Laser Paint Removal & Aluminum Alloys: Enhancing Surface and Structural Integrity

Introduction

In the aerospace industry, the integrity and performance of aircraft skin materials are critical to both safety and aerodynamic efficiency. The outer skin, primarily composed of aluminum alloys such as 2024-T351, is subject to aggressive operational environments—characterized by thermal cycling, mechanical stress, and exposure to corrosive agents. Routine maintenance mandates the removal of degraded paint coatings to assess substrate integrity and restore protective systems.

Traditional methods, including mechanical abrasion and chemical stripping, often compromise the substrate or involve hazardous byproducts. As a result, laser-based cleaning technologies have emerged as a superior alternative, offering non-contact, environmentally sustainable, and highly selective surface processing capabilities.

Principles of Laser Paint Removal

Laser paint removal utilizes high-intensity, pulsed laser energy to ablate surface coatings without materially degrading the underlying substrate. The energy input is selectively absorbed by the paint layers, resulting in localized vaporization, thermal spallation, or photomechanical delamination. This precision prevents collateral damage to the substrate and enables superior control over the cleaning depth and area.

The advantages of laser ablation include:

• Non-contact, abrasion-free operation
• High spatial resolution and process repeatability
• Minimal chemical or particulate residue
• Suitability for automation in maintenance, repair, and overhaul (MRO) environments

Experimental Evidence and Microstructural Outcomes

Study 1: Microstructural Enhancement Post-Ablation

A 2023 study published in Vacuum investigated the effects of nanosecond-pulsed laser paint removal on 2024-T351 aluminum alloy. The authors conducted tensile testing and microhardness profiling on specimens before and after treatment. Key findings included:

• Surface microhardness increased by 9.7%
• Ultimate tensile strength (UTS) improved by 6.6%
• Yield strength (YS) increased by 13.2%

Microstructural analysis via transmission electron microscopy (TEM) and scanning electron microscopy (SEM) revealed grain refinement and dislocation proliferation at the laser-affected zone, which contributed to the observed mechanical strengthening.

Study 2: Multilayer Paint Removal on Aircraft Skins

In a complementary study published in Photonics, researchers evaluated laser parameters for paint removal on Boeing 737 skin panels. The optimal conditions—laser fluence of 5.09 J/cm² and scanning velocity of 700 mm/s—achieved complete multilayer paint ablation with no damage to the aluminum substrate. Nanoindentation testing showed a 3.587% increase in surface hardness attributed to localized strain hardening and microstructural compaction.

Electron backscatter diffraction (EBSD) analysis confirmed enhanced crystallographic texture and deformation-induced grain reorientation post-laser treatment.

Mechanisms of Substrate Strengthening

The improvement in mechanical properties post-laser cleaning can be attributed to:

• Dislocation density increase from thermal-mechanical interaction
• Refined grain structures due to rapid heating and cooling cycles
• Reduction in surface contaminants, improving subsequent coating adhesion

These phenomena collectively enhance fatigue resistance, surface energy, and microstructural stability—key factors in high-performance aerospace materials.

Conclusion

Laser paint removal presents a scientifically validated, non-destructive approach for the restoration and enhancement of aluminum aircraft skins. By promoting microstructural refinement and elevating surface mechanical properties, this method aligns with next-generation MRO strategies focused on sustainability, precision, and material longevity.

Vytek's laser systems are engineered to meet these rigorous demands, delivering consistent performance for aerospace surface preparation and maintenance applications.

References

• Sun, Q., et al. (2023). Mechanical properties and microstructure characteristics of 2024-T351 aluminum alloy specimen subjected to paint removal by laser cleaning. Vacuum, 211, 111927.
• Li, W., et al. (2023). Removal Mechanisms and Microstructure Characteristics of Laser Paint Stripping on Aircraft Skin Surface. Photonics, 10(1), 96.
• Zou, W., et al. (2021). Characteristics of the audible acoustic signal in the process of laser cleaning of paint on the metal surface. Optics and Laser Technology, 144, 107388.
• Lu, Y., et al. (2020). Ultraviolet laser cleaning and surface characterization of AH36 steel for rust removal. Journal of Laser Applications, 32, 032023.