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I am a PhD Researcher that focuses on characterising the microstructural behaviour of superalloys.

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Follow this board to keep up to date with all the recent developments in self-healing coatings

In 10 seconds? Recently there has been a bunch of ongoing research into self-healing coatings. Meaning, if the coating becomes damaged a certain stimuli will cause the coating to regenerate and cover up the exposed area from further damage. Most research has focused on metallic substrates. However, research has began to look at self-healing coatings for concrete infrastructures.

Don’t believe it? Take a look for yourself at the pinned articles and find out the applications where these coatings could significantly reduce the costs of corrosion damage.

What causes the coating to self-heal? In simple terms, they use a method called encapsulation – which utilises microcapsules within the coating that contains the healing agent.

The science behind encapsulation:

  • Cracks form in the matrix wherever damage occurs
  • The crack then perforates the microcapsules, releasing the healing agent into the crack plane through capillary action
  • Contact of healing agent and catalyst, triggering polymerization that bonds the crack faces closed
8 ITEMS PINNED

Microcapsules containing multi-functional reactive isocyanate-terminated polyurethane prepolymer as a healing agent. Part 1: synthesis and optimization of reaction conditions

Abstract: Smart self-healing coatings have been attracting tremendous interest due to their capability for preventing crack propagation in the protective coatings by releasing active agents like isocyanate molecules from micro/nanocapsules. The quality of healed area and subsequent use of the healed coated module are directly related to the chemical composition of healing agent. Faster curing rate and more appropriate physical properties were anticipated for moisture curing of bulky isocyanate molecules than the low molecular weight monomeric analogous. For practical utilization of these advantages, encapsulation of such bulky isocyanate molecules was considered in this work. To this end, optimized preparation and characterization of novel single-layer polyurethane-type microcapsules, richly and efficiently loaded with bulky isocyanate molecules is described. This healing agent was prepared through the reaction of excess amount of isophorone diisocyanate (IPDI) with 2-ethyl-2-hydroxymethyl-1,3-propanediol (TMP). The healing agent was then encapsulated with a polyurethane shell via an oil-in-water (O/W) emulsion polymerization technique. The mixing rate and surfactant concentration were altered to optimize the size and shell thickness of the microcapsules. The prepared microcapsules were very stable after 10 months, and they just lost less than 7 wt% of their loaded isocyanate molecules. The microcapsules were loaded into an epoxy-based coating and the crack healing efficiency of incorporated healing agent was clearly recorded. Microcapsules containing monomeric IPDI were also prepared and crack healing efficiency of these two healing agents regarding crack healing was compared.

Pub.: 08 Dec '15, Pinned: 13 Apr '17

Dual-action smart coatings with a self-healing superhydrophobic surface and anti-corrosion properties

Abstract: This work introduces a new self-healing superhydrophobic coating based on dual actions by the corrosion inhibitor benzotriazole (BTA) and an epoxy-based shape memory polymer (SMP). Damage to the surface morphology (e.g., crushed areas and scratches) and the corresponding superhydrophobicity are shown to be rapidly healed through a simple heat treatment at 60 °C for 20 min. Electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) were used to study the anti-corrosion performance of the scratched and the healed superhydrophobic coatings immersed in a 3.5 wt% NaCl solution. The results revealed that the anti-corrosion performance of the scratched coatings was improved upon the incorporation of BTA. After the heat treatment, the scratched superhydrophobic coatings exhibited excellent recovery of their anti-corrosion performance, which is attributed to the closure of the scratch by the shape memory effect and to the improved inhibition efficiency of BTA. Furthermore, we found that the pre-existing corrosion product inside the coating scratch could hinder the scratch closure by the shape memory effect and reduce the coating adhesion in the scratched region. However, the addition of BTA effectively suppressed the formation of corrosion products and enhanced the self-healing and adhesion performance under these conditions. Importantly, we also demonstrated that these coatings can be autonomously healed within 1 h in an outdoor environment using sunlight as the heat source.

