The ASTM D6991 standard, developed by the American Testing and Materials Association (ASTM), provides a test method for measuring internal stresses in organic coatings using the cantilever (beam) method.
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This test method is mainly considered suitable for coatings such as:
Stress values are limited to one or both of these two values:
The full name of the standard in question is as follows: ASTM D6991-17e1 Standard test method for the measurement of internal stresses in organic coatings by the cantilever (beam) method.
Organic coatings are corrosion barriers between the underlying metal and the corrosive medium. With this method, the durability of the structures is preserved and resistance is gained against weather conditions, humidity, abrasion, chemicals, toughness and aesthetic appearance.
Organic coating efficiency depends on the mechanical properties of the coating system, the type and concentration of suspended inhibitors, the pretreatment of the metal surface, the adhesion of the coating to the underlying metal substrate, and other additives. The coating formulation usually contains solvent, resin (binder), pigment, filler and additives.
Stresses in coatings arise as a result of their shrinkage or expansion if the expected movements are prevented by the adhesion of the coating to the substrate.
Tensions in coatings occur for various reasons. For example,
Knowing the internal stresses in coatings is very important as it will affect coating performance and service life. If the internal tension exceeds the tensile strength of the film, cracks appear. Conversely, if the stress exceeds the adhesion between the coating and the substrate, this time the adhesion is reduced, causing the coatings to separate from each other. Quantitative information on stresses in coatings is useful in coating formulation and recommendations for their application and use.
This method is found useful for air-drying industrial organic coatings. However, it has not yet been evaluated whether it is suitable for powder and thermally curing coatings for thin coatings, eg if the thickness is greater than 0.0254 mm.
Among the numerous test, measurement, analysis and evaluation studies it provides for businesses in various sectors, our organization also provides standard testing services for the cantilever (beam) measurement of internal stresses in organic coatings within the scope of ASTM D6991-17e1 standard, with its trained and expert staff and advanced technological equipment. gives.
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