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Corrosion in daily life - Blistering

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All of us corrosion people head out of the house to work on coatings. And yet, we leave so many types of coatings behind in our house.

The most commonly seen commodity is an electric box with switches. Usually they are coated. 
This is an example of such an electric box. It shows blisters formed in the white coating. Such blistering occurs when water penetrates the pores in the coating. 

Usually such parts do not come under the 'critical' category. Hence, the coatings are not very thick. Moreover, there is no coating inspector involved during the application.

As a result, they are prone to early degradation. However, their position plays an important role in determining this time frame.

Those boxes present outside the hose are exposed to the heat and cold. Usually they will be in a shaded area. So, they may not face the rain directly.

Some boxes are inside the house in rooms. Those face the least coating damage.

The image above is from an electric box in a bathroom. Bathrooms may be technically an enclosed area. However, the atmosphere inside changes cyclically in a subtle way.

A hot shower even for 5 minutes will generate enough steam that stays in the bathroom for longer. This steam can directly go to the coating and affect the temperature in localized areas. This small rise can lead to minor polymeric changes such as opening up of the pores. Further, as the steam cools, it gets deposited on the coating and has enough time to diffuse through the enlarged pores.

However, because this is not occurring continuously, the coating does not break completely. The water accumulates underneath and expands the coating. This leads to the blisters.

Hope you enjoyed this post. Comment on this post if you have seen such occurred in your house!
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