Centrifugal pumps and corrosive acids: material compatibility CDR

Centrifugal pumps and corrosive acids: material compatibility CDR

The use of corrosive acids in sectors such as chemistry, surface treatment, pharmaceuticals, and energy requires careful plant design, strict adherence to regulations, and the installation of the right centrifugal pump that meets specific production needs. When the fluid being treated is chemically aggressive, in fact, every component in contact with the liquid becomes a potential critical point: The exact compatibility between materials thus plays a vital role in the seal and safety of the entire system.

Acids such as sulfuric and the hydrofluoric they exhibit extremely high and variable levels of aggressiveness, change behavior depending on concentration, react differently to temperature variations, and can trigger rapid and difficult-to-predict corrosive phenomena if the correct pump is not used. Using an unsuitable material in this case not only reduces the pump's useful life but can compromise the safety of environments and operators, as well as production quality and continuity.

The experience gained by CDR in the management of critical fluids, it allows for tackling complex applications by starting from the analysis of the fluid and operating conditions, to arrive at the definition of solutions that are truly consistent with the intended use. The compatibility between materials and the treated fluid thus becomes one of the main aspects in the design of a centrifugal pump.

Material Compatibility in Centrifugal Pumps: Read the Fluid Before the Pump

Talk about Material compatibility This means conducting a practical assessment of how a given fluid interacts with the surfaces it encounters along its path inside the centrifugal pump. In the case of corrosive acids such as sulfuric and hydrofluoric acids, this interaction can result in corrosion, oxidation, embrittlement, or loss of structural integrity.

Compatibility is not, however, a fixed or absolute parameter. For example, a material that performs correctly at a certain concentration may become unsuitable as the temperature increases or with prolonged contact times. For this reason, Material selection for centrifugal pumps intended for aggressive acids requires an analysis that takes into account the actual operating conditions and possible variations over time.

CDR addresses this aspect with a method based on practical experience and verified technical data, favoring plastic and fluorinated materials that guarantee chemical stability and reliability even in particularly harsh environments or for prolonged and repeated use.

Sulfuric acid (H₂SO₄): a common fluid, but far from predictable

The’sulfuric acid It is one of the most widely used reagents in the industrial sector and is used in industries such as basic chemistry, fertilizer production, metal surface treatment, refining, the energy sector, and numerous synthesis processes. This widespread use contributes to it being perceived as a “manageable” fluid, when in reality it presents high chemical complexity from an engineering standpoint.

Its aggressiveness varies significantly depending on factors such as concentration and temperature. At low concentrations, it can be relatively stable, while as these parameters increase, it exhibits a strongly oxidizing behavior, capable of rapidly attacking numerous metals and alloys. In continuous processes, in dosing lines, or in recirculation circuits, these characteristics can translate into progressive and difficult-to-intercept and contain corrosive phenomena.

For centrifugal pumps used in transferring sulfuric acid, such as the DTN-L, this means having to design and select materials taking into account not only the nominal conditions but also possible operational variations: the Material compatibility This makes it a dynamic parameter, linked to the entire plant lifecycle and not to a single operating condition.

Sulfuric acid and material compatibility: selection criteria in CDR solutions

material selection for the sulfuric acid management requires a technical approach based on chemical data, application experience, and a thorough understanding of each material's operating limits. CDR adopts differentiated solutions, calibrated to real usage conditions, avoiding generalizations that can prove critical in the medium to long term.

• Polypropylene
  Polypropylene offers good chemical resistance to sulfuric acid even at high concentrations, generally ranging from 80% to 90%, provided that temperatures remain moderate. It is a suitable solution for plants with well-controlled parameters, where no significant process variations are expected. However, as the temperature rises, its resistance can decrease significantly.

• PVDF
  PVDF guarantees superior chemical resistance compared to PP, maintaining good performance even in the presence of concentrated sulfuric acid. Its stability makes it suitable for more demanding applications, where higher temperatures are present or where greater long-term reliability is required.

• PFA / PTFE
  These materials represent the most technically complete solution for sulfuric acid. Their excellent chemical stability allows for handling high concentrations and severe operating conditions without significant degradation. For this reason, PFA is the material most recommended by CDR in critical applications, where Material compatibility must remain constant over time.

• AISI 316
  AISI 316 stainless steel can be used only at low concentrations, generally below 40%. Above this threshold, corrosion sets in rapidly and becomes difficult to control, making the material unsuitable for continuous use with sulfuric acid.

Hydrofluoric acid (HF): When the material makes a difference

The’hydrofluoric acid is used in highly specialized industrial applications, such’The chemical and petrochemical industry, the production of fluorinated compounds, metal treatment and etching, glass processing, microelectronics, and some processes in the energy sector. In all these areas, HF is considered one of the most critical fluids to manage.

