DisclaimerDisclaimer
The material presented in this presentation has been
prepared for the general information of the reader and
should not be used or relied on for specific
applications without first securing competent advice.
The Nickel Institute, its members, staff and
consultants do not represent or warrant its suitability
for any general or specific use and assume no liability
or responsibility of any kind in connection with the
information herein.
Water Chemistry Effects
Corrosion
• Dissolved Oxygen
• Chlorides
• pH
• Hardness
• Temperature
Scale
• Dissolved Solids
• Calcium Ions
• pH
• Temperature
Corrosion Of Carbon Steel In Water
0
10
20
30
0 5 10 15
22 ºC (72 ºF)
40 ºC (104 ºF)
Co
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ate
, m
py
Co
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, m
m/y
Corrosion Of Carbon Steel Effect Of Velocity In Seawater
0
25
50
0 5 10 15 20 25
~ 22ºC (72 ºF)
Co
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ate
, m
py
Co
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, m
m/y
High-velocity Seawater> 37 m/s (120 fps )
Corrosion Rate
Alloy Type mm/y mpy
625/C-276 Ni-Cr-Mo <0.03 <1
400/K-500 Ni-Cu < 0.03 <1
T-304/T-316 SS < 0.03 <1
C Steel Fe > 7.6 >300
Bacteria Effects - MIC(Microbiologically Influenced Corrosion)
Species Oxygen Metals Corrosive
Desulfovibrio No Fe, Al, Cu Sulphide
Thiobacillus Yes Fe, Cu Sulphuric Acid
Gallionella Yes Fe Fe++ to Fe+++
Mn++ to Mn+++
Prevention Of MIC
• Keep The System Clean
• Keep Water Flow > 2 m/s (6 fps)
• Use Bactericide:
– Chlorine
– Chlorine Dioxide
– Hypochlorite
– Ozone
– Non-oxidizing
Prevention Of MIC
• Remove Heat Tints After Welding
• Drain and Dry Equipment After Hydrotesting
• Use Continuous Cleaning
• Use High Pressure Hydrolancing
• Use Stainless Steel Scrapers
(Hard to Remove or Heavy Deposits)
• Use Alloy Resistant to MIC
Types of Waters
Potable Water
10-250 ppm Cl–Type 304 < 200 ppm Chlorides
Type 316 < 1000 ppm Chlorides
River Water
<250 ppm Cl–Risk of MIC if water is not treated.
Use type 316 or higher Mo grades:
2205, 904L, 2507, 6%Mo
Well Water
4-250 ppm Cl–
Risk of MIC if water is not treated.
Use type 316 or higher Mo grades.
Brackish Water >1,000
Seawater 18,000 ppm Cl–Use higher Cr-Mo grades.
Consider PRE >40 for seawater.
Marine Corrosion of C SteelRelative Corrosion Rates* – Vary with Sea Conditions
Atmospheric
Splash
Tidal
Submerged
Subsoil0.13 mm/y (5 mpy )
0.64 mm/y (25 mpy )
*Protected Harbor
Types Of Severe Crevices
Stationary O Rings
Flange Face Under Gasket
Non-Metallic Connector
Tube-to-Tubesheet Joint
Nickel Alloys PRE versusCrevice Corrosion in Seawater
PRE = % Cr + (3.3 x %Mo)
0
20
40
60
0 20 40 60 80
Ambient Temperature
Max. Depth of Attack, mm (mils)
0.5 (20) 1.0 (40) 1.5 (60) 2.0 (80)
Corrosion Of 90 Cu-10 NiIn Seawater
0
0.2
0.4
0.6
1 3 5 7 14
Time, Years
<0.3 m/s (1 fps) Tidal 0.9 m/s (3 fps)
Co
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Co
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Summary
• Reviewed Problems with Waters
• Good Corrosion Data Are Available
• Successful Service Is Possible by
Proper Selection of Alloys