It is dependent on the type of acid, the concentration of the acid, the temperature, and the budget when engineers and procurement managers are faced with the choice of whether Zirconium 702 vs Titanium should be used for acid service. Zirconium 702 (UNS R60702) performs better than titanium in reducing acid environments, notably hot hydrochloric, sulphuric, and acetic acids. On the other hand, titanium grades such as Grade 2 and Grade 12 perform better in oxidising acid settings, weight-sensitive designs, and projects that are cost-controlled. With the help of this guide, you will have a direct and data-backed foundation to make that decision with complete assurance.
Understanding the Challenges of Acid Service Environments
Why Acid Service Demands More Than Standard Alloys?
Mineral and organic acids cause metal surfaces to wear down. These acids dissolve the metals electrochemically, causing pits to form and splitting them through a process known as stress corrosion cracking (SCC). When temperatures are high, above 60 degrees Celsius, corrosion occurs at a record-breaking rate. Stainless steels that are considered standard, such as 316L, degrade rapidly in hydrochloric acid, even when only modest levels are present. Instead of using reactive metals, engineers will need to use non- reactive metals.
Critical Performance Criteria
Any product used with acid must meet three stringent rules: it must resist uniform corrosion and SCC, have sufficient mechanical strength to tolerate temperature fluctuations, and be compatible with the acid chemistry at the concentration used. If even one of these conditions is not satisfied, the apparatus can have a catastrophic breakdown. In many cases, the expenses of an unanticipated shutdown exceed the savings that result.
Operational Conditions That Drive Selection
The process uses a variety of acid recycling plants, chemical reactors, pickling lines, and urea synthesis units to process the contents. Each of these operations uses different combinations of acid species, temperatures, and fluid velocity. If you shift a titanium heat exchanger from an environment with mild nitric acid to an environment with hot, decreasing hydrochloric acid, it will collapse in a matter of months rather than years. On the basis of the facts, there is always an appropriate option.
Technical Comparison of Zirconium 702 and Titanium for Acid Service
Chemical Composition and Microstructure
According to ASTM B550, zirconium 702 is composed of more than 99.2% Zr and Hf, with Hf being a natural defect if it is less than or equal to 4.5%. When it comes into contact with oxygen, it produces a ZrO2 oxide coating that is solid and has the ability to cure itself. Because of this, it is prevented from being challenged locally, which helps reduce media. Titanium Grade 2 (ASTM B265) is a commercially pure material that possesses a coating of TiO2 that is quite stable while oxidising. However, if no inhibitors are present, it can react with reducing acids.
Mechanical and Thermal Properties
| Property | Zirconium 702 | Titanium Grade 2 |
|---|---|---|
| Density (g/cm³) | 6.51 | 4.51 |
| Tensile Strength (MPa) | 379 min | 345 min |
| Yield Strength (MPa) | 207 min | 275 min |
| Melting Point (°C) | ~1852 | ~1668 |
| Thermal Conductivity (W/m·K) | 22 | 17 |
Because it is more dense and a better thermal conductor, zirconium 702 is great at moving heat and keeping metals from rusting in shell-and-tube heat exchangers.
Corrosion Resistance by Acid Type
This table shows the most common industrial acids and how well they work:
| Acid Environment | Zirconium 702 | Titanium Grade 2 |
|---|---|---|
| Hot HCl (all strengths) | Excellent | Poor (rapid attack) |
| Hot H₂SO₄ (≤65%) | Excellent | Poor without inhibitor |
| Dilute HNO₃ | Good | Excellent |
| Concentrated HNO₃ | Moderate | Excellent |
| Acetic acid (hot, concentrated) | Excellent | Good |
| Phosphoric acid | Good | Good |
These data points are from studies on corrosion rates that NACE International and ASM Handbook Vol. 13B have published.
Application Scenarios: When to Choose Zirconium 702 or Titanium
Where Zirconium 702 Wins?
