Moisture content on the painting surface should not exceed 6% as it helps to avoid efflorescence. Use clean tools and water or solvents for painting the walls. It may appear while painting or during the drying time. V    Adjust dry off oven temperature to ensure no moisture is on the part. Surface defects are as old as paint itself and have plagued generations of paint technologists. Recoating of solvent-sensitive layers (NC/TPA) with wrong repair materials or Unfortunately, “near-perfect” still leaves room for occasional defects, coating flaws that can compromise e-coat’s protective and decorative finish. They can be avoided by lowering the surface tension of the liquid. If the central underlying substrate area is visible, the defect is known as cissing. 5 2. If the central underlying substrate area is not visible the defect is known as a dimple. N    Preventive Measures for Painting Defects Employ good surface preparation before the application of paint. • As paint films age, they become harder and less flexible and so “Something has to give”. Improper surface preparation – the substrate surface is not adequately prepared for the coating that is to be applied. Fig. Because they are often mixed up, formulators can spend hours focusing on the wrong solution. Small round depressions in the surface of the coating are known as craters. Cissing and dimpling (sometimes known as “Crawling” or “Fisheyes”) are very small circular defects, where the paint has receded to expose the underlying substrate or coating. Cratering is one of several defects which can occur during the drying of a painted surface, in which a circular depression appears in the dried film (1, 2). 1. MODEL FOR CRATER DEFECTS IN A DRYING PAINT LAYER 203 dimensionless stopping time are robust, i.e., do not depend on the particular drying model used. Often these craters have a raised outer rim; they may also have a central peak. O    Pinholes are craters that develop where the liquid has not formed a homogeneous layer, thereby leaving a depression which penetrates to the substrate. 6 #15 Dent—a mark transferred to a substrate surface from an imperfect process roll or something on a roll. Cratering—a coating effect characterized by small pock marks or depressions surrounded by a ring of coating material that projects above the general plane of the coating. In severe cases, the substrate may be visible in the center of the imperfection. P.S The paint defects looks like this: (side view) _____ _____ paint surface \ / --0-- particle below paint … DISCUSSION AND SUMMARY required for a run with no viscosification or evaporation. I    He worked at PPG on the development of Industrial Coatings and at DSM Coating Resins on Alkyd Emulsions, Powder Coatings, High Solids, Additives and complete formulations. 3 #15 Catenary or oven scratches —Streaks in the paint, always parallel to length, or small lines indicative of strip bouncing in the oven section. 3] Swelling of solvent-sensitive substrates. Cratering can be avoided by improving spray technique — applying a mist coat and avoiding air entrainment during mixing. Paint and Coating Failures The majority of paint and coating-related failures can be attributed to six primary causes. Watch this tutorial and learn easy lab tests to identify with no doubt if you face cratering or crawling. • Thin films tend to crack less than thick films. Cracks in paint are also developed when the paint is applied to bare wood or on the porous surface without applying a primer. F    The paint that we are using is 2K. Crawling and cratering, 2 common paint defects, affect both the aesthetic & protective role of the coating film. These causes are as follows. Increase paint robot productivity, throughput, first time yields and significanly reduce VOC and HAP emissions. It occurs sometimes with old paint around the edges of primers or body fillers or stopper spots. Dirt. Paint film defect causes. Corrosionpedia Terms:    Many coating defects are related to surface tension issues. Inspection with a lens may reveal a small impurity at the base. Cratering, a coating defect, is the formation of small bowl-shaped depressions in a coating film. Because they are often mixed up, formulators can spend hours focusing on the wrong solution. Cratering, a coating defect, is the formation of small bowl-shaped depressions in a coating film. Blushing is a defect in the paint film. Crawling and cratering, 2 common paint defects, affect both the aesthetic & protective role of the coating film. 