Assessment1 presentation of corrosion.ppt

Assesment 1

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Assessment 1
Abdulla Al Hosani
Corrosion Engineer

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1. Qualifications & Work Experience
HD Chemical Engineering from Higher Colleges of
Technology,Abu Dhabi Men’s College 1999-2003
Oil Movement Supervisor in Zirku Island, 1997-
1999
Plant Shift Operator, Oil/Gas/Storage of Zirku
Island, 1995-1997
Operations Diploma, Career Development Center
(CDC) ADNOC, 1992-1995

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Fitness for Service FFS of Pipes & Vessels,
Harvard Technology, July 04
Oilfield Production Chemicals & Microbiology,
Champion servo, April 04
2.Courses Attended

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(Oil Plant)
KO Drum
Surge
Sphere
1
st
Stage
Desalter
410
441
427
427
443
2
nd
Stage
Desalter
Hot Oil
Separator
433
3.Process Overview
Chemical
Injection
Monitoring
Point

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(Gas Plant)
401
K.O
Drum
Compressor
Dich. cooler Dich. Drum
K.O Drum
423
423
Feed
Drum
Stabilized
Column
Reflux
Drum
401
mixer
Stabilized
Reboiler
443
K.O Drum
3.Process Overview
Chemical
Injection
Monitoring
Point

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4.1Theory of electrochemical Corrosion
4.2Forms of Corrosion
4.4Corrosion Monitoring
4.3Corrosion Control
4.Corrosion Overview

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4.1 Theory of electrochemical Corrosion
Definition: Deterioration of a material due to reaction with its
environment.
Requirements for a Corrosion Cell:
1. Anode:-areas which give electrons & oxidation reaction occur
2. Cathode:-areas which gain electrons & reduction reaction occur
3. Electrical Path:-areas that transport electrons
4. Electrolyte:-areas that transport ions

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Sea Water
(Electrolyte)
O2 +H2O+4e-4OH
-
Fe
+2
2Fe(OH)
2+ H
2O + ½O
2
4e
-
Anode Cathode
Electrical
Path
Fe(OH)
2
2Fe(OH)
3
4.1 Theory of electrochemical Corrosion

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4.2 Forms of Corrosion
1. Uniform Corrosion:-or General Corrosion which is a uniform thinning
or metal loss of a metal
Before After
2. Galvanic Corrosion:-When two different metals are electrically connected
and placed in a conductive solution, a potential difference will exist. The
Corrosion Rate expedites on the less noble metal while reduces at the more
noble metal
Cathode
Anode

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Galvanic Corrosion Control
4.2 Forms of Corrosion (Galvanic Corrosion)
1.Minimize the use of dissimilar metals
2.Selection of metals that are close together in galvanic series
3.Electric isolation
4.Inhibitors
5.Apply coatings

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4.2 Forms of Corrosion
3. Erosion Corrosion:-accelerated rate of corrosion attack on a metal due to
the relative motion of a corrosive fluid and a metal surface.
Flow
Protective film
Metal
Erosion Corrosion Control
1.Material selection
2.Proper design
3.Coating application
4.The use of CP
5.Filtration
6.Lower flow velocity

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4.2 Forms of Corrosion
4. Crevice Corrosion:-Localized Corrosion associated with stagnant corrosives in
crevices or shielded areas
Under gasket, washers,surface deposits, disbonded coatings,
threads and lap joints
Mechanism
1.Depletion of oxygen
2.Formation of concentration cells
3.Excess production of positive charges in the solution (M
+
)
4.Migration of chloride ions
5. Hydrolysis & formation of highly acidic environment

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4.2 Forms of Corrosion
Crevice Corrosion Control:
1.Use butt welded joints instead of lap joints or fasteners
2.Close crevices in existing lap joints by continues welding
3.For flanges use proper gasket material, proper tightening of bolts and
alignment of flanges, paint flange if possible, proper flange design
4.Use filtration in early stages of the process
5.Use proper draining and flushing facilities for vessels
6.Use Coatings
7.Cathodic Protection

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4.2 Forms of Corrosion
5. Pitting Corrosion:-localized form of corrosion by which cavities are
produced in the material
Mechanism
1.Initiation
A.Damage to protective film
B.Localized damage or poor application of protective coating
C.The presence of non-uniformities in the metal surface
2.Incubation
3.Propagation
Common and one of the most dangerous form of corrosion

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4.2 Forms of Corrosion
Pitting Corrosion Control:-
1.Material selection
2.Protective Coatings
3.Cathodic Protection
4.Inhibitors
5.Operate with sufficient fluid velocity if possible
6.Use proper draining and flushing facilities for vessels
7.Pigging

