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Laser Coating Removal by Different Laser Methods
Paint removal and rust removal in marine applications can be done in a number of ways. Each method of removal must balance the energy usage, coverage rate, and removal rate. In this example, we will look at how different methods of removal balance these areas.
Paint removal and rust removal in marine applications can be done in a number of ways. Each method of removal must balance the energy usage, coverage rate, and removal rate. In this example, we will look at how different methods of removal balance these areas.
This is the second article in a series of four. You can read the fist article (Laser Cleaning Background) here.
A Panamax, being an average size commercial sea vessel, features approximately 19000 m2 of external surface area. Laser technologies like CW or QCW CO2 emitting up to 30 kW suggest good interaction with organic paint but have demonstrated removal rates only approaching 22,500 mm3/ kW-min. Comparing to surface area and volume of paint on the Panamax, the operation would take 130 days with 1 kW of laser power. This is not ideal.
Ideally, process speeds of approximately 10 times that are required so that a commercial case of utilising 4 to 6 kW of total laser power can be distributed around the vessel in 3 to 4 workshops, addressing the task in less than 1 week.
Alternatively, low energy ns pulses of 0.1 to 12 mJ may be used at high pulse repetition rates of 100 to 1000 kHz, achieving higher coverage range, when paired with faster scanning devices, while being focused into adequately small spots to maintain irradiance levels above the ablation threshold. This would result in a much lower removal rate, near 2,000 mm3/kW-min, as the increase in coverage rate by a decrease of spot size and pulse energy mathematically results in a slight increase of removal rate, in reverse proportion to pulse energy. However, the increase in removal rate is limited by the size of the smallest spot size practically and theoretically attainable.
Finally, both these technologies can thermally impact the substrate as heat continuously diffuses into the material at CW or above 200 kHz.
In part three (Detachment vs. Ablation in Laser Coating Removal) of this five part series, we’ll learn how optimisation around high pulse energy and high power can pair to increase the removal rate and quality for this unique application space.
Contact us to learn more about high powered laser paint and rust removal in marine and other applications.
Laser User Magazine (Issue 85)
