Paint Removal Research Articles

Mechanical-physical methods for paint removal of recycled bumpers for revalorization in the automotive industry

Mechanical-physical methods for paint removal of recycled bumpers for revalorization in the automotive industry

Real-Time Monitoring of Laser-Layered Paint Removal from CFRP Based on the Synergy of Laser-Induced Breakdown Spectroscopy and PLS-DA Models

Real-Time Monitoring of Laser-Layered Paint Removal from CFRP Based on the Synergy of Laser-Induced Breakdown Spectroscopy and PLS-DA Models

Removal of graffiti paint from construction materials coated with TiO2-based photocatalysts.

Graffiti on construction materials has significant social and economic impacts, especially on artistic and historical artefacts. Anti-graffiti protective coatings are used to generate low surface energies that limit graffiti adhesion to the surface, thereby reducing surface damage and facilitating removal. The anti-graffiti properties of three commercial TiO2-based coatings were tested under outdoor exposure conditions using four colours of graffiti paint (red, blue, black, and white). Chemical removers were used to clean the stained surfaces to understand the impact of the photocatalytic coatings during the conventional cleaning procedure. The effectiveness of cleaning was assessed by visual observations, colour measurements, and the percentage of residual stain. The anti-graffiti efficacy was strongly dependent on the colour of the graffiti and characteristics of the TiO2 coating. The cleaning performance of TiO2-treated samples was likely related to the photocatalytic redox reactions that decompose the graffiti. Additionally, their hydrophilicity may also prevent the adhesion and/or penetration of graffiti paint on the surface and/or pore matrix.

Study on the key parameters of ice particle air jet ejector structure

Existing ice particle jet surface treatment technology is prone to ice particle adhesion during application, significantly affecting surface treatment efficiency. Based on the basic structure of the jet pump, the ice particle air jet surface treatment technology is proposed for the instant preparation and utilization of ice particles, solving the problem of ice particle adhesion and clogging. To achieve efficient utilization of ice particles and high-speed jetting, an integrated jet structure for ice particle ejection and acceleration was developed. The influence of the working nozzle position (Ld), expansion ratio (n), and acceleration nozzle diameter ratio (Dn) length-to-diameter ratio (Ln) on the ice particle ejection and acceleration was systematically studied. The structural parameters of the ejector were determined using the impact kinetic energy of ice particles as the comprehensive evaluation index, and the surface treatment test was conducted to verify the results. The study shows that under 2 MPa air pressure, the ejector nozzle parameters of n = 1.5, Dn = 4.0, Ld = 4, and Ln = 0 mm can effectively eject and accelerate the ice particles. The aluminum alloy plate depainting test obtained a larger paint removal radius and resulted in a smoother aluminum alloy plate surface, reducing the surface roughness from 3.194 ± 0.489 μm to 1.156 ± 0.136 μm. The immediate preparation and utilization of ice particles solved the problems of adhesion and storage in the engineering application of ice particle air jet technology, providing a feasible technical method in the field of material surface treatment.

The negative effects of lead paint on different physiological systems

Lead (Pb) in paints is a serious public health hazard that has piqued the international community’s interest. Lead concentrations in lead-based paints have been assessed in several research conducted across the world. As a result, the goal of this article was to describe the findings of these research, give some knowledge of their human health consequences for law enforcement, and promote public awareness. The most notable gaps found have been highlighted in order to open the door for additional research efforts aimed at producing thorough data on this subject. Some of the evaluated studies found considerable amounts of lead in paints that were considerably over the allowable limits, despite the many regulatory controls on lead content in paints that exist worldwide. There have been reports of children cases of lead poisoning in a number of nations, including South Africa, France, Morocco, and the US. Lead levels in South Africa (145,000 ppm), China (860,000 ppm), and the US (22,550 ppm) have all been found to be high. 4,485.11 ppm in Thailand. India (104 ppm) and Palestine (6036 ppm). As a result, tight law enforcement measures pertaining to the progressive removal of paints containing lead and the management of lead content are required throughout the globe.

