Corrosion%20by

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• Corrosion by
• Hazardous Chemicals
• Otto Drescher, P.E.

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Summary

• Discuss Uses Some Properties
• Case History
• Materials Selection Guidelines

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Specific Chemicals

• Sulfuric Acid
• Nitric Acid
• Phosphoric Acid
• Chlorine
• HCl

• HF
• Organic Acids
• Caustic
• Ammonia Amines

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Sulfuric Acid

• Largest Tonnage of Inorganic Chemicals
• Major Use in Petroleum Refining, Fertilizers,
  Paints, Pigments, Dyes, Explosives, and pH
  Control
• Powerful Oxidizing Agent

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Sulfuric Acid

• Conc. Acid is 70 to 100
• Oleum (Fuming) 100 excess SO3
• Dilute Acid - lt 25
• Contaminants Greatly Effect Corrosion

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Erosion-corrosion in 93 H2SO4Carbon Steel
Nozzle 4 - 6 fps (1.2 1.8 m/s) at RT
Design Velocity Limit is lt2 fps (0.6 m/s)
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Sulfuric Acid GuidelinesMaterials Selection
F
C
Tantalum Glass Si-Iron
Boiling Point Curve
Alloy B-2, B-3, B-4
316
825 20Cb-3 904L
316
Steel
Concentration, Wt.
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Specific Chemicals

• Sulfuric Acid
• Nitric Acid
• Phosphoric Acid
• Chlorine
• HCl

• HF
• Organic Acids
• Caustic
• Ammonia Amines

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Nitric Acid

• Major Use in Ammonium Nitrate and Phosphate
  Fertilizers, Nitro Explosives, Plastics, and Dyes
• Always an Oxidizing Acid

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Nitric Acid

• Concentrated Acid is 67 to 95
• Fuming Grades are gt 99
• HF Addition Makes It Reducing
• Cl- Contaminantion Releases Nascent Cl2

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Nitric-HF Acid Pickling LineAlloy 33
(33Cr-32Fe-31Ni-1.6Mo) Tank
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Nitric Acid GuidelinesMaterials Selection
C
F
Boiling Point Curve
Tantalum Si-Iron 1815 LC Si
304L 310 LCN Titanium
67
Aluminum
Concentration, Wt.
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Specific Chemicals

• Sulfuric Acid
• Nitric Acid
• Phosphoric
• Acid
• Chlorine
• HCl

• HF
• Organic Acids
• Caustic
• Ammonia Amines

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Phosphoric Acid

• Major Use in Phosphate Fertilizers, Food
  Beverages, Drying Agents, Plasticizers, Oil
  Additives, Fire Retardants, and Insecticides
• Is a Reducing Acid, More So When Contaminated
  With Cl- and F-

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Phosphoric Acid

• Two Types of Pure Acid (85)
• C. P. Grade
• Food Grade
• Superphosphoric Acid - gt 105
• Industrial Grades May Be Contaminated With Cl-,
  F-, and Fe

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Preferential Attack in H3PO4Ambient Temperature,
Steam Traced
304
Compare Thickness
316
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Phosphoric Acid GuidelinesMaterials Selection
F
C
C-276 G-3 G-30 G-35
Alloy 28, 31
Boiling Point Curve
825/904L
317L
316L
Concentration, Wt.
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Specific Chemicals

• Sulfuric Acid
• Nitric Acid
• Phosphoric Acid
• Chlorine
• HCl

• HF
• Organic Acids
• Caustic
• Ammonia Amines

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Chlorine

• Uses - Inorganic
• Chlorides Salts
• Bleaching
• Chlorination
• Dyes
• Rockets
• Explosives

• Uses - Organic
• Drugs
• Plastics
• Solvents
• Insecticides
• PVC
• Deodorants

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Chlorine

• Poisonous, greenish-yellow gas
• Does Not Attack Metals lt 400 F (204 C),
• Except Ti
• Moisture aggravates corrosivity
• HOCl is a Powerful Oxidizing Acid

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Chlorine GuidelinesMaterials Selection

• Liquid Cl2 Carbon Steel ( Dry! )
• Cl2 Gas
• Carbon Steel to 250 F (121 C) Wall Temp
• Caution! Carbon Steel May Ignite
• Alloy 400 to 570 F (299 C) Wall Temp

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Chlorine GuidelinesMaterials Selection

• Chlorinated Organics
• Carbon Steel to 200 F (93 C) Wall Temp
• Alloys 400 200 to B.P.
• Chlorinated Waters Titanium, C-276

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Specific Chemicals

• Sulfuric Acid
• Nitric Acid
• Phosphoric Acid
• Chlorine
• HCl

• HF
• Organic Acids
• Caustic
• Ammonia Amines

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Hydrochloric Acid

• 2nd in Importance to Sulfuric Acid
• Major Use in Pickling Steels, Oil Well pH,
  Chemical Cleaning, Ore Reduction, Food
  Processing, Synthetic Rubber, and Regeneration of
  Ion Exchange Resins

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Hydrochloric Acid

• Anhydrous is Non-corrosive, Very Hygroscopic
• Strong, Reducing Acid
• Attacks Most Metals Below H2 in EMF Series
• Forms Metal Chlorides and Liberates H2

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Hydrochloric Acid

• Attacks Noble Metals Only If DO or Oxidizing
• Contaminants Are Present (Fe)
• Water Solution is 28 35
• Commercial Grade is Muriatic Acid
• Constant Boiling Mixture is 20.2

