Heat Exchanger Materials: Corrosion-Resistant Alloys for Shell and Tube and Plate Units
How to select heat exchanger materials for corrosion resistance — 316L, duplex, super-austenitic, titanium, nickel alloys and carbon steel, with application mapping and a decision table for seawater, chemical, food, HVAC and steam duties.
How heat exchanger materials are selected
Material selection is a decision about the specific stream, not about a preferred alloy. The inputs that matter are the chemistry of each fluid, chloride content, pH, operating and design temperature, dissolved oxygen or oxidising species, solids and velocity, and the cleaning chemistry the unit will see in service. A corrosion resistant heat exchanger is one whose plates or tubes, tubesheets, nozzles and gaskets have all been matched to those conditions.
Carbon steel
Carbon steel remains a sound choice for shells, frames, tubesheets and tubes in clean, non-corrosive utility services such as closed-loop hot water, steam condensate and many hydrocarbon duties. It is not suitable for aerated chloride-bearing water or acidic streams without protection. On shell-and-tube units a carbon steel shell is often combined with an alloy tube bundle when only one side is corrosive, which keeps cost proportionate to the risk.
Stainless 304 and 316L
Stainless 316L is the workhorse material for plate heat exchangers and clean tubular services, covering most clean water, glycol, oil and food-grade duties. 304 can be acceptable for low-chloride, low-temperature service. Both grades become vulnerable to pitting and crevice corrosion as chloride concentration and temperature rise together, so the chloride level and the maximum metal temperature should always be stated in the enquiry.
Duplex and super-austenitic stainless steel
Where chlorides exceed what 316L can be relied on for but a fully corrosion-resistant alloy is not warranted, duplex stainless (2205) and super-austenitic grades (904L, 254 SMO) provide an intermediate step with higher pitting resistance. They are widely used in brackish water, moderately corrosive process streams and in duties where chloride concentration can rise during upsets or shutdown.
Titanium
Titanium is the common choice for seawater, brine, hypochlorite and aggressive chloride-rich services in both plate and tubular constructions, because it resists pitting and crevice attack in conditions where austenitic stainless is at risk. It is standard in marine central cooling, aquaculture and many coastal chemical duties. Titanium is not universal — it is not the preferred answer in reducing acid environments — so the full chemistry should still be reviewed.
Nickel alloys
Hastelloy, Inconel, Alloy 20 and similar nickel-based alloys are reserved for the most aggressive services: concentrated or reducing acids, oxidising environments and high-temperature corrosive gases. They carry a significant cost premium, so selection should be confirmed against published corrosion data for the actual concentration and temperature and, where possible, against plant experience with the same stream.
Gasket and elastomer compatibility
In gasketed plate units the elastomer frequently limits the service before the metal does. NBR suits mineral oils and general water duties, EPDM is widely used for water, glycol, steam and caustic CIP but is not suitable for mineral oils, HNBR extends oil and temperature capability, and FKM is used for oils, fats and many aggressive chemicals but is unsuitable for hot caustic. Because CIP chemistry can be more demanding than the process fluid, the cleaning regime should be stated alongside the process data.
Application mapping
The mapping below shows typical starting points by service. It is a decision-support summary, not a corrosion guarantee: the final recommendation is confirmed against the actual chemistry, temperature and inspection requirements of the project.
| Application | Typical wetted material | Main consideration |
|---|---|---|
| Seawater and marine central cooling | Titanium; Cu-Ni tubes on tubular units | Chlorides, crevice corrosion, biofouling |
| Brackish and high-chloride water | 254 SMO or 2205 duplex | Chloride level combined with temperature |
| Chemical processing (acids, oxidisers) | Nickel alloys, 904L, or lined tubular units | Concentration, temperature, reducing vs oxidising |
| Food, beverage and dairy | 316L product-wetted, food-contact gasket grades | Surface finish, cleanability, CIP chemistry |
| HVAC and chilled water | 316L plates; carbon steel frame | Water treatment, low chloride |
| Steam and condensate | 316L or carbon steel depending on construction | Temperature, gasket compound limits |
| Hydrocarbons and oils | Carbon steel or 316L; NBR/HNBR/FKM gaskets | Elastomer compatibility, sulphur content |
| Corrosive effluent and wastewater | Duplex, 254 SMO or titanium | Variable chemistry, solids, upset conditions |
Material decision table
Use the table as a first filter on which materials to evaluate for a given stream, then confirm the selection with the engineering team against the actual data. It does not replace a corrosion assessment for critical duties.
| Condition | Evaluate first | Also consider | Watch out for |
|---|---|---|---|
| Clean water, low chloride, moderate temperature | 316L | 304 for low-duty service | Rising chloride during shutdown |
| Chlorides elevated but below seawater level | 2205 duplex, 904L | 254 SMO | Chloride and temperature acting together |
| Seawater or brine | Titanium | Cu-Ni tubes on tubular units | Crevice corrosion at gaskets and joints |
| Strong or reducing acids | Nickel alloys, Alloy 20 | Non-metallic or lined construction | Concentration and temperature limits |
| High design pressure | Tubular or welded plate construction | Plate-and-shell | Thicker plates or tubes change cost |
| High design temperature | Welded or brazed plate, tubular | Gasket-free construction | Elastomer temperature limit |
| Frequent mechanical cleaning required | Openable gasketed plate, tubular | Plate-and-block with removable panels | Access clearance in the layout |
| Hygienic duty with CIP | 316L with food-contact gasket grades | Controlled surface finish | CIP chemistry compatibility |
Practical guidance
Send the chemistry, chloride level, pH, operating and design temperature, and the cleaning regime, and let the engineering team recommend the material and the gasket compound together. Over-specifying drives cost; under-specifying drives failure. Where the stream is unusual or the consequence of failure is high, a documented material recommendation and, if required, third-party review is worth the time it takes.
Where to go next
Once the alloy shortlist is clear, work through the heat exchanger selection guide and compare constructions in plate heat exchanger vs shell and tube. Corrosion-resistant duties usually land on a shell and tube heat exchanger with alloy tubes or a titanium gasketed plate heat exchanger. Material choice is also the largest lever in the heat exchanger cost guide. Send your fluid chemistry and temperatures to request a material recommendation and quotation.
Frequently asked questions
What is the default heat exchanger plate material?
Stainless 316L is the workhorse material for clean water, glycol, oil and food-grade duties. Higher alloys are considered when chlorides, seawater or aggressive chemistries are present.
When is titanium used instead of stainless steel?
Titanium is the usual choice for seawater, brine, hypochlorite and other chloride-bearing streams where austenitic stainless is at risk of pitting and crevice corrosion — common in marine, aquaculture and coastal chemical duties.
What is a corrosion resistant heat exchanger?
It is a unit whose wetted materials — plates or tubes, tubesheets, nozzles and gaskets — are selected for the actual chemistry, chloride level, temperature and oxygen content of the streams, rather than a single alloy grade that suits every service.
Do gaskets matter as much as the metal?
Yes. In gasketed plate units the elastomer often limits the service before the metal does, because it must tolerate the process fluid, the cleaning chemistry and the operating temperature. Metal and gasket selection should be decided together.
How do I choose the right material?
Send the fluid chemistry, chloride content, pH, temperature and any oxidising constituents to the engineering team. Over-specifying drives cost; under-specifying drives failure, so a documented recommendation usually saves both.
Send your working conditions to Blair
Share your medium, temperatures, flow rate and pressure — Blair will return a thermal selection and indicative pricing after reviewing the available data.