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Materials
80 70 60 50 40 30 20 10 0
PRE Number
Alloy 59 Alloy 625 N10276 N06022 Alloy 31
Table 2 - PRE Number ( Pitting resistance equivalent ) using Cr + 3.3 Mo + 30 N
Grade |
PREN Range |
N06059 |
75-77 |
N10276 |
68-70 |
N06022 |
64-66 |
Alloy 31 |
52-54 |
Alloy 625 |
51-52 |
Graph 1 : PREN Chart
Table 3 - Mechanical Properties Rp0.2 Min Rp1.0 Min Rm A 2 ” % Impact J / Cm2
Min . req VdTüv WB505
340 380 690-900 40 225
Min . req B 622 310 na 690 45 na
K33 ( N06059 ) 444 ( Avg ) 478 ( Avg ) 836 Avg 62 229
Higher yield strength of Alloy 59 vs N10276 / N06022 allows for use a smaller wall thickness in seamless tubular applications allowing for reduction in cost and weight .
against a multitude of corrosive media under oxidizing and reducing conditions . Outstanding resistance against chloride-induced pitting and crevice corrosion , as well as resistance against stress corrosion cracking . Excellent resistance in mineral acids such as nitric , phosphoric , sulfuric , and salt acids , but especially against sulfur / salt acid mixtures . excellent resistance in contaminated mineral acids . Good resistance to Hydrochloric acid over entire concentration range up to 40-degree C .
Applications Refinery Crude Distillation Units overhead condensers are prone to hydrochloric acid condensation ( dew point corrosion ) leading to accelerated corrosion on tube OD side . Alloy 59 is an option in such environments and as it has good resistance to chloride induced pitting or stress corrosion which is helpful on tube ID if it has cooling water with high % of chlorides . Gas units Sulfur Condensers- Often subjected to severe corrosion due to sulfuric acid dew point corrosion . In some cases , carbon steel has life of less than one year . Alloy 59 is suitable alternative in such harsh environments . Alloy 59 can also be used in narrow temperature and concentration range for handling HF acid in Alkyl units HF catalyst . For Bio / Green diesel plants , Hydrotreating units Alloy 59 can be used for resistance to corrosion against fatty & Carbonic acids .
Petrochemicals — Acetic Acid / Formic Acid / Sulfonic Acid Condensers and other components are prone to heavy corrosion when acids are contaminated by oxidizing chlorides . Formic acid reduces but can shift to oxidizing in the presence of contaminants . The use of nickel-containing stainless steels like Alloy 59 can help to mitigate corrosion in such process conditions , while corrosion severity depends on the method of acetic acid production .
G 28A mm / a
7 |
6.6 |
|
6 5 4 3 2
1 0
|
1.3 |
0.8
Corrosion rate mm / a
|
VdTUV max |
1.3 |
N 06059 Average |
0.8 |
N10276 |
6.6 |
N06022 |
0.9 |
Graph 2 : G28 Method A ( resistance to intergranular corrosion ). Ferric sulphate and sulphuric acid boiling test 50 % H 2
SO 4
+ 42g / litre Fe 2 ( SO 4
) 3
.
0.9
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