Titanium Grade 2 CNC Machining

Corrosion is the reason

Grade 2 is unalloyed titanium. There is no deliberate alloying addition in it, and its strength reflects that: around 345 MPa annealed, which puts it in the same bracket as a mild steel. Nobody specifies Grade 2 for its strength.

They specify it for this: in chlorides, titanium is effectively immune.

Every stainless steel depends on a chromium oxide film for its corrosion resistance, and that film has a specific weakness — chloride ions attack it locally. That is the mechanism behind pitting, crevice corrosion and stress-corrosion cracking, and it is why 316 and 316L have limits in warm, stagnant or concentrated chloride service despite being the minimum grade for it.

Titanium’s oxide film is a different proposition. It is more stable in the presence of chlorides and reforms essentially instantly if it is damaged — so quickly that a freshly cut or scratched titanium surface passivates before corrosion can begin. The practical result is that Grade 2 is effectively immune to the three failure modes that limit stainless in sea water.

That is the whole reason titanium appears in:

• Sea-water and desalination plant — heat exchanger tubing, condensers, pumps, valves
• Chemical process equipment handling chlorides, hypochlorite and wet chlorine
• Chlorine and bleach production
• Anodizing racks and jigs, which sit in acid baths all day
• Offshore and marine hardware expected to survive decades without coating
• Medical implants, where the same inertness keeps the body from reacting to the metal

Add to that a density roughly 43% below steel, and you have a material that solves a corrosion problem and a weight problem at the same time. That combination is worth a great deal in the right application — and worth nothing in the wrong one, which is why the next section matters as much as this one.

What titanium does not resist

Titanium is often described as the most corrosion-resistant engineering metal, and that description is too generous to be useful. Its resistance is environment-specific, and the exceptions are sharp.

Environment	Titanium Grade 2
Sea water, brine, chlorides	Excellent — effectively immune
Wet chlorine, hypochlorite, bleach	Excellent
Oxidising acids (nitric)	Good
Reducing acids (hydrochloric, dilute sulphuric)	Poor — attacked
Hydrofluoric acid	Rapidly attacked, even dilute
Dry chlorine gas	Attacked — a specific and dangerous exception
Methanol without water	Stress-corrosion cracking risk
High-temperature oxidising service	Limited by oxide growth and oxygen uptake

Two of those deserve emphasis because they catch people out. Hydrofluoric acid attacks titanium rapidly even at low concentration — a titanium part that meets a fluoride-containing cleaning agent or etchant will not survive. And dry chlorine gas is the opposite of wet chlorine: the wet form is fine and the dry form is not, which is counter-intuitive enough that it is worth stating.

So the honest way to specify titanium is not “it resists everything” but “here is the chemical, the concentration and the temperature” — and then the alloy choice follows. Tell us those and we will say whether Grade 2 is right, whether Grade 5 is better, or whether the part belongs in a different material altogether.

Machining titanium: four compounding problems

Titanium has a reputation for being difficult, and the reputation is earned. Four properties do the damage, and they reinforce each other.

It conducts heat very poorly. Titanium’s thermal conductivity is a fraction of steel’s and a tiny fraction of aluminium’s. Cutting heat does not spread into the chip or the workpiece, so it concentrates right at the cutting edge, where it destroys tooling. This is the single largest cause of poor tool life on titanium.

It is chemically reactive when hot. At cutting temperature titanium tends to weld to the tool edge, producing a built-up edge and a smeared, torn surface rather than a sheared one. A dull edge makes this dramatically worse, which is why titanium is the material where tool sharpness matters most.

Its modulus is low. Titanium is stiff for its weight, but roughly half as stiff as steel in absolute terms. Thin walls, slender shafts and long unsupported sections deflect away from the tool, which causes chatter, poor finish, and a dimension that moves as the cut progresses.

Its swarf is combustible. Fine titanium chips will burn, and a titanium fire is a class D metal fire — extremely hot, and made worse rather than better by water. This is a real industrial hazard and it is managed rather than ignored.

What works

• Sharp tooling, always. A titanium job starts with fresh, correctly ground, high-positive-geometry tooling, and edges are replaced on condition rather than on a schedule. A dull edge on titanium does not simply cut worse — it starts the galling and heat cycle that ruins the part.
• Low cutting speeds and generous feeds. Titanium is cut slowly. The instinct to speed up when the material resists is exactly wrong, because speed converts directly into edge temperature.
• Copious coolant at high pressure, directed at the edge. Not coolant sprayed over the part — coolant delivered to the cutting zone. This is the primary heat-removal mechanism, because the material will not remove heat itself. Never machine titanium dry.
• Rigid setups and short tool overhangs. Because the material deflects, the setup has to compensate. Where a part is thin-walled or slender, that is worth saying at the enquiry so the fixturing can be planned rather than improvised.
• Decisive depths of cut. Titanium work-hardens to a degree, and a light rubbing pass generates heat without removing material — the worst combination on this material.
• Chip management. Swarf is cleared continuously so fine chips do not accumulate, and the machine is cleaned of titanium fines before the next job.

