Alloys for Caustic Soda Service by Corrosion Resistance Category

        Composition (wt. %)
Category Alloys UNS Number C Fe Cr Ni Mo Cu Others
Category A alloys are useful at all concentrations and temperatures
A. Alloy 200 NO2200 0.15 0.40 - 99 min. - - -
Category B alloys - useful to 350oF (176oC)and 50% concentration. May show useful resistance up to 600F; however, should be tested first.
B. Alloy 690 NO6690 0.03 7-11 27-31 58 min. - - -
B. Alloy 600 NO6600 0.15 6-10 14-17 72 min. - 0.5 -
B. Alloy 400 NO4400 0.30 1.0-2.5 - 63-70 - 28-34 -
B. Ebrite 26-1* S44627 0.01 Bal. 25-27 0.50 0.75-1.5 0.2 0.05-0.20 Nb
Category C alloys - Useful to 50% caustic at atmospheric boiling (300F). May exhibit resistance similar to Category B alloys, but based on limited data, should be tested before use
C. Alloy 625 NO6625 0.10 5.0 20-23 Bal. 8-10 - -
C. Alloy C-276 N10276 0.02 4-7 14-16 Bal. 15-17 - 3-4.5 W
C. Alloy B-2 N106650 0.02 2.0 1.0 Bal. 26-30 - -
Category D alloys - useful to 250oF (121oC)and 50% concentration
D. Alloy 800 NO8800 0.10 Bal. 19-23 30-35 - 0.75 -
D. Alloy 20 NO8020 0.07 Bal. 21-23 32-38 2-3 3-4 (4xC) Ti min.
Category E alloys - useful to 200oF (93oC) and 50% concentration
E. 304SS S30400 0.03 Bal. 18-20 8-10 - - -
E. 316SS S31600 0.03 Bal. 16-18 10-14 2-3 - -

* Tubing and piping only.

 

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