A study of the surface products on zinc-coated steel during laser ablation cleaning

A high-power short-pulsed Nd:YAG laser was focused onto carbon steel targets with a 13-μm-thick Zn coating. The ablation effects, the behavior and the characteristics of the laser-induced products were studied. The ablation rate was defined as the ablated volume divided by consumed laser energy, and was used as a description of ablation cleaning ability. The dependence of ablation rate on laser fluence was plotted, and the optimum processing conditions were determined. The laser induced products consisted of plasma-vapor and liquid particles. The length of the laser-induced plasma-vapor was approximately 2 cm and its existence time wavered at approximately 4 μs. It was observed that the moving direction of the liquid particles was in a small angular range that was tilted toward but symmetric to the incident laser. It was further noticed in this range that a higher moving velocity was obtained when the angle between the liquid particles and the incident laser beam was larger. The estimated highest moving velocity of the liquid particles was approximately 0.8 m/s. The analysis of the condensed particles confirmed that the laser-induced product on the target surface consisted of Zn and Fe, which mainly solidified from plasma-vapor and melt, respectively.