy, microhardness testing, and three-point bending. Results from these tests indicated the following: AFSD can sufficiently mix dissimilar steels and result in a fine-grained microstructure; depositing onto a rough surface appeared to aid bonding between the two materials with little to no adverse effects on the repair quality; and finally, depending on the chosen deposition parameters, AFSD can mix foreign surface material into the matrix or mechanically remove the bulk of the foreign surface material appearing to clean the surface during the deposition. / Master of Science / This research investigated the applicability of additive friction stir deposition (AFSD) to repair corroded steel bridge members. AFSD is an emerging technology that can deposit metals without melting and build a part layer by layer similar to 3D printing. Since this process uses relatively low temperatures, the deposited material is not melted thus reducing issues associated with rapid solidification of melted metal. Three studies were conducted to better understand the print quality of AFSD on corroded steel. First, steel was deposited onto a surface with varying sized holes drilled to different depths meant to simulate a corroded surface. Second, a high-strength corrosion-resistant steel was deposited onto a corroded steel plate cut from an old bridge. Last, steel was deposited onto a steel plate with varying prepared surfaces including paint and corrosion. The quality of the depositions was studied through microscopy and mechanical testing. Results from these tests indicated the following: AFSD can sufficiently bond two different types of steels; depositing onto a non-level surface appeared to aid bonding between the two steels; and finally, AFSD can deposit steel onto certain unclean surfaces.

Corrosion of drinking water distribution systems can cost water utilities and homeowners tens of billions of dollars each year in infrastructure damage, adversely impacting public health and causing water loss through leaks. Often, seemingly innocuous choices made by utilities, plumbers, and consumers can have a dramatic impacts on corrosion and pipeline longevity. This work demonstrated that brass pipe connectors used in partial lead service line replacements (PLSLR) can significantly influence galvanic corrosion between lead and copper pipes. Galvanic crevice corrosion was implicated in a fourfold increase in lead compared to a traditional direct connection, which was previously assumed to be a worst-case connection method. In field sampling conducted in two cities, a new sampling method designed to detect particulate lead risks demonstrated that the choice of flow rate has a substantial impact on lead-in-water hazards. On average, lead concentrations detected in water at high flow without stagnation were at least 3X-4X higher than in traditional regulatory samples with stagnation, demonstrating a new 'worst case' lead release scenario due to detachment of lead particulates. Although galvanized steel was previously considered a minor lead source, it can contain up to 2% lead on the surface, and elevated lead-in-water samples from several cities were traced to galvanized pipe, including the home of a child with elevated blood lead. Furthermore, if both galvanized and copper pipe are present, as occurs in large buildings, deposition corrosion is possible, leading to both increased lead exposure and pipe failures in as little as two years. Systematic laboratory studies of deposition corrosion identified key factors that increase or decrease its likelihood; soluble copper concentration and flow pattern were identified as controlling factors. Because of the high copper concentrations and continuous flow associated with mixed-metal hot water recirculating systems, these systems were identified as a worst-case scenario for galvanic corrosion. Deposition corrosion was also confirmed as a contributing mechanism to increased lead release, if copper pipe is placed before a lead pipe as occurs in partial service line replacements. Dump-and-fill tests confirmed copper solubility as a key factor in deposition corrosion impacts, and a detailed analysis of lead pipes from both laboratory studies and field tests was consistent with pure metallic copper deposits on the pipe surface, especially near the galvanic junction with copper. Finally, preliminary experiments were conducted to determine whether nanoparticles from novel water treatment techniques could have a negative impact on downstream drinking water pipeline infrastructure. Although increases in the corrosion of iron, copper, and stainless steel pipes in the presence of silver and carbon nanomaterials were generally small or non-existent, in one case the presence of silver nanoparticles increased iron release from stainless steel by more than 30X via a localized corrosion mechanism, with pitting rates as high as 1.2 mm/y, implying serious corrosion consequences are possible for stainless steel pipes if nanoparticles are present. / Ph. D.