The effect of laser surface textures on the corrosion resistance of epoxy coated steel exposed to aggressive environments for offshore applications

Abstract

Organic coatings are commonly applied to protect metallic structures exposed to highly corrosive environments such as those found in offshore marine scenarios. In general, steel surfaces are prepared by grit blasting prior to being coated. However, this method is associated with some negative issues such as adverse environmental impacts, and safety concerns. In this context, laser surface texturing technology is gaining attention and has been used for metal surface preparation (micromachining, drilling and functionalization) in various applications. This method offers several benefits, notably ease of automation and scalability. This paper reports an investigation on the resistance to corrosion propagation of epoxy-coated laser-textured AISI A-36 surfaces, when compared to surfaces subjected to the conventional bead and grit blasting treatments (references). Nanosecond laser surface texturing was used to create groove-like and grid-like surface patterns at the microscale level. After running accelerated corrosion tests (ISO 12944-9 standard), the performance of the epoxy coating on the laser-textured surfaces was significantly improved, indicating that the laser treatment reduces the coating delamination rate, as well as its damaged area. The surface tortuosity factor plays an important role in the effectiveness of the coatings. The results also suggest that the geometrical aspects of the groove structure (presence of recast material and V-shape) promote phenomena such as mechanical interlock and mechanical hooking of the coating. Therefore, nanosecond laser surface texturing appears to be a suitable procedure for the preparation of steel surfaces installed in offshore marine environments.