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The initial examination should be done with an optical microscope, possibly including of cross sections of the defect. PAINT DEFECTS SUMMARY LIST Pg TABLE OF CONTENTS Bleeding 4 Blistering 5 Boiling 6 Clouding 7 Cracking 8 Cratering 9 Dust Contamination 10 Industrial … The primary cause of this defect is water vapor. 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. When sagging occurs on application, it is called cold sag. Top 10 Auto Paint Repair Problems and Solutions. Sometimes such damage is due to badly prepared substrates. Some of the common defects that usually occur in painting works are explained in this article. Repairing of defects can lead to more problems, so the best strategy is to prevent them from occurring. Some primers are more effective than others at sealing plastics, but the best remedy is rigorous quality control of the plastic parts so that they do not have voids and pinholes at or just below the surface. 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. There are several simpler wetting/dewetting tests that can be used. In some cases, it may be from electrostatic wrap or other spraying effects, but it usually is caused by surface tension gradients during baking. 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. ASTM D7541 describes cotton swab, marking pen, and drawdown techniques that simulate the application of a film. However, at other times, no reason or source of the defects has been found. 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. In most worldwide automotive industries, the inspection process is still mainly performed by human vision, and thus, is insufficient and costly. They dictate almost all factors of paint correction detailing: machine selection, product selection, procedure implementation etc etc. 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. 1. All defects hurt appearance and some also can interfere with the corrosion or weathering protection aspects of the coatings. The latter are additives such as fumed silica, treated clays, microgels, and castor oil derivatives that form physical networks. There are other defects that resemble dirt such as paint drops, gun spits, and overspray. Maybe your customer had an accident, or maybe the car was exposed to aggressive atmospheric conditions. This can occur in manufacturing processes and in the auto plant itself. So as understood this is common defect in automotive industry. The term orange peel refers to a bumpy coating surface that resembles the surface of an orange. Bierwagen, G., Prog. The defects can be prevented or reduced by lowering and/or ramping or stepping voltage, adding solvent and raising the bath temperature. Sloppy paint application also can lead to popping. Formation of bubbles like shapes on the painted surface is known as blistering. With the introduction of waterborne basecoats, a new source of popping became apparent. Air bubbles trapped in paint during manufacture or application can result in bubbles, pinholes, and crater-like defects in the cured film. Dirt that shows up on or in paint films may include fibers, sanding dust, metal particles (including weld balls from the body shop), oven dirt (condensate and carbonized resin), and general dust and grit. Dirt on auto coating surfaces sometimes can be polished out, but more often leads to sanding, which produces more dirt, and repainting. As these increase, the need for automated inspection does as well. Defects and problems do occur while automotive coatings are being applied or soon after, especially during one or another of the bakes. Various volatiles cause another set of defects. 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. This begins with the development of paint formulas that contain components such as surface active additives and solvents that give the wet paint a surface that is homogeneous with low surface tension. Proper dispersion and mixing practice can reduce air entrapment during manufacture. 3] Swelling of solvent-sensitive substrates. It is critical to ensure good cleaning and pretreatment of metals and power washing and solvent wiping of plastic parts. Paint Defects. The new solventborne and waterborne three-wet processes (primer/basecoat in one application) would seem to offer relief from telegraphing involving primers. Paint Defects Advice Swelling Causes 1] Drying time too short between layers in a complete process and/ or too high a film thickness of the filler coat within the process. Craters are caused by low surface tension contamination that is on the substrate being painted, is in the paint, or falls on the paint. Org. Atomization may cause bubbles, particularly with worn or damaged gun tips or chipped bells. Blistering. 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). Correct matching of the batch size with the size of the manufacturing equipment is essential. Paint Defects play a huge role in most automotive detailing businesses. It is caused by gravity driven flow on vertical surfaces. ), Modern Approaches to Wettability: Theory and Applications, pp 375-395. The defect may be due to not cleaning the surface before painting, using the wrong solvents in spray painting or incorrect air pressure. This initially lowers the surface tension and gives a gradient that causes flow away from the edge, producing an offset bead. 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. Most automotive coatings contain solvents that must come off during the flash or be driven off during the bake. 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. Ultimately, the supplier may need to put a little more solvent in the clearcoat tank to get more flow. When they occur they must be sanded and repaired, which can lead to additional defects. FIGURE 1—Basecoat crater due to contaminant in the primer. 3D effect on dark paint surfaces on which a paint defect has been remedied. Coarse blisters, larger than 1.5 mm in diameter, generally occur in patches, although they may also be found in isolation. 