Rafael S. Peres

Black Wattle Tannin As Steel Corrosion Inhibitor

−1 Na2SO4 (pH 6.0 and 2.5). The black wattle tannin when used as a corrosion inhibitor is more effective at acidic pH, its efficiency being dependent on its concentration. At the higher pH value (pH 6.0), a blue-black film (ferric tannate) with a short-term protection against corrosion was formed in aerated aqueous solution. At pH 2.5, this blue-black film was not observed.

Marine-friendly antifouling coating based on the use of a fatty acid derivative as a pigment

This study was devoted to examining the application of copper dodecanoate as a non-contaminant antifouling pigment due to its low copper content and fatty acid nature. For this purpose, antifouling paints with mono-component epoxy resin and rosin matrixes were formulated, and their antifouling efficiency was evaluated. Before its incorporation into the different formulations, the synthesized pigment was characterized. Immersion tests in a marine environment were carried out for 12 months to evaluate the antifouling efficiency of the developed paints; the results were compared with those from a commercial paint. The antifouling efficiency of the new epoxy formulation was found to be considerably higher than that of the rosin formulation and very similar to that of the commercial paint. Most importantly, the release of copper from the epoxy paint formulated with copper dodecanoate was 73.5% lower than that of the commercial paint, suggesting prolonged activity of the developed paint.

Influence of pH in the synthesis of ferric tannate pigment for application in antifouling coatings

Ferric tannate was synthesized at pH 4 and pH 7 (FT4 and FT7, respectively) as a new class of environmentally friendly antifouling pigments. The solubility of both pigments was evaluated by gravimetric tests, showing that FT4 is more soluble than FT7. A mixture of rosin/acrylic resin (9:1 w/w) was sufficient to form an antifouling coating due to improved matrix properties. Electrochemical impedance spectroscopy (EIS) measurements were used to determine the apparent water coefficient of diffusion (D) and coating behavior. The D in the coating formulated with FT4 exhibited better values than that obtained with FT7. EIS results showed that both coatings present Fickian behavior at the initial stages of immersion, while flat Nyquist plots revealed penetration of water in the films. The physicochemical characteristics of FT4 pigment were determined by thermogravimetry and Fourier transform infrared. Immersion tests in the Mediterranean Sea demonstrated the excellent efficacy of the FT4-containing coating against marine fouling after six months of immersion.