In the published TIMET tests, unalloyed titanium showed no measurable erosion in clean seawater at 25 ft/sec (7.6 m/sec), and at 120 ft/sec (36.6 m/sec) the reported rate was 0.3 mpy (0.008 mm/y). Those are test results at the conditions the source states, not a design limit for your equipment. What they do show is that in clean seawater the erosion rate is not what constrains a titanium tube. Two other things can: suspended abrasives above a certain loading, and crevice conditions in hot concentrated chlorides. This page gives the published numbers for all three, with the test conditions attached.
What do the published velocity tests actually show?
Three data points, in clean seawater, for unalloyed titanium and Ti-6Al-4V. Read them as what they are: results at the stated conditions, not an allowable velocity.
| Seawater velocity | Unalloyed titanium erosion rate | Ti-6Al-4V |
|---|---|---|
| 0 to 2 ft/sec (0 to 0.61 m/sec) | Nil | Not reported |
| 25 ft/sec (7.6 m/sec) | Nil | Not reported |
| 120 ft/sec (36.6 m/sec) | 0.3 mpy (0.008 mm/y) | 0.4 mpy (0.010 mm/y) |
Values from the published titanium corrosion resistance manual of TIMET (Titanium Metals Corporation), erosion of unalloyed titanium and Ti-6Al-4V in seawater. Two limits on how far this carries. “Nil” means no loss measurable by the source method, not zero. And the source does not state the test geometry, whether the quoted velocity is bulk flow or local impingement, the water chemistry or the exposure duration for these rows, so the numbers rank the material rather than qualify a tube configuration. Your own design velocity still has to be checked against impingement at inlets and bends, and against flow-induced vibration.
Where titanium actually loses: abrasive loading
In clean water the erosion rate stays low across the tested velocities; what changes the picture is what the water carries. The same published source reports abrasive-addition tests from 6.6 to 23.6 ft/sec, running 2,000 hours at real-intake sand loadings and as short as 1 hour at slurry loadings. Velocity still matters, and so do particle size, hardness and impact angle; the rows below vary more than one factor at a time and should be read as screening results:
| Condition | Unalloyed titanium | 70Cu-30Ni | Aluminium brass |
|---|---|---|---|
| Clean seawater, 23.6 ft/sec, 10,000 h | Nil | Pitted | Pitted |
| 40 g/l 60-mesh sand, 6.6 ft/sec, 2,000 h | 0.1 mpy (0.0025 mm/y) | 3.9 mpy (0.10 mm/y) | 2.0 mpy (0.05 mm/y) |
| 40 g/l 10-mesh emery, 6.6 ft/sec, 2,000 h | 0.5 mpy (0.0125 mm/y) | Severe erosion | Severe erosion |
| 4 percent 80-mesh emery, 13.5 ft/sec, 17.5 h | 3.3 mpy (0.083 mm/y) | 2.6 mpy (0.065 mm/y) | Not reported |
| 40 percent 80-mesh emery, 23.6 ft/sec, 1 h | 59.1 mpy (1.5 mm/y) | 78.7 mpy (2.0 mm/y) | Not reported |
Read the last two rows carefully, because they are the honest part. At 4 percent emery loading the cupronickel is marginally better than titanium, and at 40 percent loading both rates are past 1 mm per year. Note what the last row is: a 1-hour test with the loss extrapolated to an annual rate. That is a screening number, not a service rate, and the aluminium brass column is not reported for either of those two rows, so the ranking there is incomplete. Titanium is not an abrasion-proof material; it is dramatically better at the sand loadings a real intake sees, and it stops being the answer when the stream is effectively a slurry. Values from the same TIMET manual, erosion of unalloyed titanium in seawater containing suspended solids.
