Page 744 - Corrosion Engineering Principles and Practice

694 C h a p t e r 1 5 H i g h - Te m p e r a t u r e C o r r o s i o n 695

10

Carbon steel

1
9Cr 1 Mo

S41000

0.1 Alloy 800 H
Penetration (mm) S30400

0.01

Alloy 625

0.001
Alloy 825

0.0001
0.001 0.01 0.1
P H S (atma)
2
FIGURE 15.21 Effect of H S partial pressure upon sulfidation corrosion after
2
one year in H -H S gases at 34 atma and 540°C.
2 2

It is typical that a temperature increase of 55°C will double the
sulfidation rate, whereas increasing the H S concentration by a
2
factor of 10 may be needed to double the sulfidation rate. Therefore,
changes of H S concentration are generally less significant than
2
temperature variations.