Do Not Rank Titanium and Hastelloy Without the Process Data
Titanium and Hastelloy C-family materials are not universal corrosion rankings. For an ANSI chemical process pump, the decision should begin with the real process envelope: chemical composition, concentration, normal and upset temperature, chloride and fluoride content, oxidizing or reducing conditions, solids, velocity, pressure, shutdown chemistry and the mechanical-seal environment.
The next question is equally important: what material is actually being purchased? A buyer asking for “Titanium Grade 2” or “Hastelloy C-276” may be using a familiar wrought-material name while the casing and impeller are cast components.
Start With the Process Chemistry, Not the Alloy Name
Terms such as “acid,” “chloride service,” “bleach,” “brine” or “mixed chemical” are not complete material-selection inputs.
Two systems carrying the same named chemical can create very different corrosion conditions because of differences in concentration, water content, temperature, dissolved oxygen, oxidizing or reducing contaminants, chloride or fluoride content, suspended solids, flow velocity, stagnant or crevice areas, cleaning chemicals, and startup or shutdown conditions.
The pump also contains more than a casing. A complete review may involve the casing, impeller, cover or seal chamber, shaft, mechanical-seal metal parts, seal faces, elastomers, gaskets and fasteners. Galvanic interaction and local geometry can matter even when the principal wet-end alloy appears suitable.
Define the normal and upset envelope
| Process input | Buyer should provide |
|---|---|
| Chemical | Full chemical name or composition |
| Concentration | Normal range and maximum/minimum |
| Temperature | Continuous and excursion temperature |
| Halides | Chloride and fluoride where relevant |
| Oxidation state | Oxidizing/reducing species where known |
| Solids | Percentage, particle type and approximate size |
| Hydraulics | Flow, TDH, pressure and velocity context |
| Physical properties | Specific gravity and viscosity |
| Operation | Continuous/intermittent, cleaning and shutdown conditions |
C-Family Ni-Cr-Mo Materials: Specify the Casting, Not Only the Trade Name
“Hastelloy” is a commercial alloy-family name rather than one universal pump material. When a buyer asks for a Hastelloy C-family pump, the procurement document should identify the exact alloy specification and product form for each relevant component.
A wrought alloy designation and an ASTM pump-casting designation may have related chemistry or service applications, but they are not automatically the same material specification.
Why carbon content deserves attention
| ASTM A494 cast grade | UNS | Published maximum carbon | Procurement point |
|---|---|---|---|
| CW12MW | N30002 | 0.12% | Do not assume the same metallurgy as a low-carbon C-family grade |
| CW2M | N26455 | 0.02% | Low-carbon Ni-Cr-Mo cast grade |
| CX2MW | N26022 | 0.02% | Low-carbon, higher-chromium Ni-Cr-Mo cast grade |
Do not write
Material: Hastelloy
Prefer
Component + product form + ASTM specification + exact grade + inspection scope + heat traceability.
Titanium Pump Castings: ASTM B367 Changes the Procurement Question
A request for “Titanium Grade 2” may be understandable during an early material discussion, but it does not by itself define the finished pump casting.
ASTM B367 covers titanium and titanium-alloy castings for corrosion-resistant and industrial applications. The exact cast grade should be written into the procurement specification rather than inferred from a familiar wrought-material name.
| ASTM B367 grade | UNS | ASTM description |
|---|---|---|
| C-2 | R52550 | Unalloyed titanium |
| C-3 | R52551 | Unalloyed titanium |
| C-7 | R52700 | Unalloyed titanium with palladium |
| C-8 | R52703 | Unalloyed titanium with palladium |
| C-12 | R53400 | Titanium alloy containing molybdenum and nickel |
| C-16 | R52402 | Unalloyed titanium with lower palladium range |
Hastelloy vs Titanium: Engineering Screening Matrix
This matrix structures the material review. It is not a corrosion guarantee.
Full chemistry
- Ni-Cr-Mo
- Exact alloy and oxidation state matter.
- Titanium
- Exact grade and chemistry matter.
- Buyer action
- Provide complete process composition.
Concentration
- Ni-Cr-Mo
- Behavior can change with concentration.
- Titanium
- Suitability can change with concentration.
- Buyer action
- State normal and upset ranges.
Chlorides / fluorides
- Ni-Cr-Mo
- Review localized-corrosion conditions explicitly.
- Titanium
- Halides can materially affect suitability.
- Buyer action
- Report chloride and fluoride where relevant.
Temperature
- Ni-Cr-Mo
- Affects corrosion, strength and seals.
- Titanium
- Can materially change corrosion behavior.
- Buyer action
- Provide continuous and excursion temperatures.
Product form & verification
- Ni-Cr-Mo
- Wrought name is not the casting specification.
- Titanium
- Wrought grade name is not a complete casting specification.
- Buyer action
- Define cast grade, MTR, traceability and agreed testing.
Wrought Alloy Name ≠ Pump Casting Specification
This is one of the most important procurement rules for exotic-alloy pumps. A familiar wrought-material or commercial alloy name may help describe the intended alloy family, but a cast pump casing requires a casting specification.
