Incorporation of a Coumarate Based Corrosion Inhibitor in Waterborne Polymeric Binders for Corrosion Protection Applications

Abstract

The incorporation of organic corrosion inhibitors into waterborne coatings is optimized in this work. Herein, p‐coumaric acid (4‐hydroxycinnamic acid) is modified by a butyl radical and its effectiveness as an anticorrosive free inhibitor in solution is confirmed by potentiodynamic polarization (PP). The molecule is then successfully incorporated into waterborne polymeric binders by employing different polymerization techniques in dispersed media. Whenever possible, the inhibitor is also blended into the bare latexes to compare the effect of the incorporating method. The anticorrosion performance of the obtained coatings is tested and compared by electrochemical analysis. Promising results are obtained for the coatings produced by semibatch emulsion polymerization even at the low concentration of 1.5 mg of inhibitor g−1 latex. The intact control coating without inhibitor shows an impedance of up to 106 Ω and a phase angle of 72° after 1 h of immersion in the corrosive medium, meanwhile the coating with inhibitor shows higher values, 106.7 Ω and 80°. Active corrosion inhibition is observed in the coating with inhibitor in which a defect has been done, as the impedances drop to 103.9 Ω after 24 h of immersion in the saline solution while in the control scratched coating it drops to 103.6 Ω.

Comparison of the Corrosion Inhibition Ability of Different Coumarate-Based Compounds Incorporated into Waterborne Binders

“…The coating with HCF3 obtained the maximum impedance of 10 6.2 Ω and phase angle of 82°(Figure 4D), and the one with H4 incorporated 10 6.3 Ω and a phase angle of 82°(Figure 4E). In comparison to a similar latex previously reported, 28 in which only 1.5 mg of H4/g of latex (0.3 g of H4/100 g of monomer) could be incorporated by a semibatch emulsion, the coating reported here has improved stability. While not showing as high of an initial impedance, the coating reported here maintained an impedance around 10 6.1 Ω and a phase angle around 80°.…”

“…However, the inhibitors were not able to be detected by UV because the signals of the aromatic ring of the surfactant present in the films, Dowfax 2A1, mask the inhibitor signal. Therefore, the leaching tests were performed using the free films formed from latexes with inhibitors blended in a latex synthesized by dispersion polymerization with a surfactant that does not have aromatic rings, Visiomer MPEG 2005 . The concentration of inhibitor in the blend was 3% g inhibitor/monomer weight.…”

“…Therefore, the leaching tests were performed using the free films formed from latexes with inhibitors blended in a latex synthesized by dispersion polymerization with a surfactant that does not have aromatic rings, Visiomer MPEG 2005. 28 The concentration of inhibitor in the blend was 3% g inhibitor/ monomer weight. The percentage of leaching of the additive inhibitors after 1, 5, and 24 h in contact with water (pH 7) is shown in Figure 3.…”

“…In a previous work, the inhibitory property of the butoxy p-coumaric acid (H4) derived from pcoumaric acid was investigated as a free inhibitor in solution and when incorporated into waterborne latexes by different polymerization techniques. 28 A waterborne coating made by semibatch seeded emulsion polymerization showed promising results for corrosion mitigation, even when the inhibitor was as low as 0.15% based on the polymer. The work by Quites et al also included the incorporation of H4 by dispersion polymer-ization in a continuous methanol/water phase, as well as its blending at the final control latex (without inhibitor), aiming for a higher concentration of inhibitor into the system (3% based on polymer), but it resulted in poor coatings.…”

“…Therefore, the incorporation of the coumarate-based inhibitors has been attempted in waterborne latexes, a more interesting methodology from the industrial application point of view. In a previous work, the inhibitory property of the butoxy p -coumaric acid (H4) derived from p -coumaric acid was investigated as a free inhibitor in solution and when incorporated into waterborne latexes by different polymerization techniques . A waterborne coating made by semibatch seeded emulsion polymerization showed promising results for corrosion mitigation, even when the inhibitor was as low as 0.15% based on the polymer.…”