In situations where reducing acids are present, zirconium 702 is the material that need to be utilised. It is possible for valve stems and pump shafts constructed from Zirconium 702 round bar (according to ASTM B550) to withstand the erosion and rust that damages Hastelloy choices when hot hydrochloric acid is used to pickle steel. When it comes to reactors used for the production of acetic acid and melamine, zirconium 702 bar agitator shafts are not susceptible to damage from hot organic iodides. On the other hand, galvanic corrosion causes nickel alloys to become more fragile. Additionally, zirconium 702 fasteners, which include bolts and tie-rods, are utilised in urea and fertiliser factories, which are subjected to high pressures and contain ammonium carbamate, in order to maintain the structural integrity of the plants.
Here are the core application strengths of Zirconium 702 in acid service:
• Chemical processing shafts: Agitator and pump shafts in acetic acid and melamine plants are made of Zirconium 702 round bar. These do not rust when exposed to hot organic iodides and feedstock corrosion, which is what happens to nickel alloys after just one cycle of use. They last for years and do not show any signs of corrosion.
• Valve stems in acid regeneration: Zirconium 702 valve parts can handle the high fluid velocity and erosion processes that quickly wear down PTFE-lined or Hastelloy C-276 parts when steel is pickled in HCl. This means that they do not need to be changed as often, moving the replacement frequency from months to years.
• Heat exchanger hardware: Supporting structures in urea synthesis while ammonium carbamate is being used at high pressure are tie-rods and nuts made from Zirconium 702 bar. Even Grade 2 titanium starts to break down above 180°C.
The fact that metal breaks down quickly in reducing acid environments is a recurring pain point. These traits fix that problem right away.
Where Titanium Leads?
In situations where acid systems are oxidising, designs need to be lightweight, and you want to get things that are cost-effective; titanium types are really beneficial. Grade 2 titanium is frequently used in heat exchangers for diluted nitric acid, desalination facilities, and offshore platforms. The TiO2 film that is applied to it provides excellent protection and is more affordable than zirconium. Titanium can be utilised in situations that are somewhat limited due to its Grade 12 composition (Ti-0.3Mo-0.8Ni). As a result of its strength and low weight, titanium is highly valued in the aircraft and shipbuilding industries. There are classification groups that have certified titanium for use in maritime structural applications. These groups include DNV, ABS, and CCS.
Cost and Supply Chain Considerations
Although Zirconium 702 vs. Titanium is three to five times more expensive per kilogram than commercially pure titanium, life-cycle cost analysis frequently favours zirconium in severe reducing acid operations, since equipment does not need to be replaced as frequently. This is because zirconium is more resistant to corrosion than titanium. Titanium remains the more reasonable option, particularly if you are working with a limited budget or require oxidising acid treatment.
Procurement Guide: How to Source Quality Zirconium 702 and Titanium Alloys
Key Standards and Certifications to Verify
Purchasing teams must ensure that the mill test results for Zirconium 702 round bars show that the product meets the requirements set out by ASTM B550 before making a purchase. They ought to pursue titanium sheet or tube that satisfies the criteria of ASTM B265 or B338 standards. Certified pressure equipment is a requirement of the Pressure Equipment Directive (PED) 2014/68/EU for all projects in Europe. The American Society of Mechanical Engineers (ASME) and the American Petroleum Institute (API) have developed standards that control the materials used in oil and gas pressure vessels.
Best Practices for Bulk Ordering
Whenever you place a significant purchase, it is imperative that you obtain inspection reports from organisations such as SGS, TUV, or DNV that demonstrate the complete traceability of the chemical composition. Please ensure that the supplier maintains documented heat traceability and possesses the ISO 9001:2015 quality management certification. It takes between four and eight weeks to obtain standard sizes of Zirconium 702 round bar and plates; make sure you check the availability of these materials before beginning to design your project.
Evaluating Supplier Reliability
The supplier should have a documented history of supplying big chemical and energy projects, possess several international certifications, and provide technical pre-sales assistance. These are all characteristics that are indicative of a trustworthy provider. As a result of the fact that you may obtain several types of items from the same supplier, such as bars, plates, pipe, fittings, and fasteners, the complexity and risk associated with procurement are reduced.
