A novel organic-inorganic PMMA/polysilazane hybrid polymer for corrosion protection

Polyacrylates have many interesting properties. Among them, PMMA stands out and has been widely used in coatings, paints and adhesives. However, their application is limited by low corrosion and thermal resistance. One way to enhance its properties is the addition of silicon polymers with adequate characteristics. Polysilazanes, consisting of a Si-N backbone with or without pendent carbon-containing groups, are among the most outstanding silicon polymers. In this study, hybrid materials of PMMA and polysilazane HTT1800 were synthesized via solution polymerization and deposited on metallic substrates by dip-coating. The structure and the thermal stability of the developed hybrid polymers were studied by Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The adhesion of the coatings was investigated according to the tape test standard (ASTM D3359) combined with inspection by scanning electron microscopy (SEM). The wettability of the surface was evaluated by sessile drop method. Additionally, the corrosion resistance of uncoated and coated substrates was investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves. The FTIR data evidenced the occurrence of weak interactions between PMMA and HTT1800. However, the formation of a few strong bonds could not be excluded. The addition of HTT1800 improved the thermal stability of the formed materials. Furthermore, the hydrophobicity and the adhesion between the developed coating and the metallic substrate were also improved, in comparison with pure PMMA. The potentiodynamic polarization curves and EIS analysis demonstrated that the hybrid coatings act as an efficient protective barrier by increasing the corrosion resistance and reducing the current densities compared to uncoated substrate and pure PMMA.