Technical knowledge
Titanium Grade 2 for seawater, chlorine and desalination piping
Why titanium Grade 2 is effectively immune to seawater corrosion, where it is used in desalination and chlor alkali plants, and the limits around velocity, crevices, dry chlorine and galvanic coupling that must be respected.
Why titanium behaves differently from stainless steel
Titanium forms a titanium dioxide film that is stable and self healing in oxidising environments containing water. Chloride does not break that film, so pitting and crevice corrosion in seawater are not the governing failure modes. Grade 2 is unalloyed, which gives excellent formability and weldability, with strength supplied by the section rather than by the alloy.
Composition and properties
| Item | Value | Significance |
|---|---|---|
| Titanium | Balance, about 99 % | Base metal |
| Oxygen | 0.25 % maximum | Strength control |
| Iron | 0.30 % maximum | Impurity control |
| Density | 4.51 g/cm3 | About 45 % lighter than steel |
| Minimum yield strength | About 275 MPa | Comparable with 316L |
| Thermal conductivity | Low, about a fifth of steel | Affects heat transfer design |
| Typical specification | ASTM B381 for flanges, B363 for fittings | Procurement reference |
Where Grade 2 is the standard answer
- Desalination heat exchanger tubing and water boxes. Immune to seawater and to chlorination.
- Seawater cooling and firewater systems. No corrosion allowance needed and tolerant of high velocity.
- Chlor alkali and chlorine dioxide plants. Wet chlorine service at controlled conditions.
- Offshore topside piping. Weight saving and zero maintenance over the plant life.
Limits that must be respected
- Dry chlorine is dangerous. Titanium reacts violently with dry chlorine gas. A minimum water content is required for safe use.
- Hydrofluoric acid dissolves the oxide. Avoid fluoride containing streams or control them very carefully.
- Galvanic coupling. Titanium is highly noble. Coupling it to carbon steel or aluminium accelerates corrosion of those metals; use isolation or a compatible design.
- Crevices at high temperature. Above roughly 80 C in tight crevices, Grade 2 can suffer crevice attack; Grade 7 or Grade 12 is used where that risk is real.
- Fire risk. Titanium can ignite in certain oxidising environments; review the safety case for oxygen and nitrogen dioxide service.
Questions about this topic
Does titanium corrode in seawater at all?
Practically no, in natural seawater at any service temperature. It is used for desalination tubing with wall thicknesses chosen for mechanical strength rather than for corrosion allowance.
Why is titanium more expensive but still chosen?
The material price is high, but the absence of corrosion allowance, the weight saving, the long service life and the elimination of replacement outages often make the installed cost competitive over the plant life.
Can titanium flanges be bolted to carbon steel flanges?
Yes with isolation. Use an insulating gasket kit, insulating sleeves and washers so the carbon steel does not become the sacrificial anode in the couple.
Questions about our products
What products does Hangbo Alloy supply?
Four product families, all available in nickel-based alloys, titanium, duplex and special stainless steel: flanges, butt weld pipe fittings, elbows, and seamless tube and pipe. Flanges cover weld neck, long weld neck, slip-on, blind, socket weld, threaded and lap joint patterns. Fittings and elbows cover concentric and eccentric reducers, equal and reducing tees, caps, stub ends, and 45°, 90° and 180° returns in both long and short radius, plus 3D and 5D bends for piggable lines. Seamless tube and pipe is supplied cold drawn or hot finished from 6 mm to 630 mm outside diameter.
Which alloy grades are available for these products?
More than 90 grades are published in our grade library. The most requested are Inconel 625, 718, 600 and X-750, Hastelloy C-276, C-22 and B-2, Monel 400 and K-500, Incoloy 800H, 825 and 925, duplex 2205 and super duplex 2507, 316L, 904L and 254SMO stainless steel, and titanium Grade 2 and Grade 5. Nickel-based grades can also be supplied with VIM plus ESR double melting where cleanliness or fatigue life is critical.
What sizes, wall thicknesses and pressure classes can you supply?
Flanges run from NPS ½ to NPS 24 to ASME B16.5 and from NPS 26 to NPS 60 to ASME B16.47 Series A or B, in pressure classes 150 through 2500. Butt weld fittings and elbows run from NPS ½ to NPS 48 (DN 15 to DN 1200) in wall thickness Schedule 5S through XXS. Seamless tube and pipe covers 6 mm to 630 mm outside diameter, in random lengths of about 5 to 7 metres or fixed lengths up to 12 metres. Non-standard and intermediate sizes are quoted on request.
Which material and dimensional standards do you work to?
Forged flanges to ASTM B564, B381 and A182 with dimensions to ASME B16.5 and ASME B16.47. Butt weld fittings and elbows to ASTM B366 and A403 with dimensions to ASME B16.9 and MSS SP-43. Seamless tube and pipe to ASTM B444, B423, B622, B163, B167, B861, A312, A213 and A790. Marking follows MSS SP-25 and the applicable product standard. If your project is governed by EN, DIN, JIS or a company specification, send the document and we will confirm equivalence before quoting.
Is there a minimum order quantity?
There is no minimum for standard sizes and grades held in stock, and prototypes, spares and small trial batches are accepted. Made-to-order melts and special forgings carry a minimum weight that depends on the alloy and the route, typically from about 500 kg for special grades.
What inspection and certification is issued with the goods?
Every shipment carries an EN 10204 3.1 mill test certificate quoting the actual chemical and mechanical results for the specific heat lot, together with dimensional records and heat treatment data where applicable. Testing is carried out in house by optical emission spectrometry, tensile, impact and hardness testing, plus ultrasonic and eddy current examination, with hydrostatic pressure and intergranular corrosion testing to ASTM G28 or A262 Practice E where the specification requires it. Third party inspection by SGS or another recognised agency can be arranged, and their report is issued alongside the shipment.
What are typical lead times?
Standard stock items ship within days. Common production grades such as Inconel 625 or duplex 2205 are typically a few weeks. Special chemistries, larger forgings and items that require third party inspection take longer and are quoted individually against the requirement.
How are the products packed for export?
Flanges and fittings receive a rust preventive coating, are individually wrapped and are packed in plywood cases secured with steel banding. Tube ends are capped and bundles are strapped. Packing lists quote heat numbers so every case can be cross-checked against the mill certificate on arrival. We quote EXW, FOB, CFR, CIF and DAP, and mixed-alloy orders can be consolidated into one shipment with a single documentation package.
How do I request a quotation or a sample?
Send the grade or UNS number, the dimensions including schedule or wall thickness, the governing material and dimensional standards, quantity, any heat treatment or NDT scope and the certificate type you need; a drawing is ideal for special flanges and fittings. Email [email protected] or message us on WhatsApp +86 15618279078 and we normally issue a formal quotation within 24 hours on working days. Samples and previous test reports can be arranged before the first order.
Talk to an engineer
Share your duty conditions and we will shortlist candidate alloys within one working day.