Transcript Nickel Institute Corrosion by Process Waters

Nickel Institute
Corrosion by Process Waters
R. W. Ross
Consultant
Nickel Institute
Summary
 Scaling and Corrosion
 Effects of Velocity
 Biological Effects
 Chlorides
 Rouging of SS
Water Chemistry Effects
Corrosion
Scale
• Dissolved Oxygen
• Chlorides
• pH
• Dissolved Solids
• Calcium Ions
• pH
• Hardness
• Temperature
• Temperature
Water Chemistry Effects
Corrosion Of Carbon Steel
In Water
Corrosion Rate, mm/y
Corrosion Rate, mpy
30
72 ºF (22 ºC)
20
104 ºF (40 ºC)
10
0
0
5
10
15
Corrosion Of Carbon Steel
In Low-velocity Water
Corrosion Of Carbon Steel
Effect Of Velocity In Seawater
Corrosion Rate, mm/y
Corrosion Rate, mpy
~ 72 ºF (22ºC )
50
25
0
0
5
10
15
20
25
Erosion-corrosion - Inlet
Erosion-corrosion
Flow
Erosion-corrosion
Tube Blockage
Flow
High-velocity Seawater
>120 fps (36.6 m/s)
Alloy
Corrosion Rate,
mpy
mm/y
625/C-276
<1
< 0.03
400/K-500
<1
< 0.03
718/725/925
<1
< 0.03
T-304/T-316
<1
< 0.03
C Steel
>300
> 7.62
Biological Effects
Macrofouling
• Mussels
• Clams
• Barnacles
• Plant Life
Biological Effects
Macrofouling
Bacteria Effects - MIC
(Microbiologically Induced Corrosion)
Species
Oxygen Metals
Corrosive
Desulfovibrio
No
Fe, Al, Cu Sulfide
Thiobacillus
Yes
Fe, Cu
Sulfuric Acid
Gallionella
Yes
Fe
Fe++ to Fe+++
Mn++ to Mn+++
Bacteria Effects - MIC
Type 304 SS
water tank
8 months of
service
Guam
Bacteria Effects - MIC
(Type 304 SS, Before Cleaning)
Bacteria Effects - MIC
(After Cleaning)
0.15 in. (3.8) mm)
Max. Attack
Bacteria Effects - MIC
(After Cleaning - No Attack)
Prevention Of MIC
• Keep The System Clean
• Keep Water Flow > 6 fps (2 m/s)
• Use Bactericide:
– Chlorine
– Chlorine Dioxide
– Hypochlorite
– Ozone
– Non-oxidizing
Prevention Of MIC
• Use Continuous Cleaning
• Use High Pressure Hydrolancing
• Use Stainless Steel Scrapers
(Hard to Remove or Heavy Deposits)
• Use Alloy Resistant to MIC
Prevention Of MIC - 6% Mo ALLOY
Effects of Chlorides
Crevice Corrosion Type 303
Stainless Steels
Localized Corrosion Resistance
Alloy
PRE
304
18
316
25
317
30
2205
34
2505
37
2507/Alloy 100
41
6% Mo Alloys
40 - 45
Nickel Alloys
Localized Corrosion Resistance
Alloy
PRE
316
25
6% Mo
40 – 45
625
52
22/622
65
C-276
69
2000
76
686
76
59
76
Stainless Steels for Use in Waters
Potable water
Type 304 < 200 ppm chlorides
Type 316 < 1000 ppm chlorides
River water
Risk of MIC if water is not treated
Use type 316 or higher Mo grades:
2205 904L
2507 6Mo
Well water
Risk of MIC if water is not treated
Use type 316 or higher Mo grades
Do not confuse Chloride Cl- and Chlorine Cl2
Maximum Concentration (ppm) in
Water to Avoid Crevice Corrosion
Chloride Cl-
Chlorine Cl2
304
200
2
316
1000
4
Shock dosing, such as 25 ppm chlorine for 24 hours, is common practice
and has not been found to cause problems.
Stress Corrosion Cracking (SCC)
Chloride SCC
Duplex vs T-316 Stainless Steel
Temperature, F (C)
No cracking below lines
600
Type 316
(315)
22 Cr Duplex
18 Cr Duplex
400
(204)
200
(93)
0
1
10
100
Chlorides, ppm
1000
10000
Effect of Nickel Content on
Stress Corrosion Cracking
Boiling 45% MgCl2
100
% Nickel
80
No SCC
60
Ni Alloys
40
20
SCC
Duplex SS 0
1
10
Time to Failure, hrs
6% Mo SS
100
1000
HIGH CHLORIDE
WATERS
HIGH CHLORIDE
WATERS
How does external environment
affect process equipment?
Marine Corrosion of C Steel
Relative Corrosion Rates* – Vary with Sea Conditions
Atmospheric
Splash
*Protected Harbor
25 mpy (0.64 mm/y)
Tidal
Submerged
5 mpy (0.13 mm/y)
Subsoil
Uniform Corrosion
Effect of Chromium
Weight Loss, mg. / sq. dm.
