corrosion damage and prevention raj nath mehrotra how to light up 8 extra bulbs/household in...
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CORROSION DAMAGE AND PREVENTION
Raj Nath Mehrotra
HOW TO LIGHT UP 8 EXTRA BULBS/HOUSEHOLD IN TRINIDAD?
AGEN
DAWho am I?
Why care about conserving energy?
Energy and Corrosion?
Types of Corrosion
Ways of preventing Corrosion
What this means for Trinidad?
Conclusions and Recommendations
Questions
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.
AGEN
DAWho am I?
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
Why care about conserving energy?
20.5% CAGR
Per capital Energy use in Trinidad & Tobago
AGEN
DAWho am I?
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
Energy & Corrosion?
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.
Corrosion costs approx. 3 -3.5% of GDP of countries (1) across most sectors. Utility sector
is most hit.
Regardless, all affected sectors require energy directly or indirectly
Direct Cost: Material, Maintenance, Over-design, 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
Ex
am
ple
of a
C
orro
din
g P
ipe
Co
st o
f Co
rros
ion
in U
SA
S
ec
tor B
rea
ku
p
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 solution-
Zinc
Oxidation reactionZn Zn2+
2e-
Acid solution
reduction reaction
H+H+
H2(gas)
H+
H+
H+
H+
H+
flow of e-
in the metal
Two reactions are necessary: -- oxidation reaction:
-- reduction reaction:
AGEN
DAWho am I?
Why care about conserving energy?
Energy and Corrosion?
Types of Corrosion
Ways of preventing Corrosion
What this means for Trinidad?
Conclusions and Recommendations
Questions
Corrosion
Uniform Corrosion
Galvanic
Crevice
Pitting
Intergranular
Selective Leaching
Erosion Control
Types of Corrosion
Stress Corrosion
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
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.
Fall of Silver Bridge 1967
5. Pitting
Boiler tube
304 stainless steel / acid chloride solution
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.
5th Century sword
6. Intergranular
Corrosion along grain boundaries,often where precipitate particles form.
7. Erosion Corrosion
Brass water pump
Combined chemical attack and mechanical wear (e.g., pipe elbows).
Promoted by- High flow- Turbulent conditions- Particulates in fluid
8. Selective Leaching
Preferred corrosion of one element/constituent [e.g., Zn from brass (Cu-Zn)]. Dezincification.
AGEN
DAWho am I?
Why care about conserving energy?
Energy and Corrosion?
Types of Corrosion
Ways of preventing Corrosion
What this means for Trinidad?
Conclusions and Recommendations
Questions
Corrosion Prevention
22
Use metals that passivate, form a thin, adhering oxide layer that slows corrosion.
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.
steel
zinczincZn2+
2e- 2e-
e.g., zinc-coated nail
Galvanized Steel
Metal (examples: Al, stainless steel)
Metal oxide
Transpassive
Active
Passive
Noble
Active
Pote
ntial
, E
Log i icrit
- Ep
Uses:
• Storage & handling of H2SO4
• H2SO4 cooling heat exchangers
• Various other misc. uses
Anodic Protection (1)
V
Working electrode
Reference electrode
Auxiliary electrode
Materials which have shown active passive behavior:
Solution Metal
Sulfuric acid SteelsPhosphoric acid S. SteelsNitric acid NickelNitric Solution Nickel alloysAqueous Ammonia Chromium
Apparatus used for anodic polarization studies
Anodic protection is used in metals that behaves passively after certain anodic potential is applied as shown in figure below:
Anodic Protection (2)
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
Sacrificial Anode
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
Barrier Protection
Pipeline Protection
Exterior Inspections Exterior Coating
Interior Coating
Smart & Flexible PigsThreat Monitors
Pipeline Protection
AGEN
DAWho am I?
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
Corrosion is & will continue being chief problem hurting Trindad’s growth
==
==
Proximity to Sea
Dependence on Natural Gas
Wet Corrosion
Dry/Gaseous Corrosion(High Temperature Corrosion)
Est. conservatively 3% of GDP (2)
Energy equivalent to EIGHT 150W bulbs per household running 24 hours (1)
(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
AGEN
DAWho am I?
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
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
AGEN
DAWho am I?
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
Appendix
US Energy Mix
Est. Energy Recoverable from Corrosion – Details
Metric Cost ($ or otherwise) Assumptions
GDP (1) $28.096 B
Cost of Corrosion $842.88 M Conservative estimate 3% of GDP
Cost which can be recovered $210.72M25% of total costs lost to corrosion. Ref:
NACE International.
Converting this costs in INR Terms INR 9482.4 M Approx. conversion rate 1 USD = 45 INREquivalent energy equipment that this cost saving can buy 474.12 MW
Cost of energy installation: Est. INR 20M / MW (NTPC estimates)
Power produced by this energy equipment 9103.10 MwH
No of households in Trinidad (2) 328000
Energy / household 27.75 kwHNumber of high-energy bulbs (150W) that this corresponds to 8
(1) http://www.blx.com/paginasInfoLatam.aspx?PAG_ID=38&CAT_ID=5(2) http://eprints.lse.ac.uk/29938/1/Home_improvement_grants_in_Trinidad_and_England(LSERO).pdf