In oil and gas applications, control lines made from Alloy 825 are
employed in downhole operations for hydraulic control, chemical
injection, and signal transmission. They are often chosen for
environments with high pressures, temperatures, and corrosive
elements like hydrogen sulfide (H₂S) and carbon dioxide (CO₂).
Alloy 825 provides a balance of strength, flexibility, and
resistance to sour gas corrosion, making it an ideal choice for
downhole tubing in offshore and onshore oil fields.
Alloy 825 (UNS N08825) is a nickel-iron-chromium alloy with
additions of molybdenum, copper, and titanium. It is designed to
provide excellent resistance to both reducing and oxidizing acids,
stress-corrosion cracking, and localized attack such as pitting and
crevice corrosion. Due to its superior corrosion resistance and
strength, Alloy 825 is widely used in harsh environments, including
oil and gas applications.
Corrosion Resistance Of Different Materials(G28 A Methord)
| Grade | Rate(mm/a) |
| N08825 | ≤ 0.9 |
| N08020 | ≤ 0.5 |
| N08367 | ≤ 0.5 |
| N06625 | ≤ 0.9 |
| N10276 | ≤ 10 |
| N06200 | ≤ 1.5 |
| N06022 | ≤ 1.0 |
| N06600 | ≤ 1.0 |
| N06601 | ≤ 1.0 |
825 825E Chemical Composition
| C | Sl | Mn | P | S | Cr | Mo | Ti | Cu | Fe | Al | Ni |
| ≤ | ≤ | ≤ | ≤ | ≤ | | | | | ≧ | | |
| 0.05 | 0.5 | 1.0 | 0.02 | 0.03 | 19.5-23.5 | 2.5-3.5 | 0.6-1.2 | 1.5-3 | 22 | 0-0.2 | 38-46 |
Mechanical Propertie
| Property | 825 Mln. | 825E Mln. | 2507 Mln. | 2205 Mln. | Max. |
|---|
| Tensile strength (psi) | 85000 | 95000 | 116000 | 95000 | - |
| Yield strength (psi) | 35000 | 60000 | 80000 | 70000 | - |
| Elongation (%) | 30 | 18 | 15 | 25 | - |
Size Dependant Characteristics (Based Upon Nominal Tubing
Dimensions)
| Type | O.D. | W.T. | Maximum Theoretical Working Pressure | Minimum Theoretical Collapse Pressure | Nominal Theoretical Burst Pressure |
| in. | in. | psi | psi | psi |
| Welded | 1/4 | 0.035 | 7220 | 7583 | 21014 |
| 1/4 | 0.049 | 10513 | 9979 | 29278 |
| 1/4 | 0.065 | 14769 | 21198 | 55000 |
| 1/4 | 0.083 | 34538 | 24861 | 70333 |
| 3/8 | 0.035 | 8013 | 9125 | 19901 |
| 3/8 | 0.049 | 11485 | 12262 | 27727 |
| 3/8 | 0.065 | 15815 | 15611 | 36894 |
| 3/8 | 0.083 | 21047 | 18953 | 47180 |
| 1/2 | 0.035 | 5929 | 7024 | 14984 |
| 1/2 | 0.049 | 8435 | 9530 | 20876 |
| 1/2 | 0.065 | 11509 | 12282 | 27779 |
| 1/2 | 0.083 | 15148 | 15133 | 35523 |
| Seamless | 1/4 | 0.035 | 12377 | 13000 | 29667 |
| 1/4 | 0.049 | 18022 | 17107 | 41333 |
| 1/4 | 0.065 | 25318 | 21198 | 55000 |
| 1/4 | 0.083 | 34538 | 24861 | 70333 |
| 3/8 | 0.035 | 8013 | 9125 | 19901 |
| 3/8 | 0.049 | 11485 | 12262 | 27727 |
| 3/8 | 0.065 | 15815 | 15611 | 36894 |
| 3/8 | 0.083 | 21047 | 18953 | 47180 |
| 1/2 | 0.035 | 5929 | 7024 | 14984 |
| 1/2 | 0.049 | 8435 | 9530 | 20876 |
| 1/2 | 0.065 | 11509 | 12282 | 27779 |
| 1/2 | 0.083 | 15148 | 15133 | 35523 |
Key Properties of Alloy 825:
Corrosion Resistance: Excellent resistance to a wide range of
corrosive environments, especially sulfuric acid, phosphoric acid,
and seawater. It also resists stress-corrosion cracking, making it
suitable for environments with high levels of chloride.
High Strength and Durability: The alloy exhibits good mechanical
properties at both room temperature and elevated temperatures up to
about 538°C (1000°F).
Oxidation Resistance: Good resistance to oxidation and scaling at
elevated temperatures.
Localized Corrosion Resistance: The molybdenum and copper in Alloy
825 provide resistance to reducing environments, while chromium
enhances resistance to oxidizing conditions.
APPLICATION
Key Properties:
Oil and Gas Control Lines: Alloy 825 is used in control line tubing
in oil and gas applications, particularly for downhole systems
exposed to corrosive environments with high chloride
concentrations, acids, or sour gas. These control lines deliver
hydraulic control, transmit pressure signals, or inject chemicals.
Chemical Processing: Used in chemical processing industries where
sulfuric acid, phosphoric acid, and other corrosive agents are
present.
Nuclear Fuel Reprocessing: The alloy is resistant to nitric acid
and other radioactive environments, making it suitable for nuclear
fuel reprocessing.
Heat Exchangers and Piping: Ideal for heat exchangers, piping, and
tanks exposed to seawater or industrial chemicals.