Making the Final Decision: Factors and Recommendations for Acid Service Materials
Decision Framework
If you're trying to decide between titanium and zirconium 702, there are four things to think about: the acid type (reducing or oxidising), the operating temperature, the expected service life, and the overall budget. For acid reduction at temperatures more than sixty degrees Celsius and at any concentration, zirconium 702 is the technically justified choice. Titanium grades are an excellent choice for applications involving oxidising acids, designs that are weight-sensitive, or projects with tight budgets.
Collaborate With Your Supplier Early
Your material source should be involved in the project's engineering and purchasing phases. You can use this data to choose the right grade, double-check the dimensions, and learn about certification requirements ahead of time. Its goal is to reduce the quantity of change orders and costly material replacements at the project's conclusion.
Customisation and Testing
A corrosion coupon test or review of published corrosion data for your specific acid concentration and temperature range can help you make a final decision. Both zirconium 702 vs Titanium can be fabricated into custom bars, plates, pipes, flanges, and fittings to match your exact equipment geometry.
Conclusion
Zirconium 702 vs Titanium are two good choices for acid service, but neither is superior. In situations with reducing acids, such as heated acetic acid, sulphuric acid, and hydrochloric acid, zirconium 702 provides unmatched resistance. However, in weight-sensitive applications and oxidising acid service, titanium offers reliable, cost-effective performance. Depending on the project's acid chemistry, temperature, and economics, you should modify your information accordingly. Guaranteed material quality, full traceability, and sustained supply stability are yours for the taking when you partner with a certified and experienced source.
FAQ
Can Zirconium 702 and Titanium Be Welded Together?
Direct welding of Zirconium 702 and Titanium is not standard practice because their crystal structures and thermal expansion coefficients are not the same. In mixed-material assemblies, mechanical fastening or transition fittings are used. Each metal is best welded to itself using a matching filler rod in an inert gas atmosphere.
How Does Zirconium 702 Perform Against Hot Sulphuric Acid Compared to Titanium?
Zirconium 702 can handle sulphuric acid concentrations up to about 65% across a broad temperature range. Titanium Grade 2 suffers rapid attack in these conditions without chemical inhibitors. Above 65% H₂SO₄, both materials face limitations, and nickel alloys become the standard selection.
What Are Typical Lead Times for Bulk Zirconium 702 Orders?
Standard dimensions in Zirconium 702 round bars and plates typically ship within 4–8 weeks from an established manufacturer. Custom dimensions or large-volume orders may require 8–12 weeks. Confirm stock availability and production capacity with your supplier before committing to a project schedule.
Is Titanium Suitable for HCl Service at Any Concentration?
Titanium Grade 2 is not recommended for hydrochloric acid service at any significant concentration, particularly at elevated temperatures. It can tolerate very dilute cold HCl under specific conditions, but Zirconium 702 is the correct selection for reliable HCl service.
Partner With LINHUI TITANIUM for Your Next Acid Service Project
LINHUI TITANIUM, founded in 2000 and headquartered in Xi'an, China, supplies certified Zirconium 702 and Titanium products to energy, chemical, and industrial clients across more than 60 countries. Holding PED 2014/68/EU, ISO 9001:2015, DNV, ABS, and CCS certifications, we operate as a trusted zirconium 702 vs Titanium material supplier with full product traceability and competitive pricing. Whether your project requires round bar, plate, pipe, or fasteners, our team provides technical support from specification through delivery. Contact us at linhui@lhtitanium.com or visit https://www.lhtitanium.com/ for a quotation.
References
1. ASM International — ASM Handbook, Volume 13B: Corrosion: Materials, 2005.
2. NACE International — Corrosion Engineer's Reference Book, 3rd Edition, 2002.
3. ASTM International — ASTM B550: Standard Specification for Zirconium and ZirconiBars and Wires and Wire, 2020.
4. ASTM International — ASTM B265: Standard Specification for Titanium and Titanium Alloy Strip, Sheet, and Plate, 2020.
5. Scheirs, J. & Kaminsky, W.—Feedstock Recycling and Pyrolysis of Waste Plastics, Wiley, 2006. (referenced for acid environment degradation context)
6. Schutz, R. W. & Watkins, H. B. — "Recent Developments in Titanium Alloy Application in the Energy Industry," Journal of Materials, Vol. 50, No. 9, 1998.