Effect of estrus behavior on the paint removal score of the sacral region of nulliparous Bos indicus

O objetivo deste estudo foi correlacionar o comportamento do estro com o escore de remoção de tinta da região sacral (ERT) e avaliar a associação do ERT com o número de montas e comportamentos secundários do estro em fêmeas nulíparas de Bos indicus. Vinte e quatro protocolos de inseminação artificial em tempo fixo (IATF) de três manejos foram implementados para investigação do objetivo do estudo. A comparação entre ERT 3 e ERT 2 revelou diferenças significativas nas variáveis ​monta recebidas, execução de monta, descanso de queixo, cheirar ou ser cheirada, lamber e ser lambida, favorecendo o grupo ERT 3 (P < 0,05), indicando estro. Entretanto, a comparação entre ERT 2 e ERT 1 não resultou em diferenças significativas nas características citadas, exceto no ser cheirada (P < 0,05), indicando ausência de estro para esses dois escores. O número de montas recebidas em ERT 2 e 1 foi insuficiente para apagar as marcações. Conclui-se que o ERT se mostrou um indicador eficiente da manifestação do estro. Os comportamentos de estro das vacas nulíparas na ERT 3 foram mais evidentes que os da ERT 1 e 2, e os comportamentos manifestados na ERT 1 foram semelhantes aos da ERT 2, indicando ausência de comportamento de estro. Assim, sugere-se que no futuro o ERT seja apenas dividido em duas classes.

Research on Laser Cleaning Technology for Aircraft Skin Surface Paint Layer.

In this study, a pulsed laser operating at a wavelength of 1064 nm and with a pulse width of 100 ns was utilized for the removal of paint from the surface of a 2024 aluminum alloy. The experimental investigation was conducted to analyze the influence of laser parameters on the efficacy of paint layer removal from the aircraft skin's surface and the subsequent evolution in the microstructure of the laser-treated aluminum alloy substrate. The mechanism underlying laser cleaning was explored through simulation. The findings revealed that power density and scanning speed significantly affected the quality of cleaning. Notably, there were discernible damage thresholds and optimal cleaning parameters in repetitive frequency, with a power density of 178.25 MW/cm2, scanning speed of 500 mm/s, and repetitive frequency of 40 kHz identified as the primary optimal settings for achieving the desired cleaning effect. Thermal ablation and thermal vibration were identified as the principal mechanisms of cleaning. Moreover, laser processing induced surface dislocations and concentrated stress, accompanied by grain refinement, on the aluminum substrate.

Characterization of a two-step laser paint stripping process on CFRP

This work presents a two-step non-destructive method for cleaning the surface paint of CFRP. The method combines ablation and vibration, using a pulsed laser with a wavelength of 1064 nm. The effects of laser power, beam and path overlap rate on the removal of paints are investigated. The analysis focuses on the cleaning and the damage threshold of the paints and fibers. Additionally, the study analyzed the thermal accumulation effect and fiber damage resulting from various laser parameters. The cleaned samples were analyzed for micro-morphology, elemental composition, surface roughness, three-dimensional morphology, and contact angle to demonstrate the modulation of derivatization phenomena of CFRP surface paints under different cleaning states using this method. This points to the reliability and feasibility of the relevant treatment parameters and provides a reference for the subsequent research on the practical application of laser cleaning.

Comparative study of infrared nanosecond laser surface paint removal for carbon fiber reinforced polymer and glass fiber reinforced polymer

Carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) are widely used in aerospace applications due to their excellent properties. Green and efficient laser cleaning technology has a broad development prospect in the paint removal treatment of aerospace composites. However, the lack of theoretical analysis and guidance has prevented the industrial application of laser paint removal technology. An infrared nanosecond laser is used to clean the paint layer on the surface of CFRP and GFRP, and the best paint removal process parameters are explored. Surface micromorphology and 3D morphology of CFRP and GFRP after cleaning are observed to reveal the cleaning quality. The FTIR spectrum is used to verify the cleanliness of the paint layer. In addition, the contact angle and bonding force are tested, and the experimental results show that the surface wettability of both surfaces is enhanced after cleaning, and the paint adhesion of both surfaces is improved after repainting. Temperature monitoring, acoustic signal monitoring and high-speed photography monitoring are used to monitor the two cleaning processes respectively. The temperature, amplitude intensity, and plasma size of the two in the cleaning process are compared and analyzed. Based on the monitoring results, it is found that the cleaning mechanism of fiber-reinforced composites includes thermal ablation, vibration effect and plasma impact effect.

