ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Effects of polyethylene glycol additive on zinc phosphate conversion coating of carbon steel

Jiongyan Liu, Mulin Jian, Lvyun Chen, Ningning Xu, Dong Li, and Shihuai Zhao

School of Chemistry Engineering and Technology, Tiangong University, Tianjin, China

E-mail: shhzhao2016@126.com

Received: 27 July 2021  Accepted: 8 September 2021

Abstract:

Phosphating treatment is an effective process to inhibit corrosion of steel materials. In practical application, additives often need to be introduced into phosphating bath in order to achieve some desired properties. In this paper, polyethylene glycol was used as an additive for zinc phosphating treatment. The structure of the zinc phosphate conversion coating was studied by scanning electron microscope and X-ray powder diffractometer. And corrosion resistance of the zinc phosphate conversion coating was tested by means of electrochemical impedance spectroscopy and Tafel polarization methods. Experiments show that polyethylene glycol can be used as a precipitating bed for capturing metallic ions, thus facilitating the nucleation of phosphate crystals. The growth trend of hopeite (Zn₃(PO₄)₂·4H₂O) crystal increases along (020) and (220) directions, and the crystal growth changes from axial direction to radial direction. When the concentration of polyethylene glycol was 0.8 g/L, the zinc phosphate conversion coating exhibited the most uniform and dense structure and strongest corrosion resistance. In addition, polyethylene glycol plays an important role in improving the adhesion between phosphate conversion coating and organic coating.

Keywords: Phosphating; Polyethylene glycol; Corrosion resistance; Carbon steel

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-021-01868-5

Chemical Papers 76 (1) 409–416 (2022)