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!

However, looking around, we can see corrosion everywhere!

The part shown here is the bottom part of the frame.

The coatings for such steel parts usually serve the purpose of moderate corrosion protection and more of aesthetics. If you observe, the thickness of the coatings also does not seem to be a lot.

This degrades the coating. At the places where it is not perfect anyway, the underlying steel is free to corrode.

Most importantly, corrosion is more severe at the edges. It is severe enough to chip off the material entirely. That point is a prime site for crack formation and breaking of the frame.

I recently moved to a new house. As expected, there was a lot of cleaning up to do. One of the tasks was the cleaning of the washbasin. Usually, the drain is a circular part with  5 to 6 holes for the water to flow out. What I saw was this –

I have not had a chance to analyse the material of the drain. However, a quick search tells me that this is most probably stainless steel. The water that this drain is exposed to is the bore water. Thus, the drain has encountered a lot of chlorides. There is general as well as localized corrosion.

The damage started off as a simple process of pitting. Pitting due to chlorides is one of the most common headaches for poor stainless steel. They break the passive oxide film, and reach the underlying fresh iron. This iron then reacts with the usual suspects (ions, oxygen, water) and forms what we see as the rust.

As can be seen in the picture, the thin sections of the drain between the holes have disappeared in three places. This may have happened because the pits formed continued to grow through the thickness of the material, which finally gave way and fell down the drain. The shape of the circle to the top left is distorted and we can observe a small nick in the circle. There is also a variation in the widths of each of the sections between the circles – all because of corrosion.

Then, there is the green color. This is the corrosion product ferric chloride. A quick look shows the green formation around the part between two holes at the top right. General corrosion is visible, and there may be pitting going on underneath the corrosion products.

We will have to wait and see if that small section is the next to break off.

UPDATE: It did break off.