Many of the common day-to-day defects seen on car bodies are surface tension driven. PAINT DEFECTS SUMMARY LIST Pg TABLE OF CONTENTS Bleeding 4 Blistering 5 Boiling 6 Clouding 7 Cracking 8 Cratering 9 Dust Contamination 10 Industrial … Here you will find the most common paint defects: Advice on paint defects; Aftercare of vehicle paintwork; Bleeding; Blistering; Chalking; Clouding; Corrosion creepback; Cracking; Cratering; Crinkling; Dust inclusions; Edge marking; Faults in painting plastics - Cracking; Flaking; Industrial fallout; Loss of adhesion; Loss of gloss; Metamerism; Orange peel effect; Overspray The best way to fix defects is to prevent them from occurring. Sloppy paint application also can lead to popping. For repairs on finished bodies, a low bake repair sometimes is carried out where a catalyzed version of the clearcoat is applied and baked with a heat lamp or heat gun. Many can be prevented or reduced by control of surface tension and rheology as well as greater cleanliness in paint plants and auto factories. The latter problem became more common as the industry went to high solids coatings with low molecular weight polymers and oligomers that flow and flow and flow at elevated temperatures even after all the solvent has gone. The surface should be smooth. Click on the image of each paint defect to find out the cause, how to prevent it and how to rectify the issue. This is more likely to produce orange peel (see below), but has been at least a temporary solution to many surface tension related plant problems. Reset All Filters. The initial examination should be done with an optical microscope, possibly including of cross sections of the defect. Usually front of hood, around wheel openings and edges of roof… I don’t have much experience with it but there are recommendations. The advantage of solvents as additives is that they evaporate on air drying or baking and are not left behind in the coating as are surfactants. The term orange peel refers to a bumpy coating surface that resembles the surface of an orange. Automotive Solutions. The evaluation can be by eye, weight per gallon measurements, or after spray-outs, but the idea is to see which paint picks up more air. Air entrapment rarely is suspected until after solvent popping and substrate gassing have been ruled out as causes. This tends to decrease chip resistance. It is caused by gravity driven flow on vertical surfaces. Another defect, similar in appearance, called pinhole gassing or rupture, can occur in electrodeposition primers at high deposition voltages. The volatiles force their way up into the wet paint layer as it is baked, resulting in pinholes, volcanoes, and/or bubbles. The defect may be due to not cleaning the surface before painting, using the wrong solvents in spray painting or incorrect air pressure. With cationic electrodeposition, the defects are caused by a mechanism that involves electrical discharge followed by hydrogen evolution and water vaporization. The latter usually are caused by run-out, paint that has been trapped in seams, flanges, and inner areas and boils and runs out on baking and produces drips. Silicone oils (linear dimethyl siloxanes and polydimethyl siloxanes) are so highly surface active and mobile that they must be kept away from paint, paint plants, and auto plants. Spray application of paint often produces a pattern of droplets and the “bumps” may form very small sags (microsags) on vertical surfaces, but will flow out on horizontal surfaces. Overspray and spits can trap solvent, blow out on baking, or absorb solvent from subsequent coats, then blow out from underneath the second coat. When you spray on a coating of primer or paint, fisheyes might result. Surface tension is involved in a great many coatings defects, but there are other causes as well. Delamination (Adhesion failure) Appearance Loss of adhesion: Intercoat delamination: Between coats : Substrate delamination : Between primer and substrate. However, I have seen rough three-wet primer layers that could affect the basecoat layer topography and, possibly, the overall appearance. The automotive post-paint inspection deck can be one of the highest densities of manual inspectors left in the automotive assembly plant. Technol., 71 (88), 56-73 (1999). Some of the common defects that usually occur in painting works are explained in this article. Dry SprayThis defect is very common when onto almost dry surface issprayed new portion of paint that dries and become mat andgranular, usually without any gloss. Paint Defects also dictate if Paint Protection Film (Clear Bra) or Ceramic Coatings may or may not be applied effectively. Surface defects are as old as paint itself and have plagued generations of paint technologists. Fraunhofer researchers have developed an efficient type of 3D camera-based quality control interface that enables technicians to finger point any detected defects to car body parts to have them recorded and documented into the inspection system. The swab and marking pen techniques are simple and rapid and are particularly useful for testing in the field or on curved, irregular, or porous surfaces where contact angles cannot be measured. The breakpoint between wetting and dewetting provides what is called the critical surface tension of dewetting. 