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Cratering is caused by incompatible foreign materials either in the paint or on the substrate. Cratering, or craters, are spots where paint on the coated surface has receded, often concentrically, to leave a spot with no paint. You will then see the best approach to solve your coating defects, thus reducing your development time. L    Specific Defects – Film Defects 4) Cracking • Fracture of at least the topcoat of paint with ageing, and occurs when the substrate and coating expand and contract at different rates. This is a common contamination paint defect. This is called biting, wherein a paint is moving away from a certain area causing a crater. Paint Defect Analysis, paint craters, cratering and finish quality troubleshooting and improvement in robotic electrostatic and conventional spray booth painting application systems. 4] Incorrect quantity of hardener in Body-Filler or Filler coats. Breakdowns are usually first of all seen as blistering or cratering and followed by the complete breakdown, as wholesale lifting and flaking. The reason for the formation of craters is the difference in surface tension between the liquid paint and the contaminant. If the central underlying substrate area is not visible the defect is known as a dimple. Cure—the process by which paint is converted from the liquid to the solid state. A thick film may cause out-gassing. Air bubbles trapped in paint during manufacture or application can result in bubbles, pinholes, and crater-like defects in the cured film. We have even tried using a special paint that is supposed to seal in any defects so that you can paint over the top. T    defects in coating uniformity resulting in quality problems and customer dissatisfaction. 1. We were told that this defect is caused by silicone - we have used anti-silicone wipes, anti-silicone liquid in the paint, but it does not work. Possible causes of defect/complaint Presentation of defect/complaint Z, Copyright © 2021 Corrosionpedia Inc. - The more paint you put on it, the more it separates and the paint issue just worsens. S    Usually, this moisture originates from within the porous substrate. In severe cases, the substrate may be visible in the center of the defect. Specialized Coating Systems (Pty)Ltd www.speccoats.co.za 0861 37 2468 . This may include cleaning, chemical pretreatment or surface roughening. Additionally, Jochum is a lecturer of Paint Technology courses for SpecialChem and he is a member of the SpecialChem Expert Team. This paint defects also occurred if the paint is applied to the glossy surface. Foaming and Cratering – Formation of bubbles (foaming) & resulting small round concave depressions (cratering). Z Td µ0 8d = d t˜ [26] 0 µ(t˜) 5. The paint that we are using is 2K. Hot-dip vs Cold Galvanizing: What’s the Difference? These paints have superior anti-corrosive properties and UV life resistance upto 500 hours. This is called biting, wherein a paint is moving away from a certain area causing a crater. W    D    Generally, a stress-related failure due to movement, aging, absorption and desorption of moisture and a lack of flexibility within the paint or coating film. Fibers. Probable Causes: Paint film exposed to condensation or moisture during curing, especially at low temperature (common phenomenon with amine- cured epoxies). 6 A hazy deposit on the surface of the paint film resembling the bloom on a grape, resulting in a loss of gloss and a dulling of color. Jochum writes technical articles for, amongst others, UL Prospector. The majority of paint and coating-related failures can be attributed to six primary causes. The major reason for paint cracking is the premature application of final coat before the previous coat has completely dried. Definitely avoid – reconfigure plant. Jochum develops and conducts in-company training programs and he is lecturer within the Dutch Coating Technology training program. Air entrapment rarely is suspected until after solvent popping and substrate gassing have been ruled out as causes. 05. Crown —see center. He is certified as NPDP (New Product Development Professional) by PDMA, the global leading organization on product development and innovation. ... Cissing/ Cratering. Liquid and powder paint in same plant. Reduce the film thickness to enable the gas to escape through the surface during cure. How to recognize them. Cratering during production can cause considerable costs to be incurred. The defects in a paint film which can be traced to rust forming under the paint are due mainly to insufficient preparation of the metal, including incomplete removal of millscale. Breakdowns are usually first of all seen as blistering or cratering and followed by the complete breakdown, as … Proper agitation is dependent on the header/eductor system and the circulation pump. 1. Craters. Solution. These depressions frequently have drops or bands of material at their centers and raised circular edges. 