Alloy 20-family materials, Hastelloy C-family alloys and PVDF are all important candidates, but they solve different problems. The selection must be tied to the complete process envelope and the exact material form used in the pump.
The five variables that change sulfuric-acid material selection
- Concentration: Corrosion behavior can change across the concentration range, including during dilution or upset conditions.
- Temperature: Temperature changes reaction rate, corrosion behavior and polymer mechanical capability.
- Contaminants: Chlorides, fluorides, oxidizing or reducing species and aeration may alter the shortlist.
- Velocity, solids and erosion: Hydraulic conditions and suspended material can add erosion-corrosion risk.
- Pressure-temperature capability: Polymers require a specific pressure-temperature review, not a chemistry-only decision.
Alloy 20 family — when it enters the shortlist
Alloy 20 commonly refers to a wrought alloy family. Pump casings may use a related cast grade such as CN7M depending on specification. Do not treat the commercial alloy name and casting designation as automatically identical.
Alloy 20 may enter the shortlist for selected sulfuric-acid duties, but final selection still requires the concentration and temperature range, contaminants, mechanical design and exact product form. Do not use a universal concentration or temperature boundary without a primary material source.
Hastelloy C-276 family — broader resistance, higher alloy cost
Hastelloy C-276 is often considered where mixed contaminants or chloride concerns make a narrower alloy choice uncertain. The exact cast versus wrought grade must be defined in the purchase specification, along with the complete process envelope.
Broader corrosion resistance does not make C-276 automatically best. Cost, casting and machining route, mechanical requirements, seal materials and documented corrosion data still matter.
PVDF — chemical resistance with different mechanical constraints
PVDF is a polymer option that may offer advantages in selected corrosive or purity-sensitive applications. Temperature and pressure interact, and the pressure-temperature rating must be checked for the actual design.
PVDF pump construction differs mechanically from metallic ANSI process-pump construction. Do not assume that ANSI Pumps Pro manufactures PVDF ANSI wet ends unless the specific product and specification confirm it.
Side-by-side engineering screening table
| Factor | Alloy 20 family | Hastelloy C-family | PVDF |
|---|---|---|---|
| Metallic construction | Yes | Yes | No |
| Severe mixed contaminants | Application dependent | Often shortlisted | Chemistry dependent |
| High-pressure mechanical strength | Strong metallic option | Strong metallic option | Check polymer P-T rating |
| Purity / metal-ion concern | Metallic | Metallic | Can be advantageous |
| Cost | High vs standard SS | Usually higher | Design-dependent |
| Final selection basis | Corrosion data + exact grade | Corrosion data + exact grade | Chemical chart + pressure-temperature rating |
Do not select the casing material alone
Review the impeller, shaft sleeve, seal faces, springs, gaskets, O-rings and fasteners exposed to the process. Flush or barrier fluid compatibility, temperature cycling, solids and leakage containment can be as important as the casing alloy.
The exact material form must be recorded for each wetted component. MTR and PMI records help verify identity, but they do not replace the engineering suitability review.
What to send for a sulfuric-acid pump material review
- H₂SO₄ concentration at minimum, normal and maximum
- Temperature at minimum, normal and maximum
- Water dilution and upset cases
- Chlorides, fluorides and other contaminants
- Solids, flow and head
- Suction condition and required pressure
- Existing material and failure photographs
- Pump model and size
- Required material documentation
For the broader acid-transfer decision, see the acid transfer pump selection guide. For metallic high-alloy scope, see exotic-alloy ANSI process pumps.
Request a sulfuric-acid material review
Send the installed pump model, sulfuric-acid concentration range, temperature and existing material. We can identify the material and replacement interfaces that should be checked before quotation.
Frequently asked questions
Is Alloy 20 always the best sulfuric-acid pump material?
No. The appropriate choice depends on concentration, temperature, contaminants, velocity, pressure, exact material form and the complete wetted assembly.
Are Alloy 20 and CN7M automatically identical?
No. Alloy 20 commonly refers to a wrought alloy family, while CN7M is a related cast pump grade. Confirm the exact specification and product form.
Is Hastelloy C-276 automatically better than Alloy 20?
No. C-276 may be shortlisted for more severe or mixed conditions, but cost, manufacturing form, mechanical requirements and corrosion data must be reviewed for the actual service.
Can PVDF be selected by chemistry alone?
No. PVDF selection also requires a pressure-temperature mechanical review and confirmation that the pump construction is suitable for the system.
