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INTRODUCTION
Chloride salt solutions, such as seawater,
present a challenging environment for selecting materials
with acceptable corrosion resistance. When exposed to these
solutions, most metals are susceptible to localized forms
of corrosion such as pitting, crevice corrosion and stress
corrosion cracking. Zirconium is one of the few metals that
can withstand corrosion attack from chloride salts, even at
high temperatures. This makes zirconium an ideal material
for the construction of heat exchanger equipment where seawater
is used as the cooling medium, and also in chemical processes
where hot, concentrated chloride salt solutions are used as
catalysts.
CORROSION DATA
While seawater can severely corrode
most metals, zirconium is resistant to attack. Tests performed
on zirconium samples in ocean water, at temperatures up to
200C and durations up to 275 days, all show little or no corrosion
(Table 1).
TABLE 1: CORROSION OF ZIRCONIUM IN SEAWATER
| Temperature
(°
C) |
Exposure
Time (days) |
Corrosion
Rate (mpy) |
Pitting
or Crevice Corrosion |
| 10
—15 (ambient) |
129
|
nil
|
No
|
| Boiling
|
275
|
nil
|
No
|
| 200
|
29
|
nil
|
No
|
In addition to its performance in seawater,
zirconium has shown outstanding corrosion resistance in a
wide range of chloride salt solutions (Table 2). In most cases,
this capability extends to high concentrations and elevated
temperatures of 100C and above. Zirconium can handle these
conditions without undergoing localized or general corrosion
attack, except in the most oxidizing media such as ferric
chloride and cupric chloride. Effective use of preventative
measures will allow zirconium to be used in these oxidizing
solutions as well (see Section IV: Limitations).
One of Five 1 2
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