Paint Film Thickness Research Articles

Paint Film Formation Characteristics on Conical Surfaces for Electrostatic Air Spray Painting

When a curved target surface is coated in an electrostatic spray-painting process, the paint film pattern on curved targets will deform, and the thickness will change compared with the planar target due to the curvature characteristics of the target, the inhomogeneous electric field, and the flow field. Therefore, directly using the planar deposition distribution for painting the trajectory planning of curved surfaces causes large errors and low paint transfer efficiency. A study investigating the curved surface paint film thickness distribution characteristics is presented in this research to understand the relations among the target surface curvature, the electrostatic field, and the flow field distribution. Spray-painting process simulations were performed for conical surfaces of different curvatures. Moreover, the paint particle’ trajectories, electric potential, and film deposition distribution were computed using ANSYS Fluent. The paint transfer efficiencies of these targets were computed. The results show that when the generatrix curvature of the conical surface increases gradually, the electric field intensity near the wall increases, which enhances the deposition of charged droplets on the wall. Moreover, the airflow field velocity increases as the curvature increases, which leads to a large diffusions of the spray flow field, so the paint thickness decreases, and the transfer efficiency is low.

Effect of Surface Coating Condition on High‐friction Organic Zinc‐rich Paints for HSFB Joints

AbstractWith the development of paints, high‐friction organic zinc‐rich paints with slip coefficients more than 0.45 have been advanced, making it possible to obtain more sophisticated and higher quality high strength bolted friction joints. Moreover, comparing to the inorganic zinc‐rich paints used at present, organic zinc‐rich paints are more appropriate for using in situ construction. However, since the application conditions of organic coatings have not been specified, it is recommended that a slip test should be carried out separately for each surface preparation to confirm the slip coefficient. In this study, slip tests were carried out on high strength bolted friction joint specimens to investigate the influence of high‐friction organic zinc rich paint film thickness and surface preparation on the slip coefficient. Furthermore, based on the experimental results, a surface preparation that can consistently produce a high slip coefficient is proposed.

Variable Velocity Coating Thickness Distribution Model for Super-Large Planar Robot Spraying

This study proposed a dynamic optimization method for spray gun flow to address the issue of uneven film thickness in the acceleration and deceleration section of the z-shaped spray trajectory in large plane ship segments. The method takes into account the acceleration and deceleration section of the spray trajectory and improves the film thickness distribution. The study first established a static vertical spray coating growth model of the spray gun without considering the acceleration and deceleration of the spray trajectory. Then, we used an integral method to optimize the coating uniformity and established a film thickness distribution model. The optimization of spray speed and spray spacing is crucial in the use of variable flow spray guns. It is assumed that the acceleration and deceleration sections of the spraying trajectory are linear and symmetrical, which forms the basis for establishing a mathematical model for the variable flow spray gun. To determine the flow of the spray gun at different speeds in the acceleration and deceleration sections, the pattern search method was adopted. A section of a ship was used as an example for this study. In this study, we utilized numerical simulations to compare the uniformity of paint film thickness when using a spray gun with a constant flow versus variable flow. The results indicate that when taking into account the acceleration and deceleration section of the spray trajectory, the film thickness was more uniform with a variable flow. These findings demonstrate the feasibility and effectiveness of the proposed method.

Design and Control of a Crawler-Type Wall-Climbing Robot System for Measuring Paint Film Thickness of Offshore Wind Turbine Tower

Design and Control of a Crawler-Type Wall-Climbing Robot System for Measuring Paint Film Thickness of Offshore Wind Turbine Tower

Analysis and Evaluation of Paint Film Thickness Variation due to Solvent Volatilization Based on Drying Rate Curves

During the drying process of paints, the solvent contained in the paint volatilizes and the film thickness decreases. Since this property is highly dependent on the drying temperature and can affect the quality of the paint, appropriate temperature conditions and film thickness control are required. In this study, a model based on mass transfer theory was developed to calculate the paint film thickness at an arbitrary elapsed time. As a validation test, wet film thickness was measured by a non-contact film thickness gauge and compared with the analytical results. As a result, accurate paint film thickness prediction was achieved by setting appropriate parameters for different drying conditions.