Study on Preparation Technology and Heat Conduction Mechanism of High-Purity & Ultra-Fine Alumina Powder from Scrap Aluminum Cans

In view of the increasing scarcity of bauxite resources in China, the high energy consumption and high pollution of electrolytic aluminum, and the requirements for energy conservation and environmental protection, aluminum recycling and high-value utilization of its derivatives have evolved into a crucial development requirement for the aluminum industry in the future. As an important part of the development of recycled aluminum resources, the high-value application of scrap aluminum cans has always been a hot research topic in various recycled aluminum processing enterprises and scientific research units. The traditional regeneration system of waste cans includes a series of complex technological processes such as pretreatment, paint removal, smelting system and casting system, which is difficult to control in the middle of the process. Most of the recycled scrap aluminum cans are cast and downgraded for later use, except for a part of them used as alloy materials for new cans. In this paper, combined with the research on the preparation of metal aluminum alkoxide, combined with recrystallization heat conduction to further study the effective dissolution or adsorption how to remove impurity elements to obtain high-purity aluminum alcohol salt mechanism research, and thermal effect of alcohols with different carbon chains on the synthesis of high-purity aluminum alkoxide was further investigated. Moreover, the changes in morphology and pore size distribution of hydrolyzed alumina precursor materials under different hydrothermal temperature conditions were discussed by means of the alkoxide hydrolysis-sol-gel process. Eventually, the aluminum alkoxide was obtained by the reaction of waste cans with isopropanol and heavy crystal thermal conductivity, and the high-purity aluminum alkoxide was purified by vacuum distillation. Under the hydrothermal condition of 160°C, the high-purity alumina material with a purity of 99.99% and an original crystal size of 200nm was prepared.

Application of pulsed laser ablation thermal model in nanosecond pulsed laser removal of the epoxy resin paint film

The effect of laser surface paint removal depends on the mechanism of paint removal. The mechanism of nanosecond laser removal of epoxy resin paint film on aluminum alloy surfaces was studied theoretically and experimentally. Firstly, a laser thermal paint removal model was established based on the heat conduction equation, Hertz-Knudsen equation, and Hooke's law. The adsorption relationship between the paint film and the aluminum alloy substrate molecules and the adsorption force between the paint film and the substrate were analyzed and calculated. A laser thermal paint removal model was solved using COMSOL finite element software. By analyzing the changes in temperature and thermal stress with laser fluence, we obtained the theoretical threshold for laser paint removal. Subsequently, experimental research was conducted on laser paint removal. Through theoretical and experimental studies, it was found that the paint removal threshold of nanosecond pulse laser is 0.47 J/cm2. The primary mechanism of nanosecond laser paint removal is thermal stress stripping. When the laser fluence is low, the nanosecond pulse laser can only ablate the paint on the surface, and the thermal stress between the paint film and the substrate makes it difficult to remove the paint film. As the laser fluence increases, the nanosecond laser will ablate the surface paint film, and the thermal stress between the paint film and the substrate will cause the stripping of the underlying paint film and the substrate. The primary mechanism of laser paint removal is stripping.

Effect of High-Power Laser Cleaning for Surface Contaminants Removal on SS304L

In this study, artificially formed corrosion and paint layers on 304L stainless steel (SS304L) specimen were removed using a kilowatt level high-power Nd:YAG laser. A laser power of 1140 W and a pulse duration of 89 ns were used for the corrosion removal, and a laser power of 850 W and a pulse duration of 54 ns were adopted for the paint removal. Surface composition was analyzed via electron probe micro-analysis (EPMA) and x-ray diffraction (XRD) analysis before and after the laser cleaning process, confirming that the corrosion and paint layers were successfully removed from the SS304L surface by the laser cleaning process. The effect of the laser cleaning process on the mechanical properties of SS304L was investigated. The hardness and tensile strength of the laser-cleaned specimens were analyzed to determine their mechanical properties. After the laser cleaning process, the surface hardness was slightly increased up to depths of 250 µm for the corrosion removal and up to 50 µm for the paint removal. However, only marginal changes in tensile strength and elongation were detected after the laser cleaning process. These results confirmed that laser cleaning can effectively remove surface contaminants (i.e., corrosion and paint) on SS304L with only a minimum modification of microstructure and mechanical properties.

