Effect of oxygen plasma treatment on bonding strength of epoxy coating on steel substrate

In this work, the surface of Q235 steel was pretreated by low-temperature atmospheric pressure oxygen plasma in order to improve the bonding strength between the epoxy coating and the metal substrate. The epoxy coating was prepared by electrostatic spraying. The bonding strength between the epoxy coating and the Q235 steel was characterized by a coating peeling experiment. XRD, laser scanning microscope were employed in this research to characterize the chemical and physical properties of the Q235 surface before and after treatment. The experimental results showed that oxidize occurred on the surface of the Q235 steel after oxygen plasma pretreatment, which improved the surface roughness and free energy. Meanwhile, polar groups were introduced on the steel surface. With the increase in treatment time, the bonding strength increased first and then decreased. When the treatment time was 2 min, the bonding strength reached the highest (7.51 MPa), which was an increase of 3.5 times compared with the untreated sample (1.67 +/- 0.48 MPa).