Effect of Different Cleanness of the Pre-Coat Surface on Adhesion and Corrosion Performance of A36 Steel with Epoxy Coating

Abstract

Adhesiveness and protection against corrosion are the main properties of epoxy coating, especially if the coating is applied to materials exposed to harsh environments, such as water containing chloride. However, the effectiveness of this coating also really depends on the painting process, especially the cleanliness of the substrate surface prior to coating application. Choosing the right surface preparation can optimize the coating’s capabilities. This research aims to evaluate the effect of the cleanness of the blasting process on the coating performance on the surface A36 steel. The blasting pressure on garnet blasting is 8 bar utilizing mesh 30-40 garnet, and the spraying angle is 90° with a distance of 30 cm. The spraying time is at least 5 minutes to the desired NACE standard. Painting is done at room temperature using the airless spray method with an angle of 90°, a distance of 25 cm, with a movement speed of 300mm/s with a gap of 24 hours between the first and second layers. The results showed that surface preparation influenced the paint layer thickness, where NACE 4 provided the highest thickness in the first layer. In contrast, NACE 1 yielded the highest thickness in the second layer. The pullout strength test demonstrated that NACE 2 provided the highest pullout strength, followed by NACE 3 and NACE 1, while NACE 4 resulted in the lowest adhesion strength. Likewise, corrosion rate testing showed that surface preparation affects the corrosion rate, with NACE 1 providing lowest corrosion rate.