Experimental study and mechanism analysis of a pulsed laser cleaning aluminum alloy process.

A pulse laser with a wavelength of 1064nm and a pulse width of 1µs was used to experiment on the coating of a 2024 aluminum alloy surface. The removal performance of the pulse laser cleaning coating was explored by a single factor analysis and orthogonally conditions, and the effects of the laser power, scanning speed, and pulse frequency on the quality of laser coating removal were summarized. The mechanisms of pulse laser cleaning the coating were studied. The results show that the three parameters of the laser power, scanning speed, and pulse frequency have different effects on the quality of laser coating removal. Among them, with the increase of the scanning speed and pulse frequency, the quality of laser cleaning first increases and then decreases, respectively. With the increase in laser power, the quality of laser cleaning increases. A good laser cleaning quality can be achieved at the laser power of 16.5W, a scanning speed of 600mm/s, and a pulse frequency of 30kHz. The laser cleaning coating involves a variety of mechanisms such as combustion, explosion, gasification, thermal vibration stripping, and laser plasma impact. The result can provide practical references for a better searching of the paint removal.

Research on LIBS online monitoring criteria for aircraft skin laser paint removal based on OPLS-DA.

Online monitoring technology plays a pivotal role in advancing the utilization of laser paint removal in aircraft maintenance and automation. Through the utilization of a high-frequency infrared pulse laser paint removal laser-induced breakdown spectroscopy (LIBS) online monitoring platform, this research conducted data collection encompassing 60 sets of LIBS spectra during the paint removal process. Classification and identification models were established employing principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), and orthogonal partial least squares discriminant analysis (OPLS-DA). These models served as the foundation for creating criteria and rules for the online LIBS monitoring of the controlled paint removal process for aircraft skin. In this research, 12 selected characteristic spectral lines were used to construct the OPLS-DA model, with a predictive root mean square error (RMSEP) of 0.2873. Both full spectrum and feature spectral line data achieved a predictive accuracy of 94.4%. The selection of feature spectral lines maintains predictive performance while significantly reducing the amount of input data. Consequently, this research offers a methodological reference for further advancements in online monitoring technology for laser paint removal in aircraft skin.

Simulation and Experimental Study on Continuous Wave Fiber Laser Removal of Epoxy Resin Paint Film on the Surface of 6061 Aluminum Alloy

Paint removal is an essential process in the industrial field. Laser technology provides an effective method of paint removal to replace traditional mechanical and chemical methods. This paper establishes a continuous wave (CW) laser thermal paint removal model based on heat conduction theory and Arrhenius’ law. The paint stripping process of epoxy paint film on the surface of 6061 aluminum alloy via CW laser was studied through simulation and experiment. We found that the carbonization of the paint film during the CW laser paint removal process will inhibit the laser paint removal process. Therefore, the paint removal efficiency of the CW laser is limited. The depth of CW laser paint removal increases linearly with the CW laser power density. However, during the CW laser paint removal process, due to the pyrolysis of the paint film and the reflection of the laser by the substrate, the surface temperature of the material first increases and then decreases. In addition, after laser paint removal, the surface roughness of the material after paint removal is reduced due to the melting of the base material. The model established in this article can provide a theoretical reference for studying the CW laser paint removal process.

Formation and effect of rough surface in pulsed laser removal of thick paint layer on 2024 aluminum

When using pulsed laser to remove a thick paint layer from a 2024 aluminum alloy substrate, the paint layer should be removed layer by layer, and the substrate should remain intact after the paint layer is completely removed. In this process, the formation of a rough surface on the paint increases laser absorption, changing the removal mechanism, which becomes an unstable factor for nondestructive paint removal. This study investigated the laser paint removal mechanism of fluorocarbon paint and found that when the laser fluence was 0.91 J/cm2, the main removal mechanisms were thermal stress and combustion-decomposition removal, while at 94.36 J/cm2, the main mechanism was sputtering removal. The study also investigated the relationship between surface roughness and the number of laser scans, which showed a positive linear correlation. Additionally, an equivalent model of a rough surface was established to analyze the changes in absorption, though this model has yet to be verified and further research and validation is required to confirm our findings.