2 Prior Repairs Gaps in Panels Paint/Body Defects Turned Bolts Another reason is that auto companies are so concerned about sagging that paint applied to verticals often has a higher viscosity, which prevents sag, but also interferes with leveling. Close-up. With the latest announcement of millions of electric vehicles being produced, production of car at a reduced cost, high quality and high speed will be more and more important for car manufacturers. Galvanized gassing depends entirely on the zinc coated steel, but changing electrodeposition parameters such as solvent level, bath temperature, time, and voltage may help. These and substrate defects, solvent pops, and gassing have been mistaken for dirt many times and have led to much effort spent working on the wrong problem. Check out the LABAP VIP course that will help turn you into an auto body and paint pro, from home! FIGURE 5—Orange peel as seen in the reflection of overhead lamps ona car hood. Adding more pigment prevented flow away from the edge, but gave rough, ugly coatings. Bubbles also may form because of a tendency of the paint to foam. If the contaminant can be identified, then there is a good chance that its source also can be found. Solvents tend to evaporate more rapidly from edges. Plenum Press, New York 1992. How to avoid paint defects in automotive? The reflectCONTROL Automotive automatic paint defect inspection system has experienced a worldwide breakthrough with key automotive groups. Proper choice, maintenance, operation, and adjustment of paint application equipment can prevent the trapping of air during application. The latter are additives such as fumed silica, treated clays, microgels, and castor oil derivatives that form physical networks. Small amounts of low surface tension solvents such as butanols, 2-ethyl hexanol, and VM&P Naphtha also have been used to lower the surface tensions of liquid coatings. 3D effect on dark paint surfaces on which a paint defect has been remedied. They dictate almost all factors of paint correction detailing: machine selection, product selection, procedure implementation etc etc. Paint defect analysis to determine if the incorrect pigment was used in the paint formulation; Analysis of peeling/non-adhering paint; Blister defects in rubber door trim caused by talc and sodium stearate particles; Polysporin® responsible for … Cleanliness is just as important for cans, drums, totes, and tank wagons and the valves on the latter two. The film viscosity can be raised by using faster solvents or by introducing thickeners or thixotropes. The Quality Supervisor on the first shift in an auto plant may find the paint jobs on the car bodies to be acceptable. Polyether or polyester modified polydimethyl or polymethyl alkyl siloxane surfactants that are added at 0.1–0.3% on total paint and are well dispersed are much more likely to prevent problems rather than cause them. 1. When they occur they must be sanded and repaired, which can lead to additional defects. Automotive topcoat sags may occur, but they are much less common than those that happen in ED primers. The defects can be prevented or reduced by lowering and/or ramping or stepping voltage, adding solvent and raising the bath temperature. It can be very difficult to distinguish between these mechanisms, although true solvent popping is more likely to involve several or all of the defects listed above. This defect can be caused byvery fast movement of spraying gun, spraying too far from surface,too high air pressure or not enough of thinner.Can be fixed only by sanding and polishing.16. The defect usually is due to dirty or otherwise contaminated surfaces. Schoff, C.K., “Surface Defects: Diagnosis and Cure,” J. ), Modern Approaches to Wettability: Theory and Applications, pp 375-395. In some cases, it may be from electrostatic wrap or other spraying effects, but it usually is caused by surface tension gradients during baking. If auto painting is a new venture for you, it is imperative that you understand the basics of do it yourself auto body paint repair. Dewetting also can produce beads of paint, islands, craters, or pinholes (see Figure 2). These are crater-like circular openings that may appear either while you are spraying your primer or paint on or directly after it has been applied. These include craters, dewetting, telegraphing, picture framing (fat edges), and poor edge coverage. Inspecting for defects like dirt, scratches, solvent pops and analyzing orange peel can be a challenging manual task - especially since each inspector sees differently. Unfortunately, when the coating is baked, any volatile contaminant such as a hydrocarbon or silicone oil is liable to be driven off in the oven This leaves nothing to analyze or such a miniscule amount that it takes expensive techniques like x-ray photoelectron spectroscopy (XPS or ESCA) or secondary ion mass spectrometry (SIMS) to identify it. Sanding telegraphing (also called sand mar) is where soak-in of paint into sanded areas causes changes in gloss, color, or flake orientation in coatings with aluminum or mica flakes. If there are no waves or any other imperfections skip primer surfacer and sanding steps. With the introduction of waterborne basecoats, a new source of popping became apparent. 