What long exposures at real sites show
| Location and flow | Duration | Unalloyed titanium | 70Cu-30Ni |
|---|---|---|---|
| Brixham Sea, 32.2 ft/sec (9.8 m/sec) | 12 months | Below 0.098 mpy (below 0.0025 mm/y) | 11.8 mpy (0.3 mm/y) |
| Kure Beach, 3.3 ft/sec (1 m/sec) | 54 months | 0.00003 mpy (0.00000075 mm/y) | Not reported |
| Wrightsville Beach, 2.0 to 4.3 ft/sec | 6 months | 0.004 mpy (0.0001 mm/y) | 0.9 mpy (0.022 mm/y) |
At Brixham the aluminium sample in the same test was perforated. These are multi-month and multi-year exposures at named sites, not laboratory hours, which is why they carry more weight in a design review than a single accelerated test.
The limit that actually decides your grade: crevice corrosion
Velocity rarely selects the titanium grade. Hot concentrated chlorides in a crevice do. The published 500-hour boiling tests using metal-to-PTFE crevice samples separate the grades cleanly:
| Boiling environment | pH | Unalloyed (Grade 2 class) | Ti-0.3Mo-0.8Ni (Grade 12) | Palladium-bearing (Grade 7 class) |
|---|---|---|---|---|
| Saturated NaCl | 3.0 | Failed | Resisted | Resisted |
| Saturated ZnCl2 | 3.0 | Failed | Resisted | Resisted |
| 42 percent MgCl2 | 4.2 | Failed | Resisted | Resisted |
| 10 percent NH4Cl | 4.1 | Failed | Resisted | Resisted |
| 10 percent Na2SO4 | 2.0 | Failed | Resisted | Resisted |
| Saturated NaCl plus Cl2 | 2.0 | Failed | Failed | Resisted |
| 10 percent FeCl3 | 0.6 | Failed | Failed | Resisted |
What this table supports, stated narrowly: across these seven boiling solutions with a tight crevice, the unalloyed grade failed in all of them, Grade 12 held in five and failed in the two oxidising chloride environments, and the palladium-bearing grade held in all seven. That is a grade ranking under one severe screening condition. It is not a service boundary, because the table carries no temperature range below boiling, no chloride activity, no crevice geometry other than the one used, no heat-transfer condition and no allowable attack depth. Use it to know the order of the grades and to know that oxidising chlorides separate Grade 12 from the palladium grade; use your own service data to place the actual duty. Ambient seawater is not this environment at all, and unalloyed titanium is the correct and normal selection there.
The variable this page does not resolve: temperature
The tests above are either ambient seawater or boiling. Most real duty sits between the two, and that gap is where grade selection is actually decided. The same TIMET manual states general seawater corrosion resistance to temperatures as high as 500 F (260 C), and it maps the crevice corrosion boundary for each grade as a function of temperature and pH in saturated NaCl brine. If your service is a chlorinated seawater loop at 60 C, neither the ambient data nor the boiling data answers it; the temperature and pH map does. Send the operating temperature, pH and chlorine residual with the enquiry and the duty can be placed against that boundary rather than guessed from the two extremes on this page.
Where titanium is the wrong answer entirely
| Condition | Why titanium is ruled out |
|---|---|
| Fluorine gas, and fluorides in acid aqueous service | Hydrofluoric acid can form from minute quantities and attacks titanium rapidly; the published guidance is explicit that titanium is not recommended in contact with fluorine gas |
| Slurry-grade abrasive loading | See the 40 percent emery row above: both titanium and cupronickel are failing |
| Dry chlorine or dry bromine | Titanium is attacked by the dry gas and is passivated by the presence of moisture |
Stating the exclusions is part of a usable selection page. A supplier who only lists what a metal survives has not given you enough to design with.
