Corrosion Resistance of a Sand Particle-Modified Enamel Coating Applied to Smooth Steel Bars.

Fujian Tang,Genda Chen,Richard Brow,Michael Koenigstein

doi:10.3390/ma7096632

Fujian Tang, Genda Chen + Show 2 more

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https://doi.org/10.3390/ma7096632

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Abstract

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.

Highlights

The most commonly used coatings to protect steel bars from corrosion in reinforced concrete (RC)structures are fusion-bonded epoxy (FBE) and hot-dipped galvanized zinc (HDG) [1,2,3]
This study aims to investigate the corrosion performance of sand particle-modified enamel coating in 3.5 wt% NaCl solution
The corrosion resistance of steel bars with enamel coatings modified by different percentages of sand particles was tested in 3.5 wt% NaCl solution by electrochemical impedance spectroscopy (EIS)

Summary

Introduction

The most commonly used coatings to protect steel bars from corrosion in reinforced concrete (RC). Structures are fusion-bonded epoxy (FBE) and hot-dipped galvanized zinc (HDG) [1,2,3]. The main issue with epoxy-coated bars is the reduction in bond strength or force transmissibility between steel bars and their surrounding concrete [4,5]. Hot-dip galvanized zinc coatings have two main concerns in engineering applications. The zinc coating corrodes vigorously due to the high alkaline environment in fresh concrete if no passive film is formed. The hydrogen produced in the cathodic reaction increases the porosity of adjacent cement pastes and reduces the bond strength between the bars and the concrete [7]

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