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Analysis of Coating Blister Failures and Associated Coating and Substrate Risks

Blistering is a common failure in marine coatings that can be caused by both physical, such as osmotic pressure and temperature gradients, and electrochemical forces like cathodic or anodic polarization. This paper/presentation will start by discussing the various mechanisms that lead to coating blistering, how blisters form, and how to prevent them. 

Product Number: 51220-254-SG
Author: Michael Kibler, Patrick Cassidy, Jay Ong
Publication Date: 2020
Industry: Coatings
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Blistering is a common failure in marine coatings that can be caused by both physical, such as osmotic pressure and temperature gradients, and electrochemical forces like cathodic or anodic polarization. This paper/presentation will start by discussing the various mechanisms that lead to coating blistering, how blisters form, and how to prevent them. Next, the effects of blistering on coating performance and corrosion of the underlying substrate were investigated through creating blisters on coated test panels and inspecting them for coating failure and pitting corrosion after exposure. Additionally, several ship tanks were inspected for blistering before and after one to three-year service intervals. The inspection results showed a significant number of blisters broke in the time between inspections, typically forming cracks or pinholes through the coating. Performance of blisters from tank to tank varied, suggesting service type and time of wetness may play a role in the risk of blisters breaking. Blisters seen in varying services may form due to different mechanisms as well. Pitting corrosion measurements on the lab panels showed intact blisters do not provide adequate corrosion protection to the underlying steel in all cases, depending on the service and blistering mechanism. The data suggests an intact blistered coating is not equivalent to a boldly exposed, corroding substrate, but it is also not equivalent to a tightly adherent, intact coating.

Blistering is a common failure in marine coatings that can be caused by both physical, such as osmotic pressure and temperature gradients, and electrochemical forces like cathodic or anodic polarization. This paper/presentation will start by discussing the various mechanisms that lead to coating blistering, how blisters form, and how to prevent them. Next, the effects of blistering on coating performance and corrosion of the underlying substrate were investigated through creating blisters on coated test panels and inspecting them for coating failure and pitting corrosion after exposure. Additionally, several ship tanks were inspected for blistering before and after one to three-year service intervals. The inspection results showed a significant number of blisters broke in the time between inspections, typically forming cracks or pinholes through the coating. Performance of blisters from tank to tank varied, suggesting service type and time of wetness may play a role in the risk of blisters breaking. Blisters seen in varying services may form due to different mechanisms as well. Pitting corrosion measurements on the lab panels showed intact blisters do not provide adequate corrosion protection to the underlying steel in all cases, depending on the service and blistering mechanism. The data suggests an intact blistered coating is not equivalent to a boldly exposed, corroding substrate, but it is also not equivalent to a tightly adherent, intact coating.

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