Enhanced corrosion performance of S136 steel after nanosecond pulsed laser polishing

Laser polishing (LP) has aroused great interest in view of its potential application in the mold industry, whereas few studies have reported the effect of LP on corrosion performance. Herein, the surface morphology, surface roughness, X-ray photoelectron spectroscopy analysis and corrosion performance of S136 steel after nanosecond pulsed LP were investigated and compared with those of mechanical polishing (MP). A smooth and defect-free surface of the LP specimen was obtained with a surface roughness of 0.078 μm and a surface roughness reduction rate of 56.9%. The corrosion current density of the LP specimen was 0.164 μA/cm2, which was 4.2% and 12.8% of the original and MP specimens, respectively. And prominent decreased in the number and diameter of corrosion pittings on surface of the LP specimen compared with the original and MP specimens. These results demonstrate that LP significantly improves the corrosion performance of the S136 steel, which is mainly attributed to the increase of Cr2O3 in passive film, the formation of melting layer and the decrease of non-metallic inclusions on surface of the LP specimen. Our findings provide a scientific approach for greatly improving corrosion performance while reducing surface roughness of steel.