Abstract
In order to develop waterborne silicate anticorrosive coatings to replace solvent-based anticorrosive coatings used widely in the shipping industry, epoxy modified silicate emulsions were synthesized with different contents of epoxy resin, then aqueous silicate zinc-rich coatings were prepared with the synthesized silicate emulsion, triethylamine, and zinc powder. The influence of the content of epoxy on the properties and chemical structure of the modified emulsion, mechanical properties of the silicate coatings, and corrosion behavior of the silicate zinc-rich coatings in 3.5% NaCl solution were investigated. The coating samples on steel were measured by the immersion test, Tafel polarization test, and electrochemical impedance spectroscopy (EIS) test with different immersion times. The results showed that epoxy modified silicate emulsions were successfully synthesized. With the increase in epoxy content, the viscosity and solid content of the modified emulsion increased, the impact resistance of the silicate coating rose, the pencil hardness decreased, but the adhesion was not affected. Epoxy modification can reduce, to a certain extent, the corrosion driving force of the zinc rich coating and increase the impedance of the zinc-rich coating, which decreases with the increase of immersion time in 3.5% NaCl solution. With the increase in the epoxy content, the impedance value of the zinc-rich coating increases, indicating that the ability of the coating to resist corrosive media is enhanced.
Highlights
To prevent the seawater corrosion of a ship’s hull during its navigation, anticorrosive coatings have always been used worldwide
The anticorrosive zinc-rich paint was prepared with the following composition and consisted of three components: Component A is the silicate emulsion E777-2 or epoxy modified silicate emulsion prepared as above-mentioned; Component B is triethylamine; and Component C is the zinc powders
The emulsion samples were tested by the attenuation total reflection (ATR) method with Fourier transform infrared spectroscopy (FTIR) from PERKINELMER (Waltham, MA, USA)
Summary
To prevent the seawater corrosion of a ship’s hull during its navigation, anticorrosive coatings have always been used worldwide. By using zinc powder as sacrificial anode type filler in a zinc rich coating, which has more negative corrosion potential than the protected substrate, it plays a cathodic protection role on the substrate Such coatings will release a large amount of toxic volatile organic compounds (VOCs) during its application [7]. Water-based inorganic zinc-rich coatings are mainly composed of film-forming base materials (including inorganic polymers such as silicates, phosphates, and dichromate) and zinc powder. It has excellent performance in terms of conductivity, weather resistance, and solvent resistance [9,10]. Epoxy resin was used to modify the silicate emulsion to decrease the brittleness, improve the impact resistance, and the corrosion resistance of the water-based silicate coating in this paper
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