The corrosiveness of ammonia to iron
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Excuse me: Is ammonia corrosive to iron? Can I use carbon steel pipe for coiled pipe?
If it is pure ammonia, carbon steel can be used. Ammonia is very corrosive to carbon steel. But if the ammonia water contains carbon dioxide, that is, carbonized ammonia water, stainless steel must be used. Ammonia water containing hydrogen sulfide will also aggravate the corrosion of carbon steel.
The corrosion of ammonia is less than that of pure ammonia, it seems like this! In the past, water was added to pure ammonia: lol
If it is ordinary industrial ammonia, there is no problem with carbon steel pipes. If there are special requirements for the quality of ammonia, stainless steel should be considered. For example, our factory has a kind of ammonia that has requirements for iron content, so we use 1Gr18Ni9 material.
Can you explain what the specific special requirements are?
There is no problem in using carbon steel for ammonia water. Many projects in my unit use carbon steel pipes, and the effect is very good.
You can add some corrosion inhibitor, potassium dichromate
Ammonia is corrosive to carbon steel, so sufficient attention must be paid.
Ammonia corrodes metal for two reasons: One is that ammonia can form complex ions with metal ions, and the other is that the atmosphere contains a large amount of oxygen. To explain in detail, since ammonia can form relatively stable complex ions with many metal ions, it will reduce the standard electrode potential between the metal ions and the metal elements. In the words of high school chemistry, it makes the metal more susceptible to oxidation. In addition, the earth's atmosphere is an oxidizing atmosphere, so metals become more susceptible to oxidation, which is a phenomenon of corrosion. To be more precise, what really corrodes metals is oxygen in the atmosphere, and the role of ammonia is to make corrosion easier.
In the past, refrigeration equipment was basically made of carbon steel.
There is no problem with carbon steel for pure ammonia and ammonia water, and the corrosion rate is very low.