Page 262 - Corrosion Engineering Principles and Practice
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236 C h a p t e r 7 C o r r o s i o n F a i l u r e s , F a c t o r s , a n d C e l l s 237
High level of High level of
dissolved oxygen dissolved oxygen
Paving
Anodic areas
Little or no
dissolved oxygen
FIGURE 7.27 Oxygen differential cell resulting from burial under paving
producing an oxygen concentration cell.
In the gas transmission line example shown in Fig. 7.28, the
compressed gas coming out of the station is hot, and, as it travels
down the line, it loses heat by transfer to the surrounding soil. The
result creates a cell:
• The hot pipe near the compressor is the anode
• The cooler pipe down the line is the cathode
Compressor station
Hot gas
Cathodic area
Cooler gas Anodic area
FIGURE 7.28 Concentration cell resulting from heat differential.