Experimental study on mechanical property and stone-chip resistance of automotive coatings

The damage of automotive coatings caused by stone impact is a problem that has attracted great attention from automotive companies and users. In this work, experiments were conducted to investigate the dynamic tensile properties and stone-chip resistance of automotive coatings. Four kinds of paint films and three typical coatings (single-layer electrocoat coating, single-layer primer coating, and multilayered coating) were used. Under dynamic tensile load using split Hopkinson tension bar (SHTB), the engineering stress-strain curves of the paint films at medium and high strain rates (from 50 to 600 s−1) were obtained. Results indicated that the mechanical properties of the paint films exhibited strong nonlinearity and strain-rate correlation. A modified anti-impact tester was used to complete repeatable single impact tests. The effects of some key parameters, i.e., impact velocity, impact angle, and paint film thickness, on the stone-chip resistance of coatings were systematically investigated. The influence of contact type under high-speed impact conditions was investigated as well. The surface morphologies of the coatings after impact were examined by scanning electron microscopy (SEM), and the failure mechanism of the coatings under normal/oblique impact was discussed. In all experiments, the paint films showed brittle fracture behavior.

Effect of Polyurethane Non-Transparent Coating Process on Paint Film Performance Applied on Modified Poplar

Whether modified poplar can obtain a qualified or even excellent finishing effect on European and American furniture is worthy of deep study. To evaluate whether the conventional non-transparent coating process is suitable for modified poplar, a multi-level hybrid orthogonal experiment method was carried out to start research on how factors affect the paint film performance of the non-transparent coating process. The effect of experimental factors and levels on paint film performance is pointed out, and the optimal factors and levels are found. Parameter optimization of the polyurethane non-transparent finishing process based on modified poplar is carried out. An application basis was provided for the extensive use of modified poplar wood as a substrate in the European and American furniture markets. The conclusions are: (1) gloss of paint film can be improved by increasing the number of nitrocellulose (NC) lacquer transparent topcoats, (2) adhesion and thickness of paint film can be improved by polyurethane (PU) sealing primer, (3) the initial paint film’s abrasion is influenced efficiently by the coating process and coating sanding. PU sealing primer has an efficient influence on the later abrasion of paint film. The effect of modified poplar surface pretreatment on the mass loss of paint film tends to be stable.

Research on the Influence of Different Paint Film Thickness Combination on Corrosion Resistance of Sandblasting Steel Plate

To guide the selection of paint film thickness scheme with high cost performance when spraying sandblasting steel plate. In this paper, we sprayed different film thickness with the combination of primer and topcoat on the sandblasting steel plate. The corrosion resistance was evaluated by neutral salt spray test and electrochemical test of different film thickness combinations. In addition, the corrosion morphology was analyzed by automatic inverted metallographic microscope. Furthermore, potentiodynamic polarization and electrochemical impedance (EIS) curves were used to analyze the corrosion mechanism. The self-corrosive current density (Icorr) is 1.999 × 10-12 A·cm-2 with the combination of primer and topcoat thickness (20 μm+20 μm) and the self-corrosive current density (Icorr) of low carbon steel matrix is 1.855 × 10-5 A·cm-2 from the analysis of polarization curves from kinetic potential. The impedance value on 0.01 Hz (|Z|0.01Hz) (4.56 × 1010 Ω·cm2) of the combination of primer and topcoat thickness (20 μm+20 μm) after immersing in 3.5 wt. % NaCl for 2 hours was more than eight orders of magnitude higher than the value (|Z|0.01Hz 6.52 × 102 Ω·cm2) of the low carbon steel plate after immersing for 0.5 hours. Even dipping in 3.5 wt. % NaCl for 168 hours, the |Z|0.01Hz value of the combination of primer and topcoat thickness (20 μm+20 μm) was still three order of magnitude higher than the low carbon steel plate with 0.5 hours immersion. Increasing the film thickness of the topcoat can improve the anticorrosion performance under the condition of a certain thickness of the primer. However, too thick coating will generally bring greater internal stress, which leads to the cracking of the coating in the process of use because of the change of external force and temperature, thus affecting the anticorrosion performance. When the total film thickness is certain, with the increase of the proportion of primer increase of the proportion of primer film.

