Page 456 - Corrosion Engineering Principles and Practice

422 C h a p t e r 1 0 C o r r o s i o n i n S o i l s a n d M i c r o b i o l o g i c a l l y I n f l u e n c e d C o r r o s i o n 423

in 12 of 20 samples, suggesting that sulfate reducers which did not
have this enzyme were also present in the operation [26]. In principle,
probes could be developed to detect potentially all sulfate-reducers.
However, the operation of a battery of probes could be a daunting task
where a large number of field samples have to be analyzed.
The reverse sample genome probe (RSGP) has been developed to
overcome this obstacle. With RSGP, the DNA from organisms
previously isolated from samples acquired from known field problems
is spotted on a master filter, following which DNA isolated from a
new sample is labeled with either a radioactive or fluorescent indicator
and placed on the filter. Labeled DNA from the new sample sticks to
the corresponding spot on the master filter when complementary
strands of DNA are present. Organisms represented by the labeled
spots are then known to be in the new field sample [26].
Detailed Coupon Examinations A great deal of information can be
learned by careful, in-depth examination of corrosion coupon surfaces
using commonly available analytical techniques. A wide variety of
samplers for introducing metallic surfaces of interest into a system
are available. A popular sampling device is shown in Fig. 10.11.

FIGURE 10.11
Biofilm sampling
device with Set screw
removable
“buttons.”

Body

Set screw
Stud

Stud holder

Sample Securing screw