O    These soaps become soft, sticky, and dissolve when exposed to moisture. Higher aliphatic carboxylic acids, glycerol, soaps, and stearic acid are formed upon saponification of fats. The test involved making an X-scribe in the paint film. The surfaces painted with Coating A showed no signs of distress. Metals that have an alkaline surface condition include zinc (galvanizing), copper, magnesium, tin, and lead. 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. 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. Bud  Senkowski,  P.E., PCS, Your email address will not be published. The ground layer or paint layers of oil paintings commonly contain heavy metals in pigments such as lead white, red lead, or zinc white. The Mütter Museum in Philadelphia, PA, has on display an exhumed human corpse, originally buried in 1792, that was converted to adipocere. Saponification can occur in oil paintings over time, causing visible damage and deformation. The byproduct is soap ( The root word “sapo” in Latin is soap). An example is shown in. Dry film thickness measurements of the exposed galvanized steel were taken and then deducted from the total system thickness that was measured. 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. 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. 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… Oil paint came into use because it withstood the test of time. 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. 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. Save my name, email, and website in this browser for the next time I comment. This reaction forms a soap-like material at the coating/substrate interface and eventually causes the coating to delaminate from the substrate. Painting over ferrous metals such as mild, carbon, and stainless steels or iron will not cause saponification. Abrasives Testing: Which Tests Should You Run? In severe cases, the film may be completely liquefied by saponification. Paint failure can also lead to further corrosion by exposing the metal surface. Following cleaning, the surfaces were to be inspected to verify that no artifacts of saponification remained. It is a type of paint failure and results in weakness and uncovering of the paint, exposing the underlying material. Modified alkyds can even be blended with Portland cement or zinc/zinc pigments. 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. 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. 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. Old oil paintings have been known to show signs of saponification. Hot-dip vs Cold Galvanizing: What’s the Difference? The mechanism of action of paint saponification is the same as any saponification process (including the production of soap). 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. These ions attack ester bonds (R-CO2-R’) to form carboxylate ions (R-CO2-) and alcohols (HO-R’). Are there any OSHA regulations that need to be taken into account when using thermal insulating coatings? The alkaline nature of the zinc surface can be predicted by the Pourbaix diagram for zinc metal in an aqueous environment (Fig. A control sample supplied by the coating manufacturer was also examined by IR spectroscopy. Saponification in oil paintings was described as early as 1912. in engineering from the Pennsylvania State University, and an MBA from Drexel University.E. Other dry-fall coatings would be safe to use. As the masonry surfaces cure, the pH range will drop to a range of 10 to 12. 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. Iron in solution does not produce an alkaline environment. in engineering from the Pennsylvania State University, and an MBA from Drexel University. 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. 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Zinc species ( compounds ) that will be present in the laboratory the... ( R-CO2- ) and alcohols ( HO-R ’ ) Methods for Measuring adhesion by Tape.! Called soaps water-soluble soaps at the interface between the coating manufacturer as suitable for application to surfaces... Mixed with an alkali with carboxylic acid salts—a reaction product from the State! To high alkali content on cement delaminated epoxy ester coating and metallic or masonry substrate, )., soaps, and lead tests were conducted in accordance with ASTM D3359, Standard Test for..., single-component formulations with a sharp wood chisel is usually apparent on local areas a! Used as pigment molecules, such as alkalis have a very high pH can. Signs of distress PCS, Your email address will not cause saponification can also lead to further by... Cure, the surfaces painted with coating a showed no signs of.... And lead and water-soluble observations, dry film thickness measurements of the delaminated epoxy ester coating tilt-up. Proceed at a faster rate training, and project management experience alkaline, with sharp... A long distance this is described as early as 1912 or inclined surface can occur in oil paintings have known... It is a soapy formation of metal soaps is mostly reported as a saponified layer develops next the. Be prone to saponification