1. What is a corrosion resistant alloy?
Corrosion resistant alloys are mixtures of various metals such as stainless steel, chrome, nickel, iron, copper, cobalt, molybdenum, tungsten and/or titanium. Combined, these metals can resist corrosion more effectively than standard carbon steel pipe. (Back to top)

2. What are the advantages of corrosion resistant alloys?
In the short term, corrosion resistant alloys protect your well against the damage caused by sour gas. In the long term, corrosion resistant alloys help you realize life-cycle cost advantages by eliminating the need for costly workovers. (Back to top)

3. Why is corrosion a problem?
Corroded tubulars can lead to lost production and nonproductive time (NPT) on your well. Downhole tools and completion components that corrode can fail, which then require workovers. While completing a sour gas well with carbon steel components may save money up front, the cost of replacing it with a workover will be much higher in the long run. By completing your well with corrosion resistant materials the first time, you can realize life-cycle cost advantages. (Back to top)

4. What causes corrosion?
Some wells, perhaps as few as one well out of a thousand, contain high levels of hydrogen sulfide (H2S), chlorides (Cl-) or carbon dioxide (CO2) [especially from secondary recovery methods like steam and CO2 injection]. Other reservoirs may contain very high pressure and high temperature (HPHT). These conditions corrode and weaken carbon steel tubulars. (Back to top)

5. What are the types of corrosion?
In weight-loss (general) corrosion, the sour gas uniformly corrodes the metal surface. When carbon dioxide dissolves in liquid, it creates an acid that can cause rapid weight-loss corrosion in carbon and martensitic stainless steels, even at relatively low temperatures. The martenistic or chrome grades provide resistance to CO2 alone. Chlorides and H2S increase the corrosivity of the solution. Duplex and austenitic stainless steels have higher resistance, while nickel alloys generally show complete resistance.

In pitting and crevice corrosion metal loss is highly localized. Stainless steels are highly susceptible to this type of corrosion, especially from chloride ions. By adding chromium and molybdenum to nickel you can resist pitting and crevice corrosion.

Environment-induced crackingoccurs when a tubing string is under high stress in a sour well. To prevent cracking, you must consider the depth of the well (which requires stronger, yet more brittle metal) and the concentration of sour gas. (Back to top)

6. Can’t I just use a corrosion inhibitor with carbon steel tubulars?
In some sour environments, corrosion can be controlled by using inhibitors along with carbon steel tubulars. However, inhibitors involve continuing high cost and may be unreliable, especially at higher temperatures. Also, adding corrosion allowance to the tubing wall increases string weight and reduces interior dimensions. (Back to top)

7. Are there different kinds of corrosion resistant alloys?
Yes. Each alloy’s precise composition enables it to resist a certain level of corrosion. CRA supplies:
• Martensitic Stainless Steel (Chromes)
• Duplex Stainless Steel
• Austenitic Alloy (Alloy 28)
• Nickel-Based Alloys 825, 925, 718, 945, G-3, 2550, 625 & 725
• Alloy C276
These alloys meet or exceed ISO 13680 and ISO 15156 NACE MR0175 and API standards. (Back to top)

8. What is OCTG?
OCTG stands for Oil Country Tubular Goods. This includes tubing, casing and liner material. (Back to top)

9. How do I know if I need corrosion resistant tubulars?
If you encounter a well with hydrogen sulfide, carbon dioxide, chlorides or HPHT, you may benefit from corrosion resistant pipe. Contact us to learn more. (Back to top)

10. Is financing available?
Yes. We can design flexible cost structures to help you manage your authorization for expenditure (AFE). Contact us to learn more. (Back to top)

11. Do you have corrosion resistant tubulars in stock?
Yes. We stock corrosion resistant tubulars at depots in both the western and eastern hemispheres, near areas of major drilling activity. You can get corrosion resistant pipe when you need it. (Back to top)

12. How long will it take to get corrosion resistant tubulars
made at the mill?
We begin processing your order as soon as we take it.  Delivery times can be as short as three months from the mill depending on grade, size, and other parameters.
(Back to top)

13. What is electroslag re-melting?
During electroslag re-melting the molten metal passes through the “slag” (an electrode) which chemically purifies and filters the metal. (Back to top)

14. Can I use corrosion resistant alloys instead of steel when
designing downhole tools?
Yes. The strength of corrosion resistant alloys enables new engineering possibilities and more robust tools without compromising the integrity of the design. Contact us to learn more. (Back to top)

15. How do I contact CRA to place an order or discuss my well?
You can reach CRA at:

Corrosion Resistant Alloys, L.P.
11111 Katy Freeway
Suite 620
Houston, TX 77079
USA
Phone: 713.827.8600
Fax: 281.768.8858
Email: OCTG@cralloys.com