The corrosion issue of ammonium hydroxide solution
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Is the corrosion rate of carbon steel by a urea-ammonium mixed solution at 130 degrees and 1.7 MPa extremely high? I hope the seniors can provide some guidance.
Not bad, you’re referring to the medium-voltage system
Under the operating conditions mentioned by the poster, a 10mm thick carbon steel sheet is likely to corrode and perforate within a few hours – the rate of corrosion is extremely fast!
It’s also impossible to use this material for medium-pressure applications; it’s not feasible. Usually, 316L or 316 is used instead.
We have a small urea production unit that uses a full-circulation aqueous solution system; the medium-pressure absorption process employs 316L material, with operating conditions of 1.85 and 100 degrees Celsius. According to sampling analyses, corrosion is minimal. For medium-pressure decomposition, passivation is required first to form a passivation film on the surface of the equipment; by introducing passivation air during operation, corrosion can be reduced.
I’ve never heard of using carbon steel for this purpose. Steel made of 316L material, along with passivation using 5% hydrogen peroxide, gives very good results. This post was last edited by johnnyxht on 2009-2-26 at 09:07.]
At 130 degrees and 1.7 MPa, the urea-ammonium mixed solution is in the medium-pressure absorption stage; carbon steel in contact with this substance suffers from rapid corrosion, and it’s impossible to prevent it – the container will perforate within a single day； 18-8 stainless steel can’t stop it either; it will develop perforations in just one or two months ； Urea-grade stainless steels such as 316, 316Ti, 316L, 317L, 2522, etc., have good corrosion resistance; however, in the case of erosion corrosion, it can reduce equipment made from these materials to the thickness of paper within just a few months.
1. In urea plants, anything that comes into contact with urea or ammonium methoxide cannot be made of carbon steel, regardless of the system. 2. For the very thick lining layers or pressure-bearing layers of the urea synthesis tower, once the lining is corroded through, it becomes extremely susceptible to further corrosion. 3. The urea-grade stainless steels mainly include 304-L, 316, 316Ti, 316L, 317L, 316LMOD, 25.22.2 (2RE69), SAFUREX, etc
Recently, we need to purchase special materials for use with ammonium hydroxide solution (1.6 MPa, 150 degrees Celsius) and urine (8 MPa, 350 degrees Celsius). However, the suppliers informed us that 316L and 304L materials do not perform well when used with these media, and they can suffer severe corrosion within a very short period of time – 1 to 2 years. Is this just marketing tactics or is it the truth?
You haven’t finished stating your conditions yet, have you? Is oxygen water observing at this moment? If it’s not agreeing with the person upstairs
The corrosion rate of ammonium methylate solution on corrosion-resistant materials depends on pressure, temperature, the concentration of the ammonium methylate solution, as well as the corrosion resistance of the material. It can’t be generalized
The original poster must be mistaken; given the conditions you mentioned, it’s impossible to use carbon steel – at the very least, 316L should be used. Anyone who has worked with urea knows this.
Hehe, why is the corrosion caused by ammonium hydroxide so severe? Why?