Development of alkyd-based copper sorbate coatings for anti-corrosion and anti-biofouling applications

Biofouling is a serious problem in various industrial sectors such as shipping infrastructure, cooling water systems, and aquaculture. Biofilm formation by different types of microorganisms plays a very crucial role in this biofouling process. Biofouling on metallic surfaces accelerates aggressive corrosion processes. Therefore, it is essential to develop antifouling coatings with corrosion resistance for effective protection.

In the present study, copper sorbate (CS) and copper oxide (CuO) were synthesized as antifouling pigments and characterized using a UV-vis spectrometer, Fourier transform infrared spectroscopy, X-ray diffraction, and field emission scanning electron microscopy. Both pigments in different ratios were used for the formulation of antifouling and anti-corrosion paints. Salt spray test and anti-corrosion test were performed in the presence of 3.5% NaCl solution for 30 days. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization were recorded for all the tested specimens.

The results indicate that CS-rich coatings (15%20% of CS) display higher corrosion resistance than CuO-rich coatings. The antifouling potential of the coated mild steel was evaluated by immersing them in the marine estuarine water, and surface changes were monitored at regular intervals. All coatings exhibited considerable antifouling effects up to 60 days of immersion. Notably, the CS-II coating, containing only 5% CuO with 15% of CS, showed significant fouling resistance up to 90 days. At the end of 120 days, SEM analysis confirmed that a huge number of marine microorganisms (mostly diatoms) settled on CS-I, CS-III, CS-IV, and CS-V, but minimal microorganisms were only noticed on CS-II. This could be due to the antimicrobial activity and controlled leaching behavior of both pigments in marine conditions.