A recent NACE sponsored report pegged the annual cost of corrosion in the water and wastewater sector in the USA as exceeding 36 billion dollars/year. Much of this has to do with the age of the infrastructure and the operating conditions it is exposed to, which have become significantly more aggressive than what the original design construction methods and materials are capable of handling. A specific area of focus will be on protective coating technologies, differentiating between the primary systems in use, and how to implement a protective coatings solutions-based approach to slowing or halting attack

1. Addressing Infrastructure Corrosion in the
Water and Wastewater Market

2. 2
Paul Keough is Chesterton’s Marketing Development
Manager for the Water and Wastewater Industry. He has been
with the company for 17 years and has been in the fluid sealing
industry for 37 years. Prior to his current position,
Paul was the Business Development Manager for
Chesterton, responsible for North American engineering firms in
the Mining and Wastewater Industries. He has done sealing
presentations to firms such as Fluor, AMEC, Tetra Tech, CDM
Smith, Arcadis, AECOM to name a few.
Steve Bowditch is the Global Market Development Manager for
ARC Efficiency and Protective Coatings. He has been with the
company for 27 years and is a NACE Level III CIP Inspector and
SSPC Corrosion Specialist with over 35 years’ experience in the
areas of protective coatings development and applications. He is
an active contributing member of numerous NACE Technical
Committees associated with corrosion prevention and protection
and has presented papers on corrosion and associated control
technologies.
Host
Presenter

3. 3
What will we cover
 What is corrosion’s impact to water and wastewater
infrastructure
 What mechanisms are responsible
 What are available options to address
 How protective coatings can protect infrastructure
 What coatings technologies are available
 Pro’s and con’s
 How to implement a sound coatings program
 Performance based versus product based specifications
 Manufacturer’s qualified applicators Installation
 QA/QC Testing

4. 4
Infrastructure at risk

5. 5
Annual Cost of Corrosion in Water and Wastewater
$27
$28
$29
$30
$31
$32
$33
$34
$35
$36
$37
AWWA FHWA EPA
Billion
• Blocked or broken pipes release as much as 10 billion gallons of
raw sewage every year.
• US EPA estimates that over $330B needs to be spent over the
next 20 years to upgrade existing water/wastewater infrastructures

6. 6
Life Expectancy of Buried Cast Iron Pipe
12 22 32 42 52 62 72 82 92 102
% Life Remaining 100% 96% 90% 85% 75% 63% 51% 40% 22% 12%
0%
20%
40%
60%
80%
100%
% Life Remaining vs Years in Service
“More than a million miles of pipes are nearing the end of its useful
life and approaching the age at which it needs to be replaced.”
(AWWA 2012)

7. 7
Increased US Population Shift to Urban Locales
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
1900 1925 1950 1975 2000 2025
Rural Population Urban Population
“Over 75 percent of the nation’s population is served by centralized
wastewater collection and treatment systems. “
EPA 2004

8. Common Mechanism’s of Attack

9. 9
Mechanisms
 Biogenic corrosion: SRB, SOB, H2SO4 (vapor phase)
 Acidic attack – manufactured acids (liquid phase)
 Sulfate attack (vapor phase)
 Carbonation in water (liquid phase)
 Abrasive erosion / cavitation (liquid phase)
 Chloride induced corrosion (vapor phase)

10. 10
Changing Environment is More Corrosive
Corrosivity of wastewater in USA has
changed dramatically in past 35 years
1980 1985 1990 1995
0
5
10
15
DISSOLVEDSULFIDE
CONCENTRATION(mg/l)
Corrosion Threshold
Sulfides
1980 1990 2000 2010 2020

11. 11
11
Relationship between pH and Corrosivity to Concrete

12. 12
Mechanism of Attack – Biogenic Corrosion
Partial Listing of
micro-organisms
known to be
present in and
deleterious to
concrete water
and waste
water systems
Secrete 40% H2SO4

13. 13
Mechanism of Attack - Biogenic Corrosion
Other bacteria present in the
water convert sulfates to sulfides.
This causes the rotten egg smell,
hydrogen sulfide gas (H2S).
When the dissolved oxygen
concentration falls below 0.1
mg/l, the environment becomes
anaerobic becomes septic.
H2S Gas H2S GasH2S Gas H2S Gas
pH ~ 7
D.O.<0.1 mg/l
Bacteria in the
wastewater consume
oxygen.
O2
O2 O2
Sewer
Wastewater
Bacteria

14. 14
Conditions Favorable for Producing Sulfides
 Low dissolved oxygen content
 High-strength wastewater (in terms of biological oxygen
demand)
 Low flow velocity and long detention times
 Turbulence/extensive pumping
 Elevated wastewater temperatures.

