Plate materials and gaskets: selection by medium and operating conditions

The choice of plate and gasket materials in a plate heat exchanger is not a detail question - it determines the unit’s service life, corrosion resistance and suitability for food-grade applications. Incorrectly chosen materials lead to pitting corrosion, premature gasket failure or contamination of the medium. This guide maps the common plate materials and gasket elastomers to their areas of application.

Which plate materials are available?

1.4401 and 1.4404 (AISI 316 and 316L)

The material number 1.4404 is the standard stainless steel for plate heat exchangers. It corresponds to AISI 316L and contains approximately 2 - 3 % molybdenum in addition to chromium and nickel. Molybdenum considerably improves resistance to chloride-induced pitting corrosion compared with the commonly used 1.4301 (AISI 304).

Applications for 1.4404:

• Water (drinking, heating, cooling water), including moderate chloride content
• Food and beverages (food-grade approved)
• Whey, fruit juices, mildly acidic media
• Heating, air conditioning, general mechanical engineering

Limits: with high chloride concentrations (> 200 mg/l) combined with elevated temperatures (> 50 °C), 1.4404 may no longer be sufficient. Seawater, chlorinated process water, and acidic chloride-bearing media can cause pitting.

1.4401 (without the “L” for low carbon) is also used; the difference lies in the maximum carbon content. 1.4404 (low carbon) is more resistant to sensitisation during welding and is therefore the preferred variant for plate heat exchangers.

Titanium (Grade 1 and Grade 2)

Titanium is the material of choice for chloride- and salt-bearing media where stainless steel would fail. It is practically immune to chloride pitting corrosion and resistant to seawater, brackish water, chlorinated cooling water and many acid solutions.

Applications for titanium:

• Seawater cooling circuits (offshore, shipbuilding, coastal sites)
• Brackish water and river water with high chloride content
• Chlor-alkali electrolysis and chlorine-bearing process water
• Brine circuits in refrigeration technology

Titanium is significantly more expensive than stainless steel - typically 3 - 5× additional cost for the plates. Where 1.4404 is adequate, titanium is not economically justified. Titanium is not suitable for hydrofluoric acid and some reducing acid mixtures.

Other plate materials

For special applications, Hastelloy C-276 (highly alloyed, for strongly corrosive acids), Inconel or copper-nickel alloys are also available. These specialist materials are reserved for exceptional cases.

Which plate material suits which medium?

Medium	Recommended plate material
Drinking water, heating water	1.4404 (316L)
Brackish water (< 200 mg/l Cl)	1.4404 (316L)
Brackish water (> 200 mg/l Cl)	Titanium
Seawater	Titanium
Chlorinated cooling water	Titanium
Food, whey, juices	1.4404 (316L)
Mineral oil, hydraulic oil	1.4404 (316L)
Ammonia (refrigerant)	1.4404 (316L)
Chloride-bearing acid solution	Titanium or Hastelloy
Chlor-alkali	Titanium

Which gasket materials are available?

EPDM (ethylene propylene diene monomer)

EPDM is the most widely used gasket material in plate heat exchangers. It is resistant to hot water, steam, dilute acids and alkalis, and many polar solvents. The continuous temperature limit is approximately 150 °C, with brief peaks up to 180 °C. EPDM is excellent for:

• Heating and cooling water applications
• Food and beverages (food-grade approved)
• Milk, whey, fruit juices
• Domestic hot water heating
• Steam condensate applications

EPDM is NOT resistant to mineral oils, fuels, aromatic hydrocarbons and chlorinated solvents. Contact with these media causes swelling and gasket failure.

NBR (nitrile butadiene rubber, Perbunan)

NBR is the standard for oil- and fat-bearing media. It is resistant to mineral oils, hydraulic oils, lubricating oil, fuels and aliphatic hydrocarbons. The temperature limit is approximately 120 °C (continuous), up to 135 °C under favourable conditions.

NBR applications:

• Mineral oils, hydraulic oils
• Lubricating and gear oil cooling
• Fuel applications

NBR is NOT suitable for hot water above 80 °C, ozone exposure, aromatic hydrocarbons (toluene, benzene) or esters. NBR must not be used for steam or long-term hot-water service.

Other gasket materials

FKM / Viton: fluoroelastomer for aggressive solvents, acids, aromatic hydrocarbons and high temperatures up to 200 °C. Significantly more expensive than EPDM/NBR.

PTFE: for highly corrosive media, broad chemical resistance, but poorer mechanical sealing properties; used as an encapsulation or insert.

Which gasket suits which medium?

Medium	Recommended gasket material
Heating water, cooling water	EPDM
Steam / hot water up to 150 °C	EPDM
Food, dairy, beverages	EPDM (food-grade approved)
Drinking water	EPDM (WRAS / KTW compliant)
Mineral oil, hydraulic oil	NBR
Lubricants, gear oil	NBR
Aromatic hydrocarbons	FKM / Viton
Concentrated acids	FKM / PTFE
Ammonia	Check EPDM or FKM

How do you prevent fouling and corrosion?

Beyond chemical resistance, the fouling factor indirectly influences the material choice: smooth plate corrugations and high-alloy steel reduce the adhesion of deposits and thus the fouling rate. Titanium forms an oxide passivation layer that resists biological and mineral fouling more effectively than unalloyed steel.

Important: dissimilar metals in the same fluid circuit can cause galvanic corrosion. If a titanium plate heat exchanger is connected to a stainless-steel piping system, appropriate measures (insulating pieces, potential equalisation) should be checked.

Summary

Material selection follows from a clear analysis of the medium, temperature and chloride content. 1.4404 (316L) is sufficient for most industrial and food-processing applications. Titanium is the right material for chloride- and seawater-bearing media where 1.4404 would fail. For gaskets: EPDM for water and food applications, NBR for oil. For aggressive solvents and high temperatures, FKM should be considered.