Investigation of the Effect of Zinc Phosphate Coating on the Surface Properties of Steel Pieces Used in Forming Processes

Document Type : Research Article


Department of Applied Chemistry, Faculty of Applied Sciences, Malek Ashtar University of Technology P.O. Box 15875-1774, I.R. IRAN


The phosphate coating is one of the most widely used surface treatments of ferrous and non-ferrous metals, due to its low-cost, easy mass production, and ability to afford excellent corrosion resistance, wear resistance, adhesion, and lubricative properties. In this research, formulation of drawing phosphate bath for better cold drawing performance of low carbon steel St37 pieces was investigated. The morphologies of these coatings were observed using scanning electron microscopy (SEM), and their chemical composition and structures were characterized using Energy Dispersive X-ray Spectroscopy (EDS) and X-Ray Diffraction (XRD) analysis. The Wear and friction resistances were investigated by the pin on disk method. The protective properties of phosphate coatings in a 5 wt% NaCl solution have been studied. The results showed that zinc phosphate coating essentially consists of hopeite (Zn3 (PO4 )2 4H2O) and phosphophyllite (Zn2Fe (PO4)2 4H2O) crystal structures. The corrosion resistance for the drawing phosphate coating was obtained 52 hours.  The morphologies of the crystals were needle-shaped in the drawing phosphate coating. The use of simultaneous phosphate coating and lubricant layer reduces significantly the friction coefficient (from 0.6 to 0.15).


Main Subjects

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