Sandvik 2RE10 is the grade for nitric acid service. With the very high cleanliness, the best possible corrosion resistance is achieved.
Products availible in 2RE10 include heat exchanger tubing, pipe and plate.
Typical applications are cooler/condensers, tailgas preheaters and other equipment operating with hot nitric acid.
For further information order the reference list S-1276-ENG.
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Isocorrosion diagram for Sandvik 2RE10 and 3R12 (AISI 304L) in nitric acid. The curves represent a corrosion rate of 0.1 mm/year (4 mpy).
A typical concentraison in nitric acid plants is 60%. 2RE10 can be used at 60 % concentrasion up to about 120°C (250°F), which is more 20°C(40°F) higher temperature than 304L.
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Huey testing
Huet testing (ASTM A 262 Practise C) is a common method to check the corrosion resistance of stainless steel for use in nitric acid. As the test is done in boiling nitric acid at 65 % concentrasion it reflects very the typical corrosion situation in nitric acid plant. Welding will affect the corrosion resistance and to check the effects the test samples can be heated at about 600-700C before performing the corrosion tests. As can be seen the corrosion rate of 2RE10 is very marginally affect by heat even if the samples have been heated for 100 hours.
304L shows a dramatic incerase in the corrosion rate after only 30 minutes of heating.
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Corrosion curves for 2RE10 and AISI 304L obtained from
Huey testing after sensitisation at 675°C (1250°F).
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Tail gas preheaters
The main reason for highly corrosive conditions in tail gas preheaters is that droplets of nitric acid are entrained in the tail gas from the absorption tower. When this gas enter into the heater, the droplets will settle on the hot tube wall and start boiling. The temperature of the heating medium, usually hot process gas or steam, can be very high. In this type of condition AISI 304L tends to have short service life.
Cooler/condensors
In cooler/condensors, corrosion is normally encountered at the inlet end where the first condensate is formed. If the reboiling of the first condensate occurs, the corrosive conditions become very severe, leading to the kind of attack illustrated in figure. A typical corrosion problem on tubing in grade 304L. 2RE10 can in most case solve the problem.
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