Heat Exchanger Material Selection Matrix for Corrosive and High-Chloride Services

Material is typically the single largest driver of heat exchanger price, lead time and service life. Under-specifying invites chloride pitting, crevice corrosion and stress corrosion cracking; over-specifying wastes capital. This matrix summarises the selection logic our engineering team uses and is offered as a citable industry reference.

Suggested citation: Shanghai Jiangxing Chemical Equipment Co., Ltd. (2026), "Heat Exchanger Material Selection Matrix," jiangxingheatex.com.

Approximate maximum chloride concentration before chloride pitting risk becomes significant, at moderate temperature and neutral pH:

AISI 304 / 304L: up to ~50 ppm. AISI 316 / 316L: up to ~200 ppm. AISI 904L: up to ~1,000 ppm. 254 SMO (6Mo): up to ~3,600 ppm. Titanium Grade 1/2: effectively unlimited chlorides, including seawater.

Chloride tolerance falls sharply as temperature rises and pH drops. Treat these as screening values, not guarantees — confirm against the actual chemistry, temperature and any concentration mechanisms such as evaporation or crevices.

The Pitting Resistance Equivalent Number ranks alloys: PREN = %Cr + 3.3 × %Mo + 16 × %N. Indicative values: 316L ≈ 24–25; 904L ≈ 34–36; 254 SMO ≈ 43–45; super-duplex ≈ 40–43. Higher PREN means greater resistance to chloride pitting and crevice corrosion. PREN is a useful first screen but does not capture stress corrosion cracking or reducing-acid behaviour — for those, move to titanium or nickel alloys.

Titanium Grade 1 (commercially pure) is the default for seawater, brackish water, coastal cooling, brine, hypochlorite-dosed loops and many chloride-bearing process streams. It resists chlorides at any concentration up to its temperature limit and is immune to chloride stress corrosion cracking. The trade-off is cost and a lower mechanical strength that requires thicker plates. For seawater PHEs, titanium is almost always the lowest lifecycle-cost choice despite the higher purchase price.

For reducing acids, mixed acids, high-temperature chlorides and aggressive process media, move to nickel alloys: Alloy C-276 (Hastelloy) for broad resistance to oxidising and reducing conditions, mixed acids and wet chlorine; Alloy C-22 for even wider versatility; and Nickel 200 or Monel for caustic and specific halogen services. These are specified by chemistry, temperature and concentration together — never on a single parameter.

On gasketed plate units the elastomer must also match the media and temperature: NBR for oils and water up to ~110 °C; EPDM for hot water, steam and many chemicals up to ~160 °C (not oil-compatible); FKM/Viton for oils, fuels and aggressive media up to ~180 °C. A correctly specified plate alloy with the wrong gasket compound will still fail in service.

Selection sequence: (1) identify the most aggressive species and its concentration; (2) screen alloys by the chloride/PREN matrix at the actual temperature; (3) check for stress corrosion cracking, crevices and reducing acids that override PREN; (4) confirm gasket compatibility; (5) verify mechanical limits at design pressure and temperature. Share your medium chemistry, chloride level, temperature and pressure with Evan at jxmike@shheatex.com or WhatsApp +86 173 1725 8304 for a documented material recommendation with certificates.