The protective performance of a sand particle-modified enamel coating on reinforcing steel bars was evaluated in 3.5 wt% NaCl solution by electrochemical impedance spectroscopy (EIS). Seven percentages of sand particles by weight were investigated: 0%, 5%, 10%, 20%, 30%, 50% and 70%. The phase composition of the enamel coating and sand particles were determined with the X-ray diffraction (XRD) technique. The surface and cross-sectional morphologies of the sand particle-modified enamel coating were characterized using scanning electron microscopy (SEM). XRD tests revealed three phases of sand particles: SiO2, CaCO3 and MgCO3. SEM images demonstrated that the enamel coating wetted well with the sand particles. However, a weak enamel coating zone was formed around the sand particles due to concentrated air bubbles, leading to micro-cracks as hydrogen gas pressure builds up and exceeds the tensile strength of the weak zone. As a result, the addition of sand particles into the enamel coating reduced both the coating and corrosion resistances.


Civil, Architectural and Environmental Engineering

Second Department

Materials Science and Engineering

Keywords and Phrases

Bars (metal); Calcium carbonate; Coatings; Corrosion resistance; Electrochemical corrosion; Electrochemical impedance spectroscopy; Enamels; Scanning electron microscopy; Tensile strength; X ray diffraction; 3.5 wt% NaCl solution; Cross-sectional morphology; EIS; Enamel coatings; Hydrogen gas pressure; Protective performance; Sand particles; XRD; Sand

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version

Final Version

File Type





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Publication Date

01 Sep 2014