04. Common Electrocoat Defects. The largest number of paint defects is from dirt particles 1 embedded in the paint. Craters are bowl-shaped depressions with material in … Cissing and dimpling (sometimes known as “Crawling” or “Fisheyes”) are very small circular defects, where the paint has receded to expose the underlying substrate or coating. These paint issues affect both the aesthetic & protective role of the coating film. Q    Maybe your customer had an accident, or maybe the car was exposed to aggressive atmospheric conditions. Terms of Use - Potential Cause. U    View full profile (fields of expertise, publications…), At the Origin of Cratering & Crawling… a Wetting Issue, How to Solve Cratering Caused by Defoamers. Thinners should be added as recommended by the paint supplier. Germany 44070578 GB 10 05 2000 www.standox.com THK_Paint Defects_s0120.qxd 12.09.2005 13:02 Uhr Seite 2. We were told that this defect is caused by silicone - we have used anti-silicone wipes, anti-silicone liquid in the paint, but it does not work. J    #     Lapping – Appearance of denser colour or increased gloss where wet and dry layers overlap during paint application. If the central underlying substrate area is visible, the defect is known as cissing. When you see your paint having this type of reaction, you need to stop. Class A automotive root cause analysist. Coating Defects Fault Finding Coating Defects Page 1 of 35 Issue Date: 13/05/2014 ... CRATERING/FISH EYES DESCRIPTION Paint repelled by polluting agents, forms crater like depressions with relief edges. Paint Defect Analysis, paint craters, cratering and finish quality troubleshooting and improvement in robotic electrostatic and conventional spray booth painting application systems. These depressions frequently have drops or bands of material at their centers and raised circular edges. M    E    This is a common contamination paint defect. The defects are usually around 1-3mm in diameter and are … Fish eyes are craters that have a bit of material remaining in the center. Check powder for oil or moisture introduced in reclaim, from the air supply or the virgin powder. This may include cleaning, chemical pretreatment or surface roughening. Com-Paint’s Super Acrylic Base or Acrylic Base Paint is specially formulated to ensure that repairing craters/pinholes and other CED coating-related defects is easy, effective and long lasting. In some cases, a simplified form of the drying model may be used to quickly approximate the results of the full model. Agitation of a paint tank is necessary for paint suspension, filtration and removing excess heat generated from pumping and coating. When you see your paint having this type of reaction, you need to stop. A blank area in the powder coat, which extends all the way to the substrate (diameter up to 2mm). C    Privacy Policy If the central underlying substrate area is not visible the defect is known as a dimple. The defects are usually around 1-3mm in diameter and are … They apparently occur while the painted layer is still wet enough to flow. POSSIBLE CAUSES Shaking a partially filled can of paint or using too high a speed when using a drill mixer, introducing a lot of bubbles in the paint. Jonathan. Since 2004 Jochum is an independent consultant for companies in coating and ink industry. Cratering. 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. Jochum is specialized in the field of New Product Development. - Renew or change your cookie consent, Flange Corrosion Repair & Protection: Isolating the Sealing Face, Top Corrosion Mitigation Technologies to Watch for in 2021, The Impact of Minimum & Maximum DFT Values on Coating Performance, An Intro to Pipeline Corrosion and Protection Methods, Innovative Coating Solutions for Oil Sands Equipment, Troubleshooting Cathodic Protection Systems and Function Systems. Center (crown)—the difference in thickness between the middle and edges of a sheet. THK_Paint Defects_InGB.fh9 04.10.2005 10:08 Uhr Seite 11 C M Y CM MY CY CMY K 13 Water spotting • Vehicles washed with water from ”hard” water supply • Visible on dark colors, particulary on vehicles washed in … You will then see the best approach to solve your coating defects, thus reducing your … It occurs during the curing process because of condensation of moisture occurring on a coating surface and visible as water spot. ... Surfactant diffusion also tends to reduce the severity of cratering by alleviating surface tension gradients. CAUSES The possible causes of these swelling edges are: 1. Paint cratering is the formation of air bubbles (foaming) and resulting small, round concave depressions (craters) when bubbles break in a paint film during drying. Class A automotive root cause analysist. Multinationals as well as small companies call in the help of Jochum when problems have to be solved or when assistance is needed in New Product Development. More of your questions answered by our Experts, An Understanding of Today's Wet Abrasive Blasting Equipment, Proper Pipeline Joint Isolation - History of Design, Flanges, and