Paint and coatings are widely used to protect the metallic structures from corrosion in many civil and industrial applications. In recent decades, the paint industries have directed their efforts in the search for eco-friendly and more sustainable technologies and products, according to the principles of the circular economy. Since the European Union produces annually more than 700 million tons of agricultural wastes that, potentially, can be used as resources in other production processes, the development of eco-friendly protective systems starting from agricultural wastes and by-products has attracted the interest of many industrial sectors, ranging from packaging to automotive industries. Similarly, nontoxic eco-friendly painting systems are needed in the Cultural Heritage field which must strictly comply with the requirements of effectiveness, conservation of a natural surface appearance of the protected artwork and reapplicability. Recently, the aeronautical heritage of the Second World War (WWII), consisting of aircraft or wrecks recovered from sea, lakes or ground, has been officially considered a Cultural Heritage asset, by virtue of its historical and emotional value, but very few studies are still carried out for the development of suitable treatments for a long-term conservation. In the present paper a room temperature cured cutin-based coating derived from tomato peels was developed and applied on a AA2017 T4 alloy, with corrosion behavior similar to that of alloys used for WWII aircraft. Its protective capability was compared, at similar grammage (6.5g/m2), with that offered by a bio-based coating, also derived from cutin extracted from tomato peels, but formulated for industrial purposes (curing at 200°C for 10 minutes) and applied on AA6063 alloy. The corrosion resistance of the coated samples was studied by electrochemical techniques (polarization curves and electrochemical impedance spectroscopy) during 15 days of exposure to an artificial acidic rain at pH =4.5 and 30°C. Moreover, acid rain spray tests at 30 °C were carried out for 4 weeks on cross scratched coupons. The surface morphology and the coating nature were studied before and after the corrosion tests, by Fourier-transform infrared spectroscopy (FTIR) and by scanning electron microscopy (SEM) coupled with energy dispersive x-ray analysis (EDX), performed on both surface and cross sections. The results highlighted very low corrosion rates of the substrates and very high barrier effects for both types of cutin-based bio-lacquers, suggesting that they can provide long term resistance to the tested aggressive environment. This research was carried out within the European Project JPICH - Conservation, Protection and Use - “PROCRAFT, PROtection and Conservation of Heritage AirCRAFT”.
Cutin-based coatings for corrosion protection of Al alloys
Andrea Balbo
;Vincenzo Grassi;Laura de Bellis;Sebastiano Merchiori;Monica Bertoldo;Doriana Scittarelli;Federica Zanotto;Cecilia Monticelli
2022
Abstract
Paint and coatings are widely used to protect the metallic structures from corrosion in many civil and industrial applications. In recent decades, the paint industries have directed their efforts in the search for eco-friendly and more sustainable technologies and products, according to the principles of the circular economy. Since the European Union produces annually more than 700 million tons of agricultural wastes that, potentially, can be used as resources in other production processes, the development of eco-friendly protective systems starting from agricultural wastes and by-products has attracted the interest of many industrial sectors, ranging from packaging to automotive industries. Similarly, nontoxic eco-friendly painting systems are needed in the Cultural Heritage field which must strictly comply with the requirements of effectiveness, conservation of a natural surface appearance of the protected artwork and reapplicability. Recently, the aeronautical heritage of the Second World War (WWII), consisting of aircraft or wrecks recovered from sea, lakes or ground, has been officially considered a Cultural Heritage asset, by virtue of its historical and emotional value, but very few studies are still carried out for the development of suitable treatments for a long-term conservation. In the present paper a room temperature cured cutin-based coating derived from tomato peels was developed and applied on a AA2017 T4 alloy, with corrosion behavior similar to that of alloys used for WWII aircraft. Its protective capability was compared, at similar grammage (6.5g/m2), with that offered by a bio-based coating, also derived from cutin extracted from tomato peels, but formulated for industrial purposes (curing at 200°C for 10 minutes) and applied on AA6063 alloy. The corrosion resistance of the coated samples was studied by electrochemical techniques (polarization curves and electrochemical impedance spectroscopy) during 15 days of exposure to an artificial acidic rain at pH =4.5 and 30°C. Moreover, acid rain spray tests at 30 °C were carried out for 4 weeks on cross scratched coupons. The surface morphology and the coating nature were studied before and after the corrosion tests, by Fourier-transform infrared spectroscopy (FTIR) and by scanning electron microscopy (SEM) coupled with energy dispersive x-ray analysis (EDX), performed on both surface and cross sections. The results highlighted very low corrosion rates of the substrates and very high barrier effects for both types of cutin-based bio-lacquers, suggesting that they can provide long term resistance to the tested aggressive environment. This research was carried out within the European Project JPICH - Conservation, Protection and Use - “PROCRAFT, PROtection and Conservation of Heritage AirCRAFT”.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
