Why Titanium Is the Material of Choice for Chemical Processing
Titanium and titanium alloys have earned their reputation as the ultimate material for corrosive chemical processing applications. With exceptional resistance to virtually all oxidizing and neutral corrosive media, titanium piping systems can provide service lives exceeding 30 years in environments that would destroy stainless steel in months. While the initial material cost is higher, the total cost of ownership often favors titanium due to eliminated maintenance, zero product contamination, and unmatched service life.
At CoreMetal Steel, we supply titanium pipe and tube in all standard grades for chemical processing, heat exchanger, and offshore applications. This guide covers titanium material selection, corrosion resistance, and design considerations for chemical process piping.
Titanium Grades for Chemical Processing
| Grade | Designation | Composition | Key Properties | Typical Chemical Applications |
|---|---|---|---|---|
| Grade 1 | CP Ti (pure) | 99.5% Ti min | Most ductile, best formability | Mild corrosive services |
| Grade 2 | CP Ti (pure) | 99.0% Ti min | Best all-around corrosion resistance | Chlor-alkali, bleach, oxidizing acids |
| Grade 5 (6Al-4V) | Ti-6Al-4V | 6% Al, 4% V | Highest strength, heat treatable | High-pressure, high-temperature services |
| Grade 7 | CP Ti + 0.15% Pd | Pd enhanced | Enhanced crevice corrosion resistance | Reducing acid services |
| Grade 12 (Ti-0.3Mo-0.8Ni) | Ti-0.3Mo-0.8Ni | Mo + Ni alloyed | Crevice corrosion resistance in brines | Sour gas, chloride services |
| Grade 16 (Ti-0.15Pd) | Ti-0.15Pd | Pd enhanced | Similar to Gr.7, improved weldability | Chemical processing, sour gas |
Corrosion Resistance in Chemical Environments
Acid Resistance
| Chemical | Concentration | Temperature | Grade 2 Rate | Recommendation |
|---|---|---|---|---|
| Hydrochloric acid (HCl) | 1-5% | 20C | 0.005 mm/yr | Acceptable with aeration |
| Hydrochloric acid | Above 5% | Above 40C | Severe attack | NOT recommended |
| Sulfuric acid (H2SO4) | 1-5% | Boiling | 0.05 mm/yr | Good resistance |
| Sulfuric acid | 5-20% | Ambient | 0.001 mm/yr | Excellent resistance |
| Nitric acid (HNO3) | All concentrations | Up to boiling | 0.001 mm/yr | Outstanding resistance |
| Phosphoric acid (H3PO4) | All concentrations | Up to 120C | 0.001 mm/yr | Outstanding resistance |
| Chromic acid | All concentrations | Up to boiling | Negligible | Ideal material |
| Organic acids (acetic) | All concentrations | Up to boiling | Negligible | Excellent resistance |
Alkali and Salt Resistance
- Sodium hydroxide (NaOH): Excellent resistance at all concentrations up to boiling
- Potassium hydroxide (KOH): Excellent resistance across all conditions
- Chlorides: Outstanding resistance to chloride-induced pitting and SCC
- Seawater: Zero corrosion rate in flowing or stagnant conditions
- Hypochlorite: Outstanding – titanium is the standard material for chlor-alkali plants
Environments Where Titanium Performs Poorly
- Reducing acids without oxidizers: HCl above 5%, dilute H2SO4 without dissolved oxygen
- Anhydrous conditions: Dry chlorine gas, methanol without water
- Hydrofluoric acid (HF): Severe attack at all concentrations
- Hot concentrated phosphoric acid with fluoride ions
Key principle: Titanium requires an oxidizing environment (or dissolved oxygen) to maintain its passive film. Reducing conditions can cause rapid attack.
Design Considerations for Titanium Piping
Mechanical Properties
| Grade | Yield Strength (MPa) | Tensile Strength (MPa) | Elongation (%) | Max Service Temp (C) |
|---|---|---|---|---|
| Grade 2 | 275 | 345 | 25 | 315 |
| Grade 5 (Ti-6Al-4V) | 830 | 900 | 14 | 400 |
| Grade 12 | 345 | 483 | 20 | 315 |
Pressure Rating Considerations
- Titanium Grade 2 has approximately 2/3 the yield strength of 316L stainless steel
- Wall thickness may need to be increased compared to stainless steel equivalent
- Titanium Grade 5 offers higher strength (comparable to high-strength steels) but reduced corrosion resistance in some environments
- ASME B31.3 allows stresses up to 137 MPa for Grade 2 at ambient temperature
Galvanic Compatibility
- Titanium is noble (cathodic) to virtually all other engineering metals
- Connecting titanium to steel, aluminum, or copper alloys will accelerate corrosion of the less noble material
- Avoid direct contact with less noble metals – use insulating flanges or dielectric unions
- Titanium-to-titanium connections are preferred wherever possible
Hydrogen Absorption
A unique concern with titanium in chemical service:
- Titanium can absorb hydrogen in reducing acid environments
- Hydrogen absorption leads to embrittlement (hydride formation)
- Hydrides form when hydrogen content exceeds 150 ppm
- Mitigation: Palladium-containing grades (Gr.7, Gr.16) resist hydrogen uptake
- Cathodic protection must be carefully controlled (max -0.7V vs Ag/AgCl)
Common Chemical Processing Applications
Chlor-Alkali Industry
- Brine piping and headers
- Chlorine wet gas cooling and drying systems
- Caustic soda (NaOH) evaporation and concentration
- Hypochlorite production and storage
- Titanium Grade 2 is the standard material for chlorine wet services
Organic Chemical Processing
- Acetic acid reactors and distillation columns
- Terephthalic acid (PTA) production
- Phenol and caprolactam processes
- Fatty acid processing
- Essential oil and fragrance manufacturing
Petroleum Refining and Petrochemical
- Sour water strippers (H2S + NH3 + chloride)
- Overhead condensers in crude distillation
- CO2 removal systems (amine regeneration)
- Alkylation unit heat exchangers
- Grade 12 or Grade 16 preferred for sour service
Desalination
- MSF (Multi-Stage Flash) evaporator tubing
- MED (Multi-Effect Distillation) heat exchangers
- RO high-pressure piping
- Brine heaters and heat recovery sections
- Titanium Grade 2 is the premium material for top-brine sections
Standards and Specifications
| Product Form | ASTM Standard | ASME Standard |
|---|---|---|
| Seamless Pipe | B338 | SB-338 |
| Welded Pipe | B338 / B862 | SB-338 / SB-862 |
| Seamless Tube | B338 | SB-338 |
| Welded Tube | B338 / B862 | SB-338 / SB-862 |
| Plate, Sheet, Strip | B265 | SB-265 |
| Bar and Billet | B348 | SB-348 |
| Forgings | B381 | SB-381 |
| Fittings | B363 | SB-363 |
Conclusion
Titanium pipe and tube offer unmatched corrosion resistance for the most demanding chemical processing environments. While the initial investment is higher than stainless steel or nickel alloys, the extended service life, zero maintenance cost, and product purity make titanium the most cost-effective choice for many applications over the life of the plant.
CoreMetal Steel supplies titanium pipe and tube in all standard grades (Grade 2, Grade 5, Grade 7, Grade 12, Grade 16) per ASTM B338 and related specifications. Contact our technical team at tracy@coremetalsteel.com for material recommendations and competitive pricing on titanium piping systems.