Precision features are held to ±0.01 mm with ISO 2768-m as the general tolerance block — see tolerances we hold. On titanium the tolerance is achievable; what changes is the time and the tooling cost of getting there, and that shows up in the quotation.

Where Grade 2 is the right choice

• Sea-water and desalination components — tubing, condensers, pumps, valves, fittings
• Chemical plant handling chlorides, hypochlorite or wet chlorine
• Chlorine and bleach production equipment
• Anodizing racks, jigs and fixtures in acid service
• Medical implants and surgical instruments, where inertness and biocompatibility are required
• Offshore and marine hardware that must not corrode and must not be heavy
• Heat exchangers, where titanium’s thin-wall tubing and corrosion immunity combine
• Any chloride duty beyond what 316L can hold, where a coating is not acceptable

Where Grade 2 is the wrong choice

The requirement is strength. Grade 2 is around 345 MPa annealed — comparable to mild steel. Where strength-to-weight is the reason for using titanium, the grade is Grade 5 at roughly 950 MPa.

The environment is a reducing acid, hydrofluoric acid, or dry chlorine. Titanium is attacked quickly in all three. Those duties belong to a different material entirely, and the chemical has to be stated before a grade is quoted.

A chloride duty that 316L already handles. In flowing sea water at moderate temperature, 316L performs adequately and costs a fraction of titanium, and it machines far more easily. Titanium earns its cost where the chloride duty is beyond 316L — warm, concentrated, stagnant, creviced, or where a decades-long life without maintenance is the requirement.

The part geometry is too thin or slender for the material’s stiffness. Because titanium’s modulus is low, a design that works in steel may chatter in titanium. Where a part is thin-walled or has a high length-to-diameter ratio, that should be reviewed before the material is fixed.

Cost is the binding constraint and corrosion is not. Titanium is expensive material that is also slow to machine — the two penalties compound. Verifying that the duty genuinely needs titanium is worth doing before the drawing is released.

Finishing titanium

Titanium resists corrosion on its own, so finishing is usually about appearance, surface hardness or specific service requirements rather than protection.

• Anodizing — grows the oxide film to a controlled thickness. Titanium oxide produces colour by light interference rather than pigment, so different thicknesses give different colours with no dye involved. The film is also thicker and harder than the natural oxide. Common on medical instruments, colour-coded hardware and consumer parts.
• Passivation — removes surface contamination, particularly iron picked up from tooling and fixturing, which would otherwise show as rust spots on a titanium part.
• Sand blasting — a uniform matte surface, often used before anodizing or as a finish in its own right.
• Polishing and brushing — titanium takes a good finish, and it is used on visible and medical parts.
• Pickling — removes heat tint and alpha case from welded or heat-treated parts.

One contamination point is worth stating plainly: titanium picks up iron from steel tooling, fixtures and brushes, and that iron then rusts on the surface of a corrosion-resistant part. It looks like the titanium has failed when it has not. Keeping steel away from finished titanium parts, and passivating after any operation where contact occurred, is the standard control.

All finishing runs through our vetted partner network, managed under one quality process. The grades we run across every process are listed on the materials page.

What to put on the drawing

Instead of	Write
Titanium	Titanium Grade 2, where corrosion resistance is the driver
Titanium, needs strength	Wrong grade — Grade 5 reaches roughly 950 MPa against Grade 2’s 345 MPa
Titanium, hydrofluoric acid or reducing acid	Wrong material — titanium is attacked
Titanium, dry chlorine gas	Attacked — a specific exception to titanium’s chlorine resistance
Titanium, chloride duty 316L handles	316L costs and machines far less — check whether titanium is needed
Titanium, thin wall or slender section	Say so — low modulus means the setup is planned around deflection
Titanium, surface finish critical	Say so — galling and built-up edge are the main finish risks
Titanium, colour or hardened surface	Anodizing is the route — and colour comes from film thickness, not dye

The three lines that decide most Grade 2 specifications are the chemical and the temperature, whether the duty is genuinely beyond 316L, and whether the geometry suits a low-modulus material. The first settles whether titanium works at all. The second settles whether it is worth the cost. The third settles whether the part can be machined to the tolerance on the drawing.

Material is bought against your drawing for your job, and every batch ships with a material certificate (MTR) tracing the grade to its mill heat plus pre-shipment photos of the actual parts. Orders start at 50 pieces per style and material, samples from a single piece in 5–10 days, and production runs in 25–35 days after sample approval. Send the drawing through the request a quote form and the reply comes back within 24 hours with DFM feedback — including a note on the geometry, the coolant strategy and the finishing route where any of them need settling.