15. 15
Mechanism of Attack - Biogenic Corrosion
SO4
2- HS- H2S
H2S Gas H2S Gas
H2S Gas
H2S H2S
H2S
In water at pH 7, about 50%
of the dissolved sulfide
converts to H2S gas.
0.00
1.00
2.00
3.00
4.00
5.00
6.00
0
200
400
600
800
1000
1200
3 4 5 6 7 8 9 10
H2S(aq)andHS-insolution(mg/L)
H2S(g)inair(ppm)
pH
H2S(g)
H2S(aq)
HS-

16. 16
Mechanism of Attack - Biogenic Corrosion
On the surfaces above the
water, H2S gas is converted
to strong sulfuric acid by
Thiobacillus bacteria.
This acid corrosion, not
“aging”, then dissolves the
infrastructure.
SO4
2- HS- H2S
H2S
Thiobacillus
+ O2 = H2SO4
Acid Attacks
Concrete
And virtually nothing is
being done to stop it from
happening.

17. 17
Mechanism of Attack - Biogenic Corrosion
 Where to look
 Influent pump stations
 Manways
 Head works
 Bar screen chambers
 Primary clarifiers
 Grit chambers

18. 18
Mechanisms of Attack - Manufactured Acids
 Primarily seen in industrial wastewater systems
 Attack can occur in liquid & vapor phase
 Rate of attack dependent on concentration, solubility & flow
 pH below 12.5 – potassium and sodium depletion
 pH below 10.0 – calcium hydroxide depletion
 pH below 8.0 – calcium-silicate-hydroxide gel depletion
 Acid – Base reaction
 Caused by the reaction of an acid and the calcium hydroxide portion of
the cement paste
 Soluble calcium salt which produces a highly soluble calcium salt
Ca(SO)4 by product.
 These soluble salts are easily removed from the cement paste
weakening the paste’s structure as a whole.

19. 19
Manufactured Acids - pH Effect on Concrete
Source L.A.County San District
0.001 0.01 0.1 1.0
Corrosion Rate (in./year)
7
6
5
1
0
pH
Corrosion
Range
4
3
2
0.25
200 yr
100 yr
50 yr
20 yr
8 yr
The life cycle of
concrete with a pH
of 2 compared to a
pH of 4 is 85%
shorter

20. 20
Mechanisms of Attack – Sulfate Attack
 SO4 ions react with Ca(OH)2
 Na2SO4 + Ca(OH)2 => CaSO4
 CaSO4 + C3A => CaO-Al2O3-31H2O
 Gypsum(CaSO4) & Tri-calcium
sulfoaluminate (CaO-Al2O3-
31H2O) are much larger
compounds.
 Resulting expansive forces
cause micro-cracking, exposure
of structural steel &
disintegration
Where to look
• Splash zones (wet/dry)
• Wherever H2SO4 attack occurs

21. 21
Mechanisms of Attack – Carbonation
 Ca(OH2) + CO2 Ca(CO3) +
H2O
 Forms carbonic acid which
causes slow acidic attack of
cement paste due to lowered
pH
 Pore blocking characteristics
Where to look
• Secondary clarifiers
• Aeration basins – O2 reactors
• Chlorine contact basins
• Outfalls

22. 22
Mechanisms of Attack – Abrasive Attack
 Suspended solids in flowing
wastewater
 Wears cement paste – then
aggregate can be dislodged
 Influenced by size, quantity of
suspended solids plus velocity
 Prevalent in collection
systems or plant inlet
structures
Where to look
• Collection systems
• Plant inlet

23. 23
Mechanisms of Attack – Chloride Intrusion
 Chloride ions (Cl-) are found in
coastal regions and industrial
flows.
 Soluble Cl- are transmitted
into concrete structure by
capillary transport.
 Cl- disturb passive oxide film
on rebar initiating active
corrosion cells.
 Rate of reinforcement
corrosion increases by over
1000%
Where to look
• Coastal Regions
• Pipes
• Manholes
• Chambers
• Treatment plant

24. What Technologies are Available

25. 25
Methods to Address
Protective linings material selection
 Design and fabrication details
 Evaluation programs
 Periodic inspections
Process changes (wherever possible)
 Reduce slime layers by removing debris (grit and sand)
 Control dissolved sulfide through chemical addition
 Reduce H2S gas release by reducing turbulent flow
 Protect sensitive surfaces from the effect of acid generation