Multi-objective Optimization of Spraying Trajectory Planning for Large Ship Blocks using Evolutionary Computation

Automated spraying is among the priorities in the development of China’s shipbuilding industry today with the increased consciousness of product quality, processing efficiency and environmental friendliness. The research topic is derived from a true case of a shipyard. A mobile truss platform hoisted with a six-axis robot is deployed for large ship blocks spraying. This paper studies the trajectory planning problem of spraying. A spray distribution model based on βdistribution is established, NSGA-III is applied to minimize working time and the variance of paint film thickness, and maximize paint utilization.

Analysis of Paint Film Thickness Distribution Based on Particle Method Considering Time Series Change of Flow

Analysis of Paint Film Thickness Distribution Based on Particle Method Considering Time Series Change of Flow

The importance of underpaint corrosion caused by damage to paint on steel structures

The impact of varying the dry paint film thickness (DFT) on the underpaint corrosion of steel plates obtained from the floor of an offshore oil platform is evaluated. The specimens were all prepared using the same material and paint scheme, and the DFT and exposure conditions in a salt spray chamber were varied and compared with the results obtained in a real situation. The results indicated that corrosion initiated at sites where the paint was damaged, may be more important than corrosion through the undamaged paint due to permeation, even in cases where the DFT is thin. In specimens whose substrates were previously damaged, there were pathological manifestations of osmotic blistering. The underpaint corrosion that occurred after the paint was damaged in the field occurred at an intensity like that observed for the tested specimens.

Modeling and simulation of electrophoretic deposition coatings

Electrophoreticdeposition (EPD) coating is one of the key processes in automotive manufacturing. Here, car bodies are moved through a tank of paint in which electrically charged paint particles lead to a successive increase of the paint film thickness on the car body. This paint film is used to protect the car body from corrosion. However, in order to properly protect the car body from corrosion, it is required that the whole surface area is covered by a certain paint film thickness. To ensure that, there is a high demand for an accurate simulation tool, which not only avoids the need for expensive prototypes but also allows to detect potential problems in early development stages. To that end, in this work, we are proposing a novel simulation tool based on the finite difference method (FDM). The proposed tool considers exact physics and employs a dedicated overset grid methodology to allow for a high resolution discretization of entire car bodies. Based on this overset grid scheme, the whole domain is modeled in a coarse resolution, whereas the space around the car body is discretized using a high resolution grid. Employing this scheme eventually allows for an accurate and efficient simulation of industrial EPD coating processes. Experimental evaluations based on an analytical analysis and an industrial scenario confirm the accuracy and scalability of the proposed methods.

Experimental Design and Spray Technology Research of Ship Paint Spraying Robot

A wall climbing robot for ship painting is designed. The robot is the separation of the paint output device and the main machine of the painting equipment to realize the painting operation of the wall climbing robot. The test environment and test method design of the robot are introduced in detail, and the painting process of the robot is verified. On this basis, the thickness of paint film and the related aspects of spraying process are studied, so as to eliminate the random error caused by experience and technical techniques, and to achieve the established film thickness and the stability of paint film coating. Improve automatic spraying process and labor productivity.

Colour variation in drying paint films

Color variations due to changes in paint film thickness and pigment content were studied experimentally. Three paints with differing concentration (0.5%, 2% and 4% by weight) of spherical blue pigments were applied with varying film thickness (310, 490, 730 μm) on stainless-steel substrates and dried in an oven while the paint surfaces were photographed. Weight loss due to solvent evaporation from the paint was recorded. The color of the dried paint films was measured. Surface tension driven convection was observed in drying paint films, which caused movement of pigment particles. An analytical model was used to predict solvent concentration gradients in the paint films and calculate Marangoni numbers, which determined the velocity of fluid motion. All motion stopped when the Marangoni number became small. Pigment particles tended to cluster around the edges of convection cells and produce changes in color, especially when the paint films were thin and the pigment fraction low. Increasing either the amount of pigment or the paint thickness made the paint color lighter, as a larger number of pigment particles increases reflection of light. Paints with high pigment concentration are less likely to see changes in color.

