Organic coatings are extensively used as protective coatings in several industries including the automotive and aircraft industries. The last few years have witnessed an increased interest in improving not only the mechanical properties but also the corrosion protection properties of organic coatings. Among the currently investigated methods of improving the performance of organic coatings is the incorporation of additives in the organic paint matrix. Vapor grown carbon nanofibers (VGCNFs) are a class of carbon fibers that are produced by catalytic dehydrogenation of a hydrocarbon at high temperatures. Depending on the method of synthesis and the post-treatment processes, the diameter of the VGCNFs is normally in the 10-300 nm range. The small size, light weight, high aspect ratio, and unique physical, thermal, mechanical, and electrical properties of VGCNF make it an ideal reinforcing filler in polymer matrix nanocomposites to enhance the mechanical properties of the pure polymeric material in high performance applications in several industries such as the automotive, aircraft, battery, sensors, catalysis, electronics, and sports industries. The main objective of the current investigation was to study the corrosion protection offered by the incorporation of VGCNFs into a commercial alkyd paint matrix applied to the surface of mild steel coupons. The corrosion protection was investigated by immersing samples in air saturated 3% NaCl solution (artificial seawater). The samples were studied by electrochemical impedance spectroscopy (EIS) along with other measurements, including electrochemical (open circuit potential, cyclic voltammetry), chemical (salt spray test), electrical conductivity, and surface analysis (SEM, AFM, optical profilometry, and nanoindentation). The study involved the investigation of the effect of the weight percent (wt %) of the VGCNF as well as the coating film thickness on the corrosion protection performance of the coated steel samples when exposed to the corrosive electrolyte. By way of contrast, the EIS behavior of steel coupons coated with a paint coating incorporating different weight percents of powdered silicon carbide (SiC) particles was also studied. The EIS spectra were used to calculated and graph several corrosion parameters for the investigated systems. At the end, the studied coatings were ranked in order of their anticorrosive properties.

<p>Multifunctional additive manufacturing has the immense potential of addressing present needs within structural health monitoring by enabling a new additive manufacturing paradigm that redefines what a sensor is, or what sensors should resemble. To achieve this, the properties of printed components must be precisely tailored to meet structure specific and application specific requirements. However due to the limited number of commercially available multifunctional filaments, this research investigates the in-house creation of adaptable piezoresistive multifunctional filaments and their potential within structural health monitoring applications based upon their characterized piezoresistive responses. To do so, a rigid polylactic acid based-filament and a flexible thermoplastic polyurethane based-filament were modified to impart piezoresistive properties using carbon nanofibers. The filaments were produced using different mixing techniques, nanoparticle concentrations, and optimally selected manufacturing parameters from a design of experiments approach. The resulting filaments exhibited consistent resistivity values which were found to be less variable under specific mixing techniques than commercially available multifunctional filaments. This improved consistency was found to be a key factor which held back currently available piezoresistive filaments from fulfilling needs within structural health monitoring. To demonstrate the ability to meet these needs, the piezoresistive responses of three dog-bone shaped sensor sizes were measured under monotonic and cyclic loading conditions for the optimally manufactured filaments. The characterized piezoresistive responses demonstrated high strain sensitivities under both tensile and compressive loads. These piezoresistive sensors demonstrated the greatest sensitivity in tension, where all three sensor sizes exhibited gauge factors over 30. Cyclic loading supported these results and further demonstrated the accuracy and reliability of the printed sensors within SHM applications.</p>