Abstract
Three different coated steel systems were aged in natural or artificial seawater, in neutral salt spray (NSS), and using alternate immersion tests in order to evaluate the aggressiveness of the different ageing conditions. Commercial epoxy coatings were applied onto steel (S355NL), hot-galvanized steel (HDG), and Zn-Al15 thermal spraying coated steel. The defect-free systems were immersed in artificial seawater at 35 °C for 1085 days and in natural seawater for 1200 days and were characterized by electrochemical impedance spectroscopy (EIS). Panels with artificial defects were immersed for 180 days in artificial seawater and, regarding adhesion, were evaluated according to ISO 16276-2. In parallel, the three coated systems were submitted to cyclic neutral salt spray (NSS) for 1440 h: defect-free panels were regularly evaluated by EIS, while the degree or corrosion was measured onto panels with artificial defect. After NSS, defect-free panels were immersed in artificial seawater at 35 °C for further EIS investigations. Finally, alternate immersion tests were performed for 860 days for the three defect-free coated systems and for 84 days for panels with a defect. The results showed that, for defect-free panels, immersions in natural or artificial seawater and NSS did not allowed us to distinguish the three different systems that show excellent anticorrosion properties. However, during the alternate immersion test, the organic coating system applied onto HDG presented blisters, showing a greater sensitivity to this test than the two other systems. For panels with a defect, NSS allowed to age the coatings more rapidly than monotone conditions, and the coating system applied onto steel presented the highest degree of corrosion. Meanwhile, the coating systems applied onto HDG and the thermal spray metallic coating showed similar behavior. During the alternate immersion test, the three coated systems with a defect showed clearly different behaviors, therefore it was possible to rank the three systems. Finally, it appeared that the alternate immersion test was the most aggressive condition. It was then proposed that a realistic thermal cycling and an artificial defect are needed when performing ageing tests of thick marine organic coating systems in order to properly rank/evaluate the different systems.
Highlights
The sea is a potentially huge source of energy, but the development of Marine Renewable Energy (MRE) technologies able to harness that energy is at a relatively early stage [1]
An effective solution to protect against corrosion is organic coatings [2,3] which can be applied with high thicknesses and/or can be associated with cathodic protection [4]
This work aimed to study the ageing of an epoxy coating system applied onto three different metallic substrates, using different ageing tests in natural or artificial seawater, neutral salt spray, and an alternate immersion test, in order to evaluate the aggressiveness of the different ageing conditions
Summary
The sea is a potentially huge source of energy, but the development of Marine Renewable Energy (MRE) technologies able to harness that energy is at a relatively early stage [1]. Part of the problem is that seawater is an aggressive medium, and that metallic structures are submitted to corrosion. An effective solution to protect against corrosion is organic coatings [2,3] which can be applied with high thicknesses and/or can be associated with cathodic protection [4]. Epoxy-based marine coatings have been widely applied for the anticorrosion of metallic materials due to their low cost and their efficiency in aggressive mediums such as seawater [5,6]. All organic coating formulations have to be tested before being applied in order to offer a guarantee in terms of lifetime and effectiveness [7] because they suffer from degradation from the environment. Much research has been devoted to evaluating the performance of organic coatings using natural or artificial tests [2,8,9,10,11,12,13,14,15,16]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