26. 26
 Vinyl sheet liners
 Polyurethane/Polyurea
 Bag systems
 Cementitious
 Calcium aluminate
 Concrete additives
 Epoxies
 Solvent cut/coal tar
 100% solids reinforced

27. 27
What Coatings Technologies Are Available?
 Anchored or adhered thermoplastic (vinyls)
 Spray applied elastomeric polyurethanes
 Polyureas
 Mat reinforced linings
 Polyester/Vinylester
 Trowel applied aggregate filled lining
 Calcium aluminates
 Epoxies
 Spray applied high solids -amine cured epoxies
 Bottom Line
 They ALL can fail and they ALL have limitations

28. 28
Vinyl Liners
 In use for >40 years
 60-180 mil thick vinyl sheet
 Adherent surface must be
flush and flat
 Adhesive mounted and hot
gas sealed joints
 More difficult to use in rehab
 Primary mode of failure is
joint failure, leakage,
blistering and delamination
28

29. 29
Spray Applied Polyureas/Polyurethanes
 Elastomeric urethane technology
 Aliphatic or aromatic based
 Typically 100% solids
 Good elastic modulus for flexing
applications
 Good chemical resistance.
 Rapid cure provides shorter
return to service times
 Isocyanates create hazardous
exposures
 Prone to sheet delamination due
to low wet out properties during
application

30. 30
Mat reinforced linings
 Fiberglass saturated sock, mat or
chopped strand reinforced.
 Typically used with polyester or
vinyl ester resins
 Excellent chemical resistance
Good chemical resistance
 Poor elastic modulus for flexing
applications
 Creates explosive/flammable
environment during application
 Moisture sensitive
 Prone to sheet delamination due
to wicking along glass strand

31. 31
Trowel applied aggregate reinforced epoxies
 Silica/quartz reinforced, typically
used with BisA/F or epoxies
 Excellent chemical resistance
 Low permeability
 High wet adhesion
 High tensile strength
 High abrasion resistance
 High wet adhesion
 High elastic modulus for flexing
applications

32. 32
Spray applied reinforced epoxies
 Silicate reinforced, typically used
with BisA/F or epoxies
 Excellent chemical resistance
 Low permeability
 High wet adhesion
 High tensile strength
 High flexural strength
 Moderate abrasion resistance
 Low elastic modulus for flexing
applications
 Corrosive hazards

33. 33
Critical Properties to Consider
 Thickness
 Smooth concrete (<36 grit finish appearance) allows for 30-60 mil dry film
thicknesses
 If concrete roughness is> than a 36 grit finish sandpaper increase to 60-120
mil dry film thickness
 Flexural strength
 Necessary for flexing and vertical misalignment which can commonly occur
buried wastewater treatment and collection systems.
 Values of 4,000 psi or greater for flexural strength and 5 x 106 psi or less for
flexural modulus are good.
 Tensile strength
 Necessary to calculate overburden-bearing capacity and is of paramount
importance to resistance to ground water infiltration.
 Tensile strengths of 1,800 psi are considered excellent

34. 34
Critical Properties to Consider
 Bond Strength
 The bond of the coating to the substrate is perhaps the key element to
achieving a long service life.
 Bond strength to wet concrete should exceed the cohesive strength of the
concrete, usually above 400 psi.
 Permeability
 Permeability is the property that controls passage of corrodents through the
coating to the substrate.
 If all other properties and chemistry are equivalent, the coating exhibiting
the highest permeability will typically fail first.
 A permeability of 10-6 perm inches is typically acceptable.
 Chemical resistance
 Resistant to acidic immersion
 Resistant to bacterial organisms

35. 35
Qualified Applicators
 Utilize applicators experienced with specified manufacturers
products
 Request 3+ years of experience with 5 or more projects
completed
 Other endorsements such as SSPC QP or ICATS, NACE pre-
qualify experience and knowledge but not necessarily with
your specified products
 Should have a staff person certified to a coatings inspection
program such as NACE CIP, SSPC MCI, FROSIO, ICORR.
 Certified for confined space, handling hazardous chemicals,
PPE, low OSHA EMR

36. 36
QA/QC Inspection
 Shift from product based to performance based specifications
 “What you want it to accomplish not how you want it built”
 All specifications need standardized tests to describe how a
product may be qualified to a approved material
 ASTM, NACE, ICRI, ACI etc.
 QA/QC logs and inspection hold points
 Sole source “turnkey supply/apply”
 Regular inspections
Surface decontamination Surface cleanliness Ambient environmentals
Surface profile/roughness Material log Wet film thickness
Dry film thickness Holiday Test

37. 37
? QUESTIONS ?