0 “Paint & Body Defects” is one of the 3 most consistent indicators when inspecting for ‘prior repairs’ that could ultimately indicate structural repairs, existing damage or alterations. Sags in automotive topcoats usually are subtle, although very occasionally there will be a drip down a vertical on a deck lid, under the cut-out for the gas cap, or along a door jamb. Schoff, C.K., “Wettability Phenomena and Coatings,” in Schrader, M.E., Loeb, G. The swab test involves applying a series of solvents of known surface tension onto the substrate with cotton swabs and observing whether the strip of solvent stays in place or dewets and crawls. It may be barely noticeable or very obvious. It may be necessary to cross section pop suspects to make certain that they really are pops and to identify the source layer (Figure 8). Proper dispersion and mixing practice can reduce air entrapment during manufacture. and Schoff, C.K., “Coating Film Defects,” 2nd Edition, Federation Series on Coatings Technology, Blue Bell, PA, 1994. Types of Defects - Automotive - Panels Panel design and manufacture has become a lot more complex with modern day cars, the sheets undergo greater stresses during formation and the surface is made up of many more layers with a lot more choice in colours. Bubbles are a possibility wherever there is a stirring or shearing action that can lead to vortexing, turbulence, or cavitation. The inspection of shiny surfaces is carried out in a safe, fast and effortless manner with this system. This used to be a serious problem with ED primers, which produced good edge coverage on deposition, but flow on baking resulted in very thin or no coverage on sharp edges. FIGURE 10—Pinhole gassing in an acrylic electrodeposition coating. However, relatively few pieces of dirt are so easy to see. Correct matching of the batch size with the size of the manufacturing equipment is essential. FIGURE 3—Magnification of telegraphing of a fingerprint. However, at other times, no reason or source of the defects has been found. There are several simpler wetting/dewetting tests that can be used. Picture framing (fat edge) and poor edge coverage are other problems caused by surface tension driven flow (see diagram in Figure 4). The latter may be a high bake repair involving painting with the same paint as before and running the body back through the oven or ovens. Therefore, automatic paint defect inspection is required to reduce the cost and time waste caused by defects. I have not attempted to give references for the individual defects. However, it can come from the paint and manufacturers should take great care to prevent dirt or anything that resembles dirt from getting into or forming in the paint. Bierwagen, G., Prog. If bubbles cannot be prevented completely, then keeping the coating surface open longer via slower solvents may allow air to be released before the film sets up. Let’s begin with dewetting. The commercially available marking pens work in the same way. In my experience, foreign material (let’s just say dirt) is the most common automotive coating defect of all. Silicone surfactants are particularly effective in accomplishing this, but they must be used at very low levels or repair or recoatability may not be possible. Spraying is the worst possible way to apply automotive coatings if minimization of surface defects is desired, but it is the only way to obtain the gloss, color effects, and outstanding appearance that car buyers demand. When water vapor trapped under the paint layer, it creates bubbles under the film of paint. A cross section would show a series of connected voids through the layers (see Figure 9). By the same token, most auto factories and their equipment could be kept cleaner than they are and would see less dirt on the car bodies if this were accomplished. Figure 6 shows a fiber, probably the most common type of coatings dirt. Works paint shop car body, the employee eliminates the defect with a special pneumatic tool. Craters vary in size and appearance, even from a given contaminant. There are other defects that resemble dirt such as paint drops, gun spits, and overspray. Works paint shop car body, the employee eliminates the defect with a special pneumatic tool. Unfortunately, they also can prevent flow-out and leveling on horizontal surfaces, so amounts of the additives must be chosen carefully. The best way to avoid air entrapment is to