Titanium

Materials ·

Titanium and its alloys (primarily Grade 2 commercially pure and Grade 5 Ti-6Al-4V) offer a unique combination of very high corrosion resistance in seawater, oxidizing acids, and chlorinated environments with low density (60 percent of steel), making titanium pump components the material of choice for seawater, hypochlorite, and nitric acid service where even Hastelloy may be inadequate or where weight reduction is critical.

History

Titanium was discovered as an element by William Gregor in Cornwall, England in 1791 and independently named by Martin Heinrich Klaproth in 1795. However, pure metallic titanium could not be extracted until Wilhelm Kroll developed the Kroll Process in Luxembourg in 1940, which remains the primary commercial titanium production method today. Titanium pump components were first produced in the 1950s in the USA for aerospace and nuclear applications. IMI Titanium in Birmingham, England pioneered commercial titanium pump casings for the offshore oil industry in the 1970s. The offshore North Sea expansion of 1975 to 1985 established titanium as the standard material for seawater lift pump impellers on production platforms.

Key Properties

  • Density: 4.51 g/cm3 — 60 percent of steel, 57 percent of Hastelloy C-276 density
  • Tensile strength: 345 MPa (Grade 2 CP); 895 to 1100 MPa (Grade 5 Ti-6Al-4V)
  • Excellent fatigue strength in seawater — superior to all austenitic stainless steels
  • Biocompatible — no ion release in body fluids (medical device applications)
  • Excellent thermal stability up to 300 degrees C for commercially pure Grade 2

Corrosion and Chemical Resistance

  • Outstanding resistance to seawater at all temperatures and flow velocities
  • Resistant to nitric acid at all concentrations and temperatures
  • Resistant to wet chlorine, hypochlorite, and chlorinated water at ambient temperature
  • Resistant to oxidizing acids generally: chromic, perchloric, and dilute sulfuric with oxidizing agent present
  • Not suitable for hydrofluoric acid, fuming sulfuric acid (oleum), or reducing acids at elevated temperature
  • Not suitable for dry chlorine gas at elevated temperature — pyrophoric risk above 300 degrees C

Grades and Standards

  • Grade 1 (ASTM B265): softest commercially pure Ti — high ductility for forming diaphragms
  • Grade 2 (ASTM B265): standard commercially pure Ti for pump casings and impellers
  • Grade 5 (ASTM B265): Ti-6Al-4V alloy — high strength for pump shafts in demanding service
  • ASTM B367 covers titanium casting grades C-1 and C-5 for investment cast pump bodies
  • ASME Section VIII and Section III cover titanium pressure vessel and pump code compliance

Applications

  • Seawater intake and lift pump impellers and casings on offshore oil platforms
  • Chlorine and hypochlorite solution transfer pump wetted parts
  • Desalination high-pressure pump internals where seawater velocity causes erosion of other materials
  • Nitric acid manufacturing process pump casings and impellers
  • Naval shipboard seawater pump systems where weight reduction is critical
  • Bioprocess equipment pump wetted parts in pharmaceutical manufacturing

Advantages

  • Best weight-to-corrosion-resistance ratio of any metallic pump material available commercially
  • Outstanding erosion-corrosion resistance in high-velocity seawater service above 5 m/s
  • No biofilm adhesion in seawater — long-term performance without biocide treatment
  • Excellent cryogenic toughness maintained to very low temperatures
  • Passive oxide film reforms instantly if damaged — self-healing corrosion protection

Limitations

  • Very high material cost — 5 to 8 times more expensive than 316L per kilogram
  • Extremely difficult to machine — requires sharp tooling, low cutting speeds, and coolant throughout
  • Cannot be welded with steel or stainless — risk of brittle intermetallic compounds at welds
  • Hydrogen embrittlement possible in galvanic contact with dissimilar metals in seawater
  • Galling risk on mating titanium-to-titanium surfaces — requires surface treatment or dissimilar face materials

Selection Criteria

  • Specify Grade 2 CP titanium for all seawater pump casings and impellers above 30 degrees C or at velocities above 5 m/s where duplex stainless is inadequate
  • Specify Grade 5 (Ti-6Al-4V) for high-stress applications such as pump shafts in aggressive media
  • Avoid mixing titanium and steel fasteners in seawater assembly — galvanic corrosion risk to steel
  • Use PTFE or PVDF bushings as insulators where titanium contacts dissimilar metals in assemblies
  • Budget 2 to 3 times longer lead time versus 316L or duplex — limited casting foundries exist globally

Top 10 Manufacturers

  • 1. TIMET (Titanium Metals Corporation, USA) — ~20% of titanium pump material market; mill products for pump fabricators
  • 2. ATI Inc. (USA) — ~16%; titanium plate, sheet, and bar for pump casing fabrication
  • 3. VSMPO-AVISMA (Russia) — ~15%; world largest titanium sponge and ingot producer for global supply
  • 4. Kobe Steel Ltd. (Japan) — ~10%; titanium mill products and pump component castings
  • 5. Sulzer Ltd. (Switzerland) — ~7%; titanium pump casings for seawater and chemical service applications
  • 6. Flowserve Corporation (USA) — ~6%; ASTM B367 cast titanium pump components for offshore service
  • 7. Precision Castparts Corp. (USA) — ~5%; investment cast titanium Grade 2 pump bodies
  • 8. Weir Group PLC (UK) — ~4%; titanium impellers for North Sea seawater injection pump systems
  • 9. Baoji Titanium Industry Co. (China) — ~4%; Grade 2 and Grade 5 bar and forgings for pump component machining
  • 10. Allegheny Technologies Inc. (USA) — ~3%; specialty titanium forms for niche pump applications