Under alkaline conditions, the concentration of hydroxide (OH-) ions is high. Saponification on wall paints is the result of the alkali reacting to oil, or in this case, the alkaline surface reacting to oil-based coatings forming a soap-like substance that is both soft and gooey– but not essentially fun to touch and The ground layer or paint layers of oil paintings commonly contain heavy metals in pigments such as , . If saponification occurs, then the adhesive strength of the coating can suffer; over time the coating chips off, exposing the inner surface to the corrosive environment. Definition - What does Saponification mean? For example, modifications that employ diisocyanate as a substitute for dibasic acids result in products commonly referred to as uralkyds. They differ from fats since they don’t have triglyceride ester of three fatty acids which can be attributed to the anaerobic bacteria. In this defect, soap patches are formed on the paint surface and paint … The saponification reaction forms water-soluble soaps at the interface between the coating and metallic or masonry substrate. U    Problem Occurs when solvent-borne paints are affected by alkalis in the presence of moisture. These formulations incorporate a modified alkyd. Running Defect of Paint 8. Some alkyd formulations will not undergo saponification. The dry fall coatings were spray applied at a DFT range of 3–8 mils and reached a full cure in seven days at 77 F. Following the spray application, there were no apparent problems. Corrosion products of certain metal surfaces such as zinc (galvanized) surfaces increase the amount of reactive hydroxide ions that can react in saponification. As the masonry surfaces cure, the pH range will drop to a range of 10 to 12. Since humidity is essential for the saponification reaction to occur, it is not unexpected that the most prevalent failures were in areas adjacent to the roll-up doors. Painting over ferrous metals such as mild, carbon, and stainless steels or iron will not cause saponification. abrasive blast cleaning A method of preparing surfaces before painting by the use of abrasive, such as grit propelled Higher aliphatic carboxylic acids, glycerol, soaps, and stearic acid are formed upon saponification of fats. The field investigation consisted of visual observations, dry film thickness measurements, and adhesion tests. Q    We recognize soaps as wax-like products, modified through the addition of fragrances and skin-care additives (emollients) to become consumer cleaning and bathing products. Saponification occurring in paint layers of artworks represents a serious degradation process affecting the appearance and stability of paintings. sodium palmitate . If the wet film thickness is much too high, excessive sagging can result in pools of paints forming on horizontal surfaces or in corners which could re… Saponification is widely used in industry to produce acids and alcohols. If the paint is likely to be in contact with alkaline solutions, as in some industrial environments, non However, within several months of application, delamination was observed on the interior galvanized deck ceilings that were coated with the epoxy ester dry fall coating (Coating B) and within the immediate vicinity of a series of roll-up doors (, There were significant areas of coating delamination found on the interior galvanized steel decking that had been coated with the epoxy ester dry fall coating (Coating B) and were in the immediate vicinity of roll-up doors (. Higher aliphatic carboxylic acids, glycerol, soaps, and stearic acid are formed upon saponification of fats. A Pourbaix diagram is used to predict the tendency of a metal surface to develop alkaline condition in an aqueous environment. P    NaOH). At its very basic level, saponification is the term given to the process in which vegetable oils and animal fats are converted into soap. - 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. T    sodium palmitate . While somewhat bizarre, the event again demonstrates how saponification will convert any oil or fat into soap. Adipocere, also known as corpse wax or the fat of graveyards, is a product of decomposition that turns body fat into a soap-like substance. An adhesive tape was applied to the scribe and then lifted off of the surface. X    Once the surfaces were prepared, a primer specific for galvanizing was to be applied and then overcoated with one or two coats of a 100% acrylic dry fall coating. Some polyvinyl acetate (PVA) water-borne latexes can also be broken down by saponification. Runs, sags and curtains are the downwards movement of paint that can appear shortly after the application and before the setting of the paint. The essential step in the soap-making process is the incorporation of an alkaline substance, like lye (sodium hydroxide, NaOH). Saponification can occur in oil paintings over time, causing visible damage and deformation. The dry fall coatings were spray applied at a DFT range of 3–8 mils and reached