4140 Steel in Downhole parts

[Shibuz]

Would 4140 (RC 18-22) be a smart choice for downhole parts? I am worried about corrosion (H2S, CO2, Cl). How will temperature effect the material?

I was told to do "phosphate coating" on 4140 to prevent corrosion in downhole environmnets. Is this reccommended? If so, what type of phosphate coating is best? zinc or manganese?

If 4140 is not reccommended, which material would be the best?

Thanks,
SZach

 

[TVP]

4130 with Mo additions is a more standard grade for 18-22 HRC downhole applications. I am not very familiar with phosphate coatings for these applications, so I will defer to some of the others on this point.

 

[Carburize]

I don't see any reason why the 4140 would not be a good choice - with the controlled hardness it would resist the H2S and it is also good against quite high levels of chlorides - the limit of its resistance to CO2 would be the same as 4130. The phosphate coasting won't do anything to improve down-hole corrosion resistance but may give better "shelf-life" before use.

 

[richardbuss]

Hi Szach,

I supply AISI 410 stainless for downhole applications where corrosion resistance is needed due to gas.

REgards
Richard

 

[stanweld]

More info is required of your downhole conditions. What are the %H2O, %CO2, %H2S? What is the temperature? In severely corrosive environments, 410 S.S to Alloy C-276 have been used.

Film forming inhibitors are often added, especially when using low alloy steels.