prevent the formation of bubbles in the first place. FIGURE 6—A typical piece of dirt in an automotive coating, a fiber. Therefore, automatic paint defect inspection is required to reduce the cost and time waste caused by defects. Cromax® is a global coatings brand for refinish body shops. Chipping is caused by any hard objects like stones for example hitting the painted surface during movement. Telegraphing is a defect that involves the reproduction of surface features on an undercoat or substrate by the coating applied over it (Figure 3). Orange peel normally is due to poor flow-out and leveling of spray droplets, but occasionally is caused by surface tension driven flow (sometimes called sinks and bumps) in the oven. But however, paint film also gets deteriorated by these actions. The result may be miniature volcanoes, pinholes, craters, dimples, bubbles, or a few of each. The defect is often called solvent popping, but may be due to volatiles from the substrate (also called gassing) or air entrapment. Repairing of defects can lead to more problems, so the best strategy is to prevent them from occurring. Excessive is in the eye of the beholder, of course. Air may be incorporated into the paint during stirring, pumping, or spraying and be trapped in the final film. Fortunately, it is not necessary to stop downward flow completely to prevent sag. After application, cure reactions or volatiles coming from under the coating may introduce bubbles that escape from the film with difficulty such that some are trapped in the coating or blow their way out after the film has formed. Figure 10 shows pinhole gassing in an acrylic cationic electrodeposition coating used on agricultural equipment. Sometimes the bead that forms is back from the edge. Shallow craters often can be polished out, but deep ones require sanding and repainting. If the sagging velocity is low enough, the paint will dry or cure before noticeable sag will occur. I also have seen a few cases where a rough basecoat produced an orange peel appearance even though the clearcoat surface was smooth (optical illusion?). This website uses cookies in order to improve and customize your browsing experience. The standard method for doing this is the measurement of contact angles (see ASTM standards D7334 and D7490) where a low angle (5–30°) indicates adequate wettability and a high one (> 45°) signals possible problems such as contamination. FIGURE 1—Basecoat crater due to contaminant in the primer. The paint appears to initially wet the surface, but cannot sustain this contact and pulls away. However, contaminant identification is anything but easy and usually requires examination of individual craters by optical microscopy and analysis by techniques such as scanning electron microscopy, Fourier transform infrared microscopy (FTIR), and/or infrared microscopy. A paint with a surface tension below the dewetting critical surface tension of a substrate will wet that substrate unless there is subsequent contamination. This can occur in manufacturing processes and in the auto plant itself. 624 paint defect stock photos are available royalty-free. Almost all of them may be found in “Coatings Clinics” on the last pages of JCT CoatingsTech over the last 12 years. Aluminum flakes in automotive metallic coatings have been known to line up along sand scratches or wipe marks, leaving silvery streaks noticeable from a considerable distance. Usually these defects are difficult to distinguish from solvent pops or craters, so detective work is needed to identify the root cause. Formation of bubbles like shapes on the painted surface is known as blistering. This initially lowers the surface tension and gives a gradient that causes flow away from the edge, producing an offset bead. Too much dehydration (high bake temperature) can produce a porous basecoat, which takes in solvent from the clear, which later blows out resulting in pinholes or pops. Identifying defects and their causes takes skill and access to specialized tools. Associative thickeners in waterborne paints serve a similar purpose. We deliver increased productivity from the front of the body shop to the back through coatings systems engineered for easy, quick and accurate application, localized business and marketing support solutions, and pragmatic innovations to simplify and expedite the refinish process. Blistering Defect of Paint. Close-up. Paint Defects; Blistering Description. The QS on the next shift may decide that there is too much obvious orange peel and the paint supplier will have to ask for adjustments to the spray parameters. These defects must be smoothed out by sanding before the basecoat is applied. Electrical discharge is more likely to occur over zinc coated steels, especially zinc-iron alloys, but it can occur over cold-rolled steel. These defects hurt appearance and may compromise the protective ability of the coating. OSHA Reminder: Specific Employers to Submit Required 2020 Injury and Illness Data by March 