Quantitative evaluation of surface cleanliness of weathering steel treated by continuous wave laser

A 3 kW continuous-wave (CW) laser was used for the laser cleaning of weathering steel with artificial corrosion pits. Specimens with different degrees of corrosion were obtained by NaCl deposition in artificial pits of 10 mg/m², 100 mg/m² and 1000 mg/m² through constant dew point dry and wet cycles for one year. To develop quantitative evaluation methods that can be applied on-site, the cleanliness of the laser-cleaned surface was evaluated through visual observation, turning time, and photographic analysis. The results reveal that the photometric analysis based on the CIE L*a*b* color space can be used to evaluate the surface cleanliness of surfaces treated with a CW laser, which is consistent with the results of the turning time test. The color difference of the surface before and after the laser treatment can be used as a quantitative index to evaluate cleanliness. The proposed laser surface treatment procedures can provide a reference for cleaning corroded weathering steel structures and achieve cleanliness of more than 80 % and a longer turning time.