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Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Chemical and Biochemical Engineering

Supervisor

Zhu, Jingxu

2nd Supervisor

Zhang, Hui

Co-Supervisor

Abstract

Zinc-rich powder coatings (ZRPCs) are promising environmentally friendly alternatives to solvent-borne zinc-rich coatings. There are several difficulties and challenges with formulating and manufacturing these coatings. A novel technique without extrusion was assessed to avoid excessive wear of the screws during the conventional extrusion of zinc-rich powder coatings. ZRPCs were formulated by selecting a suitable polyester resin, determining the zinc content, additive dosages, etc., and applied as a single layer. An additional wetting agent further improved the surface quality. A double-layer system consisting of ZRPC as a basecoat and a polyester topcoat was designed. The PDMS as an additive imparted hydrophobicity and self-healing to both coatings. In addition, a 30% recovery of self-healing efficiency was provided by PDMS after the wiping test. The coating system exhibited superior corrosion resistance in a 3000-h neutral salt spray test. The formulation offers novel ways to manufacture high-performance powder coatings for heavy-duty applications.

Summary for Lay Audience

Zinc-rich coatings provide decoration and protection when applied onto different substrates. In terms of anti-corrosive coatings, they protect the metallic substrates from corrosion, which naturally occurs and damages the materials. Solvent-borne liquid coatings still dominate the coating market for anti-corrosive purposes. In the past decades, zinc-rich powder coatings (ZRPCs) have become more appealing than liquid coatings in the market because of their economical, ecological, environmental, and energy-saving benefits.

In this study, two subprojects are included to improve zinc-rich powder coatings. The first subproject is to investigate the surface quality of single-layer ZRPCs by finding the appropriate polyester resin, dosages of additives, and zinc content. Further addition of a wetting agent improved the surface quality. A novel press bonding technique was assessed and applied to avoid the excessive wear of the screws during the conventional extrusion process. The polyester resin CRYLCOAT 4488-0, zinc content of 83 wt.%, dosages of additives, and particle size of the binders were experimentally optimized. The addition of 1.5 wt.% of the wetting agent was determined. The corrosion resistance of the formulated ZRPC was tested by a neutral salt spray test.

The second subproject is to investigate the effect of PDMS on a double-layer coating system consisting of 80 wt.% ZRPC as a basecoat and a black polyester topcoat. PDMS imparted hydrophobicity and self-healing to both coatings. A 30% recovery of self-healing efficiency was obtained by adding PDMS 28 days after the wiping test. The basecoat containing 0.025 wt.% PDMS in the binder and additive portion, with the topcoat containing 0.05 wt.% coating system, presented excellent corrosion protection in a 3000-h neutral salt spray test. The formulation provides novel approaches to manufacturing anti-corrosive powder coatings for heavy-duty and decorative applications.

In this study, two subprojects are included to improve zinc-rich powder coatings. The first subproject is to investigate the single layer surface quality of ZRPCs by finding the appropriate polyester resin, dosages of additives, and zinc content. Further addition of a wetting agent improved the surface quality. A novel press bonding technique was assessed and applied to avoid the excessive wear of the screws during the conventional extrusion process. The polyester resin CRYLCOAT 4488-0, zinc content of 83 wt.%, dosages of additives, and particle size of the binders were experimentally optimized. The addition of 1.5 wt.% of the wetting agent was determined. The corrosion resistance of the formulated ZRPC was tested by neutral salt spray test.

The second subproject is to investigate the effect of PDMS on a double layer coating system consisting of 80 wt.% ZRPC as a basecoat and a black polyester topcoat. PDMS imparted hydrophobicity and self-healing to both coatings. A 30% recovery of self-healing efficiency was obtained by adding PDMS during 28 days after the wiping test. The basecoat containing 0.025 wt.% PDMS in the binder and additive portion, with the topcoat containing 0.05 wt.% coating system presented excellent corrosion protection in a 3000-h neutral salt spray test. The formulation provides novel approaches to manufacture anti-corrosive powder coatings for heavy-duty and decorative applications.

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Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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