Chemical and petrochemical piping – material selection for corrosive media
In short: in chemical piping the material must always be chosen for the medium, concentration and temperature.
- Acid-resistant stainless (1.4404, 1.4571): the most common starting point.
- Super-austenitic and duplex (904L, 1.4462, 1.4410): for more aggressive and chloride media.
- Nickel alloys, titanium or zirconium: for the most aggressive acids.
- The whole joint: flange, gasket and bolting must also suit the medium.
This guide is for technical buyers, maintenance staff and designers in chemical and petrochemical plants.
Why is chemical material selection hard?
- Many corrosion mechanisms. General corrosion, pitting, crevice corrosion, stress-corrosion cracking and intergranular attack. Each one is resisted by a different material property.
- The conditions matter, not just the name. The same acid at another concentration or temperature can need an entirely different material.
- The weakest component decides. A good pipe material is useless if the gasket or bolts cannot withstand the medium or the environment.
- Welding. Welded joints can behave differently from the base metal, which is why "L" and stabilised grades matter.
Material overview
| Situation | Typical material | Note |
|---|---|---|
| General corrosive media, process water | 1.4404 (316L) | The workhorse of the chemical industry |
| Welded structures at elevated temperature | 1.4571 (316Ti) | Stabilised grade |
| Chlorides, risk of stress-corrosion cracking | 1.4462 (duplex) | Also higher strength |
| Strongly chloride, saline media | 1.4410, 1.4501 (super duplex) | – |
| Sulphuric and phosphoric acid in certain ranges | 904L (1.4539) | Super-austenitic |
| Strongly acidic, oxidising or reducing media | Alloy 625, C-276, C-22, 59 | Nickel-based alloys |
| Chloride, oxidising media | Titanium Grade 2 / 7 | – |
| Special acids | Zirconium 702 | – |
This is guidance only. The designer selects the final material from corrosion data and process knowledge.
The complete package
- Pipes: acid-resistant, duplex, super-austenitic and nickel-alloy pipes to EN 10216-5 / EN 10217-7 / ASTM.
- Fittings: EN 10253-3 / -4, ASTM A403, ASTM A815 (duplex).
- Flanges: in the same material, or carbon-steel lap-joint flanges with stainless stub ends.
- Gaskets: PTFE or another type chosen for the medium.
- Bolting: A4-70, duplex or special alloys, depending on the environment.
- Valves: lined, diaphragm and bellows-seal valves, safety valves, flame arresters.
- Expansion joints: with stainless or high-alloy bellows chosen for the medium.
Buyer checklist
- Medium: name, concentration, temperature, pressure.
- Grade with EN and UNS number.
- Standard and size for every component.
- Gasket and bolting material, for the medium and the environment.
- Testing: e.g. corrosion testing, PMI, if specified.
- Certificate: 3.1 or 3.2.
- Delivery: scheduled, or time-slotted for shutdowns.
Common mistakes
- Only the pipe material is specified, not the gasket or bolting.
- Non-"L" grade in welded structures, where intergranular corrosion can occur.
- Duplex pipe with non-duplex fittings or flanges.
- Goods receipt without PMI, where similar-looking grades can get mixed up.
Frequently asked questions
When is 1.4571 required instead of 1.4404?
When the design calls for a stabilised grade, typically for welded structures at elevated temperature. In many cases the two are interchangeable, but the designer decides.
Do you supply nickel-alloy fittings and flanges too?
Yes. We supply pipe, fittings, flanges and bar in nickel alloys, titanium and zirconium.
Do you quote small quantities?
Yes. We work with no minimum order.
Request a quote
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Related: Stainless steel pipes · Duplex, nickel alloys, titanium · Flange gaskets · Valves · 1.4571 · 1.4462
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