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4.2 Forms of Corrosion
6. Intergranular Corrosion:-localized form of corrosion at grain boundaries or
the area adjacent to it.
Control :
1.Impurities at grain boundaries
2.Enrichment of one of the alloying elements at grain boundaries
3.Depletion of one of the alloying elements at grain boundaries
Intergranular Corrosion is caused by :
1.Lowering carbon content to less than 0.03% & adding stabilizers
2.Proper welding procedure

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4.2 Forms of Corrosion
7. Selective Leaching:-is the removal of one element from a solid alloy by
corrosion processes
Metal composition & structure
Dezincification of yellow brass
Control
1. material selection
2. Removal of oxidizers
3. coatings

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4.2 Forms of Corrosion
8. Stress Corrosion Cracking:-cracking induced from the combined influence
of tensile stress and specific corrosive environment.
Control
1.Cathodic protection
2.Heat treatment
3.Inhibitors
4.coating
Particular alloy & particular corrosive medium

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4.3 Corrosion Control
1. Design
2. Material Selection
3. Coating
5. Chemicals
4. Cathodic Protection
6. Pigging
7. Dead leg flushing

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4.4 Corrosion Monitoring
1.Corrosion coupons:-specimen of the same material of the equipment
exposed to the actual environment of the equipment.
Demonstrates the corrosiveness of the environment & degradation mechanisms
Test the effectiveness of corrosion inhibitor and corrosion management system
Does not represent the actual corrosion rate
Short or long term
Corrosion rate is presented in MPY or mm/year (1 MPY = 0.0254 mm/yr)

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4.4 Corrosion Monitoring(Corrosion Coupons)
Corrosion Rate Calculation
Corrosion Rate= W / t x a x 
Where,
W Weight loss
t Time of exposure
a Area of exposure
 Metal density

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4.4 Corrosion Monitoring
2.Electric Resistance Probes:-determines metal loss by electric resistance
methods

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4.4 Corrosion Monitoring(ER Probes)
Fast response and used for trending
Type of attack is not known, fault readings as deposit precipitates, small cross
sectional area
Operating principle
R = L / A
Where,
R Electrical resistance of the section
 Electric resistivity of the section
L Length of the measuring section
A Cross sectional area of the section

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4.4 Corrosion Monitoring
Dynamic Corrosion Monitoring ( DCM ):Side stream corrosion monitoring of
the 42”MOL
RDC
To MOL
From MOL
Hydrogen
Probe
ER
Probe
LPR
Probe
Disk
Coupon
Ladder Strip
coupons

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4.4 Corrosion Monitoring
Water & Deposit Analysis :
O
2Content
PH
Microbial
•SRB count
•HAZE test
•APS Reductase Antibody method
Metal ions

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Water & Deposit Analysis :
chloride ions
Dissolved H
2S
4.4 Corrosion Monitoring

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5. Lab Study
35
o
C1 Month stagnant
condition
SRB count 100 b/L to 10,000 b/L
HAZE 2 platonic & 2 sessile SRB
Corrosion Rate8.8 MPY
Results
Lab SRB culturing and effects on corrosion rate

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Results discussion
•Threat of MIC in our system
•Possibility of having highly active SRB in our system in stagnant
waters
•the ability of SRB to spore and re-grow whenever nutrient is
available.
•Importance of Dead leg flushing & biocides

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6. Case Study
6.1Case 1:
A pin hole leak at the 16”Free water knock out drum outlet header to
427 area
Internal Glass flack coating
2.5 years in service
Failure
Flow
Pin hole

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Failure Analyses
Coating failure resulted in severe localized erosion corrosion
Turbulent flow
Bare metal
Protective layer
Protective coating
Not to rely on protective coatings.
Difficult to achieve good surface preparation, apply coating & to test small size pipes.
Proper application of coating
Use cement coating
Observations & Recommendations

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6.2Case 2:
Sea
Water
inlet
Sea
Water
outlet
Lob Oil
inlet
Lob Oil
outlet
Failed
Plugs
Failure
Shoot out of a carbon steel plug from the shell side of a lob oil cooler
Shell side Sea water
Tube sideCompressor lob oil
Exchanger materialStainless Steel
Plug materialCarbon Steel

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Failure Analyses
Galvanic corrosion between SS and carbon steel
Recommendations
Change the plug material to the same material as the exchanger body

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7. Observations &
Recommendations
7.1Enhance Corrosion Awareness
Prepare a glass box containing different
corrosion samples, and install in ZCC building
E-mail Distribution related to Corrosion,
Corrosion Cost & Corrosion Failures
7.2Toolbox meetings
Prepare posters

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