A Unique Set of Characteristics Creates Intrinsic Value
Titanium’s accelerating usage in global markets is attributable to its distinctive combination of physical and metallurgical properties. The key to best utilizing titanium is to exploit these characteristics, especially as they complement one another in a given application, rather than to just directly substitute titanium for another metal.
Exceptional Strength-to-Weight Ratio
Titanium’s excellent tensile and yield strength combined with its low-density results in the highest strength-to-weight ratio of any of today’s structural metals. Especially when it is alloyed, titanium is as strong as steel, yet its specific gravity is only 56% that of steel. This is a prime advantage for its use in aerospace, of course, and also for such diverse applications as deep-well tubing strings and offshore risers in the petroleum industry, surgical implants and golf club heads.
Titanium’s yield strengths range from 25,000 psi (172 MPa) for commercially pure (CP) Grade 1 to above 200,000 psi (1380 MPa) for heat-treated beta alloys. The densities of titanium-based alloys range between 0.160 lb/in3 (4.43 g/cm3) and 0.175 lb/in3 (4.85 g/cm3).
Titanium’s low density, roughly 56% that of stainless steels and half that of copper and nickel alloys, means greater metal volume per pound compared to other materials. In conjunction with its strength, this often means components can be made smaller and/or lighter. This is the basis for many aerospace applications, and also for rotating or reciprocating components such as centrifuges, pumps and automotive valves and connecting rods.
Titanium’s low density, combined with its natural corrosion resistance, also gives it advantages over other materials in aggressive environments. Based on its strength and the fact it needs no corrosion allowance, it can be specified in thinner cross-sections, using less metal per unit of area. On a dimensional or per-piece basis, this effectively offsets its higher per-pound cost, especially when life cycle costs are also considered. Based on this, downhole oil and geothermal well production tubulars and logging tools are being produced from titanium alloys. In marine service, pleasure boat components, naval surface ships and submarine cooling water systems are growing markets for titanium, driven by its lightweight and immunity to seawater corrosion.
Excellent, Natural Corrosion Resistance
Titanium is a reactive metal, meaning it spontaneously forms a natural oxide film (mainly TiO2) in the presence of any oxygen. Whenever there is any amount of air or water in a process stream or environment, the oxide film forms and protects the metal from corrosive attack. If the film is scratched or damaged, the metal surface repairs itself instantly. The highly adherent film is exceptionally resistant to a broad range of acids and alkalis, as well as natural, salt and polluted waters. Titanium’s corrosion resistance together with its low density, high strength and erosion resistance, make it ideal for numerous chemical processing and marine uses, as well as architectural applications.
Corrosive Environments Where Titanium’s Oxide Film Provides Resistance
Chlorine and Other Halides
Fully resistant to moist chlorine and its compounds.
Fully resistant to solutions of chlorites, hypochlorites, perchlorates and chlorine dioxide.
Resistance to moist bromine gas, iodine and their compounds is similar to chlorine resistance.
Immune to corrosion in all natural, sea, brackish and polluted waters.
Immune to Microbiologically Influenced Corrosion (MIC).
Oxidizing Mineral Acids
Highly resistant to nitric, chromic, perchloric and hypo chlorous (wet chlorine gas) acids.
Corrosion resistant to sulfur dioxide, ammonium, carbon dioxide, carbon monoxide, hydrogen sulfide and nitrogen.
Inorganic Salt Solutions
Highly resistant to chlorides of sodium, potassium, magnesium, calcium, copper, iron, ammonia, manganese and nickel.
Highly resistant to bromide salts.
Highly resistant to sulfides, sulfates, carbonates, nitrates, chlorates and hypochlorites.
Generally very resistant to acetic, terephthalic, adipic, citric, formic, lactic, stearic, tartaric and tannic acids.
Corrosion resistant in organic process streams of alcohols, aldehydes, esters, ketones and hydrocarbons, with air or moisture.
Low corrosion rates in hydroxides of sodium, potassium, calcium, magnesium and ammonia.
(Please note: The above information on corrosion resistance is provided only as a general overview. Before specifying titanium in any aggressive environment, consult corrosion experts. The information is adapted from “Shedding New Light on Titanium in CPI Construction,” by James S. Grauman and Brent Willey, Chemical Engineering, August 1998.)