a full cure in seven days at 77 F. Following the spray application, there were no apparent problems. It is important to note that this exists within the stable range for water (the area within the dotted lines) while exhibiting a pH level of 8.5 to 10.5. Recall from Figure 1that it is the hydroxide ions (OH-) that react with the oil, alkyd, or fat to form glycerides and soaps. Oil-based paints that utilize alkyd esters, epoxy esters, or linseed oil derivatives in their composition can saponify when exposed to an alkaline environment and moisture. Paint failures on stucco walls, cause, diagnosis, cure & prevention methods: This article describes common building exterior & interior painting mistakes when painting on modern stucco building exteriors, describes how to diagnose paint failures on buildings, and outlines a procedure for diagnostic field inspection & lab testing of failed painted surfaces. Metals that have an alkaline surface condition include zinc (galvanizing), copper, magnesium, tin, and lead. The reactions sometimes damage oil paintings when heavy metals used in pigments react with free fatty acids (the "oil" in oil paint), forming soap. 2). Suitable for GCSE Chemistry revision. Hot-dip vs Cold Galvanizing: What’s the Difference? Oil paints are composed of pigment molecules suspended in an oil binding medium . When the areas of delaminated coating were tested for adhesion properties, the results indicated generally poor coating adhesion with ratings in the range of 2A to 3A. This article explores the many facets of saponification, including the chemical and environmental conditions that must be present for saponification to occur, and how it contributes to paint adhesion failures. F    Zinc, being amphoteric, is soluble in acid and base (alkaline) solutions, but the species present will be a function of equilibrium between the zinc species. These ions attack ester bonds (R-CO2-R’) to form carboxylate ions (R-CO2-) and alcohols (HO-R’). Oil paint came into use because it withstood the test of time. Bud holds a B.S. in engineering from the Pennsylvania State University, and an MBA from Drexel University. He has an extensive background in the engineering, application, and inspection of coatings and linings used in nuclear and fossil-based service water and chemical storage facilities, and is the primary instructor for KTA’s Nuclear Inspection training course. Solution Prevent by using Leyland Trade Alkali Resisting Wall Primer.Where saponification has already occurred, strip, wash, allow to QC Paint Inspection Services for Contractors, QA Paint Inspection Services for Facility Owners, Non Destructive Testing and Examination (NDE & NDT), Steel Inspection QC Services For Fabricators/Contractors, Quality Assurance/Quality Verification (QA/QV) For Owners, Coating Assessment and Painting Priority (CAPP®) System, Developing Opinions of Probable Cost for Maintenance Painting, Water Tank Engineering and Inspection Services, Coating Performance (Accelerated Weathering and Corrosion Testing) Services, American Water Works Association Lab Testing, Test Panel Preparation and Coating Services, Coating Failure Analysis, Specifications, and Expert Witness, Commercial Inspection and Design Services, Walkway Audits and Floor Maintenance Consulting, QP1 – Field Application to Complex Industrial Structures, QP2 – Field Removal of Hazardous Coatings from Complex Structures, QP3 – Shop Application of Complex Protective Coating Systems, SSPC-QS 1, Standard Procedure for Evaluating a Contractor’s Advanced Quality Ma, Blended Online Basic Coating Inspection Course, Commercial Coatings Installation and Inspection, 5 Signs that Your Building May Have Moisture Intrusion Issues, A Comprehensive Overview of Wood Coatings. However, within several months of application, delamination was observed on the interior galvanized deck ceilings that were coated with the epoxy ester dry fall coating (Coating B) and within the immediate vicinity of a series of roll-up doors (Fig. Old oil paintings have been known to show signs of saponification. Paint saponification renders the paint mixture soft and water-soluble. It was anticipated that this process would remove all of the saponification products. The ground layer or paint layers of oil paintings commonly contain heavy metals in pigments such as lead white, red lead, or zinc white. Epoxy esters are oil-based coatings with epoxy resins. In severe cases, the film may be completely liquefied by saponification. He is a registered professional engineer in several states; a certified nuclear coatings engineer; and a NACE-certified Coatings Inspector Level 3 (peer review). [5] All figures courtesy of the author. The source of the alkaline surface is the galvanizing itself. Adhesion was rated on a scale of 0A to 5A according to the amount of coating removed by the tape, with 5A being best (no coating removed). A unique characteristic of the failed coating areas, and the actual cause of the coating failure, was the presence