Experiences with Thermal Spray Zinc Duplex Coatings on Road Bridges

Road bridges are typically designed with a 100-year lifetime, so protective coatings with very long durability are desired. Thermal spray zinc (TSZ) duplex coatings have proven to be very durable. The Norwegian Public Roads Administration (NPRA) has specified TSZ duplex coatings for protection of steel bridges since 1965. In this study, the performance of TSZ duplex coatings on 61 steel bridges has been analyzed. Based on corrosivity measurements on five bridges, a corrosivity category was estimated for each bridge in the study. Coating performance was evaluated from pictures taken by the NPRA during routine inspections of the bridges. The results show that very long lifetimes can be achieved with TSZ duplex coatings. There are examples of 50-year old bridges with duplex coatings in good condition. Even in very corrosive environments, more than 40-year old coatings are still in good condition. While there are a few bridges in this study where the coating failed after only about 20 years, the typical coating failures are due to application errors, low paint film thickness and saponification of the paint. Modern bridge designs and improved coating systems are assumed to increase the duplex coating lifetime on bridges even further.

Research on Spray Trajectory Atomization Based on Mathematical Analysis

The most important part of the spraying process is the paint film thickness uniform and how to plan the spray path. The paper is optimize the trajectory of spray gun by establishing mathematical model. Based on the analysis of the factors affecting the thickness distribution of paint film, establishing the thickness of single-trajectory spraying model, and analysis the relationship and surface geometry invariant to simplified the model, getting the optimal solution by using overlapping thickness model based on the movable surface, useing MATLAB to establish model of the curve surface. Then using projection to establish the thickness distribution model of any curve surface. Then use cloud sectioning to optimize the curve surface and establish the thickness of paint film in double trajectory.

Simulation of Non-Destructive Testing on Weld Surface Crack of Metal Structure by Electromagnetically Stimulated Infrared Thermography

With the wider use of metal welded structure in engineering machine, on-line inspection on weld crack is of great significance. This paper reports an emerging nondestructive approach----electromagnetically stimulated infrared thermography technique, for the detection and characterization of surface cracks. According to the electromagnetic thermal coupling analysis theory, different abnormal temperature field distributions caused by various crack dimensions , coil lifting heights, stimulated frequencies and paint film thickness were obtained, via 3D finite element analysis (FEA).The results show that the weld surface crack detectability are greatly influenced by the crack width and the paint layer thickness, with coil life-off height decreasing and electromagnetic excitation frequency increasing, the maximum abnormal temperature difference increases. There is a certain reference value for further research on the design of the electromagnetically stimulated control device.

Prediction of the Thickness of a Thin Paint Film by Applying a Modified Partial-Least-Squares-1 Method to Data Obtained in Terahertz Reflectometry

We applied a multivariate analysis method to time-domain (TD) data obtained in terahertz (THz) reflectometry for predicting the thickness of a single-layered paint film deposited on a metal substrate. For prediction purposes, we built a calibration model from TD-THz waveforms obtained from films of different thicknesses but the same kind. Because each TD-THz wave is approximate by the superposition of two echo pulses (one is reflected from the air–film boundary and the other from the film–substrate boundary), a difference in thickness gives a relative peak shift in time in the two echo pulses. Then, we predicted unknown thicknesses of the paint films by using the calibration model. Although any multivariate analysis method can be used, we proposed employing a modified partial-least-squares-1 (PLS1) method because it gives a superior calibration model in principle. The prediction procedure worked well for a moderately thin film (typically, several to several tens of micrometers) rather than a thicker one.

The Effects of Paint Film Thickness on the Reflection Echo Height of Ultrasonic Testing

The Effects of Paint Film Thickness on the Reflection Echo Height of Ultrasonic Testing

The Influence of Thickness of Nitrocellulose Wood Lacquer on Formaldehyde Emission Rates

This study aimed to investigate the influence of the paint film thickness on formaldehyde emission rates. A small-scale environmental chamber was set up to test the formaldehyde emission from wood lacquer with different thicknesses. In all experiments, the temperature, the airflow rate and the relative humidity were the same, which were set to 23 °C, 1000 L/s, 45 %, respectively. The emission rates of formaldehyde were calculated through the double exponential decay model. Results showed that the peak concentration was dependent of the paint film thickness. The thicker the film thickness was, the slower the emission rate was.