Transcript Corrosion Damage and prevention

HOW TO LIGHT UP 8 EXTRA BULBS/HOUSEHOLD IN TRINIDAD?
CORROSION DAMAGE AND PREVENTION
Raj Nath Mehrotra
Why care about conserving energy?
Energy and Corrosion?
Types of Corrosion
Ways of preventing Corrosion
What this means for Trinidad?
Conclusions and Recommendations
Questions
AGENDA
Who am I?
Who am I?
30 years of academic, research and industrial sector experience. Greatest
industry experience was with the leading energy manufacturer of India –
NTPC Ltd. (makes over 30% of India’s energy needs)
Physical Metallurgist, Corrosion specialist and failure analyst for the
Energy sector
Education:
• MBA – The University of Delhi, India
• M. Tech & B. Tech - Indian Institute of Technology – Kanpur, India
Personal: Friend to many, Confidante to a few, Husband to one, Father to
one, Leader to more, Employee to one, Inspiration to some, Judge of none.
Why care about conserving energy?
Energy and Corrosion?
Types of Corrosion and Prevention Methods
Ways of preventing Corrosion
What this means for Trinidad?
Conclusions and Recommendations
Questions
AGENDA
Who am I?
Why care about conserving energy?
20.5% CAGR
Per capital Energy use in Trinidad & Tobago
Why care about conserving energy?
Energy and Corrosion?
Types of Corrosion and Prevention Methods
Ways of preventing Corrosion
What this means for Trinidad?
Conclusions and Recommendations
Questions
AGENDA
Who am I?
Energy & Corrosion?
Example of a
Corroding Pipe
Corrosion is the degeneration of
materials by chemical reactions.
Examples: Rusting of power plants,
automobiles, buildings and bridges,
Fogging of silverware, Patina formation
on copper.
Regardless, all affected sectors require energy
directly or indirectly
Direct Cost: Material, Maintenance, Overdesign, use of Costly material
Indirect Cost: Plant shut-down, loss of
production, contaminations of products, loss
of products (leakage etc.), liability in accidents
(1) http://www.corrosion-doctors.org/Principles/Cost.htm
Sector wise CprrCost
Cost of Corrosion in USA
Sector Breakup
Corrosion costs approx. 3 -3.5% of GDP of
countries (1) across most sectors. Utility sector
is most hit.
Significance of Corrosion: Utllities
San Bruno, CA, USA
Sep 2010 Gas Pipeline Explosion
9 Dead
Cause: Pipeline Corrosion
Significance of Corrosion: Infrastructure Impact
Charlotte, NC, USA
May 2000 Lowe’s Motor Speedway Bridge Collapse
114 injured
Cause: Structural Corrosion
Corrosion Process – The Concept
Corrosion occurs because of the natural tendency for most metals to return to their natural state;
e.g., iron in the presence of moist air will revert to its natural state, iron oxide.
Corrosion requires 4 components in an electrochemical corrosion cell: 1) An anode; 2) A cathode; 3)
A conducting environment for ionic movement (electrolyte); 4) An electrical connection between
the anode and cathode for the flow of electron current.
If any of the above components is missing or disabled, the electrochemical corrosion process will be
stopped.
Eg: Corrosion of Zinc by an acid solutionZinc
Acid solution
H+
e-
flow of
Zn
in the metal
2e-
Two reactions are necessary:
-- oxidation reaction:
Oxidation reaction
Zn2+
H+
H+
+
H +
H
H+
H2(gas)
H+
reduction reaction
-- reduction reaction:
2H++2e-®H2 (gas)
Why care about conserving energy?
Energy and Corrosion?
Types of Corrosion
Ways of preventing Corrosion
What this means for Trinidad?
Conclusions and Recommendations
Questions
AGENDA
Who am I?
Types of Corrosion
Uniform
Corrosion
Erosion
Control
Stress
Corrosion
Galvanic
Crevice
Corrosion
Selective
Leaching
Pitting
Intergranular
1. Uniform Corrosion
Formerly a ship
2. Galvanic Corrosion
 Dissimilar metals are physically joined in the
presence of an electrolyte.
 The more anodic metal corrodes.
Bilge pump - Magnesium shell cast around a
steel core.
Galvanic Series (Mg – Cu – Ni – Ag – Au – Pt)
3. Stress Corrosion
Fall of Silver Bridge 1967
A structure that has SCC sensitivity, if subjected to stresses and then
exposed to a corrosive environment, may initiate cracks and crack growth
well below the yield strength of the metal.
Consequently, no corrosion products are visible, making it difficult to
detect or prevent; fine cracks can penetrate deeply into the part.
4. Crevice Corrosion
Narrow and confined spaces
5. Pitting
Pitting is a localized form of corrosive
attack. Pitting corrosion is typified by the
formation of holes or pits on the metal
surface. Pitting can cause failure, yet the
total corrosion, as measured by weight loss,
may be minimal.
Boiler tube
304 stainless
steel / acid
chloride
solution
5th Century sword
6. Intergranular
Corrosion along grain boundaries,
often where precipitate particles form.
7. Erosion Corrosion
Brass water pump
Promoted by
- High flow
- Turbulent conditions
- Particulates in fluid
Combined chemical attack and mechanical wear (e.g.,
pipe elbows).
8. Selective Leaching
Preferred corrosion of one element/constituent
[e.g., Zn from brass (Cu-Zn)]. Dezincification.
Why care about conserving energy?
Energy and Corrosion?
Types of Corrosion
Ways of preventing Corrosion
What this means for Trinidad?
Conclusions and Recommendations
Questions
AGENDA
Who am I?
Corrosion Prevention
Use metals that passivate, form a thin, adhering oxide
layer that slows corrosion.