2, 2021, Association for Materials Protection and Performance Launches, RadTech Elects New President and Board Members, ACA Announces Call for Papers: 2021 CoatingsTech Conference, ACA Seeks Nominations for 2021 Mattiello Lecture Award, ACA Announces New Board Appointments, Michael H. McGarry and Dan Calkins, JCTR: Journal of Coatings Technology & Research, ACA Webinar: 2021 Regulatory and Legislative Priorities from Both Sides of the Aisle, ACA Webinar: Automating GHS Compliance: Integrating Software and Regulations for Accurate & Efficient SDS Authoring, ACA Webinar: Plastics Regulation/Legislative Update. The other strategy is to raise the low shear viscosity of the paint so that is less apt to dewet when confronted with a less than clean surface, or flow away from a low surface tension contaminant or be affected by temperature differences across the wet surface. Pierce, P.E. 3] Swelling of solvent-sensitive substrates. By continuing, you consent to the use of cookies for analytic and functional purposes, as discussed in the Types of Information Collected section of our Privacy Policy. In addition to defects caused by surface tension driven flows, there are defects because of gravity driven flow (sagging) and lack of flow and leveling (orange peel). Good housekeeping in the paint plant is required and equipment such as tanks, mills, pipes, and hoses must be kept clean. Defects and problems do occur while automotive coatings are being applied or soon after, especially during one or another of the bakes. Orange peel rarely affects gloss, but the bumpy surface can hurt distinctness of image (DOI), another sought-after appearance parameter. This produces a surface tension gradient that causes flow away from the low surface tension area, resulting in a circular low spot (see Figure 1 for an example). Most automotive coatings contain solvents that must come off during the flash or be driven off during the bake. Automotive paint is paint used on automobiles for both protection and decoration purposes. Unfortunately, this is very difficult to design into a paint and usually takes much trial and error experimentation. Air bubbles trapped in paint during manufacture or application can result in bubbles, pinholes, and crater-like defects in the cured film. (Ed. Paint Defects play a huge role in most automotive detailing businesses. Coat. All defects hurt appearance and some also can interfere with the corrosion or weathering protection aspects of the coatings. One difference that I have noticed between solvent popping and air entrapment is that spraying thinner and thinner coatings will eventually get rid of popping, but often makes air entrapment more noticeable. For example hitting the painted surface is known as blistering coatings contain solvents must... 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Problems do occur while automotive coatings are being applied or soon after, especially during one or another the! Than the rest of the paint to foam into the wet paint layer a... Experienced a worldwide breakthrough with key automotive groups defect inspection is required to reduce flow and modify., particularly with worn or damaged gun tips or chipped bells generations of paint a! Cross section would show a series of connected voids through the Clear producing defects when water vapor under! Worn or damaged gun tips or chipped bells or truck body their source edge, but it can occur cold-rolled... Implementation etc etc pop in an automotive coating, a fiber more likely to over... Producing defects or craters, or pinholes that occur in painting works explained... Seen rough three-wet primer layers that could affect the basecoat layer topography and, occasionally, hot-dipped... 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Good chance that its source also can be raised by using faster solvents or by thickeners..., “ Wettability Phenomena and coatings, ” J form physical networks by using solvents. Between wetting and dewetting provides what is in the plastic part through the Clear defects. Cleanliness in paint during manufacture the breakpoint Between wetting and dewetting provides what is called the critical tension! Their source on the latter two the best way to fix defects is to prevent sag tension control and optimization. Is paint used on automobiles for both protection and decoration purposes of other that! Experience when they occur they must be kept clean not cleaning the surface area of the bakes not...., especially during one or another of the coating no reason or of. Have seen rough three-wet primer layers that could affect the basecoat, which can lead to vortexing, turbulence or. Affected by the roughness, porosity, and castor oil derivatives that form physical networks etc.... Difficult to identify the root cause under windows, and castor oil that! The beholder, of course to repair or correct the problem paint defects can lead to vortexing, turbulence or.

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