Corrosion Resistance Performance of Epoxy Coatings Incorporated with Unmilled Micro Aluminium Pigments

Abstract

The current work is in continuation of our previous work where we reported changes in the properties of epoxy coatings using two different types of hardener in different stoichiometric ratios. The best results-oriented coating stoichiometry was then taken in this research for further modification with the incorporation of 1, 2 and 3 wt.% micro aluminium (Al) pigments designed for coating carbon steel panels. After 7 d of curing, the coated panels were characterized using X-ray diffraction (XRD), (SEM) scanning electron microscopy, (TGA) thermogravimetric analysis, pendulum hardness, a scratch test and nano-indentation. Electrochemical tests were carried out for various exposure periods of time, i.e., 1 h, 7 d, 14 d, 21 d and 30 d, in a 3.5% sodium chloride (NaCl) solution. For the coatings, we found that the presence of 1% Al provided the highest corrosion resistance after exposure periods in the NaCl solution. We also found that prolonging the immersion time decreases the corrosion resistance after 7 d, but increasing the time of immersion to longer periods (14 d, 21 d and 30 d) enhances the corrosion resistance and reduces the degradation of the coatings.

Keywords

• epoxy coatings
• aluminium powder
• corrosion
• nanoindentation
• electrochemical techniques