ENGINEERING VISUAL — Wrought Alloy Name ≠ Cast Pump Specification
| Common buyer request | What must be clarified | Main risk |
|---|---|---|
| “Titanium Grade 2” | Applicable ASTM B367 cast grade | Wrought terminology used as a complete casting specification |
| “Titanium-Pd” | Exact B367 grade and Pd range | Alloy family requested without exact cast grade |
| “Hastelloy C-276” | Exact applicable ASTM A494 cast grade | Wrought trade name treated as automatic casting equivalent |
| “Special alloy wet end” | Exact material for each wetted component | Different parts supplied in different materials without clear approval |
Manufacturing Risks Buyers Should Understand
The purchaser does not need to become a foundry metallurgist, but understanding the principal manufacturing risks makes the inspection plan much more useful.
Titanium: contamination and surface integrity
Molten titanium is highly reactive. The casting route must control contamination and metal–mold interaction, and the finished surface must meet the agreed specification.
One titanium-specific concern is a hardened oxygen-enriched surface reaction layer commonly referred to as alpha-case. The buyer should ask how surface contamination is controlled, how reaction layers are removed when necessary, how repair welding is handled, and whether metallographic or hardness verification is required by the project specification.
Ni-Cr-Mo castings: chemistry and heat-treatment records
Instead of writing one heat-treatment temperature for every C-family casting, define the exact ASTM A494 grade and require the heat-treatment condition and supporting record applicable to that grade when project documentation requires it.
Material Verification: MTR, XRF, OES and Heat Traceability
Material verification should answer one question: can the supplied evidence connect the approved specification to the physical component in front of the buyer?
Material Verification Workflow
Updated from the existing 7-point concept so XRF and OES are no longer presented as equivalent tools.
XRF and OES do different jobs
| Verification question | Handheld XRF | OES / suitable laboratory chemistry |
|---|---|---|
| Rapid alloy sorting | Strong application | Possible |
| Ni / Cr / Mo verification | Strong application | Yes |
| Carbon measurement | No | Yes |
| Low-carbon grade verification | Insufficient alone | Appropriate when supported by method/specification |
| Replaces MTR | No | No |
| Proves heat traceability | No | No |
NDT: The Method Is Not the Acceptance Criterion
A procurement line saying only “PT + RT required” is incomplete. A useful NDT requirement identifies the component, examination method, coverage, area of interest, procedure/reference, acceptance criteria, reporting requirement and any personnel qualification requirement.
PT — Surface-breaking indications
ASTM E165/E165M defines penetrant-testing practice but does not itself supply universal acceptance criteria. The project specification must define what is acceptable.
RT — Material-appropriate references
ASTM E446 is for steel castings. Titanium castings have titanium-specific reference radiographs under ASTM E1320.
The Wet End Is Only Part of the Chemical Compatibility Review
A premium casing alloy does not compensate for an incompatible mechanical seal or gasket. Review the complete wetted system.
| Component | Engineering review |
|---|---|
| Casing | Cast grade, pressure boundary, inspection and traceability |
| Cover / seal chamber | Material, sealing geometry and process exposure |
| Impeller | Alloy, hydraulic trim, balance and erosion risk |
| Shaft | Material, process exposure and mechanical interface |
| Mechanical-seal metallic parts | Corrosion compatibility and design |
| Seal faces | Process compatibility, solids and lubrication |
| Elastomers / gaskets | Chemical concentration and temperature |
| Flush / barrier fluid | Interaction with the process and seal arrangement |
Seal-support plans should follow the application
Do not select an API 682 piping plan only because the pump uses an exotic alloy. Plan selection depends on process properties, pressure, temperature, hazard, seal arrangement and operating requirements.
Replacement Projects: Material Upgrade and Mechanical Fit Must Be Reviewed Together
Exotic-alloy projects often begin after an existing stainless-steel or lower-alloy wet end has experienced corrosion. That does not mean the replacement scope should be defined only as “same pump, but titanium” or “same pump, but Hastelloy.”
For an ANSI B73.1 replacement project, review the installed pump reference, pump size and frame, flow and TDH, suction conditions, speed, casing interfaces, impeller geometry, seal chamber, shaft arrangement, base and piping interfaces, required alloy, and required documentation.
Goulds 3196 replacement engineering review →
Durco Mark III replacement engineering review →
Do not promise a universal service-life multiplier. The objective of a material upgrade is to reduce the failure mechanism identified in the actual service; expected life depends on qualified corrosion data, operating history and complete pump design.
Exotic-Alloy Pump Inspection Checklist
Before issuing the PO, define what evidence must be delivered with the pump or component.
Material
- Exact cast/wrought specification
- Exact grade by component
- Heat identification
- Material certificate / test report
- Approved deviations
Chemistry verification
- PMI scope
- XRF locations where applicable
- OES / laboratory chemistry where required
- Acceptance limits linked to specification
Casting & fabrication
- Required manufacturing documentation
- Heat-treatment documentation
- Weld-repair disclosure
- Titanium surface-integrity requirements if applicable
NDT & dimensions
- PT / RT scope
- Applicable reference standard
- Defined acceptance criteria
- Approved drawing and critical dimensions
What to Send for an Engineering Review
A useful RFQ does not need to start with a perfect datasheet. Start with what is available.
Process data
- Chemical / process composition
- Concentration range
- Normal and maximum temperature
- Chloride / fluoride where relevant
- Solids, SG and viscosity
Hydraulic data
- Required flow
- TDH / differential pressure
- Suction condition
- Pump speed where known
Existing equipment
- Manufacturer/model reference
- Pump size/frame
- Nameplate photo
- Existing material and seal arrangement
Quality documents
- Material certification
- PMI/OES requirement
- NDT requirement
- Third-party inspection if required
Need the material reviewed before quotation?
Send the process chemistry, temperature, existing pump model and available material requirements.