Its danger is not solely linked to toxicity, but primarily to its ability to attack a wide range of materials. Unlike other strong acids, hydrofluoric acid also reacts with silicates, making vulnerable glass, ceramics, and numerous materials commonly used in industrial plants. Furthermore, this fluid also attacks numerous metals, which become rapidly degradable upon contact and with effects that can manifest in very short periods of time.

For the Centrifugal pumps for transferring HF, like how gamma XTN-BL, the choice of materials therefore becomes a fundamental step with no room for approximation. In these applications, the material compatibility it is the factor that determines the very possibility of operating safely and continuously, directly influencing the reliability of the plant and the protection of operators.

Hydrofluoric acid and material compatibility: unavoidable choices

In the case of hydrofluoric acid, the truly compatible options they are few and must be applied within well-defined limits, taking into account concentration and operating conditions.

• PTFE / PFA
  These materials ensure reliable compatibility with hydrofluoric acid at concentrations up to 50%. Their chemical inertness makes them the go-to choice for HF applications, especially when long-term operational continuity and safety are required. PFA, in particular, is widely used by CDR in the manufacture of centrifugal pumps designed for this type of fluid.

• PVDF
  PVDF, on the other hand, can only be used at low concentrations of hydrofluoric acid, generally below 30–40%. Above these values, the material no longer provides adequate resistance, resulting in a significant increase in the risk of degradation.

• AISI 316
  It is not compatible with hydrofluoric acid. The chemical reaction occurs rapidly, making this material unsuitable for any continuous application involving HF.

• Polypropylene
  Not compatible with hydrofluoric acid and therefore unusable. The action of HF rapidly compromises the integrity of the material.

For this reason, in applications with hydrofluoric acid, CDR directs its solutions towards configurations in PFA, ensuring safe fluid management and a correct assessment of material compatibility in relation to actual operating conditions.

CDR centrifugal pumps and corrosive acids: apply theory to the process

Translating these considerations into practical choices, a clear line emerges: For sulfuric acid, CDR proposes centrifugal pumps made of PP, PVDF, and especially PFA; for hydrofluoric acid, PFA becomes the reference solution.

These choices arise from a detailed analysis of the process and from experience gained on real systems. Material compatibility is evaluated as an integral part of the project, allowing for risk reduction and an increase in the overall reliability of the system.

Technical expertise as an operational guarantee

The handling of corrosive acids requires solutions built around the fluid and operating conditions. In this context, the Material compatibility with the liquid to be pumped represents the foundation upon which the safety and longevity of centrifugal pumps are based.

CDR offers its clients a technical approach comprised of analysis, informed material selection, and ongoing support over time, including after-sales service, in the’alignment and in the maintenance of the systems. A concrete value for companies working with aggressive fluids and seeking solutions designed to operate over time without interruptions.

Contact us for a consultation and to discover all our products and services dedicated to process pumps for sectors Industrial, chemists and pharmaceuticals.

Frequently Asked Questions

Which materials are compatible with sulfuric acid in centrifugal pumps?

PP, PVDF, PFA and PTFE are used for sulfuric acid, each with precise limits. PP withstands concentrations of 80–90% at moderate temperatures. PVDF offers superior resistance even with concentrated acid. PFA and PTFE are the most comprehensive solution for severe conditions. AISI 316 is permissible only below 40%.

Which materials should be chosen for a centrifugal pump that must transfer hydrofluoric acid (HF)?

For hydrofluoric acid, the reference choice is PTFE or PFA, which are reliably compatible up to 50% concentrations. PVDF can only be used at low concentrations, typically below 30–40%. AISI 316 steel and polypropylene are not compatible with HF and degrade rapidly, so they should not be used.

Why is hydrofluoric acid more difficult to handle than other strong acids?

Hydrofluoric acid is critical because, in addition to being toxic, it attacks a wide range of materials. Unlike other strong acids, it also reacts with silicates, making glass and ceramics vulnerable, and it rapidly corrodes numerous metals. For this reason, in HF pumps such as the XTN-BL range, material compatibility determines operational safety.

Why does the compatibility of materials with sulfuric acid change with concentration and temperature?

Sulfuric acid at low concentrations can be relatively stable, but as the concentration and temperature increase, it becomes highly oxidizing and rapidly attacks many metals and alloys. A suitable material in one condition can then become inadequate in another. For pumps such as the DTN-L, materials should be chosen taking into account operational variations over time.

Why is PFA the material recommended by CDR for pumps that handle corrosive acids?

PFA is recommended because it has excellent chemical stability and handles concentrated sulfuric acid and severe conditions without significant degradation. It is also the reference solution for fluoric acid up to 50%. It maintains consistent performance over time, reducing the risk of degradation and the need for maintenance in critical applications.

What risks does using an unsuitable material in a pump for corrosive acids entail?

Inappropriate material accelerates component corrosion and reduces the pump’s service life. It can cause leaks, breakdowns, and unplanned plant shutdowns, as well as contaminating the fluid. Degradation is often rapid and difficult to detect at first, and can compromise the safety of environments and operators and the continuity of production.