Corrosion behavior of 5-hydroxytryptophan (HTP)/epoxy and clay particle-reinforced epoxy composite steel coatings

Abstract

The corrosion behavior of 5-hydroxytryptophan (HTP), and clay particulate reinforced epoxy coatings is studied on a steel substrate that is used widely in pipelines and tanks. The corrosion behavior was studied in sodium chloride (3.5 wt. % NaCl) solutions that simulate potential seawater exposure at pH 3 and 7. X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) were used for microstructural characterization of the samples. The thermal stability was characterized using Thermogravimetric Analysis (TGA). The underlying corrosion reactions and reaction products were also elucidated via Fourier Transform Infrared Spectroscopy (FTIR). Electrochemical impedance spectroscopy (EIS) and in-situ observations of interfacial blisters were used to study the underlying degradation mechanisms. Electrochemical impedance spectroscopy revealed that for prolonged exposure of about 90 days and above, the composite materials exhibited better corrosion resistance at a pH of 3 as seen by the higher diameter of the Nyquist plot. Fewer corrosion products were observed on the scribed areas of the HTP samples in the scribe test in pH of 3 corroding environment. This signifies improved adhesion of the coatings in that environment for the HTP/epoxy coatings. The results obtained also show that a 1 mm blister size was observed in the pristine epoxy sample while no ABOUT THE AUTHOR Ngasoh Fayen Odette obtained a Bachelor degree in Chemistry and Materials Science from the University of Buea, Cameroon in 2010. She also received her M.Sc. in Materials Science and Engineering from the African University of Science and Technology (AUST) in Abuja, Nigeria in 2013. She is actively involved in the research and design of composites using locally sourced materials. She also extensively works in the characterization of these materials for better understanding of their underlying properties. She is certain that the finding from her work will be of interests to researchers in the world of corrosion and composite coatings.

Mechanical Properties of Epoxy/Clay Composite Coatings on an X65 Steel Substrate

“…However, epoxy coatings are prone to damage by surface stresses and indentation/wear phenomena that can occur during service (Saba et al, 2019), (Kalidindi & Subasri, 2014). Coating materials can also result due to abrasive wear phenomena (Ngasoh et al, 2020). Nano-indentation testing can, therefore, be used to evaluate the coating resistance and durability of clay-reinforced epoxy coatings.…”