Corrosion cause and effect: Osmotic blistering of thermoset organic coating films on metal substrates
There are many descriptions and so-called categories of corrosion formation on metal substrates. Some of these categories include: dissimilar metal corrosion, galvanic corrosion, intergranular corrosion, filiform corrosion, attack corrosion, atmospheric corrosion, stress corrosion, pinpoint corrosion, general corrosion, localized corrosion, pattern corrosion, caustic agent corrosion, and osmotic blistering. Each of these corrosion categories could be a primary topic of discussion, so to include all of them would not be practical in a single article. Instead, this article will focus on the conditions and common causes of osmotic blistering.
In order to understand how protective coatings work in terms of corrosion protection, one must begin by knowing what conditions must be present to cause corrosion cell development. For corrosion cells to develop on metal surfaces, four conditions must exist. There must be an anode, a cathode, a conductor, and an electrolyte (typically water). Electron flow is best illustrated by examining how a battery works, as shown in Figure 1.