ASTM D 1653 is a standard test method used to determine the permeability of organic coatings to water vapor and gases. The test involves immersing coated test panels in water or other liquids, and measuring the rate of water vapor or gas transmission through the coating.
The permeability of coatings is an important property to measure, as it can impact the overall performance and durability of the coating. Coatings that are permeable to water or other substances can allow them to penetrate the coating and reach the underlying substrate, potentially causing corrosion, discoloration, or other forms of damage.
Testing the permeability of coatings in immersion is particularly important because it simulates the conditions that the coating may be exposed to in real-world applications, such as when submerged in water or other liquids. More permeable coatings that are immersed in water or other liquids can be susceptible to a phenomenon known as osmotic blistering.
Osmotic blistering is a type of coating failure that occurs when water or other substances are able to penetrate through the coating and create a pressure differential between the coating and the underlying substrate. This pressure differential can cause water to be drawn into the coating, resulting in the formation of blisters or bubbles. Over time, these blisters can expand and rupture, leading to delamination of the coating and exposure of the substrate to further damage.
Osmotic blistering is more likely to occur in coatings that have high levels of permeability to water or other substances, as this makes it easier for water to penetrate through the coating and create the pressure differential needed to initiate blistering.
Permeability testing can help manufacturers and users of coatings to better understand the performance of the coating in these conditions, and to make informed decisions about the suitability of the coating for a particular application. Engineers who specify coatings for potable water tanks, for example, would benefit to pay special attention to the permeability of the coatings they specify. For more information, contact a High Performance Coating Consultant here.
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