Hybrid laser cleaning characteristic of marine barnacles fouling attached on Al alloys

In previous papers, the nanosecond laser has been proven to be an effective tool for removing the settlement of soft-fouling microorganisms (biofilm, microbial film, and microbiofoulings). This work is a continued study on laser cleaning of marine biofouling. The authors attempt to develop a hybrid laser treatment method to control the hard-shelled barnacles attached to Al alloys. Morphologies of the laser-cleaned surfaces were evaluated by a digital camera, 3D optical microscopy, and scanning electron microscopy. Furthermore, a high-speed camera and fiber optic spectrometer were used to capture the specific laser cleaning dynamic behaviors and characterize the chemical compositions of laser-induced plasma, respectively. The shell structures of the barnacles cannot be removed by a nanosecond fiber laser but continuous CO2 laser, while for the base plates of the barnacles the result is the opposite. Hence, a step-by-step CO2/nanosecond hybrid laser cleaning process is proposed to conquer the attached barnacles fouling. The cleaning strategy follows a top-down principle of the barnacles' structures. In the first step, the CO2 laser is utilized to heat the external shell; thus, the upper parietal shell and the main body are entirely peeled off. In the second step, the nanosecond laser is employed to remove the lower remaining base plate, cement layer, and biofilm. Laser cleaning mechanisms of barnacles included heating, stripping, and ablation.