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. FIGURE 4—Diagram showing a thin edge (poor coverage) and a fat edge. This article surveys some of the defects that automotive coatings experience when they are applied. Many of the common day-to-day defects seen on car bodies are surface tension driven. Irregular spraying can give thick spots that pop as do electrostatic spray wrap, fat edges, or sags. A paint with a surface tension below the dewetting critical surface tension of a substrate will wet that substrate unless there is subsequent contamination. Final sand with 500 grit by hand or DA w/interface pad. Solvents tend to evaporate more rapidly from edges. The defect usually is due to dirty or otherwise contaminated surfaces. The defects which are commonly found in paint work are as follow. Fortunately, it is not necessary to stop downward flow completely to prevent sag. Let’s begin with dewetting. 4] Incorrect quantity of hardener in Body-Filler or Filler coats. 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. Automotive Solutions. This website uses cookies in order to improve and customize your browsing experience. It reduces sensitivity to airborne contaminants. Defects and problems do occur while automotive coatings are being applied or soon after, especially during one or another of the bakes. 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. 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. Blisters appear as swellings on the surface of the paint and vary considerably in both size and density. This guide on identifying and solving the most common paint defects goes over some common paint defects including, but not limited to acid rain, clearcoat yellowing, peeling, rail dust, and staining. Air entrapment rarely is suspected until after solvent popping and substrate gassing have been ruled out as causes. If the contaminant can be identified, then there is a good chance that its source also can be found. 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. The problem is most probably caused by too thick a coat trapping solvents into the film, or by air bubbles. The breakpoint between wetting and dewetting provides what is called the critical surface tension of dewetting. Easy to UseMore Comfortable Feels Better Easy to detect from the distance Designed to remove nibs and paint defect by hand easier and faster resulting in a better finish. Bubbles also may form because of a tendency of the paint to foam. 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. 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. Below you can find all the information about paint defects in our handy, interactive tool. A cross section would show a series of connected voids through the layers (see Figure 9). Telegraphing is a defect that involves the reproduction of surface features on an undercoat or substrate by the coating applied over it (Figure 3). I hope you enjoy this blog. 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 Schoff, C.K., “Wettability Phenomena and Coatings,” in Schrader, M.E., Loeb, G. Shallow craters often can be polished out, but deep ones require sanding and repainting. In this case, the edge probably has heated up faster on baking than the rest of the part or panel. Most current formulations give edge coverage and smooth coatings. 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 … Dewetting also can produce beads of paint, islands, craters, or pinholes (see Figure 2). Sagging can be reduced or prevented by raising the low shear rate viscosity of the paint and/or applying thinner coats of paint. The best way to fix defects is to prevent them from occurring. However, contact angle measurements require specialized equipment and are not practical in the field. These defects must be smoothed out by sanding before the basecoat is applied. 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. The surface should be smooth. Close-up. The main cause of this defect is flow due to surface tension: flow away from residues such as finger oils and sanding dirt or flow away from sharp edges of sand scratches. However, relatively few pieces of dirt are so easy to see. Wetting and flow on sanded areas are affected by the roughness, porosity, and the increased wettability of the abraded surface. Paint School JPS-E / Paint technology / 1. How to avoid paint defects in automotive? 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. 0 Use this guide to better understand the various paint and body defects. Nearly all coatings people are familiar with craters, but they may not know much about them. This maximizes wetting of undercoats and minimizes surface tension gradients that might occur due to contamination or temperature differences. Other surface tension-related defects include dewetting, telegraphing, and picture framing. Popping involves the formation of defects by the blowing out of trapped solvent or other volatiles during baking. How To Fix Automotive Paint Defects June 7, 2019 Roadkill Customs How To & DIY This video addresses several questions about how to fix common paint defects such as paint runs, solvent boil, removing dust from paint, and several other tips and tricks of the trade. Many plastics have a thin, but relatively dense “skin” at the surface, but if this skin is missing, has been removed by sanding or itself has voids, there is nothing to prevent volatiles from traveling up into the paint. The volatiles force their way up into the wet paint layer as it is baked, resulting in pinholes, volcanoes, and/or bubbles. Dehydration of these basecoats can lead to pops in clearcoats applied over them. The best way to prevent or reduce these defects is to develop a combination of surface tension control and rheology optimization. Therefore, automatic paint defect inspection is required to reduce the cost and time waste caused by defects. Electrical discharge is more likely to occur over zinc coated steels, especially zinc-iron alloys, but it can occur over cold-rolled steel. Delamination (Adhesion failure) Appearance Loss of adhesion: Intercoat delamination: Between coats : Substrate delamination : Between primer and substrate. 2 Prior Repairs Gaps in Panels Paint/Body Defects Turned Bolts 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. 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