CORROSION RESISTANCE OF HASTEllOY®AllOYS - Haynes ...

PHOSPHORIC ACID
ISOCORROSION DIAGRAMS·
HASTELLOY® alloys B-2, C-276, C-22, G-3, G-30 and HAYNES® alloy No. 25
have acceptable corrosion resistance at most concentrations and
temperatures. The maximum rates were observed in boiling 85 percent acid for
all of these alloys.
Commercial grades of phosphoric acid encountered during the
production of wet process or superphosphoric acid quite frequently contain
numerous impurities. These impurities, basically fluorides and ferric salts,
serve to change the basic character of the acid. Alloys G-3 and G-30 have
demonstrated excellent resistance to wide variety of acid compositions,
presumably because of their high chromium contents.
HASTELLOY® Alloy B-2
Resistance to Phosphoric Acid
350.-------,,-----,-------r-----r---,----.----,-------.-------,
u..
300
l-
75
e:{
a:
w
0....
2 w
I-
50
0
10
20 30 40 50 60
CONCENTRATION, WEIGHT PERCENT
70
80
HASTELLOY® Alloy C-276
Resistance to Phosphoric Acid
350.-------r-------r----,----,----.----,-------.------,------,
Corrosion rates in parentheses are in mm/year.
u..
300
l- e:{
a:
w
0....
2 w
I-
50
100
o 10 20 30 40 50 60
CONCENTRATION. WEIGHT PERCENT
•All test specimens were solution heat-treated and in the unwelded condition.
71