På senare år har efterfrågan på stålmaterial av låg vikt ökat, speciellt inom transportsektorn. Genom att addera Al till stål sänks densiteten vilket gör att FeAl-legeringar är ett lovande material för fordonskonstruktion. Vätskekorrosionsegenskaper undersöktes av 3D – printade FeAl prover som innehöll 0 – 10 vikt% Al och 0,1 vikt% Zr för att bestämma hur korrosionsegenskaperna förändrades med avseende på Al – innehållet. Korrosionsresistansen var i stor utsträckning beroende av huruvida en passiv film av Al2O3 bildades på ytan eller ej. Korrosionshastigheten bestämdes genom EIS – och PDP – analyser utförda i 3,5 vikt% NaCl-lösning samt genom viktförlusttester i 1 M HCl respektive 0,5 M H2SO4. Vidare karaktäriserades proverna genom XRF, XRD, EDS, SEM och optisk mikroskopi vilket bland annat visade på att samtliga prover var enfassystem samt att den kemiska sammansättningen var enligt förväntan. Vidare indikerade optisk mikroskopi och SEM att ett högre Al – innehåll resulterar i att proverna blir mer porösa. Elektrokemiska tester antyder att ett Al – innehåll om 10 vikt% förbättrade korrosionsresistansen. Detta antyder möjligen, men kan inte definitivt fastslås från de utförda experimenten, att det krävs 10 vikt% Al för att en passiv film som täcker hela materialytan ska bildas. Korrosionshastigheten var 7 – 10 gånger högre vid viktförlusttest jämfört med elektrokemiska test. Detta förklaras genom att den skyddande passiva filmen bröts ned under de sura förhållanden som viktförlusttesten utfördes i medan den passiva Al2O3 filmen kunde bestå i de pH – neutrala förhållanden som elektrokemiska test utfördes vid. Detta speglar att bildandet och stabiliteten av Al2O3-filmen är vitalt för att sänka korrosionshastigheten. / In recent years the demand for lightweight ferritic steels has increased, particularly for transport applications. The addition of Al lowers the density, hence making FeAl alloys promising materials for such constructions. Aqueous corrosion properties of 3D – printed FeAl samples ranging from 0 – 10 wt% Al and containing 0.1 wt% Zr were investigated to determine how the Al content affects the corrosion resistance. The corrosion rate was found to greatly depend on the formation and stability of a protective passive film of Al2O3 forming on the material surface. A corrosion rate was obtained via EIS and PDP in 3.5 wt% NaCl as well as via weight loss testing in 1 M HCl and 0.5 M H2SO4. Additionally, XRF, XRD, EDS, SEM and optical microscopy tests were carried out to characterize the samples. XRF and EDS confirmed that the elemental composition of the samples was as expected and XRD indicated that all samples were single phase systems. Furthermore, optical microscopy and SEM indicated that higher Al content makes the samples more porous. Electrochemical testing indicated that addition of 10 wt% Al greatly improves the corrosion properties suggesting that it may require 10 wt% Al to form a passive film that covers the whole surface, although this cannot be said for certain from these experiments. Moreover, the corrosion rate was 7 – 70 times lower during electrochemical testing compared to weight loss testing, in which the passive film breaks down due to the acidic conditions. This emphasizes that the stability of the Al2O3 film is vital for slowing down the corrosion rate of FeAl alloys.

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.