Post on 06-Feb-2018
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CORROSION AND CORROSION PROTECTION
A short introduction course
by Roy Johnsen, Professor NTNU
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WHO IS ROY?
Siv.ing. NTH 1979
Dr.ing. NTH 1984
Scientist SINTEF 1981-1985
Research Manager Statoil 1985-1991
Director CorrOcean 1991-2003
Professor Corrosion and Surface protection IPM/NTNU 2004 ->
Sabatical 2011/2012 Statoil Autumn 2011
Qatar Petroleum Spring 2012
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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GOALS FOR THIS LECTURE
I will try to explain to you: why corrosion can occur
why coupling between different metals can cause severe corrosion (=galvanic corrosion)
how reduce the probability of corrosion to initiate and grow
that stainless steel is not always stain less (rustfri)!
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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Henningsvr- Lofoten October 2009
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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Petronas Twin tower January 2010
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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WEATHER WALL FROM THE EKOFISK FIELD Same material as for Petronas TwinTower
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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Hardangerfjord Bruravik Brimnes July 2010
WHY?
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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E6 Minnesund - Kollomoen
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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COMMUNICATION BOUY
INFORMATION: Instrument buoy on 100 m
water depth
Concrete anchor on the seabed
Metal hook made from AISI 316 to fasten the anchor line
Design life time 10 years
Dilemma:
Shall I use a fiber rope or galvanized wires for
the anchor line?
SEABED
Concrete anchor
Metal hook
SEAWATER
Instrument buoy
Anchoring
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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EXTREEME FAILURE CASES
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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DIFFERENT TYPE OF FAILURES On Statoil operated installations 1997-2007
FATIGUE
31%
CORROSION
31%
WEAR
5%
HYDROGEN EMBRITTLEMENT
FABRICATION
BRITTLE FRACTURE
INSTALLATION 2%
LIQUID METAL EMBRITTLEMENT
CREEP
3%
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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LITTERATURE
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WHAT IS NEEDED TO GET CORROSION STARTED
Metal + Water
CORROSION can occur
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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HOW TO AVOID CORROSION?
Metal +
Water
CORROSION can occur
Remove the water and stop the corrosion
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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-2 86420 141210 16
0
-1.2
-0.4
-0.8
1.6
1.2
0.8
0.4
2.0
-1.6
PASSIVITY
CORROSION
IMMUNITYCORROSION
*A
H2O/H2
O2/H2O
pH
E(V)
POURBAIX DIAGRAM Carbon steel
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
Does not say anything about the corrosion rate
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WATER BASED CORROSION
We need: Water present A metal with Anodic and Cathodic
reactions
Anodic reaction = Cathodic reaction
A: Fe => Fe2+ + 2e-
C: O2 + 2H2O + 4e- => 4OH-
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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TYPES OF CORROSION
Uniform corrosion Galvanic corrosion Localized corrosion
Pitting corrosion Crevice corrosion Stress corrosion cracking
CO2/H2S corrosion Flow induced/erosion corrosion Corrosion fatigue Bacterial corrosion Wear Tribo-corrosion
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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DIFFERENT CORROSION TYPES
Uniform corrosion
Galvanic corrosion
Crevice corrosion
Pitting corrosion
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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Stress Corrosion Cracking
CO2-Corrosion
Erosion corrosion
Hydrogen Induced Stress Cracking
DIFFERENT CORROSION TYPES, cont.
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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GALVANIC SERIES
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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GALVANIC CORROSION
Two different metals in the same electrolyte and in metallic contact.
Corrosion rate depends on: Actual metals
Area ratio between the metals
A
A - noble B un-noble
A
Metall A Metall B
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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GALVANIC CORROSION
ALWAYS VALID: Current from Un-noble metal IA = Current to noble metal IC
iA*AA = iC*AC
ia, ic = current densities (A/m2)
Metal A Un-noble
Metal B Noble
IA IC
I
NOT WANTED: Small un-noble alloy connected to a big noble alloy!
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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USE THE GALVANIC SERIES!
Heat exchanger
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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90/10 CuNi Titanium
Coating
HOW TO AVOID GALVANIC CORROSION? Always cote the noble metal!
If coating failure: iCuNi=iTi*ATi/ACuNi
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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PREFERENTIAL WELD CORROSION
Base metal
Weld metal
Heat affected zone
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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IMPORTANT FACTORS FOR CORROSION
Electrolyte composition
Temperature
Oxygen content
Chloride content
CO2 and/or H2S content
Oxidizing species (e.g. chlorine)
pH
Velocity
Content of solids (e.g. sand)
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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HOW TO REDUCE THE PROBABILITY OF CORROSION?
Select a material that does not corrode in the actual environment (if possible)
Apply a coating
Cathodic protection
Change and/or modify the environment
Change the design
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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MATERIAL SELECTION
NORSOK M-001 and ISO 21457 are valuable guideline documents
REMEMBER:
Quality control during supply/delivery is important NORSOK M-650
Material compability when connecting materials (i.e. galvanic corrosion)
Stainless steel is never stain less (rustfrie) if you exceed critical process parameters
Design parameters shall be followed in operation
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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EXPERIENCE WITH AISI 316 In chloride containing environment
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
PIPE FOR SEAWATER TRANSPORT INSTRUMENT TUBING
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CORROSION PROTECTION through coating
PATER NOSTER - SWEDEN INSTALLATION IN THE NORTH SEA
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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HOT DIP GALVANIZING (varmforsinking)
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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TYPES OF COATING
We normally talk about three types of coating: 1. Metallic coatings
Electrolytic applied Chemical Welding Thermal spraying
2. Ceramic coatings Thermal sprayed Deposited
3. Organic coatings Rubber lining Polymer layers Paints
Thermal spraying
Overlay welding
Painting
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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METALLIC COATINGS
Two classes of metallic coatings 1. The coating is more noble than the substrate
Cathodic coating
2. The coating is less noble Anodic coating
1 2 Nickel Zinc
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CATHODIC PROTECTION IN PRACTICE
Propeller to be protected
Wire to connect anode and object
Anode
Ifea "Materialvalg for instrumenter og ventiler", des. 2011 roy.johnsen@ntnu.no
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SACRIFICIAL ANODES
Aluminum alloys
Zinc alloys
Magnesium alloys (seldom)
Flush mounted
Stand off
Bracelet
Zinc anode after 4 years in use