Corrosion Resistant SteelsCast Irons

Prepared by

Robert Merryfield

What is Stainless Steel

Any steel with 11% or more chromium

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

Ferritic

» Wholly Ferritic Structure-Balance of Chemistry

» Wrought Designation-Type 442» Low Impact Properties» Replaced by 300 Series » Can not be hardened

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

Austenitic 300 Series

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

2% Mo]

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]

Duplex Stainless Steels Metallurgical Structure 50% Ferrite-

50%Austenite 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

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

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

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

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

material?No……the 1-14 Ph range only

tells us part of the story.

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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% CONCENTRATION - H 2SO4

316SS (to 10%)Elcomet KR55Y30

316SS (to 75oF, 25%)

Elcomet K (to 150oF)

Allow 48 (to 75oF, 25%)

SteelElcomet KY-30TantalumAllow 48 (above 80%)

Y-30R55MonelTantalum

Elcomet K (to 150 oF)

Y-30Tantalum

(to 374oF)

Y-30R55Tantalum

Elcomet K (to 150 oF)

R55 (to 250oF)Tantalum

(to 374oF)

Corrosion Resistant Chart Sulfuric Acid

Most common chemicals

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

H2O - Water

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, P&P, Specialty Chemicals, WTP

H2SO4 cont’d

Materials : See chart Pump types : ANSI, Taber, Self Priming Seals : Carbon/Ceramic (>90%)

T.C. or special Carbon Viton elastomers (Teflon above 125o F)

DO NOT FLUSH WITH WATER

H2O2 (Hydrogen Peroxide)

Properties : Stable; s.g 1.2 Hazards : Fire; Explosive;Toxic and

strongly irritating. Releases Oxygen when transferred

Distribution : Trains, Trucks Uses : Bleaching textiles, Wood Pulp;

Hair; Rocket Fuel; Water Treatment; P&P

Pump Mat’l : 316SS or Aluminum

H2O2 cont’d

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.

Sodium Hydroxide (NaOH)

Properties : White. s.g 1.55 max. < 80cP viscosity

Hazards : strong irritant. Corrosive to tissue

Distribution : Trains, Trucks, Barges Uses : Chemical manufacture;

P&P; detergents; electro plating; food additive; bleaching; dyeing

Pump types : ANSI; Self Primer; Taber

Sodium Hydroxide cont’d

Pump materials:50% <125F- Iron, Steel

>125F- 316SS73% or >170F - Nickel

Mechanical seals: Carbon/T.C. (no SiC)

EPR (no Viton)

Hydrochloric Acid (HCl) Properties : Colorless -slightly yellow, fuming. Concentration <38% s.g. 1.19

Hazards : Toxic, strong irritant to tissue.

Uses : Pickling, scale removing, food processing, pharmaceuticals

Pump types : ANSI; Self Pimer; Taber

Hydrochloric Acid cont’d

Pump materials: Hast. B/C, FRP <30%

Mechanical seals: Carbon/CeramicViton

Water (H2O) Hazards: drowning or shortage. Properties: Steep Pv curve (limiting

us to 350o F max.) Specials : High temp. water has

no lubricity. Pump mat’l: D.I. or SS Mech. Seal: Carbon/Ceramic (cold

water) see supplement for Hot water.