Powder Pack Capacitor Blistering

What is a blister in coating?

Blistering is described as the formation of bubbles that range in various sizes and elevations within the coating. These bubbles can be broken or unbroken. Blisters are a unique surface defect because they form between the coating and substrate and will guarantee no adhesion due to enclosures at the part surface.

Does blistering affect coating performance?

Blistering is a common coating failure, and for many years, the causes and mechanisms of blistering have been studied to characterize and determine the effects on coating performance and underlying substrates. These studies have led to a better, but still incomplete, understanding of blistering and its effects on a substrate, such as corrosion.

What causes anodic blistering?

Anodic blistering usually begins below a pore or microdefect in the coating or next to a macrodefect like a scribe or crack in the coating. 3,4 In the case of blistering at small defects or pores, corrosion will begin where oxygen and ionic species, often salts like NaCl, are able to pass through the coating to the substrate and initiate corrosion.

What are the pH values of anodic blisters?

Values of pH in anodic blisters are slightly acidic or neutral. In the case of solvent entrapment, the substrate is not affected by blistering. However, a blistered coating is a weakened coating and more susceptible of sustaining ionic permeability and other electrochemical factors leading to more aggressive corrosion conditions.

Is blistering a coating failure?

Unacceptable blistering is considered coating failure—just the same as damaged and openly corroding areas. A major risk of blistering is whether the blisters will break during continued service, resulting in open corrosion and potential damage to the substrate.

What causes non-osmotic blisters during coating application?

These non-osmotic blisters, which we call bubbles, are often associated with characteristics of the substrate or environmental conditions during coating application. In many locations, the coating application season is limited to a time when environmental conditions are favorable (i.e., typically in late spring, summer and early fall).