of a deposit on the epoxy ester coating in the failed areas. At these locations, the coating had to be scraped off with a sharp wood chisel. Sagging This type of defect is more prominent when a thick layer of paint is applied on a vertical or inclined surface. V    Heavy metal salts are often used as pigment molecules, such as in lead white , red lead , and zinc white . Essentially, the field investigation revealed the following. Saponification could be an issue only with dry-fall coatings that contain an epoxy ester-modified alkyd. Bud has over 35 years of coating engineering, inspection, training, and project management experience. It is a type of paint failure and results in weakness and uncovering of the paint, exposing the underlying material. No coating delamination was observed on surfaces that were painted with Coating A. Adhesion tests conducted on galvanized deck surfaces that were painted with Coating A revealed excellent coating adhesion, with an ASTM D3359 rating of 5A. I    Comment from Eduardo Garrido , (10/2/2014, 4:45 PM) Saponified paint may become sticky and discolored. He has an extensive background in the engineering, application, and inspection of coatings and linings used in nuclear and fossil-based service water and chemical storage facilities, and is the primary instructor for KTA’s Nuclear Inspection training course. The test involved making an X-scribe in the paint film. In addition, medium-rich paint containing dark brown and black pigments dries at a slower It is believed to be widespread, having been observed in many works dating from the fifteenth through the twentieth centuries; works of different geographic origin; and works painted on various supports, such as canvas, paper, wood, and copper. Oddly, the same process of converting animal fat to soap has also been documented with human corpses. Saponification Formation of soap patches on the painted 10. Required fields are marked *. When sagging occurs over a long distance this is described as a curtain. Formation of … Y    A control sample supplied by the coating manufacturer was also examined by IR spectroscopy. The byproduct is soap ( The root word “sapo” in Latin is soap). However, the surfaces will still be prone to saponification if oil-based or conventional alkyd coatings are used. The analyses determined that the failed coating and control sample of the coating were consistent in formulation with a calcium carbonate-filled epoxy ester coating. H    In severe cases, the film may be completely liquefied by saponification. Both coating systems were essentially 50% solid, single-component formulations with a solvent blend of hydrocarbons. Saponification in art conservation Saponification can occur in oil paintings over time, causing visible damage and deformation. The solvent phase was designed to evaporate so rapidly that any overspray would become a dry powder as it fell through a vertical distance of eight feet. Soaps are salts of fatty acids and fatty acids are monocarboxylic acids that have long carbon chains (at least 10) e.g. O    Beyond this region, corrosion occurs at higher pH values and will produce saponification. J    Yet, over time the saponification reaction has led to damage of many (but not all) oil paintings made in the fifteenth through twentieth centuries. Soaps are salts of fatty acids and fatty acids are mono that have long carbon chains (at least 10) e.g. Further inside the buildings, where HVAC limited humidity, it was demonstrated that the epoxy ester coating could be used successfully over the galvanized surfaces. Bud has over 35 years of coating engineering, inspection, training, and project management experience. M    Z, Copyright © 2021 Corrosionpedia Inc. - Because paints are used to protect metal materials from environmental dangers such as corrosion, the risk of failure due to paint saponification should be considered. Surfaces containing the failed epoxy ester coating were to be washed with pressurized water with enough pressure (5,000–10,000 psi) to remove all of the deteriorated coatings. B    Paints are particularly prone to saponification when covering certain metal surfaces such as zinc, magnesium, copper, lead and tin, which can generate alkaline conditions from corrosion. When saponification has occurred, the surface must be stripped, washed and allowed to dry out completely before repainting. (Wicks ZN, Jones FN Other dry-fall coatings would be safe to use. This chemical transformation breaks down large molecules into smaller components and produces molecules that are more polar than esters. The reaction produces alcohol and fatty acid salts called soaps. Excess OH- ions are what makes an aqueous solution basic just as excess H+ ions make a solution acidic. Where can I find a coating that is chloride and sulfur corrosion-resistant? Paint saponification can thus be associated with corrosion. With respect to CUI, how well do thermal insulating coatings retard the spread of corrosion? Saponification is a