Lecture 16

Question 1

What are the two main ways to measure corrosion in the lab?

Answer 1

Weight loss of a metal using beads or coupons over a given time.

Electrochemical measurements by measuring the anodic current i_A and cathodic current i_Cof the iron coupon in an electrical circuit in real time.

Question 2

list the steps for iron corrosion measurement using change in metal weight

Answer 2

• Pretreat coupon or bead by polishing or cleaning them with an acid and base
• Weigh and incubate for a period of time under the desired aqueous medium
• after incubation, coupons/beads are cleaned and weighed to determine weight loss

This method gives the general corrosion rate (mm/year) since some areas of the coupon may corrode faster due to pitting.

It is best to have abiotic controls to account for abiotic corrosion.

Question 3

What is the corrosion rate formula?

Answer 3

pg 6

Question 4

What microbial strain can be used for EMIC? for CMIC?

Answer 4

for direct corrosion: D. ferrophilus strain IS5
for indirect corrosion D. vulgaris (DVH)

Question 5

What can IS5 use acetate for? formate for?

Answer 5

D. ferrophilus can use acetate as a carbon source and can use formate as an electron donor.

Question 6

What does D. vulgaris do to lactate?

Answer 6

It oxidizes organic acids like lactate to acetate.

Question 7

Does the addition of formate to a IS5 culture increase or decrease the corrosion rate?

Answer 7

It decreases it.

Question 8

What has a higher corrosion rate? D. vulgaris + Sulfate + beads +….
1. lactate
2. acetate

Answer 8

lactate, since it can oxidize it to acetate so facilitates the reduction of sulfate.