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Corrosion by Hazardous Chemicals Otto Drescher, P.E.

Corrosion by Hazardous Chemicals Otto Drescher, P.E. Discuss Uses & Some Properties Case History Materials Selection Guidelines. Summary. Sulfuric Acid Nitric Acid Phosphoric Acid Chlorine HCl. HF Organic Acids Caustic Ammonia & Amines. Specific Chemicals.

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Corrosion by Hazardous Chemicals Otto Drescher, P.E.

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

  2. Discuss Uses & Some Properties Case History Materials Selection Guidelines Summary

  3. Sulfuric Acid Nitric Acid Phosphoric Acid Chlorine HCl HF Organic Acids Caustic Ammonia & Amines Specific Chemicals

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

  5. Conc. Acid is 70% to 100% Oleum (Fuming) – 100% + excess SO3 Dilute Acid - < 25% Contaminants Greatly Effect Corrosion Sulfuric Acid

  6. Erosion-corrosion in 93% H2SO4Carbon Steel Nozzle 4 - 6 fps (1.2 – 1.8 m/s) at RT Design Velocity Limit is <2 fps (0.6 m/s)

  7. 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.%

  8. Sulfuric Acid Nitric Acid Phosphoric Acid Chlorine HCl HF Organic Acids Caustic Ammonia & Amines Specific Chemicals

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

  10. Nitric Acid • Concentrated Acid is 67% to 95% • Fuming Grades are > 99% • HF Addition Makes It Reducing • Cl- Contaminantion Releases Nascent Cl2

  11. Nitric-HF Acid Pickling LineAlloy 33 (33Cr-32Fe-31Ni-1.6Mo) Tank

  12. Nitric Acid – GuidelinesMaterials Selection ° C °F Boiling Point Curve Tantalum Si-Iron 1815 LC Si 304L 310 LCN Titanium 67% Aluminum Concentration, Wt.%

  13. Sulfuric Acid Nitric Acid Phosphoric Acid Chlorine HCl HF Organic Acids Caustic Ammonia & Amines Specific Chemicals

  14. 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-

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

  16. Preferential Attack in H3PO4Ambient Temperature, Steam Traced 304 Compare Thickness 316

  17. 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.%

  18. Sulfuric Acid Nitric Acid Phosphoric Acid Chlorine HCl HF Organic Acids Caustic Ammonia & Amines Specific Chemicals

  19. Chlorine • Uses - Organic • Drugs • Plastics • Solvents • Insecticides • PVC • Deodorants Uses - Inorganic • Chlorides Salts • Bleaching • Chlorination • Dyes • Rockets • Explosives

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

  21. 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

  22. 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

  23. Sulfuric Acid Nitric Acid Phosphoric Acid Chlorine HCl HF Organic Acids Caustic Ammonia & Amines Specific Chemicals

  24. 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

  25. 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

  26. 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%

  27. HCl Pitting CorrosionAlloy 825 Pickling Hook in Heated Acid Contaminated With Fe+++

  28. 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.%

  29. Sulfuric Acid Nitric Acid Phosphoric Acid Chlorine HCl HF Organic Acids Caustic Ammonia & Amines Specific Chemicals

  30. 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

  31. SCC of Alloy 400 in HFBubble Caps Exposed to Aerated Vapors

  32. HF Acid – GuidelinesMaterials Selection °C °F Boiling Point Curve 400 200, 400, C-276, C-22, 686 Concentration, Wt.%

  33. Sulfuric Acid Nitric Acid Phosphoric Acid Chlorine HCl HF Organic Acids Caustic Ammonia & Amines Specific Chemicals

  34. 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)

  35. Organic Acids • Rank in Corrosivity: Formic > Acetic > Propionic > Butyric • Aeration & Temperature Increase Corrosion • Contaminants (e.g. Cl-) Increase Corrosion

  36. Crevice CorrosionAcetic Acid-Acetic AnhydrideDistillation Column at 248 °F (120 °C) 316 Bubble Cap Attack Due to Oxygen-Concentration Cell

  37. Selective CorrosionBoiling Acetic Acid Weld Metal Corroded More Than Base Metal Base Metal Corroded More Than Weld Metal

  38. 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

  39. Sulfuric Acid Nitric Acid Phosphoric Acid Chlorine HCl HF Organic Acids Caustic Ammonia & Amines Specific Chemicals

  40. 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

  41. Caustic Cracking of SteelHeating Coil in 50% NaOH General Corrosion Stress Corrosion Cracking

  42. Caustic SodaCorrosion Rates for 304 °C °F >30 mpy (0.76 mm/y) Boiling Point Curve 1 - 30 mpy (0.03 – 0.76 mm/y) < 1 mpy (0.03 mm/y) Freezing Point Curve Concentration, Wt.%

  43. Caustic SodaStress Corrosion Cracking Zones °C °F 304 Boiling Point Curve C Steel Freezing Point Curve Concentration, Wt.%

  44. Caustic Soda – Chlorate FreeCorrosion Rates for Alloy 200 °C °F >5 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) < 0.1 mpy (0.003 mm/y) Freezing Point Curve Concentration, Wt.%

  45. Sulfuric Acid Nitric Acid Phosphoric Acid Chlorine HCl HF Organic Acids Caustic Ammonia & Amines Specific Chemicals

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

  47. 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)

  48. 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

  49. Discussed Specific Chemicals Reviewed Use & Some Properties Presented Materials Selection Guidelines for Each Chemical Summary

  50. The End Questions?

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