Conquer Corrosion with Materials Selection | 2017 Offshore Europe Cinema Seminar
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Transcript of Conquer Corrosion with Materials Selection | 2017 Offshore Europe Cinema Seminar
Conquer corrosion with materials selection Offshore Europe 2017 cinema seminar
Clara Moyano, ImechE IEng Beng
Innovation Engineer
• As an innovation engineer and expert metallurgist working across the globe, Clara deals with all sorts of challenges. She is often involved in discussions on materials selection, including advice to oil and gas producers working on new platforms around the world.
• Clara specialises in areas such as tackling corrosion, and materials selection for design specifications. She also advises on quality certifications and regulations around the manufacturing of metals.
Speaker biography
Objectives
• Current market trends & material challenges
• Corrosion mechanisms in Oil & Gas
• Best practices to fight corrosion
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• Choice from 300,000 alloys
• Operations/technology shifts
• Design/performance expectations evolving
• Tight regulations
• Cost increases
• Lack/loss experience
• Unknown territories and failures
• Onshore shale & offshore/deep water
Onshore Shale &
Offshore / deep
water
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Corrosion Challenges
Choice from
300,000 alloys
Operations /
Technology
shifts
Tight
regulations Cost increases
Design /
performance
expectations
evolving
Lack / loss
experience
Unknown
territories and
failures
Cost of Corrosion
Source: NACE
https://www.nace.org/uploadedFiles/Publications/ccsupp.pdf5
• One report relates $276 billion per year
Corrosion in Figures
Source: NACE
https://www.nace.org/Corrosion-Central/Corrosion-101/Testing-for-Localized-Corrosion/6
• Summary of 363 corrosion failures within a major chemical processing company
• Pitting is the second biggest concern for failure
• Pictures of offshore corrosion
Examples of Corrosion
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What is corrosion?
Degradation of the materials’ properties due to interactions with their environments• Inevitable to some extent
• Primarily associated with metallic materials,all material types susceptible
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• Extreme operating temperatures
• Very corrosive media (H2S, C02, Chlorides, Organic Compounds, etc)
• Severe ambient conditions (Hot and humid climates, seawater nearby, etc)
• Improper design
• Low quality equipment & material
• Microbial action
Causes Leading to Corrosion?
Extreme Operating
TemperaturesVery Corrosive Media (H2S, C02,
Chlorides, Organic Compounds, etc)Severe Ambient Conditions
(Hot and Humid Climates,
Seawater Nearby, etc.)
Improper design
Low Quality Equipment
& Material
Microbial Action
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• Pitting Corrosion
• Crevice Corrosion
• Galvanic Corrosion
• Stress Corrosion (Chloride & Sulphide induced)
• Other
Common Types of Corrosion
Pitting Corrosion
Crevice Corrosion
Galvanic Corrosion
Stress CorrosionChloride & Sulphide Induced
Other
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Pitting Corrosion
• Corrosive attack causing rapid penetration of the base material thickness
• One of the most damaging and common causes of failure
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• Large surface areas will become cathodic, pits will become anodic and will corrode.
• This is similar to a small sacrificial anode trying to protect a structure.
Pitting Corrosion Mechanism
e-e- Low pH
High Cl
Stainless Steel
Aqueous Chloride
Solution Cl-
O2
(dissolved)
Passive
Surface
Oxide
++++++++++++++++
- - - -Anode - Active
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Crevice Corrosion
Localised surface attack in the gap or crevice betweentwo joining surfaces
• Can be formed between two metals or a metal andnon-metallic material
• Tubing clamps are a prime example
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• The two metals must be widely separated on the galvanic series
• They must be in electrical contact
• Their surfaces must be bridged by an electrically conducting fluid
Galvanic Corrosion: An Electrochemical Process
The two metals must
be widely separated
on the galvanic series
They must be in
electrical contact
Their surfaces must
be bridged by an
electrically
conducting fluid
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• The best practice is using the same material when different components are coupled together.
