The simple answer to the question of whether Zirconium 702 vs Titanium performs better in hydrochloric acid (HCl) service is that Zirconium 702 is superior in the majority of HCl situations. For example, engineers and procurement managers ask this question. At temperatures where commercially pure titanium (Grade 2) experiences rapid corrosion, it is durable enough to withstand concentrated and boiling hydrochloric acid. Titanium, on the other hand, has a number of distinct advantages in some situations that involve lower acid concentrations or weight-sensitive applications. This comparison provides you with all the information you need to choose whether metal is suitable for your project.
Understanding Zirconium 702 and Titanium: Properties and Industrial Relevance
What Is Zirconium 702?
Zirconium 702 (UNS R60702) is available for purchase on the market. It is zirconium that is in its purest form and satisfies the requirements of ASTM B550. The primary components consist of a minimum of 99.2% Zr and Hf, with the remaining 4.5% being hafnium that is naturally present. Rather than being of nuclear quality, it is of industrial grade. Because the hafnium remains, the pricing is rather inexpensive. The manner in which the metal responds to rust is not altered by this. It has a melting point of approximately 1852 degrees Celsius, a density of 6.51 grams per cubic centimetre, and outputs 22 watts of heat per metre-K. A ZrO₂ oxide film is formed when the metal comes into contact with oxygen. This film shields the metal from reducing acids and provides it with a means of self-defence.
What Are the Key Titanium Grades for Acid Service?
Titanium type 2 (UNS R50400) is the most common type of titanium; it is also the type that is considered to be the best available for purchase. The addition of vanadium and aluminium to Ti-6Al-4V (Grade 5) results in an increase in tension (up to 950 MPa), but it also increases the likelihood that the material will rust. In both cases, an inactive film composed of TiO2 is utilised. In oxidising conditions, it functions very well; but, in reducing acid situations, such as when there is more than a specific amount of hydrochloric acid present, it does not function as effectively.
Side-by-Side Physical Properties
| Property | Zirconium 702 | Titanium Grade 2 |
|---|---|---|
| Density (g/cm³) | 6.51 | 4.51 |
| Melting Point (°C) | ~1852 | ~1668 |
| Tensile Strength (MPa) | ≥379 | ≥345 |
| Yield Strength (MPa) | ≥207 | ≥275 |
| Thermal Conductivity (W/m·K) | 22 | 21.9 |
| ASTM Standard | B550 / B551 | B265 / B337 |
Zirconium 702 vs Titanium: Performance in Hydrochloric Acid Environments
Corrosion Resistance Mechanisms
Zirconium 702 keeps its stable, self-healing oxide film even in places with reducing acids. Data on corrosion that has been made public shows that it can handle up to 20% HCl at boiling point with corrosion rates below 0.13 mm/year. On the other hand, Titanium Grade 2 can react with HCl in amounts greater than 1% to 2% if there isn't an oxidising inhibitor present. When titanium gets hot, its passive film breaks down quickly. This causes pitting and, eventually, stress corrosion cracking (SCC).
Corrosion Rate Comparison Table
| Condition | Zirconium 702 Corrosion Rate | Titanium Grade 2 Corrosion Rate |
|---|---|---|
| 10% HCl, 25°C | <0.05 mm/yr | ~0.5–2 mm/yr |
| 10% HCl, boiling | <0.13 mm/yr | Rapid attack |
| 20% HCl, 25°C | <0.13 mm/yr | Not recommended |
| 1% HCl, 25°C | Negligible | Acceptable |
These numbers agree with what NACE International and the ASM Handbook say about the amount of corrosion.
Weldability and Fabrication
You can weld Zirconium 702 vs titanium well with GTAW (TIG) and the right inert gas to make parts that won't rust. It is possible to weld Titanium Grade 2, and there is a well-established supply chain for fabrication. A bigger range of tools can also be used to machine it. Zirconium 702 round bar stock (ASTM B550) has a fully recrystallised grain structure, making it easy to machine parts such as heavy bolts, valve plugs, and agitator shafts.
