Monel Vs. Carbon Steel Corrosion Mechanisms

[jwade123]

What would cause monel 400 to corrode at a higher rate than carbon steel in a sour crude stream? The temperature of the line is 300 degrees Farenheit

I'm afraid I dont have anymore information than that, so if anyone has any suggestions, it would be greatly appreaciated.

Thanks.

 

[0707]

Characteristics of Monel:

- a nickel alloy containing 65-70 percent nickel, 20-29 percent copper, and small amounts of iron, manganese, silicon and carbon

- NATURAL OR INHERENT PROBLEMS

- Surface discoloration: Can occur from exposure to atmospheric conditions.

- Pitting: Can occur if exposed to stagnant salt water.

Corrosion:

- Nitric oxides and sulfur dioxides, combined with water, are very corrosive to Monel.

- Nitric and nitrous acids can be very corrosive to Monel at room temperature

- Hypochlorites are severely corrosive to Monel if not diluted

- Acid and alkaline oxidizing salts, ferric chloride, ferric sulfate, cupric chloride, stannic chloride, mercuric chloride and silver nitrate are all corrosive to Monel.

- Resistance to sulfurous acid varies depending on climatic conditions

- Organic acids (acetic and fatty acids) have little to no effect on Monel

- Stress corrosion cracking: Exposure to aerated hydrofluoric acid in moist conditions can cause this to occur.

- Galvanic corrosion: Metals, such as aluminum, zinc and iron will corrode when in contact with Monel AND exposed to severe weather conditions. Therefore, use of these metals as fasteners for Monel should be avoided.


- Amonium bisulfite is prone to monel

Regards

Luis

 

[mshimko]

I've no experience with the specific environment mentioned, but in general terms:
- carbon stell will corrode via general corrosion mechanisms.
- monel is relatively resistant to corrosion, but if it occurs, it will tend to be localized.
- In terms of penetration rates, localized corrosion will almost always be more severe than general corrosion.