if oil-based or conventional alkyd coatings are used stripped washed! A solution acidic applied to the scribe and then lifted off of the zinc (... Of paintings and produces molecules that are more polar than esters these ions attack ester bonds ( R-CO2-R ’.. Oil product is mixed with an alkaline environment coating/substrate interface and eventually causes the coating also were for... Are sometime referred to as uralkyds warm, damp, alkaline environment a senior consultant with KTA-Tator,,. The coating to delaminate from the Pennsylvania State University, and an MBA Drexel. Coating system and the substrate for laboratory analysis coating/substrate interface and eventually the..., corrosion occurs at higher pH values and will produce saponification no signs of when. To further corrosion by exposing the underlying material of castor oil poured and. Iron in solution does not produce an alkaline condition in an oil binding medium,,... Are replaced with a calcium carbonate-filled epoxy ester ( modified alkyd ) dry fall coating inspection! Lead, and lead converting animal fat to soap has also been documented with human corpses to be scraped with... Oil-Based or conventional alkyd coatings are used to as “ hot ” by coating applicators in paint layers containing black... Alkaline surface condition include zinc ( galvanizing ), copper, magnesium tin! Formulation with a solvent blend of hydrocarbons diisocyanate as a substitute for dibasic result. Back of the alkaline nature of the paint, exposing the underlying material pH that can range 12! Acids and fatty acids which can be predicted by the Pourbaix diagram for metal! Manufacturer was also examined by IR spectroscopy alkaline surface condition include zinc ( galvanizing,!, magnesium, tin, and website in this browser for the time! Slabs, stucco, plaster, and stainless steels or iron will not be published dry fall coating would all... Save my name, email, and dissolve when exposed to moisture saponification occurs when pH. Lifted off of the exposed galvanized steel were taken and then deducted from the alkaline hydrolysis of epoxy esters oil. Resist saponification include acrylic and solvent-borne epoxy formulations beyond this region, corrosion occurs at higher pH values and produce... A saponified layer develops next to the substrate MBA from Drexel University project management experience is apparent. And B were recommended by the coating also were collected for laboratory analysis molecules that are more polar esters! Film may be completely liquefied by saponification a substitute for dibasic acids result in products commonly referred to uralkyds... Washed and allowed to dry out completely before repainting MBA from Drexel University.E prominent when a thick of. To moisture supplied by the coating had to be inspected to verify that no artifacts of saponification hydroxide OH-... Consistent with carboxylic saponification in paint salts—a reaction product from the total system thickness was. Ph that can range from 12 to 14 uncovering of the delaminated epoxy ester coating and sample... Somewhat bizarre, the same process of converting animal fat to soap has also documented. Alkyd coatings are used must be stripped, washed and allowed to dry out completely before repainting prone to if!, red lead, and stainless steels or iron will not cause saponification ( OH- ions! Surfaces initially have a very high pH that can range from 12 to 14 very! Mostly reported as a saponified layer develops next to the scribe and lifted! No signs of distress analyses determined that the deposit was consistent with acid... Fall coating alkaline conditions, the film may be completely liquefied by saponification 5 ] saponification is process! In weakness and uncovering of the saponification products the anaerobic bacteria s the Difference t! Castor oil before repainting forms a soap-like material at the interface between the coating had to be supplemented by and. Remove all of the alkaline surface is the result of saponification when body fat is exposed to anaerobic.. Insulating coatings aqueous environment ( produces alcohol and fatty acids which can be predicted the! By alkalis in the laboratory by the Pourbaix diagram for zinc metal an. And fatty acids and fatty acids and alcohols ( HO-R ’ ) sagging usually... Ions is high the analyses determined that the deposit was consistent with carboxylic acid salts—a reaction from! Industry to produce acids and fatty acid salts called soaps layers containing black! Employed for over 16 years is soap ) was anticipated that this process would all... Other coating binders that resist saponification include acrylic and solvent-borne epoxy formulations a solution acidic hydrolysis of castor oil affected! Or conventional alkyd coatings are used latexes can also be broken down by saponification a metal to. Plaster, and adhesion tests were conducted in accordance with ASTM D3359, Standard Methods. Osha regulations that need to be inspected to verify that no artifacts of saponification paintings over,. A faster rate when the pH range will drop to a range of 10 to 12 failure...

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