the Best Available Design, Bituminous Coatings: When and How to Use Them, A Guide to Flash Rust Prevention and Protection (free PDF). Cratering can be repaired by abrading and cleaning the surface, then recoating. Abstract. Cratering plays a very important role in the coatings industry. B    Which will be used to customize the exact shade-matched spray … Coating defects are numerous and this section will not address every one, but it will provide some common defects related to the electrocoat tank, potential causes and their solutions. Improper surface preparation – the substrate surface is not adequately prepared for the coating that is to be applied. THK_Paint Defects_InGB.fh9 04.10.2005 10:08 Uhr Seite 1 C M Y CM MY CY CMY K Paint defects – inevitable but manageable. Lapping – Appearance of denser colour or increased gloss where wet and dry layers overlap during paint application. This chapter presents a discussion of organic coating defects that occur on application or during drying and baking. Are there any OSHA regulations that need to be taken into account when using thermal insulating coatings? Evans PL(1), Schwartz LW, Roy RV. These can appear due to the use of contaminated painting tools or embedded contaminants on the substrate or coating. R    Where can I find a coating that is chloride and sulfur corrosion-resistant? Cratering can also occur when trapped air or solvent bubbles which have burst leave small craters as the coating dries, leaving the coating insufficient time to flow into a uniform film. Y    It is also possible, Undissolved silicone. A Mathematical Model for Crater Defect Formation in a Drying Paint Layer. It’s basically paint not sticking in this area. This is old paint materials lifting/swelling when new paint is applied. 2] Filled areas are too thin or are not sufficiently isolated. K    Because they are often mixed up, formulators can spend hours focusing on the wrong solution. Coating Defects Craters. Cissing and dimpling (sometimes known as “Crawling” or “Fisheyes”) are very small circular defects, where the paint has receded to expose the underlying substrate or coating.If the central underlying substrate area is visible, the defect is known as cissing. X    These causes are as follows. Causes of cratering include: Gel particles. H    Not anymore with this tutorial! The defects in a paint film which can be traced to rust forming under the paint are due mainly to insufficient preparation of the metal, including incomplete removal of millscale. The defects are usually around 1-3mm in diameter and are … It has been established that cratering can lead to catastrophic fracture under the cycle load. Usually these defects are difficult to distinguish from solvent pops or craters, so detective work is needed to identify the root cause. Watch video tutorial by Jochum Beetsma and learn how to solve two common coating defects: crawling & cratering. Paint defects can have many causes. If the central underlying substrate area is visible, the defect is known as cissing. concave depressions (cratering). Jonathan. Insufficient pre-treatment (eg oil and grease residues). Cratering —a coating effect characterized by small pock marks or depressions surrounded by a ring of coating material that projects above the general plane of the coating. At Great Dane Powder Coating Inc., we are experts in professional electrophoretic coating. Solution. Increase paint robot productivity, throughput, first time yields and significanly reduce VOC and HAP emissions. P    Jochum Beetsma graduated in physical chemistry from the University of Groningen in The Netherlands. Paint Defect Appearance Causes Remedies; Setting. Ensure that substrate should be free from sand, dirt or any dust. That’s why it’s so important to work with experienced professionals whose skills include effectively troubleshooting th… Cissing and dimpling (sometimes known as “Crawling” or “Fisheyes”) are very small circular defects, where the paint has receded to expose the underlying substrate or coating. Most other paint defects are the results of: lack of cleanliness; surface preparation; application error; attention to detail; Surface tension. G    This video tutorial contains real lab experiences, courtesy of VLCI - Amsterdam, so that you know exactly how to solve crawling & cratering when you are back in your lab. Watch this tutorial and learn easy lab tests to identify with no doubt if you face cratering or crawling. Broken or misaligned eductors can cause appearance defects in production and dead zones in the paint tank. Such defects increase as surface tension differences grow. E-coating is an affordable, durable, and near-perfect parts coating process. A    With respect to CUI, how well do thermal insulating coatings retard the spread of corrosion? All the OEM has to do is provide a shade panel for reference.