Help Help Corrosion Problem
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The medium is steamed ammonia and concentrated ammonia water. A good iron plate is 20mm thick and the whole sheet. Why does the bulging appear after using it for a month?
From a visual inspection, it seems that the cleaning before painting was not done well. It looks like there is no anti-rust primer on the corroded areas. Let’s clean and paint again.
The main reason is that it is bulging. It was a flat plate when it was first used. Is it corroded?
You can first measure the thickness to see how thin the steel plate is. Liquid ammonia is relatively less corrosive to steel, but ammonia will accelerate corrosion in an environment with air or carbon dioxide. In addition, what is the temperature and pressure inside the steel plate? If there is vaporization, the pressure may increase.
The concentrated ammonia vapor should be inside... and your photo was taken from the outside... so I prefer the impression of external corrosion when looking at the photo. 1. The rust removal paint on the surface is not good enough. 2. What is the surface temperature? You should use high-temperature paint. 3. After checking the relevant information, it is recommended to use Alloy 825 with a corrosion rate of 0.2 MILS/YR. The above opinions are for your information.
The storage tank has been replaced. I cut the steel plate and saw that the bulging area has become two layers. This means that the steel plate has been corroded by penetration and looks like two steel plates stacked on top of each other. Is it a material problem?