Definition - What does Non-osmotic Blistering mean?
Non-osmotic blistering is a type of epoxy coating defect. Non-osmotic blistering occurs when bubbles or pores form within or on one of the surfaces of a coating. For the blistering to be considered non-osmotic, it must occur without water exposure being a major factor.
Non-osmotic blistering can be very detrimental to achieving and maintaining a successful coating.
Corrosionpedia explains Non-osmotic Blistering
Non-osmotic blistering is essentially any type of coating blistering that is not caused by water or humidity. When water or humidity is to blame for the blistering, it is considered osmotic blistering.
Non-osmotic blistering can occur for a variety of reasons. One such reason is applying an additional coating too soon. If the prior coating layer has not had time to cure, then the coating placed on top of it may trap vapors in between the layers, which causes non-osmotic blisters. Another reason is excessive exposure to sunlight directly after the coating has been applied, which causes uneven solidification of the coating, resulting in trapped vapors that cause blistering to occur.
One of the major negative effects of non-osmotic blistering is the fact that the blisters can be broken. When the blisters break, the coating can fall apart and the adhesion of the coating to the surface of the material that has been coated can be lost. When this happens, the base material is exposed to the environment. Another failure mode that could occur as a result of non-osmotic blistering is within the pore of the blister itself. If the pore is between the base material and the coating, then there will be a portion of the base material surface that is not coated; this can increase the risk of localized corrosion.