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HCl Pitting CorrosionAlloy 825 Pickling Hook in
Heated Acid Contaminated With Fe
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Hydrochloric Acid GuidelinesMaterials Selection
C
F
Boiling Point Curve
B-2, B-3 Zirconium Tantalum
400 Air Free
C-Family
200, 400
825
Concentration, Wt.
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Specific Chemicals

• Sulfuric Acid
• Nitric Acid
• Phosphoric Acid
• Chlorine
• HCl

• HF
• Organic Acids
• Caustic
• Ammonia Amines

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Hydrofluoric Acid

• Major Uses are Refrigerants, Fluorocarbons,
• Etch/Polish Glass, Pickling, Ore Processing
• Acidification of Oil Wells
• Is a Weak, Reducing Acid
• Anhydrous HF and HF Acid are Very Hazardous
• Commercial Grades are 48 70
• Fluoride Ions Less Aggressive Than Chloride

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SCC of Alloy 400 in HFBubble Caps Exposed to
Aerated Vapors
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HF Acid GuidelinesMaterials Selection
C
F
Boiling Point Curve
400
200, 400, C-276, C-22, 686
Concentration, Wt.
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Specific Chemicals

• Sulfuric Acid
• Nitric Acid
• Phosphoric Acid
• Chlorine
• HCl

• HF
• Organic Acids
• Caustic
• Ammonia Amines

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Organic Acids

• Major Uses are Dyeing, Pigments, Pesticides,
  Tanning, Esters, Alcohols, Organic Chemicals
• Are Weak, Reducing Acids
• Less Corrosive as Carbon Chain Lengthens (or as
  Molecular Weight Increases)

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Organic Acids

• Rank in Corrosivity
• Formic gt Acetic gt Propionic gt Butyric
• Aeration Temperature Increase Corrosion
• Contaminants (e.g. Cl-) Increase Corrosion

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Crevice CorrosionAcetic Acid-Acetic
AnhydrideDistillation Column at 248 F (120 C)
316 Bubble Cap
Attack Due to Oxygen-Concentration Cell
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Selective CorrosionBoiling Acetic Acid
Weld Metal Corroded More Than Base Metal
Base Metal Corroded More Than Weld Metal
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Organic Acids GuidelinesMaterials Selection

• IGA Probable, if Low C Not Used
• SCC Possible, if Chlorides Present
• 304L For Storage and Low Temperatures
• 316L For Higher Temperatures
• 6 Mo Alloys if Crevices Cl- Present
• May Need 6 or Higher Mo Alloy Welds

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Specific Chemicals

• Sulfuric Acid
• Nitric Acid
• Phosphoric Acid
• Chlorine
• HCl

• HF
• Organic Acids
• Caustic
• Ammonia Amines

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Sodium HydroxideCaustic Soda

• Major Uses are Sodium Compounds, Metallurgical
  (Aluminum), Glass, Rayon Fibers, Cellophane,
  Paper Industry, Detergents, Bleaching, Whitening
  Products, Soaps, Cleaning (Dissolves Organics),
  pH Control
• Strong Alkali
• KOH Is Very Similar to NaOH

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Caustic Cracking of SteelHeating Coil in 50
NaOH
General Corrosion
Stress Corrosion Cracking
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Caustic SodaCorrosion Rates for 304
F
C
gt30 mpy (0.76 mm/y)
Boiling Point Curve
1 - 30 mpy (0.03 0.76 mm/y)
lt 1 mpy (0.03 mm/y)
Freezing Point Curve
Concentration, Wt.
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Caustic SodaStress Corrosion Cracking Zones
F
C
304
Boiling Point Curve
C Steel
Freezing Point Curve
Concentration, Wt.
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Caustic Soda Chlorate FreeCorrosion Rates for
Alloy 200
F
C
gt5 mpy (0.13 mm/y)
Boiling Point Curve
1 - 5 mpy (0.03 0.13 mm/y)
0.1 - 1 mpy (0.003 0.03 mm/y)
lt 0.1 mpy (0.003 mm/y)
Freezing Point Curve
Concentration, Wt.
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Specific Chemicals

• Sulfuric Acid
• Nitric Acid
• Phosphoric Acid
• Chlorine
• HCl

• HF
• Organic Acids
• Caustic
• Ammonia
• Amines

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Ammonia

• Major Uses are Organic Compounds, Drugs,
  Plastics, Dyes, Fertilizers, Explosives,
  Production of Nitric Acid, Ammonium Salts,
  Refrigerant, Cleaning Agents
• 4th Most Important Chemical

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Ammonia GuidelinesMaterials Selection

• Anhydrous Ammonia Is Non-corrosive
• Except for SCC of Steel
• NH3 H2O NH4OH
• Water Dilution Forms Ammonium
• Hydroxide - Inhibits SCC of Steel
• Ingress of Water and O2 Corrosive to Cu and
  Cr-free Ni Alloys (Even ppm)

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Ammonia GuidelinesMaterials Selection

• Corrosion of Steels Through Stainless Steels May
  Be Caused By CO2 Contamination (Ammonium
  Carbamate)
• Chloride Contamination Can Reduce Life of
  Stainless Steel Equipment

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Summary

• Discussed Specific Chemicals
• Reviewed Use Some Properties
• Presented Materials Selection Guidelines for
  Each Chemical

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The End

• Questions?