Grade 2 titanium handles most seawater and chemical service, but in hot, tight, chloride-rich crevices it can start to corrode where a plain commercially pure grade has no answer. Grade 12 is the grade the chemical and process industries reach for at that point: a small molybdenum and nickel addition that pushes back the crevice-corrosion limit and adds strength, at a fraction of the cost of the palladium grades. This guide covers what Grade 12 is, the exact conditions where Grade 2 gives out, how far Grade 12 extends the envelope, and how to specify and verify it.
What is Grade 12, and where does it sit between Grade 2 and Grade 7?
Grade 12 is titanium with a nominal 0.3% molybdenum and 0.8% nickel addition, UNS R53400, Werkstoff 3.7105. The alloying is small, so it fabricates and welds much like commercially pure titanium, but the molybdenum and nickel raise both strength and crevice-corrosion resistance above Grade 2.
On the corrosion ladder for hot chlorides and brines, Grade 12 sits in the middle: better than the commercially pure grades, below the palladium grade (Grade 7), and far cheaper than Grade 7 because it uses no precious metal. When a stream is too aggressive for Grade 2 but does not justify palladium, Grade 12 is usually the grade that closes the gap. The reducing-acid end of that decision is covered in our Grade 7 reducing-acid guide, and the choice among the plain CP grades in our CP titanium grade selection guide.
When does Grade 2 start to fail, and what does Grade 12 fix?
Grade 2's weak point is crevice corrosion: in tight gaps such as under gaskets, in rolled tube-to-tubesheet joints, or beneath deposits, the chemistry inside the crevice turns acidic and the protective film breaks down. This becomes a real risk once hot chloride service climbs above roughly 70 to 80°C in tight crevices. Below that, Grade 2 is normally fine; above it, a tight crevice in brine is where failures start.
Grade 12 fixes exactly this failure mode. The molybdenum and nickel keep the film stable in the acidified crevice, pushing the safe service window for hot brine and chloride crevices well past where Grade 2 gives out, with reports of useful crevice resistance to over 250°C in high-temperature brine. For a designer, that means Grade 12 lets a hot-brine heat exchanger or vessel stay in titanium instead of jumping to a much more expensive alloy.
How far does Grade 12's crevice resistance actually extend?
The ranking below is the practical decision order for hot chloride and brine crevice service. The figures are orientation values from titanium corrosion literature, not design guarantees, because real service depends on temperature, pH, chloride concentration and crevice tightness.
| Grade | Crevice resistance in hot chlorides | Relative cost | Note |
|---|---|---|---|
| Grade 2 (CP) | Limited; risk above roughly 70 to 80°C in tight crevices | Lowest | Workhorse below the crevice threshold |
| Grade 12 (Ti-0.3Mo-0.8Ni) | Extended; useful to over 250°C in hot brine | Moderate | No precious metal, adds strength |
| Grade 7 (Ti-Pd) | Highest of the three | High (palladium) | For reducing acids and the most severe crevices |
Two limits matter when specifying. First, Grade 12 improves crevice resistance but is not a reducing-acid grade; in low-pH service, roughly below pH 3, its advantage narrows and Grade 7 becomes the right call. Second, higher temperature does not always mean worse crevice attack, so the actual stream chemistry, not just the peak temperature, decides the grade. Where the medium attacks titanium itself, the conversation moves to nickel alloys, which is why we keep both families in scope for chemical equipment.
Where does Grade 12 belong, and where does it not?
Grade 12 is a chemical-process and brine grade. It is specified for heat exchangers and condensers on hot brine or chloride cooling water, evaporators and crystallizers, vessels and piping in chlor-alkali and brine service, and geothermal and high-temperature high-pressure duties where crevice corrosion would end Grade 2 too early. Its extra strength over Grade 2 also helps in pressure parts.
It is not the grade for strongly reducing acids, where the pH is too low for its mechanism to help and Grade 7 earns its palladium. It is also unnecessary below the crevice threshold, where Grade 2 already does the job at lower cost. The general chemical and heat-exchanger case for Grade 2 is covered in our Grade 2 chemical and heat-exchanger guide, and the seawater side in our titanium seawater corrosion resistance guide.
Standards, forms and equivalents
Grade 12 is a mill-product grade in the common wrought forms. Specify the form standard that matches the part, and note the cross-system designations so a buyer using any naming convention lands on the same metal.
| Property | Detail |
|---|---|
| UNS number | R53400 |
| Werkstoff-Nr. | 3.7105 |
| Nominal composition | Ti-0.3Mo-0.8Ni |
| Bar and billet | ASTM B348 |
| Sheet, strip and plate | ASTM B265 |
| Tube (seamless and welded) | ASTM B338 |
| Certificate | EN 10204 3.1 with heat number and full chemistry |
How to read the Grade 12 mill certificate when it arrives
Grade 12 costs more than Grade 2 for two reasons, and both have to be visible on the certificate before the material is accepted:
| Check on the MTC | What to verify | Why it matters |
|---|---|---|
| Molybdenum and nickel by heat | Confirm the certificate reports molybdenum near 0.3% and nickel near 0.8% for the delivered heat, not just the words Grade 12. | These two elements are the entire reason for the upgrade, so a certificate that omits them does not prove you received Grade 12 rather than relabelled Grade 2. |
| Mechanicals at the ordered form and size | Read the yield and tensile against the standard for the form you ordered, since plate, tube and bar are tested on different bases. | Grade 12 runs stronger than Grade 2, but the acceptance line still has to match the ordered form and size. |
Then close the loop on traceability: the heat number on the certificate must match the marking on the tube, plate or bar. The trap buyers miss is accepting a certificate that names Grade 12 but never prints the actual molybdenum and nickel results, which leaves the single thing you paid for unverified. This is the same acceptance discipline our other grade guides use, adapted to the two elements that define Grade 12.