process that involves the conversion of fat, oil, or lipid, into soap and alcohol by the action of heat in the presence of aqueous alkali (e.g. 1(ix) Paint terminology and definitions abrasion resistance Resistance to frictional rubbing. Saponification occurring in paint layers of artworks represents a serious degradation process affecting the appearance and stability of paintings. Iron in solution does not produce an alkaline environment. A similar Pourbaix diagram can be drawn for copper, lead, magnesium, and tin metal surfaces in an aqueous (water) environment. A real life example of a saponification failure is discussed in-depth to aid in understanding the process. The work location was in Fort Walton Beach, FL. Corrosionpedia Terms:    5). Following cleaning, the surfaces were to be inspected to verify that no artifacts of saponification remained. A Pourbaix diagram is used to predict the tendency of a metal surface to develop alkaline condition in an aqueous environment. Your email address will not be published. N    Saponification may result in both desirable and undesirable effects. S    E    Analysis of the waxy material at the interface of the delaminated coating was found to be consistent with the carboxylic acid salts produced by alkaline hydrolysis of an ester. G    The saponification process is one of the oldest chemical reactions known to humans and has been widely used in the production of soap for centuries. Saponification is a hydrolysis reaction that oc-curs readily in oil-based coatings when the ester links that bond the fatty acids to the synthetic resins are broken down. Saponification is a process that involves conversion of fat, oil or lipid into soap and alcohol by the action of heat in the presence of aqueous alkali (e.g. Saponification is a soapy formation of paint due to an attack by alkaline paint. Generally paint saponification occurs when the pH is higher than 10. The alkaline nature of the zinc surface can be predicted by the Pourbaix diagram for zinc metal in an aqueous environment (. Abrasives Testing: Which Tests Should You Run? NaOH). This reaction forms a soap-like material at the coating/substrate interface and eventually causes the coating to delaminate from the substrate. Dry film thickness measurements of the exposed galvanized steel were taken and then deducted from the total system thickness that was measured. As there is no reversal to the paint saponification process, the entire painted surface needs to be prepared, cleaned and dried, after which a new paint with alkali-resistant properties can be applied. Paint reconstructions demonstrate that saponification of white pigments causes a significant decrease in light reflection. The lye provides a source of hydroxyl ions (OH-) that digest and break down the structure of the oil or fat and produce various triglycerides. K    Loss of adhesion may occur as a saponified layer develops next to the substrate. 11. These soaps become soft, sticky, and dissolve when exposed to moisture. 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). Paint saponification is the process of a hydrolytic breakdown of ester bonds within a paint due to alkaline conditions and moisture. Paint saponification is the process of a hydrolytic breakdown of ester bonds within a paint due to alkaline conditions and moisture. Other coating binders that resist saponification include acrylic and solvent-borne epoxy formulations. D    Saponification of paints occurred when the painted surface is exposed to chemicals such as alkalis. Figure 2 is a Pourbaix diagram that shows the zinc species (compounds) that will be present in the solution. Infrared spectroscopy revealed that the deposit was consistent with carboxylic acid salts—a reaction product from the alkaline hydrolysis of epoxy esters (saponification). Samples of the coating also were collected for laboratory analysis. Both Coatings A and B were recommended by the coating manufacturer as suitable for application to galvanized metal substrates. Bud holds a B.S. The mechanism of action of paint saponification is the same as any saponification process (including the production of soap). Saponification is a chemical reaction that occurs when oil product is mixed with an alkali. It is a type of paint failure and results in weakness and uncovering of the paint, exposing the underlying material. Some polyvinyl acetate (PVA) water-borne latexes can also be broken down by saponification. The Mütter Museum in Philadelphia, PA, has on display an exhumed human corpse, originally buried in 1792, that was converted to adipocere. The moisture can be present in the original wet coating; as atmospheric humidity that passes through the cured coating film and reaches the alkaline substrate; or, in the case of cementitious materials, as free moisture from the mix, ground water, or leaks (water intrusion). The passive zone (pH 8.5–10.5) is where a surface layer of zinc hydroxide (ZnOH2) forms and zinc metal corrosion does not occur. The alkaline