Anti-corrosion carbon-based composite epoxy coating for marine industry

• Main Author: Artemova, Anastasiia
• Other Authors: Huang Yizhong
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Engineering::Materials
• Online Access: https://hdl.handle.net/10356/142799
• Institution: Nanyang Technological University

Corrosion and biofouling are severe global problems that cost hundreds of billion dollars annually. The protective coating is the most widespread technology among various methods used in anti-corrosion and anti-fouling. Traditional coating materials (e.g., Crbased, Zn-based, or biocide-containing anti-corrosive/fouling coatings) suffer from poor performance, environmental hazards, and high cost. This project aims to develop coating materials with carbon nanomaterials additives that provide triple protection (anti-corrosion, anti-fouling, and anti-decay) and are also environmentally friendly, non-cytotoxic, low cost, and long-lasting. In this manuscript, the performance in the corrosion protection of the graphene oxide-based and carbon nanotubes-based composite coatings were investigated. Based on the literature review, the corrosion mechanism is complex, and a number of factors affected on it, such as coating composition, environmental conditions, and design. Several mechanisms of the corrosion protection are described, cathodic and anodic protection, inhibitors and coatings, which were chosen as an object of the investigation due to the most comprehensive anticorrosion technology. Composite coatings consist of binder, pigments, solvent, and additives. The first two components are the most important in the anti-corrosion protection. For the marine industry, the most common binder is epoxy resin and polyurethane. Bisphenol A epoxy resin was used to control the cost-effectiveness of the development coating. Different pigments can provide anti-corrosion protection, but the carbon-based pigments are the most perspective one, therefore was used as an object for this research work. Carbon-based materials are excellent materials for applications in the coating due to its exceptional chemical inertness, outstanding mechanical strength, non-cytotoxicity, and unique antibacterial/anticorrosive properties. Besides graphene oxide (GO), other carbon nanomaterials such as nitrogen-doped graphene oxide (N-GO), cylindrical and conical carbon nanotubes (cyl-, con-CNT), nitrogen-doped carbon nanotubes (N-CNT) are chosen and synthesized for anti-corrosion pigment purpose, and physicochemical properties of materials are explored to have better understanding of the nature of the pigment. It was hypothesized that nitrogen doping of the carbon nanomaterials would improve the protection properties. This thesis focused on the investigation of the influence of the carbon-based materials on the coating and coating performance under different aggressive conditions, which are described in four chapters. The first chapter described the performance of the carbon-based coatings system in the 3.5% NaCl solution. The effect of the different carbon-based materials on the coating performance is introduced, and the electrochemical parameters were investigated. It was found that nitrogen contain decreases the corrosion rate in four times, however, carbon-based pigments - in only two times in comparison with pure epoxy coating. Secondary, the impact of the ultraviolet radiation on the coating degradation was explored, and the degree of the coating degradation was calculated. It was shown that carbon-based pigments absorb the UV radiation and prevent the coating from deterioration. The carbon nanotubes due to the structure provide better prevention form the UV radiation and pitting corrosion. In the third part, the effect of the immersion to the sodium chloride solution was studied. The importance of the structure of the pigment materials and its composition was established. The nitrogen-doped carbon nanotube composite coating showed the lowest absorption volume, and corrosion rate, and however the nitrogen-doped graphene oxide composite coating absorbs much water it still decreases the corrosion rate, prevent the pitting corrosion and hydrolytic degradation. Finally, the coating behavior under weathering degradation was explained, and the mechanism of the protection by the nitrogen-doped pigments was formulated. The novelty of this research is that the impact of the structure and composition of the carbon-based nanomaterials were studied, as well as using nitrogen-doped graphene oxide and nitrogen-doped carbon nanotubes as anti-corrosion pigment was reported for the first time. The recommendation for future research, such as investigation of the concentration and nitrogen percentage influence on the protection properties are suggested to reach the highest effectiveness of the coating. This fundamental study is the first step in solving the global problem of corrosion.