Galvanic series: mixing dissimilar materials
A properly designed cathodic protection system can protect
offshore structures from the onset of galvanic corrosion15
Stress Corrosion Cracking (SCC)Under the combined effects of stress and certain corrosive environments
materials can be subject to this very rapid and severe form of corrosion
The stresses must be tensile and can result from loads applied in service,
or stresses set up by the type of assembly
Corrosive media
Tensile Tensile
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Stress Corrosion Cracking (SCC)• Most damaging environment is a solution of chlorides in water, such
as sea water, particularly at elevated temperatures
• As a consequence, stainless steels are limited in their application
for holding hot waters (above about 50°C) containing even trace
amounts of chlorides (more than a few parts per million).
Series 300 stainless
steels are especially
vulnerable to
chloride-induced SCC
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Other Types of Corrosion
General
MIC
Intergranular
Anaerobic Bacteria
H2S GAS
Thiobacillus
Bacteria creates
Sulphuric Acid
MIC Intergranular
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• Zone 1 – Topsides
• Zone 2 – Splash Zone
• Zone 3 – Tidal
• Zone 4 - Seawater
Corrosive Challenges in an Offshore Rig
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• Corrosion rate trend +/- >1mm a year
Corrosive Challenges in an Offshore Rig
• Selecting materials and controlling corrosion for a given application is one of the main design steps towards a safe and cost efficient system, yet a commonly overlooked stage.
• Benefits
• Asset safety and integrity
• Optimum performance with minimal maintenance and shutdown time
• Longer life expectancy
• COST SAVINGS
Implications of Corrosion Control
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Benchmarking Alloys
• Factors Limiting Pitting in Stainless Steel
• PREN - Pitting Resistance Equivalent Number
• Developed to reflect and predict the pitting resistance of an alloy.
• Note – there are several variations of the formula for PREN in the nitrogen value.
• The following definition is from NACE MR0175 / ISO 15156-2003, part 3, para 6.3.
• PREN = % Cr + 3.3 x (% Mo + 0.5 x % W) + 16 x % N
• Cr = chromium
• Mo = Molybdenum
• W = Tungsten
• N = Nitrogen
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• Table showing least to most resistant alloys
Corrosion Resistance: Pitting & Crevice
Most
Resistant
Least
Resistant
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• Table showing elevated temperature rating factors
Operating Pressure & Temperature
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• Diagram showing corrosion resistance vs strength
Strength vs Corrosion Resistance
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• Diagram showing average price vs. availability
Cost vs. Availability
26
• Operating conditions, including temperature, pressure and media contained
• Environment
• Legislation and internal regulations
• Cost
• Availability
• Lead time
• Expected life time of the equipment
• Safety
Materials Selection Criteria
KNOW YOUR PROCESS AND CONTROL IT
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According to industry standards such as NORSOK M-001, Materials Selection standard:
“At galvanic connections between dissimilar materials without isolation/distance spool, it can be assumed that the local corrosion rate between the interface is approximately 3 times higher than the average corrosion rate’’.
Does Size Matter?
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Suparcase™ Principle
• Good Tube Grip = Harder Rear Ferrule
• Suparcase™ process perfected by Parker gives the Differential Hardness & Improved Corrosion Resistance
• Some competitor hardening process corrode i.e. Nitride Hardening
• 30+ years in service
Over 100 million
pieces in service
without failure due to
corrosion or cracking
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• 40% cheaper
• Not counting downtime or safety
Tubing installation life cycle costs:example
** Figures exclude material cost increase
40%
cheaper
Not counting
downtime or
safety
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Summary
1. Know your process
2. Correct material selection
3. Corrosion control strategy
4. Avoid complexity
5. Use high quality equipment
6. Think long term
7. Question low cost supplies
8. Do not intermix materials if alternatives are available
9. Use NACE & NORSOK equipment as required
10. Do not be afraid to ask…It’s all about control and cost effectiveness
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Contact for further information
Clara Moyano, ImechE IEng Beng
Innovation Engineer
T: +44 (0)1271 313151E: [email protected]
Questions and discussion
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