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Corrosion, physical characters, and synergetic effects of SAPP and SM in polyurethane coating on galvanized steel

Niloofar Taleghani and Mohammadreza Mohammadzadeh Attar

Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran, Iran



Received: 11 June 2022  Accepted: 28 September 2022


For enhancing the corrosion resistance of polyurethane coatings, the behavior of strontium aluminum polyphosphate (SAPP) and sodium molybdate (SM) on bare galvanized steel was investigated by DC polarization after 24 h of immersion. The synergetic effect of SAPP and SM, at different ratios, was studied and evaluated for up to 24 h. The obtained results show that the ideal mixture had the lowest icorr; therefore, the lowest corrosion rate. Moreover, the morphological properties of the samples were reviewed via scanning electron microscope, energy-dispersive X-ray analysis, and atomic force microscope that concurred the generation of barrier on the surface. Results revealed that samples were immersed in a mixture of pigments with a uniform texture covering the main galvanized layer. A polyurethane coating containing a mixture of SAPP and SM was prepared at the optimum ratio with the optimal λ for this mixture. This coating was applied to galvanized steel, and then, samples were immersed in 3.5 wt% NaCl solution for 60 days and were further studied by electrical impedance spectroscopy (EIS). Moreover, gloss, hardness, and laboratory tests were measured within 60 days. An appropriate relationship between EIS results and non-destructive tests was obtained. There is a reasonable correlation in decreasing hardness and gloss of samples, their physical properties, and Rc, their corrosion resistance over time.

Keywords: Molybdate; SAPP; Corrosion resistance; EIS; Hardness; Gloss

Full paper is available at

DOI: 10.1007/s11696-022-02525-1


Chemical Papers 77 (3) 1497–1506 (2023)

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