Maruthamuthu, S. et al. - Teesside's Research Repository

Observation by epi-fluorescence microscope
A loopful of culture was taken for the fluorescence studies. In a clean glass slide the smear
was prepared. Two drops of 0.01% aqueous solution of acridine orange was added to the
smear, incubated for 10 minutes, the excess stain was washed with sterile distilled water.
Morphology of the cells was studied under the oil immersion (100X) epi-fluorescene
microscope.
Corrosion studies
(a) Weight loss measurement
Cupronickel coupons of 5 x 1cm size with a hole on the top were used for weight loss
experiments. The coupons were machine polished to mirror finish, degreased with
trichloroethylene and rinsed with deionized water. Four systems were designed by using
Chavara water. System I consisted water alone. System II consisted of chavara water with
nitrogen-free medium without bacteria. System III had chavara water and nitrogen-free
medium along with bacteria AG1, whereas system IV consisted of chavara water and
nitrogen-free medium with bacteria AG3. The pre–weighed coupons were immersed in
Chavara water and nitrogen-free broth inoculated with and without bacteria. Three coupons
were exposed in a conical flask and duplicate cells were made for each system. Totally six
coupons were used for the weight loss for each system. The average weight loss and standard
deviations (SD) were calculated. The broth was continuously replaced once in 3 days to
maintain the biofilm alive. Nitrogen-free medium without bacteria acted as the control
system. The weight loss of the metal obtained in milligrams was converted to corrosion rate in
millimeter per year (mm/y) using the formula (Treseder et al., 1991).
437 X Weight loss (mg)
Corrosion rate (mm/y) = ----------------------------------
Area (cm 2 ) X Time (h)
Electrochemical studies
(a) Potential measurements
5