Investigations of Press Bonded Zinc-Rich Powder Coatings
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.