You use materials suitable for this temperature range. Austenitic steels 304 and 316 will not good for this temperature range of 450 to 850 Deg. C. Stabilised steels 321 or 347 may be good even 310H also u can try.

Nelaturi V Raghavaiah Thanks for the response.

Some studies indicated better resistance of 310 SS and Nickel base alloy 740 to type - 2 hot corrosion. It appears that a minimum Cr content of 25 wt% is required for a better corrosion life. Aluminum also helps by forming a protective Al2O3 layer but not Mo or Co. APMT Kanthal type material (22Cr-5Al-3Mo-Fe) may be better than 304 SS but the issue is molybdenum which will cause acidic fluxing by the reaction:

Al2O3 + 3MoO3 = 2Al3+ + 3MoO42-

Dear Anshuman,

High temperature sulfidation is probably the most common high temperature corrosion nemesis in the refining industry, since there are very few “sweet” refineries still in operation. Sulfidation corrosion typically is of concern in sour oil services starting at temperatures in the 500F (260C) range. Up to that point, carbon steels are often acceptable, except in the most highly sour environments. In this case, “sour” means hydrogen sulfide (or other active sulfur compounds) containing oils.

Prevention

(1) Prevention of hydrogen and use austenitic steel

The 300 series austenitic stainless steels (containing 18%+ chromium) have substantial resistance to sulfidation and are often the material of choice under the more harsh sulfidation conditions, corroding at only 1-2 mpy even up to ~750F (~400C) when hydrogen is not present; though their susceptibility to chloride cracking at lower temperatures when moisture is present means that austenitic stainless steels are no panacea for sour oil process equipment.

(2) Increasing silicon content

Silicon content imparts significant resistance to sulfidation corrosion for carbon steels in the 500-650F (260-342C) range. Over the long haul, silicon containing fittings and pipe will corrode at significantly lower rates, such that if you do not have thickness monitoring locations (TML) on each of the low silicon containing components, you may be at risk of an unexpected sulfidation failure.

(3) Managament of change

Better management of change (MOC) that effectively communicates increasing sulfur components in feedstocks to the inspection group, so that inspection intervals can be adjusted appropriately.

Hope content is helpful for you.

Ashish

Ashish Thakur Thanks for the response but you didn't understand the question. I was asking about oxidation of metals in SO2 service. Request you to read the question again. The query was regarding a gas-gas exchanger and no. H2S is involved. The "Sulfidation" you are talking about is well covered by API 939C.

Dear Anshuman,

Sorry for rewriting.

You can go with substitute alloys 12Cr-SNi-4Al better in mechanical property as well fouling prevention.

If you wish to property compare , you can choose 310 instead of 304.

Higher corrosion rates from oxidation, hot corrosion, and sulfidation have increased consumption of materials that contain critical and strategic minerals and in many cases have limited productivity. Substitute materials having greater resistance to high temperature corrosive atmospheres above 600 degree C compared to austenitic stainless steels such as AISI 304, 316, and 310, with the goal of conserving critical metals such as Cr and Ni.

The substitute materials are based on Fe-Cr-Ni-Al compositions. Iron-aluminum alloys have exceptional corrosion resistance to high-sulfur environments. Sulfidation resistance of a 12Cr-SNi-4Al alloy with minor additions of Ti, Mn, and Si alloy is four to five times greater than that of AISI 304 (18Cr-8Ni) and 316 (18Cr-12Ni) stainless steel and three times greater than that of AISI 310 (2SCr-20Ni) stainless steel. Oxidation resistance is superior to that of types 304 and 316 and equivalent to that of type 310 stainless steel. Mechanical properties approach those of type 310 stainless steel. I would suggest to go with 310. Fouling of 310 in H2S does take place at lower rate in comparison to AISI 304 and 316.

Hope this is helpful for you.

Ashish