När en metall är omgärdad av en elektrolyt, så som havsvatten, kommer det att byggas upp en naturlig potential. Det sker en elektronvandring mellan materialet och havsvattnet och ju större potentialskillnad desto större sannolikhet att metallen kommer korrodera. Korrosion är en stor och viktig fråga för offshorekonstruktioner och byggnader.  För att uppnå en konstruktions designade livslängd kan åtgärder vidtas med hänsyn till kapitalkostnader och drift- och underhållskostnader.  Denna studie syftar till att jämföra ekonomiska för- och nackdelar hos de två korrosionsskyddssystemen Galvanic Anode Corrosion Protection (GACP) och Impressed Current Cathodic Protection (ICCP) på havsbaserade vindkraftsfundament. Det förstnämnda systemet använder offeranoder och det sistnämnda är ett katodiskt korrosionsskydd med hjälp av påtryckt ström.  Studien bestod av flera steg av litteraturstudier där teori om korrosion och korrosionssystem användes för att till slut kunna jämföra valda korrosionsskyddssystem.  Resultatet visar att GACP har fler fördelar och färre nackdelar än ICCP och skulle därmed vara mer ekonomiskt fördelaktig i marina miljöer. GACP ger också önskad effekt direkt vid installation och behöver inte någon strömkälla, ICCP är mer komplicerat och är inte effektivt förrän hela systemet är monterat och i drift. Dessutom behöver ICCP extra strömkälla samt kablage. / When a metal is surrounded by an electrolyte, such as seawater, a natural potential will be built up. An electron migration between the material and the seawater will happen and the greater the potential difference, the greater the probability that the metal will corrode. Corrosion is an important issue when it comes to offshore structures. In order to achieve a structure designed lifetime, measures can then be taken with regard to capital costs and operating and maintenance costs. This study aims to compare the economic advantages and disadvantages of the two, Galvanic Anode Corrosion Protection (GACP) and Impressed Current Cathodic Protection (ICCP), corrosion protection systems on offshore wind power foundations. The first mentioned system uses sacrificial anodes and the second is a cathodic corrosion protection by an applied current. The study consisted of several stages of literature studies where theory of corrosion and corrosion systems was used to finally be able to make a comparison between selected corrosion protection systems. The result shows that GACP has more advantages and fewer disadvantages than ICCP and would thus be more economical. GACP, for example, is efficient during installation and does not need an additional power source, but ICCP is more complicated and not efficient until complete assembly of the entire system and requires additional power source and cables. Right now, there is no design standard available with detailed requirements and advice has been given as for galvanic anodes systems.

Hierarchical arrangement of biological composites such as nacre and bone containing high filler (ceramic) content results in high strength and toughness of the natural material. In this study we mimic the design of layered bone microstructure and fabricate an optimal multifunctional bio-nanocomposite having strength, toughness and corrosion resistance. Poly (butylene adipate-co-terephthalate) (PBAT), a biodegradable polymer was used as a substrate material with the reinforcement of LDH (Layered double hydroxide) as a nanofiller in different concentrations to achieve enhancement in mechanical properties as well as processing related thermostability. Corrosion resistance was increased by mimicking a layered structured which incorporated a tortuous diffusion path.

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Magnesium and its alloys are considered as the potential biomaterials due to their biocompatibility and biodegradable characteristics but suffer from poor corrosion performance. Various surface modification techniques are employed to improve their corrosion resistance. In present case, laser surface melting was carried out on AZ31B Mg alloy with various laser energy densities using a continuous wave ytterbium laser. Effect of laser treatment on phase and microstructure evolution was evaluated by X ray diffraction and scanning electron microscopy. Multi-physics thermal model predicted time temperature evolution along the depth of the laser treatment zone. Additionally, electrochemical method and bio-immersion test were employed to evaluate the corrosion behavior in simulated body fluid medium. Microstructure revealed grain refinement and even distribution of Mg17Al12 phase along the grain boundary for laser treated samples leading to substantial enhancement in the corrosion resistance of the laser treated samples compared to the untreated alloy. The laser processed samples also possessed a superior wettability in SBF solution than the untreated sample. This was further reflected in enhanced bio-integration behavior of laser processed samples. By changing the parameters of laser processing such as power, scanning speed, and fill spacing, a controllable corrosion resistance and bioactivity/biocompatibility of the implant material was achieved.

Call number: LD2668 .T4 1965 K21 / Master of Science