Metal oxide
Metal (examples: Al,
stainless steel)

Use metals that are relatively unreactive in the corrosion environment.

Use inhibitors (substances added to solution that decrease reactivity); slow oxidation/reduction
reactions by removing reactants like O2 gas by reacting it w/an inhibitor).

Slow oxidation reaction by attaching species to the surface. Apply physical barriers: films and
coatings, paint

Reduce T (slows kinetics of oxidation and reduction)

Cathodic (or sacrificial) protection; attach a more anodic material to the one to be protected.
Galvanized Steel
Zn2+
zinc
2e- 2esteel
zinc
e.g., zinc-coated nail
22
Anodic Protection (1)
Uses:
• Storage & handling of
H2SO4
Transpassive
Noble
• Various other misc. uses
Potential, E
•H2SO4 cooling heat
exchangers
Passive
- Ep
Active
Active
Log i
icrit
Anodic Protection (2)
Anodic protection is used in
metals that behaves passively
after certain anodic potential is
applied as shown in figure below:
V
Materials which have shown active
passive behavior:
Solution
Metal
Sulfuric acid
Steels
Phosphoric acid
S. Steels
Nitric acid
Nickel
Nitric Solution
Nickel alloys
Aqueous Ammonia Chromium
Reference electrode
Working electrode
Auxiliary electrode
Apparatus used for anodic polarization studies
Sacrificial Anode
This field is located in Viosca Knoll, block 786, southeast of New Orleans. It lies in water depths of
approximately 1754 feet (535 meters). Petronius is the largest free-standing structure in the world. Texaco's
choice was Galvotec-CW-III Aluminum Sacrificial Anodes for their Petronius cathodic protection
system. http://www.galvotec.com/img/texaco.jpg
Barrier Protection
Here the metal is protected from atmosphere by creating barrier (coatings) that resist
penetration. These are three types:
•
Inorganic Coatings
• Ceramic
• Phosphate
• Anodic Oxides
•
Organic Coatings
•
Inhibitors
Pipeline Protection
Smart & Flexible Pigs
Threat Monitors
Pipeline Protection
Exterior Coating
Exterior Inspections
Interior Coating
Why care about conserving energy?
Energy and Corrosion?
Types of Corrosion and Prevention Methods
Ways of preventing Corrosion
What this means for Trinidad?
Conclusions and Recommendations
Questions
AGENDA
Who am I?
Corrosion is & will continue being chief problem hurting Trindad’s growth
Energy equivalent to EIGHT 150W bulbs
per household running 24 hours (1)
Est. conservatively
3% of GDP (2)
Proximity to Sea
Dependence on Natural Gas
==
==
Wet Corrosion
Dry/Gaseous Corrosion
(High Temperature Corrosion)
(1) Assumes that only 25% of the cost of losses due to corrosion can be recovered. (2) Actual might be higher, esp. closer to 5% of GDP for Trinidad
Why care about conserving energy?
Energy and Corrosion?
Types of Corrosion and Prevention Methods
Ways of preventing Corrosion
What this means for Trinidad?
Conclusions and Recommendations
Questions
AGENDA
Who am I?
Conclusion & Recommendations
• Conclusion: Corrosion is a natural degenerative process affecting metals. It would continue
to have paramount effect on any economy, more so on Trinidad & Tobago’s economy as it
tries to grow.
•Recommendations:
• Educate & adopt Best practices for:
• Students
• Partners
• Industry
•
Research & Collaborate:
• Setup joint corrosion research lab
• Gather greater government attention and resources
•
Partner with:
• Leading industries
• Top worldwide universities
Why care about conserving energy?
Energy and Corrosion?
Types of Corrosion and Prevention Methods
Ways of preventing Corrosion
What this means for Trinidad?
Conclusions and Recommendations
Questions
AGENDA
Who am I?
Questions
Email: [email protected]
Appendix
US Energy Mix
Est. Energy Recoverable from Corrosion – Details
Metric
Cost ($ or otherwise)
GDP (1)
$28.096 B
Cost of Corrosion
$842.88 M
Cost which can be recovered
$210.72M
Converting this costs in INR Terms
Equivalent energy equipment that
this cost saving can buy
Power produced by this energy
equipment
INR 9482.4 M
474.12 MW
9103.10 MwH
No of households in Trinidad (2)
328000
Energy / household
Number of high-energy bulbs
(150W) that this corresponds to
27.75 kwH
(1)
(2)
8
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http://eprints.lse.ac.uk/29938/1/Home_improvement_grants_in_Trinidad_and_England(LSERO).pdf
Assumptions
Conservative estimate 3% of GDP
25% of total costs lost to corrosion.
Ref: NACE International.
Approx. conversion rate 1 USD = 45 INR
Cost of energy installation: Est. INR
20M / MW (NTPC estimates)