## 3 Results and Discussion
### Influence of Liquid Medium on the Cleaning Effect of Corrosion Layer  
In the context of enhancing laser cleaning by incorporating a water layer, the facilitative role of the water medium during laser treatment was investigated. Experimental comparisons were conducted as a preliminary step to analyze the effects of various water layer heights on the cleaning process. The experimental images following laser cleaning, used for comparison (each group of air cleaning, control group is Figure 8a including all subsequent experiments), for the results of media-assisted cleaning with water; microscopic observation revealed that when the initial addition of water height was 0.1 mm, the laser-induced intensification of the surface resulted in a flat surface appearing with laser tracks (the cleaning mechanism is illustrated on the left side of Figure 9). When the water height was doubled, the surface and the dry cleaning showed distinct differences; the laser tracks were mostly absent, with only a few shallow traces remaining (as indicated by the arrow in Figure 8c. At this point, the surface became flat. However, with the further increase in water layer height, small melted and solidified lumps appeared (in Figure 8d (the cleaning mechanism is presented on the right side of Figure 9). Subsequently, as the water layer height continued to rise, the lumps increased, and when the height reached 2 mm (as shown in Figure 8f, substances resembling the state of corroded material appeared on the surface. This indicated that the water layer height had reached 2 mm, which posed an even greater obstacle to the cleaning process. Figure 8: Microscopic morphology under the action of water layer: (**a**) 0 mm; (**b**) 0.1 mm; (**c**) 0.2 mm; (**d**) 0.5 mm; (**e**) 1 mm; and (**f**) 2 mm. Figure 7: The relationship between SiO\({}_{2}\) height and removal depth. The three-dimensional topography is shown in Figure 10. Utilizing the findings from micro-metallography, the sample was laser-scanned to generate a three-dimensional morphology map. The resulting figure is depicted below: at a water layer height of 0.1 mm, the surface's overall heterogeneity is heightened, and the height discrepancy reaches 14 um, which confirms the intensification of ablation from the three-dimensional topography. For the more pronounced change (Figure 10c), the surface topography is not noticeably smoother at this stage, with a height difference of approximately 8 um. Despite this, the overall color is similar, with the green area comprising 95% of the surface area, and the overall plane is not inclined, as evidenced by the subsequent roughness, which is smoother at this point in the planar surface. As for subsequent changes, from the three-dimensional morphology of the map, it is evident that the number of protrusions increases; the overall height difference also reaches about 23 um. At this juncture, it can be observed that the water layer seems to inhibit the cleaning effect that would otherwise be observed. Figures 11 and 12 depict the variations in surface roughness and the depth of rust layer removal. Figure 11 illustrates the disparity in roughness with and without water-assisted cleaning. Compared to the control group without water assistance, surfaces cleaned with water exhibit greater smoothness, achieving optimal roughness between 0.8 and 1.0 um without surface damage. However, an increase to 0.5 mm results in a significant rise in roughness. From Figure 12, it is evident that complete removal of the rust layer is  
Figure 10: Three\(-\)dimensional morphology under the action of water layer: (**a**) 0 mm; (**b**) 0.1 mm; (**c**) 0.2 mm; (**d**) 0.5 mm; (**e**) 1 mm; and (**f**) 2 mm. Figure 9: Schematic diagram of mechanism conversion. (**Left**): ablation–vaporization mechanism; (**Right**): stripping mechanism. achievable up to 0.2 mm, beyond which complete cleaning efficacy diminishes. At this point, cleaning efficacy is inhibited rather than enhanced. In contrast to the approximately 3 \(\upmu\)m optimal roughness, Sa, achieved by [PERSON] et al.