Best Impeller Material for Nitric Acid and Oxidizing Chlorides — Titanium Grade 2 ANSI Pump Parts
When chemical plant reliability engineers specify pump components for nitric acid service, oxidizing chloride environments, or wet chlorine processing, Titanium Grade 2 (ASTM B367 Gr. C-3) is often the definitive material choice. This article explains why Titanium Grade 2 outperforms stainless steels and duplex alloys in specific corrosive applications — and when you should choose it for your Goulds 3196 or Durco Mark III replacement pump parts.
Why Titanium Grade 2 for ANSI Chemical Process Pumps?
Titanium Grade 2 is commercially pure titanium with excellent corrosion resistance in oxidizing environments. Unlike stainless steels that rely on chromium oxide passivation, titanium forms an extremely stable, tenacious titanium dioxide (TiO₂) passive film that instantly self-heals in the presence of oxygen or oxidizing agents.
⚠️ Quality & Compliance Assurance
All pumps and components from ANSI Pumps Pro are manufactured to ASME B73.1 dimensional specifications. Each shipment includes certified Material Test Reports (MTRs), CMM dimensional inspection reports, and hydrostatic test certificates (1.5× MAWP). 100% dimensional interchangeability guaranteed. Full material traceability from heat number to your receiving dock.
This unique property makes Titanium Grade 2 the preferred impeller and casing material for:
- Nitric Acid (HNO₃) — All concentrations up to boiling point. Titanium is virtually immune to nitric acid attack across the entire concentration and temperature range. This is titanium’s strongest application — if your process involves nitric acid at any concentration or temperature, Titanium Grade 2 is the most corrosion-resistant, cost-effective material available.
- Oxidizing Chlorides — Wet chlorine gas, chlorine dioxide, sodium hypochlorite (bleach), and chlorinated brines. Titanium resists pitting and crevice corrosion that rapidly destroys 316SS and even CD4MCuN Duplex SS in these environments.
- Chlorinated Organics — Chlorinated solvents, vinyl chloride monomer, and chlor-alkali process streams.
- Seawater & Brine — Complete immunity to seawater corrosion at all temperatures up to 260°F (127°C).
Titanium Grade 2 vs. Hastelloy C-276 — Which One Do You Need?
| Criteria | Titanium Grade 2 | Hastelloy C-276 |
|---|---|---|
| Best Application | Nitric acid, oxidizing chlorides, wet chlorine | Mixed acids, reducing acids (HCl, H₂SO₄), severe corrosive media |
| Nitric Acid Resistance | Excellent — all concentrations to boiling | Good — but titanium is superior and more cost-effective |
| Sulfuric Acid Resistance | Poor in reducing conditions. Only suitable with oxidizing inhibitors (Fe³⁺, Cu²⁺) present | Excellent — handles H₂SO₄ across wide concentration and temperature ranges |
| Hydrochloric Acid | Not recommended — rapid attack | Excellent — one of the best alloys for HCl service |
| PREN / Pitting Resistance | ≥ 30 | ≥ 64 |
| Relative Cost | $$ | $$$$ |
| Density | 4.51 g/cm³ (56% lighter than steel) | 8.89 g/cm³ |
Application Limits — When NOT to Use Titanium
Titanium Grade 2 has critical limitations that every specifying engineer must understand. Specifying titanium for the wrong application can lead to catastrophic failure within hours.
- Reducing Acids — Hydrochloric acid (HCl) and sulfuric acid (H₂SO₄) in reducing conditions will attack titanium. For these applications, specify Hastelloy C-276 (for mixed acids) or Zirconium 702 (for pure HCl). In sulfuric acid service with strong oxidizing inhibitors (Fe³⁺, Cu²⁺, HNO₃), titanium may be viable — but only after a qualified corrosion engineer reviews the specific process conditions.
- Dry Chlorine Gas — Titanium reacts violently with dry chlorine. It requires a minimum of 1.5% moisture content to maintain passivation. Never use titanium in dry chlorine service.
- Anhydrous Environments — The TiO₂ passive film requires trace moisture or oxygen. Fully anhydrous reducing conditions can lead to rapid, unpredictable attack.
- High-Temperature Chloride Crevice Corrosion — Above 200°F (93°C), Titanium Grade 2 can suffer crevice corrosion in concentrated chloride solutions. For these conditions, specify Titanium Grade 7 (ASTM B367 Gr. Pd7B) which adds 0.12–0.25% palladium for enhanced crevice resistance.
Our Titanium Grade 2 ANSI Pump Parts
As a specialized ANSI process pump replacement manufacturer, we cast and machine the following components in ASTM B367 Grade C-3 Titanium. Our pumps and parts are 100% interchangeable with Flowserve Durco Mark III and ITT Goulds 3196 series pumps.
| Component | Goulds Item # | Durco Part # | Available Frame Sizes |
|---|---|---|---|
| Impeller (Open) | 101 | Part No. 2 | All Goulds frames / All Durco Groups |
| Casing (Volute) | 100 | Part No. 1 | STX / MTX / LTX / XLT-X / Groups 1–3 |
| Shaft | 122 | Shaft Assembly | All Goulds frames / All Durco Groups |
| Shaft Sleeve | 122 | Sleeve (Part of Assy) | All Goulds frames / All Durco Groups |
| Stuffing Box Cover | 184 | Part No. 14 | All Goulds frames / All Durco Groups |
Lead Time & Rush Order Availability
Titanium castings require specialized foundry scheduling due to the reactive nature of molten titanium. Here’s what to expect:
- 📦 Standard Lead Time: 6–10 weeks for titanium cast and machined parts — manufactured with full EN 10204 3.1 MTR, PMI, and dimensional inspection
- ✅ Stock Availability: Select Titanium Grade 2 impellers and casings for common frame sizes may be in stock — contact us for current inventory
- 🔥 Emergency Rush Orders: 3–4 weeks — Request expedited foundry allocation
Disclaimer: ANSI Pumps Pro is an independent aftermarket manufacturer. Goulds and 3196 are registered trademarks of ITT Corporation. Durco and Mark III are registered trademarks of Flowserve Corporation. All OEM part numbers are used for compatibility reference only. We are not affiliated with or endorsed by ITT Goulds or Flowserve.
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