A unique graphene composite coating suitable for ultra-low temperature and thermal shock environments

Abstract

Traditional epoxy resin is prone to cracking and losing its protective properties under ultra-low temperature and thermal shock environments. The reason for coating failure is thermal stress damage caused by the mismatch of the thermal expansion coefficient (CTE) between the coating and substrate. Moreover, the brittleness of epoxy resin (EP) increases in ultra-low temperature environments. In order to reduce the CTE of the composite and improve the toughness of the coating, negative expansion graphene (GP) modified by a silane coupling agent (MP) is used as the filler of EP. The thermal stress of the coating under ultra-low temperature of −196 °C was analyzed by finite element simulation and the stress damage mechanism was explained. The simulation results show that the thermal stress of the coating decreases by 10–15 MPa after adding MP@GP. Simultaneously, MP@GP can act as a lamellar physical barrier, extend the penetration path of corrosive media, and inhibit the electrochemical corrosion of the metal surface. After 20 thermal shock tests, the MP@GP/EP coating remains intact without cracks and the |Z|0.01 Hz value of the 1 % MP@GP/EP coating reaches the highest at 3.99 × 1010 Ω·cm2. Therefore, the coating has unique thermal shock and corrosion resistance under multiple synergistic effects.