Corrosion Resistant Steels Cast Irons

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Corrosion Resistant SteelsCast Irons

• Prepared by
• Robert Merryfield

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What is Stainless Steel

• Any steel with 11 or more chromium

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• Five General Categories of Stainless Steel
• Ferritic
• Martensitic
• Precipitation-Hardening
• Austenitic
• Duplex

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Ferritic

• Wholly Ferritic Structure-Balance of Chemistry
• Wrought Designation-Type 442
• Low Impact Properties
• Replaced by 300 Series
• Can not be hardened

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Martensitic

• 12 Chrome Steels (No nickel)
• 400 Series
• Wrought-410, 416, 440
• Cast CA-15, CA-120, CA6-NM
• Tough w/Hardness to500 HB
• Applications
• Pump Components Shafts and Sleeves
• Hydraulic Cylinders
• Wear Rings
• Used in API Pumps not CPI

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Precipitation-Hardening

• Chrome-Nickel Steel
• Martensitic Structure
• Contains Copper-Precipitates
• Designation
• 17-4PH and 15-5PH Wrought
• CB7Cu Cast
• High Strength
• 80,00 psi Tensile Solution Condition
• 120,000 psi Aged Condition
• Corrosion Resistance-Between 300 400 SS

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Austenitic 300 Series

• Most Prevalent in the CPI
• Nickel gt8-Structure Austenitic
• 18-8 SS (304) original
• 316- Cast-CF8M 18 Cr-9Ni-2.5Mo
• 316-Greater Pitting Resistance
• Alloy 20- Cast CN7M 18 Cr-30 Ni-2 Mo

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Austenitic Superalloys

• Nickel Based
• Nickel-Chromium-Molybdenum Alloys
• Hastelloy C-276 Cast CW-12MW
• Hastelloy C-22 Cast CX-2MW
• Inconel 625 Cast CW-6MC
• Nickel-Molybdenum Alloys
• Hastelloy B Cast N7M

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Duplex Stainless Steels

• Metallurgical Structure 50 Ferrite-50Austenite
• High Strength with Good Ductility
• Excellent Resistance to SCC in Sea Water
• Good Abrasion Resistance
• Used in Fertilizer Plants
• Grades
• Ferallium 255 Cast CD4MCU
• 2205

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Additional Corrosion Resistant Alloys

• Nickel
• Used for Severe Caustic Environments
• Nickel-Copper Monel Cast M-35
• Excellent in Sea Water Applications
• Zirconium Titanium
• Excellent When SCC is Problem for Other SS

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Cast Irons

• Unalloyed Gray and Ductile
• Corrosion resistance equal to or better than
  steel
• Excellent dampening affect
• Poor ductility but high compressive strength
• low cost
• High Nickel Austenitic Cast Iron (NiResist)
• 18 or more Nickel content
• Resist to Conc. Sulphuric Phosphoric Sea water

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Cast Irons (Cont.)

• High Chromium Cast Iron
• Alloyed with 12 to 30 Cr
• Resistant to Oxidizing Acids, i.e. Nitric Acid
• Also saline solutions, organic acids and marine
  environments
• Extremely Abrasion Resistant

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Copper Alloys

• Copper Alloys used in many environments because
• Corrosion Resistance
• Good Electrical and Thermal Conductivity
• Ease of fabrication and welding
• Resistance to biofouling

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Brasses

• Brass is an alloy of Copper and Zinc
• Excellent corrosion resistance to aqueous
  solutions
• Corrosion resistance decreases with Zinc content
  greater than 15.
• Susceptible to dealloying or dezincification

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Bronzes

• Bronzes are Copper and Tin
• Addition of Tin and Phosphorus to copper
  produces good resistance to flowing seawater
• Aluminum Bronze
• Excellent resistance to impingement corrosion
• Al provides increased corrosion resistance
• Resistant to Phosphoric, Sulfuric, NaCl
• Especially resistant to brackish water

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Labour proprietary materials

• R-55 55 Nickel material designed for
  H2SO4 at higher temperatures
• A-48 Duplex material, similar to CD4MCu
• Elcomet K similar to Alloy 20
• Y-17 similar to Hastelloy C
• Y-30 similar to Hastelloy B

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So, all I need is the Ph value to select a
suitable material?

• Nothe 1-14 Ph range only tells us part of the
  story.

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What info do you need?

• Concentration of all the chemicals
• Normal and maximum temperatures
• Presence of solids
• Life expectancy of the material

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Corrosion Resistant Chart Sulfuric Acid
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Most common chemicals

• H2SO4 - Sulfuric Acid
• HCl - Hydrochloric Acid
• NaOH - Sodium Hydroxide (Caustic)
• H2O2 - Hydrogen Peroxide
• H2O - Water

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H2SO4 (Sulfuric Acid)

• Properties Clear, odorless, oily. s.g. up
  to 1.84
• Hazards Strong irritant to tissue.
  Reacts violently with water.
• Global Production 165 million t/yr
• Distribution Trains, Trucks, Barges
• Uses Fertilizers, Paints, Explosives,
  Batteries, PP, Specialty Chemicals, WTP

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H2SO4 contd

• Materials See chart
• Pump types ANSI, Taber, Self Priming
• Seals Carbon/Ceramic (gt90)
• T.C. or special Carbon Viton elastomers
  (Teflon above 125o F)
• DO NOT FLUSH WITH WATER

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H2O2 (Hydrogen Peroxide)

• Properties Stable s.g 1.2
• Hazards Fire ExplosiveToxic and
  strongly irritating. Releases Oxygen when
  transferred
• Distribution Trains, Trucks
• Uses Bleaching textiles, Wood Pulp
  Hair Rocket Fuel Water Treatment PP
• Pump Matl 316SS or Aluminum

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H2O2 contd

• Pump types Self Primers or TFA
• Mech. Seals SiC/SiC or GFT/Ceramic Viton or
  Teflon
• Major customers FMC Dupont Elf
  Autochem Tank Car Manufacturers
• Specials Pump to be pickled to ensure
  clean inside.

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Sodium Hydroxide (NaOH)

• Properties White. s.g 1.55 max. lt 80cP
  viscosity
• Hazards strong irritant. Corrosive to
  tissue
• Distribution Trains, Trucks, Barges
• Uses Chemical manufacture PP
  detergents electro plating food additive
  bleaching dyeing
• Pump types ANSI Self Primer Taber

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Sodium Hydroxide contd

• Pump materials 50 lt125F- Iron, Steel gt125F-
  316SS 73 or gt170F - Nickel
• Mechanical seals Carbon/T.C. (no SiC) EPR
  (no Viton)

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Hydrochloric Acid (HCl)

• Properties Colorless -slightly yellow,
  fuming. Concentration lt38 s.g. 1.19
• Hazards Toxic, strong irritant to
  tissue.
• Uses Pickling, scale removing, food
  processing, pharmaceuticals
• Pump types ANSI Self Pimer Taber

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Hydrochloric Acid contd

• Pump materials Hast. B/C, FRP lt30
• Mechanical seals Carbon/Ceramic Viton

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Water (H2O)

• Hazards drowning or shortage.
• Properties Steep Pv curve (limiting us to
  350o F max.)
• Specials High temp. water has no
  lubricity.
• Pump matl D.I. or SS
• Mech. Seal Carbon/Ceramic (cold water)
  see supplement for Hot water.