Pub.: 04 Jan '17, Pinned: 13 Apr '17

Environmentally-friendly smart coatings for materials protection: State of the art and future perspectives

Abstract: Qatar Foundation Annual Research Forum Proceedings, Volume , Issue 2013, November 2013. The huge economic impact of the corrosion of metallic structures is a very important issue for all modern societies. Reports on the corrosion failures of bridges, buildings, aircrafts, automobiles, and gas and oil pipelines are not unusual. It is estimated that corrosion and its consequences cost developed nations between 3% and 5% of their gross domestic product. The process involving hexavalent chromates is the most effective and most widely used conversion coatings for corrosion protection for many metals and alloys. However, the carcinogenic effect and environmental waste due to chromates are well documented. The concept of 'self-healing', 'self-repairing' or 'smart' materials has in recent years been developed experimentally in new types of manufactured materials creating a new class of multifunctional materials of self healing properties. Such properties add functionality to the materials to heal themselves automatically after mechanical, physical or chemical damages caused, for example, by scratch, impact, abrasion, erosion, friction, corrosion, wear, fire, ice, etc. The development of active corrosion protection systems for steels, Al and Mg substrates is an issue of prime importance in key industries, including petroleum, chemicals, transportation. The present work provides new insights towards the development of new protective systems with self-healing functionality. The proposed coatings characterize with the self-healing ability, ease of application at low cost and safety. When the new chromate-free surface treatments are applied prior to Fluoropolymer top coating, the coatings exceed 2000-hour salt spray tests. The approach described herein can be used in many industrial applications where active corrosion protection of materials is required.

Pub.: 22 Nov '13, Pinned: 13 Apr '17

Inhibition of Mild Steel Corrosion using Chitosan–Polyvinyl Alcohol Nanocomposite Films by Sol–Gel Method: An Environmentally Friendly Approach

Abstract: Coatings tailored to corrosion protection of metallic substrates are of the utmost relevance to ensure reliability and long-term performance of coated parts as well as the product value of the coated materials. Presently, there is a strong emphasis on the development of advanced functional and smart coatings for corrosion protection in different technological applications. This work aimed to develop a novel coating based on chitosan and PVA to evaluate its corrosion inhibition effect on mild steel. Chitosan/PVA films were coated on mild steel by dip coating technique. Sol–gel protective coatings have shown excellent chemical stability, oxidation control and enhanced corrosion resistance for metal substrates. Further, the sol–gel method is an environmentally friendly technique of surface protection which has traditionally been used for increasing corrosion resistance of metals. Films so formed were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), the thermal property of the chitosan–PVA film was examined by differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Corrosion protection behavior of these coated mild steel substrates in 0.1 N HCl solutions was evaluated by potentiodynamic polarization studies (Tafel), linear polarization studies (LPR), and electrochemical impedance spectroscopy studies (EIS). The experimental results showed that the chitosan/PVA composite coatings were superior to pure chitosan in corrosion protection. EIS measurements and Tafel polarization method have proven that corrosion resistance of mild steel in 0.1 N HCl solutions, increases with increasing the number of layers of chitosan/PVA films. The results indicated that the polymer film adhered to the mild steel surface and inhibited the mild steel corrosion in 0.1 N HCl. Coatings tailored to corrosion protection of metallic substrates are of the utmost relevance to ensure reliability and long-term performance of coated parts as well as the product value of the coated materials. Presently, there is a strong emphasis on the development of advanced functional and smart coatings for corrosion protection in different technological applications. This work aimed to develop a novel coating based on chitosan and PVA to evaluate its corrosion inhibition effect on mild steel. Chitosan/PVA films were coated on mild steel by dip coating technique. Sol–gel protective coatings have shown excellent chemical stability, oxidation control and enhanced corrosion resistance for metal substrates. Further, the sol–gel method is an environmentally friendly technique of surface protection which has traditionally been used for increasing corrosion resistance of metals. Films so formed were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), the thermal property of the chitosan–PVA film was examined by differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Corrosion protection behavior of these coated mild steel substrates in 0.1 N HCl solutions was evaluated by potentiodynamic polarization studies (Tafel), linear polarization studies (LPR), and electrochemical impedance spectroscopy studies (EIS). The experimental results showed that the chitosan/PVA composite coatings were superior to pure chitosan in corrosion protection. EIS measurements and Tafel polarization method have proven that corrosion resistance of mild steel in 0.1 N HCl solutions, increases with increasing the number of layers of chitosan/PVA films. The results indicated that the polymer film adhered to the mild steel surface and inhibited the mild steel corrosion in 0.1 N HCl.

Pub.: 08 Nov '16, Pinned: 13 Apr '17