nature of the zinc surface can be predicted by the Pourbaix diagram for zinc metal in an aqueous environment (Fig. Other dry-fall coatings would be safe to use. Epoxy esters, oil and alkyd resins can saponify when applied to galvanized surfaces that experience humid conditions. Iron in solution does not produce an alkaline environment. Saponification can be destructive to paint films. Metals that have an alkaline surface condition include zinc (galvanizing), copper, magnesium, tin, and lead. Coating B was an epoxy ester (modified alkyd) dry fall coating. The observation that the paint become sticky during this process is due to these polar molecules as well, which tend to interact well with other polar surfaces. These surfaces are sometime referred to as “hot” by coating applicators. in engineering from the Pennsylvania State University, and an MBA from Drexel University.E. Saponified paint may become sticky and discolored. The optical effects of saponification are perceptible, and depend on the colour and hiding power of both the He is a registered professional engineer in several states; a certified nuclear coatings engineer; and a NACE-certified Coatings Inspector Level 3 (peer review). Oil-based paints that utilize alkyd esters, epoxy esters, or linseed oil derivatives in their composition can saponify when exposed to an alkaline environment and moisture. Saponification can be destructive to paint films. Bud  Senkowski,  P.E., PCS, Your email address will not be published. Definition - What does Paint Saponification mean? Modified alkyds can even be blended with Portland cement or zinc/zinc pigments. Dry film thickness measurements were obtained in general accordance with ASTM D7091, Standard Practice for Nondestructive Measurement of Dry Film Thickness of Nonmagnetic Coatings Applied to Ferrous Metals and Nonmagnetic, Nonconductive Coatings Applied to NonFerrous Metals. Masonry surfaces with an alkaline condition include new concrete, tilt-up slabs, stucco, plaster, and mortar. Making soap in the laboratory by the alkaline hydrolysis of castor oil. These masonry surfaces are characteristically alkaline, with a pH range of 8 to 14. Painting over ferrous metals such as mild, carbon, and stainless steels or iron will not cause saponification. There was no evidence of the waxy film that was found underneath Coating B (, Infrared (IR) spectroscopy was used to analyze the failed coating and the waxy substance found on the back of the failed Coating B removed from the galvanized surfaces on the interior decking (, The source of the alkaline surface is the galvanizing itself. Paint failure can also lead to further corrosion by exposing the metal surface. Save my name, email, and website in this browser for the next time I comment. The polar components are prone to interaction with water molecules, making the paint mixture more soluble in water and weakening the paint's ability to adhere to a surface. It occurs on fresh (un-matured) cement surface or plaster due to high alkali content on cement. Notify me of follow-up comments via e-mail address Name: * Email Address: * Website: Save my name, email, and website in this browser for the next time I … Causes and Prevention of Paint Failure Ponderosa Protective Coatings are an essential part of any coating, they are incorporated in the manufacture for proper appliedapplication, proper leveling on the surface Paintand proper drying. E. Bud Senkowski is a senior consultant with KTA-Tator, Inc., where he has been employed for over 16 years. Coating A was an alkyd coating modified with approximately 15% Portland cement. The surfaces painted with Coating A showed no signs of distress. 1: The saponification process. A    W    Formation of metal soaps is mostly reported as a consequence of the interaction of lead white or zinc white with oil binder. rich paint layers containing carbon black pro-vided a quantity of free fatty acids that allowed the saponification to proceed at a faster rate. Ester groups are replaced with a urethane linkage and superior alkali resistance compared to conventional alkyds. Separation occurred between the coating system and the substrate. The underlying substrate in these areas was shiny. Corpse wax is the result of saponification when body fat is exposed to anaerobic bacteria in a warm, damp, alkaline environment. The interior surfaces of galvanized steel roof decking applied in a large warehouse were painted by the direct application of two different dry fall alkyd coating systems. , Jones FN Running Defect of paint due to alkaline conditions, the surfaces were to inspected! Saponification reaction forms a soap-like material at the interface between the coating were consistent in saponification in paint with a wood. Industry to produce acids and fatty acids and alcohols an adhesive Tape applied... ) cement surface or plaster due to high alkali content on cement soft and water-soluble of converting animal to... 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