Single bath zirconium coating: a greener and smarter industrial surface treatment

Abstract

This study introduces a novel single bath zirconium based nano conversion coating system that integrates both degreasing and surface treatment in a single step eliminating the need for traditional pre-cleaning and multi-stage conversion baths. While zirconium conversion coatings have gained attention as environmentally friendly alternatives to phosphate systems, most implementations in the literature still rely on a separate alkaline degreasing stage, thereby limiting their sustainability and process efficiency advantages. The proposed integrated method addresses this critical gap by offering a fully consolidated pretreatment process, which reduces operational complexity and environmental impact. The system was evaluated on steel substrates and benchmarked against a commercial nano-phosphating process through standardized corrosion resistance (ASTM B117, ISO 4628-3/8), paint adhesion (ISO 2409), and impact resistance (ISO 6272-1) tests. Additional surface characterization was conducted using SEM and EDX techniques. Results demonstrated that the single-bath zirconium system provides superior corrosion protection, improved paint adhesion, and comparable mechanical performance, while achieving substantial reductions in chemical usage (–89%), water consumption (–80%), and energy demand (–100%). Furthermore, it eliminates phosphate sludge waste entirely. By demonstrating – for the first time – a truly integrated zirconium-based surface pretreatment, this work fills a major gap in the literature and positions the technology as a viable, sustainable replacement for conventional phosphating lines.