100
250M Lot
44 Months
75
50
25
0
0
2
4
6
8
10
% Chromium
12
14
16
18
Alloy C in Marine Atmosphere
56 Years of Exposure
Type 304 Fastener In Marine Tide
After 6 Months
Type 304 Fastener Above Marine Tide
After 6 Months
Crevice Corrosion
Crevice Corrosion of Alloy 825
Heat Exchanger Tubing – Shell Side
85° F, Aerated Seawater
Crevice Corrosion of Alloy 625
Waterbox With Deaerated, Treated Seawater
165° F
235° F
165-235° F
Crevice Corrosion of Alloy 825
Heat Exchanger Tubesheet – Water Side
225° F, Deaerated, Treated Seawater
Tube to Tubesheet Joint
Types Of Severe Crevices
Stationary O Rings
Flange Face Under Gasket
Non-Metallic Connector
Tube to Tubesheet Joint
Corrosion of 90-10 Cu-Ni
in Seawater
Corrosion Rate, mpy
0.6
0.5
0.4
0.3
<1 fps
Tidal
3 fps
0.2
0.1
0
1
3
5
Time, Years
7
14
Marine Fouling
18 Months in Quiet Seawater
C Steel
Aluminum
Fouling of Titanium Waterbox
3 mo. Exposure
Fouling of Titanium Waterbox
6 mo. Exposure
Effect of Chlorination
<1 fps Seawater Flow
Max. Attack, mils
90-10 Cu-Ni
T-304
30
20
10
0
0
1
4
Total Oxidant, ppm
90-10 Cu-Ni Alloy
Fouling - Quiet Seawater
3 Mo
9 Mo
18 Mo
3 Yr
4 Yr
5 Yr
90-10 Cu-Ni Intake Piping
Desalination Plants
90-10 Cu-Ni Alloy
Seawater Piping Systems
90-10 Cu-Ni Alloy
Seawater Heat Exchangers
Pumps - Impellers
Rouging of Stainless
Steels
High Purity Water
Water For Injection (WFI)
Why Use Stainless Steels (316L)
for Pharma & Biotech?
Good corrosion resistance and excellent batch
to batch cleanability
Good structural properties for process
equipment
Easily formed, fabricated and welded
What about Rouging?
What is Rouging?
Rouging is a general term used to
describe several species of
predominately iron oxide deposits on
the wall of piping and vessels in high
purity water systems.
Rouging is not New!
Rouging is not unique to the
pharmaceutical and biotech
industries. Was recognized over 40
years ago with rouging of SS vessels
at Savannah River.
Where is Rouge often Found
Water systems, usually high purity water and
clean-steam systems
Distillation and clean-steam generating
equipment
Rouge found on wall of vessels, piping and
polymer gaskets (Teflon®) downstream of
where originated
Is Rouge Harmful?
No reports or evidence that rouging is
precursor to a SS corrosion failure.
We are not in a position to comment on
whether rouge is harmful to the product
being produced. Common practice is to
remove rouge.
Rouging
Generally a loose powdery deposit, but can be
tightly adherent
Hydrated or partially hydrated ferric oxide (Fe2O3)
or ferroso-ferric oxide (Fe3O4)
Usually occurs in high purity (0.5-1.0 µS/cm),
high temperature water (60 – 100 C)
Rouging
Reddish brown rust color, but can range from
orange to blue-black.
Origin is uncertain but generally thought to be
ions or colloids that are formed at one
location and transported in the solution to
another where they are precipitated.
Removed by acid cleaning in nitric,
phosphoric, citric, or oxalic acid.
Rouging - Types
Type 1 – Corrosion of Steel, Deposits Downstream
Pumps prime suspects – cavitation or erosion when velocity
over ~ 100fps and higher temperatures
Delta ferrite in cast impellers may contribute by eroding easier
and higher iron content
Type 2 – Corrosion Product of Stainless Steel
Type 3 – Corrosion Product of Stainless Steel in Steam
Systems > 100 C
Rouging of Stainless Steels
Rouging over 4 years
inside electropolished
Type 316L - column still
used to produce ultrapure water for
pharmaceutical use
Rouging of Stainless Steels
De-rouging & Passivation
3 Steps
Cleaning – detergent wash followed by
thorough water rinse
De-rouging chemical treatment
Passivation followed by thorough water rinse
Electrochemical Coloring
Proprietary electrochemical processes –
invented in 1972 by Inco, further developed
in Japan
• Interference between the
light beams refracted from
the substrate and the
surface of the oxide film
creates color
• Appearance and color vary
with immersion time and
surface finish
Incident
light
Color
Oxide
Experience Music Project
Summary
 Discussed Scaling and Corrosion
 Described Effects of Velocity
 Reviewed Biological Effects
 Discussed Chlorides
 Summarized Rouging of SS
Questions ?