What this means for the order
| Order line | What to state |
|---|---|
| Grade and standard | Grade 2 to ASTM B338 for ambient seawater tube; Grade 12 or Grade 7 where hot chloride crevice conditions are credible |
| Service data to share | Medium, chloride concentration, temperature, pH, free chlorine dosing, and expected suspended solids |
| Velocity | State the design velocity so the wall thickness and support spacing are checked against vibration, not erosion |
| Inspection | State the ultrasonic acceptance class and method standard for the tube, and any eddy current requirement |
| Certificate | EN 10204 type 3.1 with heat and pour numbers |
One consequence worth stating plainly, because it changes a drawing: in clean flowing seawater the published erosion rates are low enough that titanium tube is normally sized by pressure and vibration rather than by a corrosion allowance on the wall. One practical note from quoting this work: on titanium seawater tube the governing design limit is usually flow-induced vibration and support spacing, not metal loss. That changes what your RFQ should ask us to confirm.
Specification detail with sources
Corrosion and erosion values above are from the published titanium corrosion resistance manual of TIMET (Titanium Metals Corporation): erosion of unalloyed titanium and Ti-6Al-4V in seawater at 0 to 2, 25 and 120 ft/sec; erosion in seawater containing suspended solids at the stated abrasive loadings and durations; erosion at named seawater locations over 6 to 54 months; and resistance to crevice corrosion in boiling solutions from 500-hour tests using metal-to-PTFE crevice samples. Grade identities and limits are per ASTM B338 for seamless and welded tube; the composition figures quoted here are the corresponding grade identities, with ASTM B348 cited only where bar is the product form. Grade 2 under UNS R50400 with oxygen at 0.25 percent maximum and tensile strength at 345 MPa minimum in the annealed condition, Grade 7 under UNS R52400 with palladium at 0.12 to 0.25 percent, and Grade 12 under UNS R53400 with molybdenum at 0.2 to 0.4 percent and nickel at 0.6 to 0.9 percent.
Scope note on the crevice data: those results describe boiling concentrated solutions with a deliberately tight metal-to-PTFE crevice over 500 hours. They are a grade-ranking test, not a prediction of service life in your equipment, and they do not describe ambient seawater, where unalloyed titanium is the normal selection. Beiyu Titanium supplies the tube and bar to the standards named above with an EN 10204 type 3.1 certificate by order scope; the corrosion data is published third-party test data, not Beiyu test results.
Frequently asked questions
Is there a maximum seawater velocity for titanium condenser tube? The published data do not give one. TIMET reports 0.3 mpy (0.008 mm/y) at 120 ft/sec (36.6 m/sec) in clean seawater, which says erosion is not the first constraint, but the source does not state the test geometry or whether that velocity is bulk or impingement. In practice the governing limits come from flow-induced vibration, support spacing and inlet impingement, which are mechanical design questions and belong in your tube design basis, not in a corrosion table.
Does sand in the intake change the answer? In the same TIMET manual, at 40 g/l of 60-mesh sand and 6.6 ft/sec over 2,000 hours, unalloyed titanium ran 0.1 mpy while 70Cu-30Ni ran 3.9 mpy in the same test. Titanium is far better at real intake loadings. At slurry loadings both materials fail, and the honest answer there is that neither is the right selection.
When do I have to leave Grade 2? When hot concentrated chlorides can sit in a crevice. Grade 12 covers most of that range; free chlorine or ferric chloride pushes the selection to the palladium-bearing grade. The mechanism and grade logic is in Grade 12 titanium in hot brine and crevice service and Grade 7 titanium in reducing acids.
How does titanium compare with cupronickel overall for seawater? The material comparison across seawater duty is in titanium versus stainless and copper nickel in seawater.
What tube standard applies? ASTM B338 covers seamless and welded titanium tube for condensers and heat exchangers; the guide is at the ASTM B338 titanium tube and pipe guide.
Send the service data with the RFQ
Send medium, chloride concentration, temperature, pH, chlorine dosing, suspended solids and design velocity along with grade, standard, dimensions and quantity to the Beiyu RFQ page. Reviewed by Penn Ma, 15 years in titanium mill product export. Last reviewed: 2026-09-01.