PRESENTER: IP MOLOBELA
APRIL 29, 2011
Microbiologically influenced
corrosion in water infrastructures
and pipe line materials
College of Science, Engineering and
Technology
Civil and Chemical Engineering Department
University of South Africa
Outline
 What is MIC?
 How do they form and induce
corrosion?
 What impacts do they have in the
water industry?
 What kind of surface materials do
they attack?
 How can they be removed or
controlled?
Microorganisms – everywhere
 Some are bad (destructive)
 Some are good (non destructive)
What is MIC?
 MIC - causative agent of biofouling
and biocorrosion
 MIC - cause deterioration of metals
as a result of the metabolic activity
of
microorganisms-(forms
by
biofilms)
 Biological activity modify the
structural chemistry of the materials
- corrosion
How do MIC form?
Do microorganisms “eat” metals?
Types of Microorganisms
Aerobes – oxygen consuming
Involve in metal
degradation
Anaerobes – non- oxygen consuming
Groups
Categorized as (Acid producing,
Sulphate reducing, Nitrate reducing and Iron
reducing biofilms) - (Gallionella, Sphaerotilus,
Pseudomonas, Klebsiella, Eneterobacter,
Acinetobacter, Bacillus, Aeromonas, and
Legionella)
Cont.
Sulphate Reducing Biofilms (SRB)
Cathodic depolarisation
(proposed by Wolzgen and Vulgt, 1934)
MIC mechanism
type materials
steel and iron
SRB- consumes H2
through
Hydrogenase enzymes
depolarise
cathode
corrosion (end product)
Equa: SO42- + 8H S2- + 4H20
Cathodic depolarisation
SRB
Biocorrosion and biofouling of
water pipe materials and other
infrastructures
Corroded section
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Sulphur Reducing Bacteria
Desulfovibrio vulgaris
Desulfuromonas
acetoxidans
Impact of MIC in the water industry
 Cause fouling of water pipe materials and
other infrastructures
loss in billions of revenues annually
 Reduces efficiencies of water structures
cooling towers, heat exchangers
etc
 Affect the quality of drinking water health risk hazards (production of H - not environmentally friendly)
Cont.
2
 Causes odour
 Debris from corroded materials-end up in
human systems from consumption of
drinking water
carcinogenic and
mutagenic
Type of materials
All materials
 Stainless steel
 Iron
 Aluminium alloys
 Titanium alloys
 Cooper
 Nickel
Note: Specific bacterial group – affect –
specific materials
Prevention of biocorrosion or MIC
 Temperature control - can reduce /
minimise corrosion enhancing bacteria
(20- 350C is the most desirable
temperature range for growth of most of
the microbes)
 Do not allow dead-spots to form in any
water pipe line material or infrastructure.
These stagnant environments provide the
best environment for biofilms to form
and bacteria to grow.
 Material development
more alkaline
environment
likely
to
reduce
corrosion, but some of the bacteria
prefer an alkaline environment, so
diagnosis of the type of bacteria for the
individual corrosion problem is required.
 To understand biocorrosion and MIC – it
is important to integrate physical and
chemical phenomena with microbial
physiology
Cont.
• Collaborative research on biofouling and
biocorrosion (scientists from different
expertise)
I thank you!!!!!!!!!
Cartoons