Nanosecond Laser Passivation Mechanism of Q235B Carbon Steel Surface

Aiming at the problem that traditional blackening technology and chemical passivation method may cause pollution to the environment in the process of enhancing the corrosion resistance of the material surface, the surface of Q235B carbon steel was treated by nanosecond pulse fiber laser. The surface morphology, oxide film thickness, chemical composition and corrosion resistance of the material were characterized by scanning electron microscopy, x-ray photoelectron spectroscopy and electrochemical workstation, respectively. The impact of different laser single-pulse energy densities and spot overlap rates on the density, stability and corrosion resistance of the surface oxide film layer was studied. The results show that when the laser fluence is 3.96 J/cm² and the spot overlap rate is 80%, the material surface has the best corrosion resistance. When the laser fluence is too high, a porous yellow-brown metal oxide film is formed on the material surface, which damages the material matrix and leads to secondary corrosion, causing a decrease in corrosion resistance.