The Institute of Laser for Postgraduate Studies discusses a master’s thesis on wet laser cleaning of single and multi-layer acrylic polyurethane coatings on 6061-T6 aluminum alloy.

A master’s thesis submitted by the student Abeer Amer Abbas, entitled:

“Wet Laser Cleaning of Single and Multi-Layer Acrylic Polyurethane Coatings on Aluminum 6061-T6”

was discussed at the Institute of Laser for Postgraduate Studies – University of Baghdad, under the supervision of Assistant Professor Dr. Ziad Eyad Taha.

Laser cleaning is an advanced and environmentally friendly technique for removing contamination, rust, paint, and other unwanted materials from surfaces. Laser paint removal in a wet environment, such as water, does not release corrosion products into the air nor damage the substrate surface. This work addresses the main factors affecting the wet laser cleaning process for removing a dark gray glossy acrylic polyurethane coating from a system consisting of one to three layers applied to the surface of a 6061-T6 aluminum alloy.

The liquid layer, along with the use of a nanosecond pulsed fiber laser, enabled the successful removal of multi-layer coatings while preserving the integrity of the substrate by adjusting the laser energy density and scanning speed during the cleaning phase. The results showed that the cleaning threshold was 8.91 J/cm² and 700 mm/s, which corresponds to the optimal cleaning threshold parameter of 8.91 J/cm² and a scanning speed of 400 mm/s. The damage-causing cleaning threshold was 10.82 J/cm² at a scanning speed of 700 mm/s.

Variations in surface roughness, microhardness, and cleaning performance were also evaluated for each parameter (laser energy density and scanning speed). The combined effects of thermal and mechanical forces dominate the mechanism of paint removal by wet laser cleaning. Detailing the laser-water interaction is a series of processes including electron multiplication, plasma, thermal explosion, and bubbles.

This study explores nanosecond pulsed wet laser cleaning of single-layer coatings (SLC) and multi-layer coatings (MLC) of acrylic polyurethane, with controlled functional activation of the surface via modified roughness to improve substrate adhesion.

The thesis was accepted with an Excellent grade, as it fulfills the requirements for obtaining a Master’s degree in Laser Applications.