CORROSION RESISTANCE OF HASTEllOY®AllOYS - Haynes ...

ISOCORROSION DIAGRAMS*
HASTELLOY® Alloy G-30
Resistance to Phosphoric Acid
(
Corrosion rates in parentheses are in mm/year.
g Region of corrosion rate instability.
(0.5)
20 mpy 150
(
LL
cj 250
w
o
W
0:
~ 200
«
0:
w
Q...
~
~ 150
Boiling Point Curve
u
cj
w
0
W
100 0:
I-
:::::>
«
0:
w
Q...
~
w
I-
50
100
o
10
20
30
40
50
60
70
80
CONCENTRATION, WEIGHT PERCENT
Comparison of HASTELLOY®
Alloy G-30 and Alloy 625
in Commercial Phosphoric Acid*
CORROSION RATE IN MM/YEAR
0.25 2.5
25
250
0 0
10.0 6
5.0
a
c;>
(')
.......
L{)
C\J
CD
(f)
I­
W
«
.0:
Z
o
(jj
o
0:
0:
o
U
LL
o
4.0 0 0
cP6
3.0 0
00
0
2.0
60
Cb
1.0
OP 2 0 S
t
6 P 2 0 S + 2000 ppm CIo
P 2 0 S + 0.5% HF
o
f=«0:
1.0 10 100 1000 10,000
0.8
0.7
CORROSION RATE OF ALLOY 625 (MPY)
The corrosion resistance of HASTELLOY alloy G-30 in a variety of environments is shown in this
charI. The corrosivity of commercial phosphoric acid is a result of several variables such as
concentration, temperature, impurity levels (manufacturer) and origin of the phosphate rock. Wide
variations in corrosion rates are possible in acids of the same concentration but from different
sources. Hence, corrosion tests were conducted in acids from a number of suppliers and the
performance of alloy G-30 relative to alloy 625 is shown as a function of the corrosion rate of alloy
625. Within certain severity of the acid, alloy G-30 shows 2-3 times better corrosion resistance than
alloy No. 625. In acids of high severity all the alloys exhibit corrosion rates in excess of 2.5mm/yr
(100 mpy).
•All test specimens were solution heat-treated and in the unwelded condition.
73