Application-Based Comparison: Which Material Fits Your Industry Needs?
Chemical Processing and Acid Regeneration
When it comes to making structures for chemical plants that use HCl, zirconium 702 is the best metal. Some installations that have been recorded are the pipes in HCl synthesis units, the acid regeneration columns in steel pickling plants, and the pump shafts in acetic acid reactors. The stems and plugs made of zirconium 702 are stronger than those made of Hastelloy C-276 or PTFE because they can handle the high flow rates and erosion-corrosion processes that weaken those materials over time.
Aerospace, Medical, and Weight-Sensitive Applications
Titanium is about 30% lighter than zirconium, but it is stronger for its weight. Because of this, it is the best material for structures in space, orthopaedic implants, and marine hardware that needs to be light. Ti-6Al-4V is the standard metal for spaceships. This isn't a problem because HCl exposure is either not there or very low. Titanium isn't weak in reducing acids, though. Making this with titanium is the smart thing to do from a technical point of view.
Cost and Supply Chain Factors
Zinc 702 costs more per kilogram than titanium grade 2; the difference is usually between 3¢ and 5¢. What changes in the lifecycle cost scenario is when you think about how often parts need to be changed, unexpected downtime, and lost product purity during acid service. When purchasing materials for long-term chemical plant contracts, Zirconium 702 vs Titanium often has a lower total cost of ownership because it lasts longer. This is true even though it costs more up front.
How to Choose Between Zirconium 702 and Titanium for Your HCl Applications?
Evaluate Acid Concentration and Temperature First
The two most important things in the choosing process are the working temperature and the concentration of HCl. You should use zirconium 702 for your process if it needs to work with HCl amounts above 2% or temperatures above 60°C. Titanium Grade 2 can only be used in HCl that is very weak (less than 1%), at room temperature, or with an oxidising agent to protect its passive film.
In order to pick either metal, you should think about the following:
– The HCl level must be above 2% at all times (zirconium 702) and below 1% at room temperature (titanium may work).
Zirconium 702 is a good choice for acid service as long as the temperature is above 60°C. Titanium is a better material for use in places that are cold or not acidic.
- HCl concentration: Above 2% at any temperature → specify zirconium 702; below 1% at ambient → titanium may suffice.
- Operating temperature: Above 60°C in acid service → zirconium 702; cryogenic or ambient non-acid service → titanium is cost-effective.
- Mechanical load: High-torque rotating shafts or high-pressure fasteners → both grades qualify; fatigue cycling in acid → zirconium 702 preferred.
- Weight constraints: If component mass directly affects system performance (aerospace, mobile equipment) → titanium.
- Budget and lifecycle cost: Short project timelines or non-corrosive service → titanium saves upfront cost; long-term chemical plant service → zirconium 702 reduces replacement and downtime costs.
You can avoid having to make expensive changes in the middle of a job if you think about these things before you send out a material request.
Industry-Specific Recommendations
Zr702 should always be used for the wet parts when chemical plants and EPC companies need to specify tools for processes that use HCl. OEMs who are making heat exchangers for making fertiliser or urea should use zirconium 702 tie-rods and bolts that are machined from round bar because ammonium carbamate is very corrosive. Distributors who carry metals that don't rust should keep both types on hand, since each is used in a different group of industries.
Finding Reliable Suppliers and Ensuring Quality: Tips for Procurement Managers
Certifications to Require from Any Supplier
You need to get material certifications when you buy things for big business. For titanium, ask for mill test reports (MTRs) that are in line with ASTM B265/B337 and ASTM B550 for zirconium 702 vs titanium. You should ask for more than just certificates. You should also see proof of quality management systems. Some of the standards that matter are ISO 9001:2015, PED 2014/68/EU, and API-aligned quality plans. If a seller has approvals from DNV, ABS, CCS, BV, and GL, it means that they have been checked out by a third party and are qualified to work on marine and offshore projects.