Research on online monitoring of aircraft skin laser paint removal thickness using standard curve method and PCA-SVR based on LIBS.

High-frequency pulse lasers, applied in the form of rapid scanning, act upon the surface of aircraft skin paint layers, thereby removing the paint layers, exhibiting characteristics of efficiency and eco-friendliness. Real-time monitoring of the paint removal effect and prevention of substrate damage necessitates the continuous monitoring of paint removal thickness. Combining Laser-Induced Breakdown Spectroscopy (LIBS) online monitoring technology enables laser-controlled paint removal under multiple effects coupling, meeting the requirements of airworthiness maintenance. This paper, based on a high-frequency nanosecond infrared pulse laser paint removal LIBS monitoring platform, conducts research on laser paint removal thickness LIBS online monitoring of aluminum alloy plates coated with dual-layer paint. Spectra corresponding to the removal thickness of each group are collected and, respectively, paint removal thickness monitoring models based on LIBS spectra are established using the standard curve method and Principal Component Analysis-Support Vector Regression (PCA-SVR) algorithm. When monitoring paint removal thickness using the standard curve method, the intensity of five Ti element characteristic spectral lines selected is correlated with the paint removal thickness, and segmented curve fitting according to the paint layer structure satisfies the segmented curve fitting of topcoat and topcoat + primer. Among them, the average coefficient of the curve fitting of the Ti II 589.088 nm characteristic spectral line is 0.89, and the root mean square error (RMSE) is 12.28 μm. Its performance is superior in the five standard curves; thus, its fitting equation is used as the criterion for paint removal thickness monitoring. To further improve monitoring accuracy, research on paint removal thickness monitoring models based on PCA-SVR is conducted. Compared to the traditional univariate standard curve method, the PCA-SVR model does not require segmented monitoring. After parameter optimization, the average fitting coefficient reaches 0.97, and the RMSE is 2.92 μm. The results indicate that the PCA-SVR-based paint removal thickness monitoring model has higher accuracy, thereby forming the basis for paint removal thickness monitoring. Through comparative research on paint removal thickness monitoring models, two types of paint removal thickness monitoring criteria are obtained, providing model solutions for high-precision monitoring and automation of aircraft skin laser paint removal thickness.

Simulation and experimental study of the evolution of shock waves during laser paint removal

This paper studies the spatiotemporal evolution of shock waves during laser paint removal. In order to study the evolution process of laser-induced plasma shock waves, we developed a laser-plasma shock wave evolution model based on the mass, momentum, and energy conservation theory. The evolution process of laser-induced plasma is studied by simulation and experiment. The simulation and experimental results show that the simulation model can accurately simulate the evolution of the plasma shock wave. In addition, by comparing the ablation depth and paint film thickness, we found that stripping is the primary mechanism of nanosecond pulsed laser paint removal. The ablation is the secondary paint removal mechanism. In summary, this study provides a new way of studying the evolution process of acoustic waves during laser removal paint.

Simulation Study of the Mechanism of Action in the Process of Nanosecond Pulsed Laser Paint Removal

Simulation Study of the Mechanism of Action in the Process of Nanosecond Pulsed Laser Paint Removal

Simulation and Experimental Study of Nanosecond Pulse Laser Removal of Epoxy Paint on 6061 Aluminum Alloy Surface

Laser paint removal is a new cleaning technology that mainly removes paint through thermal ablation and mechanical stripping mechanisms. This paper established a thermal-mechanical coupling laser removal model of paint based on the heat conduction equation, Newton’s second law, and Fabbro’s theory. The removal process of epoxy resin paint film on an aluminum alloy surface via a nanosecond pulsed laser was studied using finite element simulations and experimental measurements. The simulation and experimental results show that the nanosecond pulse laser’s primary paint removal mechanism is the mechanical stripping caused by thermal stress and plasma shock. The laser paint removal threshold is 1.4 J/cm2. In addition, due to the different generation times of plasma shock and thermal stress, the mutual superposition of stress waves occurs in the material. This results in a discrepancy between the actual and thermal stress differences. Moreover, the thermal stress difference causes the maximum actual stress difference to fluctuate. The simulation model established in this paper can provide a reference for studying the thermal-mechanical coupling process of laser paint removal.