Materials Selection For Systems Handling Water

Technical Seminar SeriesChemical Process Industry

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.

Summary

Scaling - Corrosion

Effects of Velocity

Biological Effects

High Chloride Waters

Water Chemistry Effects

Corrosion

• Dissolved Oxygen

• Chlorides

• pH

• Hardness

• Temperature

Scale

• Dissolved Solids

• Calcium Ions

• pH

• Temperature

Water Chemistry Effects

Corrosion Of Carbon Steel In Water

0

10

20

30

0 5 10 15

22 ºC (72 ºF)

40 ºC (104 ºF)

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Corrosion Of Carbon Steel In Low-velocity Water

Corrosion Of Carbon Steel Effect Of Velocity In Seawater

0

25

50

0 5 10 15 20 25

~ 22ºC (72 ºF)

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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

Erosion-corrosion - Inlet

Erosion-corrosion

Flow

Erosion-corrosionTube Blockage

Flow

Biological EffectsMacrofouling

• Mussels

• Clams

• Barnacles

• Plant Life

Biological EffectsMacrofouling

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+++

Bacteria Effects - MIC(Type 304, Before Cleaning)

Bacteria Effects - MIC(After Cleaning)

3.8 mm (0.15 in.)

Max. Attack

Bacteria Effects - MIC(After Cleaning - No Attack)

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

Prevention Of MIC6% Mo Alloy (N08367) Used

HIGH CHLORIDE WATERS

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

Type 304 Fastener In Marine Tide After 6 Months

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)

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Summary

• Reviewed Problems with Waters

• Good Corrosion Data Are Available

• Successful Service Is Possible by

Proper Selection of Alloys

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