Evaluating Supplier Capability Beyond Raw Material
A reputable provider should offer more than just sheets and bars cut to the appropriate length. Conduct a check to determine whether the provider is able to provide approved welding processes, tracking documentation, and cutting that is tailored to your precise specifications. If you check the quantity of each type and shape that is in stock, such as round bars, plates, pipes and fittings, you will be able to use a single source for your bill of materials. When the products that come from many sources are compatible with one another, it is much simpler to work on major electric power construction projects. Taking this strategy also helps save money on the purchase of items.
Building Long-Term Supply Relationships
Purchasing everything at once puts your project at risk because prices are subject to change and due to the possibility of deliveries being late. When it comes to chemical plants that need to purchase items over a period of several years, procurement managers should discuss framework agreements with the suppliers they choose. Among these should be inspection methods, quality hold points, and lead times that have been mutually agreed upon. Using this process guarantees that there will be a consistent flow of zirconium 702 and titanium over the entirety of a project.
Conclusion
It is recommended to use Zirconium 702 vs Titanium rather than Titanium Grade 2 when working with hydrochloric acid when the acid concentration is greater than 2% or when the temperature is high. It is the most suitable material for applications that involve hydrochloric acid (HCl) due to the fact that it possesses an oxide film that can mend itself, does not break when subjected to stress in reducing media, and has been effectively utilised in chemical processing in the past. Titanium continues to be the ideal metal for use with alternatives to hydrochloric acid where weight, biocompatibility, or affordability are the most essential requirements. You should always check a supplier's credentials before signing a contract and ensure the metal you are using is appropriate for the task.
FAQ
Can titanium be used in hydrochloric acid at all?
However, this makes the process more difficult. For most industrial HCl work, zirconium 702 is a safer choice.
How long does zirconium 702 last in acid service?
If you explain zirconium 702 parts correctly, they can last 15 to 25 years in a chemical plant that never stops. This is because they don't rust more than 0.13 mm per year in boiling 10% HCl. How long something lasts depends on how fast it moves, how the temperature changes, and how much force is applied to it. As part of your plant's repair plan, you still need to do regular inspections, regardless of what the material is.
What certifications should I request from a zirconium 702 or titanium supplier?
If the equipment is going to be used in Europe for pressure service, at the very least, ask for MTRs that meet ASTM standards, ISO 9001:2015 approval, and PED 2014/68/EU. It is normal for projects in the ocean or at sea to need approval from a classification society like DNV, ABS, BV, or GL. It's even more proof when big deals use third-party inspection records from SGS, TÜV, or Bureau Veritas.
Is zirconium 702 pricier than titanium?
It does cost three to five times as much per kilogram as titanium Grade 2. But zirconium 702 lasts longer and needs to be replaced less often, so over a 10–20-year plant operating period in HCl-intensive service, it usually has a lower total lifecycle cost.
Partner with LINHUI TITANIUM for Zirconium 702 and Titanium Supply.
Oil, gas, and chemical companies in more than 60 countries have bought metals from LINHUI TITANIUM since 2000. These metals are of high quality and don't rust. Zr702 and titanium come in many grades and forms, and we sell many different goods made from them, like round bars, plates, pipes, and custom fittings. These items have been approved by ISO 9001:2015, PED 2014/68/EU, DNV, ABS, BV, and GL. If you need a confirmed Zirconium 702 provider for a big EPC contract, please contact our technical team directly at linhui@lhtitanium.com or visit www.lhtitanium.com.
References
1. ASM International. ASM Handbook, Volume 13B: Corrosion: Materials. ASM International, 2005.
2. NACE International. Corrosion Data Survey: Metals Section, 6th Edition. NACE International, 1985.
3. ASTM International. ASTM B550: Standard Specification for Zirconium and Zirconium Alloy Bars and Wires. ASTM International, 2022.
4. Schemel, J. H. ASTM Manual on Zirconium and Hafnium, 1977. ASTM International, 1977.
5. Schutz, R. W., and Thomas, D. E. "Corrosion of Titanium and Titanium Alloys." ASM Handbook, Volume 13B: Corrosion: Materials. ASM International, 2005.
6. Kofstad, P. High Temperature Corrosion. Elsevier Applied Science, 1988.
