Resistance to localized corrosion by Inconel 625

The below table shows the high temperature tensile strength for the annealed and aged resistance to corrosion Inconel 625:

Temperature Yield Strength Tensile Strength Elongation Reduced Area
oF oC Ksi MPa Ksi Mpa % %
75 23 129.4 892 181.9 1254 32.0 48.4
100 38 131.7 908 182.2 1256 32.6 49.2
200 93 125.9 868 178.4 1230 29.6 47.0
300 149 119.8 826 172.4 1189 30.9 50.2
400 204 119.5 824 169.7 1170 30.7 52.4
500 260 117.6 811 165.5 1141 31.0 52.7
600 315 113.4 782 159.5 1099 32.4 54.2
650 343 117.4 809 159.8 1102 31.1 53.5

The high nickel, chromium and molybdenum amounts make the Inconel 725 alloy resistance to the wide range of corrosive conditions. It is particularly resistant to the conditions such as carbon dioxide, chlorides and hydrogen sulfide that are obtained in the deep sour gas wells. In these conditions, the Inconel 625 alloy causes resistance to the corrosion, pitting, hydrogen embrittlement and stress corrosion cracking. The below table shows the functionality of alloy in the standard analysis performed to determine the resistance to sulfide stress cracking in the sour well conditions.

Alloy Condition Yield Strength Hardness Time (days)
Ksi or MPa Rc
INCONEL alloy 725 Cold Worked 90.0 621 25 30
Age Hardened 117.6 811 37 30
Age Hardened 128.6 887 40 30
Age Hardened 130.8 902 41.5 30
INCONEL 625 Cold Worked 125.0 862 30.5 42
Cold Worked 160.0 1103 37.5 10
INCONEL 718 Age Hardened 120.0 827 30 42

The below table shows the excellent resistance to the stress corrosion cracking at the elevated temperatures up to 450oF or 230oC in the rigorous sour conditions in the presence of elemental sulfur.

Alloy Stress-Corrosion Cracking at:
350°F

(177°C)

375°F

(191°C)

400°F

(204°C)

425°F

(218°C)

450°F

(232°C)

475°F

(246°C)

500°F

(260°C)

Inconel 725 No No No No No Yes No
Inconel 625 No Yes No No No Yes No
Inconel 718 Yes Yes No No No Yes No

The Inconel 625 alloy is approved for using in the sour gas wells. It shows superior resistance to the general and localized corrosion in the brines and sea water. The below table describes the outcomes of analysis made on the crevice corrosion in the sea water:

Alloy Condition Corrosion

Initiation (days)

Sites

Attacked %

Depth

Attacked, inch

Inconel 725 Age Hardened 0 0
Inconel 625 Annealed 2-5 25-75 0.010

From the above table we can easily understand that the Inconel 625 alloy is superior for using rather than inconel 625 in the resistance to crevice corrosion initiation.  The results of C-ring analysis in the rigorous 25% sodium chloride, 0.5% acetic acid, 1g/l sulfur conditions with 120 psi 825 kPa hydrogen sulfide are observed.

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Isha Changotra has wide experience in metals industry and is working for a renowned super alloys manufacturer located in China and United States. With extensive insight in metals and high performance super alloys, she aims to provide most useful information for folks engaged under this niche.

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Posted in Inconel 625 alloy plate, Inconel 625 Wire, resistance to corrosion Inconel 625 plate, Resistance to corrosion Inconel 625 Rod

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Metals, Alloys-Information Guide

Super metals and alloys

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