How to specify Grade 12 on an RFQ
Because Grade 12 is chosen by service conditions, the most useful RFQ describes the duty, not just the part. State the medium and chloride content, the operating temperature and any crevice geometry (gasketed joints, rolled tube ends), the form and dimensions in metric with the tolerance, the quantity, and the certificate requirement. Naming the actual brine and temperature lets the supplier confirm Grade 12 is the right call rather than a leaner or a palladium grade. The full field list is in our titanium bar RFQ checklist. Beiyu supplies Grade 12 bar, sheet and plate, and tube on an RFQ basis with EN 10204 3.1 documentation that reports the molybdenum and nickel against the specified composition.
Fabrication and welding behaviour
Grade 12 fabricates like the CP grades it grew out of: it forms, machines and welds with standard titanium practice, and the small molybdenum and nickel additions do not demand a new workshop skillset. Welding follows the usual titanium rules: clean joint preparation and full inert gas shielding of the heated zone until the metal cools, with weld colour as the working acceptance indicator. Matching filler keeps the joint’s crevice resistance in family with the parent metal; welding Grade 12 with a plain CP filler quietly rebuilds the weaker metal into the most exposed part of the equipment. For buyers, the practical line is to state the welding consumable expectation on fabrication-bound orders.
What a crevice failure actually looks like
Crevice corrosion does not announce itself on open surfaces: it starts where the environment stagnates, under gaskets and flange faces, beneath scale and deposits, under bolt heads and in tube-to-tubesheet joints. Inside those gaps the trapped solution acidifies and the passive film loses its repair supply, and by the time staining or leakage shows at the edge, the attack underneath is established. The buying consequence is that crevice resistance is partly a design property: gasket choice, deposit control and drainable geometry decide how hard the alloy’s chemistry has to work. Grade 12 widens the safe window over Grade 2; it does not make crevice-free design unnecessary.
Handling and identity in the plant
Store Grade 12 apart from carbon steel so embedded iron does not stain the surface or seed local attack, keep heat numbers legible through fabrication, and carry the certificate identity into the equipment file. For pressure and chemical service, the material record is part of the asset. Iron smeared into a titanium surface during handling is a documented starting point for localized attack in service, and it is the cheapest failure cause to prevent.
Procurement notes from the export desk
Grade 12 sits in a price band between Grade 2 and the palladium grades, which makes it the value answer when hot chlorides are the driver, but only if the order is written cleanly. Confirm the form standard for each item, bar, plate, tube or forged blank, rather than one blanket line; for forged components, quote Grade 12 titanium forgings against the drawing; state the service medium on the RFQ so the mill’s review checks the right failure mode; and where the equipment builder needs both ASTM and ASME SB certification, say so up front, since dual certification is routine at production and awkward afterwards. Beiyu reviews each Grade 12 line against mill capability before quoting, with EN 10204 3.1 documentation and heat-number traceability by order scope.
FAQ
What is the difference between Grade 2 and Grade 12 titanium?
Grade 12 adds about 0.3% molybdenum and 0.8% nickel to commercially pure titanium. It fabricates much like Grade 2 but resists crevice corrosion in hot brine and chlorides well beyond Grade 2's limit and carries more strength. Use Grade 2 below the crevice threshold and Grade 12 when hot tight-crevice chloride service would put Grade 2 at risk.
What is the UNS number for Grade 12 titanium?
Grade 12 titanium is UNS R53400, Werkstoff 3.7105, nominal composition Ti-0.3Mo-0.8Ni. It is supplied as bar to ASTM B348, sheet and plate to ASTM B265, and tube to ASTM B338.
When should I choose Grade 7 instead of Grade 12?
In strongly reducing or low-pH acid service, roughly below pH 3, Grade 12's advantage narrows and the palladium grade, Grade 7, becomes the right choice. Grade 12 is the more economical answer for hot brine and chloride crevice corrosion where the pH is not strongly acidic.
Does Grade 12 titanium resist crevice corrosion better than Grade 2?
Yes. Its molybdenum and nickel keep the protective film stable inside hot acidified crevices, extending useful crevice resistance in brine well past Grade 2's limit, with reports beyond 250°C, at much lower cost than the palladium grade.
References
- ASTM B265, B348 and B338, standard specifications for titanium plate, bar and tube products: astm.org
- ASTM G48 adjacent crevice testing practice for titanium alloys, when required by project specification.
- EN 10204, Metallic products, types of inspection documents (CEN)
Request a quote for Grade 12 titanium
To quote Grade 12 titanium for hot brine or crevice-corrosion service, Beiyu needs: the form (tube, plate, sheet or bar), the standard, the dimensions and tolerance in metric, the quantity, and the service conditions (medium, chloride content, temperature, crevice geometry), plus the certificate level (EN 10204 3.1 or 3.2). Send the drawing or spec and we review each line against mill capability before quoting, with EN 10204 3.1 documentation and heat-number traceability reporting the molybdenum and nickel content. Contact Beiyu Titanium for an RFQ.