Material selection is the first specification decision on any static mixer, and it is where the most expensive mistakes happen: a 316L mixer ordered by habit can be destroyed by a duty a PP mixer would shrug off. The quick-reference table below compiles ratings from two published compatibility charts — the STC Valve chart (A–F scale, 48-hour exposure) and the Euromixers/SD Pack mixer materials table (A–D scale, ambient temperature). Both are guidance only; verify against your exact concentration and temperature before ordering.
Compatibility Quick Table
| Chemical (typical duty) | PP | PTFE | 304 SS | 316L SS |
|---|---|---|---|---|
| Acetic acid, 20% | A | A | B | A |
| Acetic acid, 80% | A | A | F | B |
| Acetone | A | A | A | A |
| Hydrochloric acid, 20% | B | A | F | F |
| Sodium hydroxide, 50% | A | A | B | B |
| Sodium hypochlorite, <20% | A | A | C | C |
| Sulfuric acid, 10–75% | A | A | F | F |
| Salt water (NaCl) | A | A | B | B |
| Diesel fuel | A | A | A | A |
| Citric acid | A | A | B | A |
Ratings: A excellent · B minor effect · C moderate, not for continuous use · F not recommended. Source: STC Valve chemical compatibility chart (48 h exposure). 316L column reflects the 316 ratings; low-carbon grades track closely at ambient temperature.
Three Findings Worth Internalizing
1. Stainless is not a universal default. In the table, 316 stainless scores F — not for continuous use, at all — in mid-range sulfuric acid and 20% hydrochloric acid, and only C in hypochlorite, while PP holds A in all three. Notice how concentration flips the verdict: acetic acid at 20% rates A on 316, but at 80% it drops the 304 rating to F. The chart row you need is the one with your concentration, not just your chemical.
2. Fluoropolymer does not mean solvent-proof. The Euromixers table rates PVDF only D (not recommended) in acetone — where plain PP keeps an A — and B in aniline. PVDF's fluorine backbone resists acids and oxidizers superbly, but ketones, esters and amines attack it. That is the opposite of the intuition most engineers carry into a materials meeting.
3. In chlorinated water service, plastic usually beats metal. Sodium hypochlorite below 20% — the workhorse chemical of water treatment — rates A on PP and PTFE but only C on either stainless grade. This is why our SK-PP elements and all-PP mixers see constant duty in dosing loops, alongside PP-lined steel housings where pressure rules out all-plastic bodies.
Temperature Ceilings
| Material | Typical continuous-service ceiling | Note |
|---|---|---|
| PP (polypropylene) | ≈ 54 °C (130 °F) | Published drum-pump guide ceiling; cost-effective, weakest at temperature |
| PVDF (Kynar) | ≈ 80 °C (175 °F) | Same guide; strongest plastic on acids/oxidizers, weak on ketone solvents |
| PTFE (Teflon) | ≈ 80 °C+ in that guide; inherently higher | Chemically near-inert; chosen for the worst duties, softest mechanically |
| SS316L / metals | up to 300 °C in our SK series | Also the only route for hygienic + high-pressure combinations |
Ceilings from the Indco chemical-resistance guide (drum-pump service) and our own SK series rating: metallic −50 °C to +300 °C, plastics −10 °C to +80 °C. Always derate for your actual concentration and pressure.
ASTM Grades to Put in the Spec
Public-sector mixer specifications (e.g. New York State OGS 464117, inline static mixers) define the material callouts worth copying: elements in carbon steel per ASTM A53, PVC or CPVC per ASTM D1784, stainless per ASTM A312 (304L or 316L), PVDF per ASTM D3222, PTFE per ASTM D1710, and FRP per ASTM C582. Specifying the standard number, not just the trade name, is what makes quotes comparable between vendors. For duties beyond these four materials — high-temperature caustic, hot concentrated acid — we build elements in Hastelloy C-276 and virgin PTFE; for pure economics on benign duty, the SS316L cartridge remains the default.
Selection Rules
Three rules resolve most material meetings in under a minute. First, rank the threat: if the chemical attacks metals (HCl, mid-range H₂SO₄, hypochlorite), shortlist plastics; if it attacks plastics (ketone solvents against PVDF) or runs hot or hygienic, shortlist stainless. Second, check pressure: above what an all-plastic body can hold, move to a lined steel shell — PTFE-lined for the worst chemistry, PVC-lined where economy rules. Third, put the ASTM grade and the concentration on the drawing, and make the vendor confirm both in writing. Related reading: our food-grade static mixer guide covers the sanitary-polish side of 316L selection.
Frequently Asked Questions
Is 316L stainless steel always more chemically resistant than plastics?
No — published charts rate 316 stainless F in 10–75% sulfuric acid and 20% hydrochloric acid, and C in hypochlorite, while PP rates A in all three. Stainless wins on strength, temperature and hygiene; plastics win on many wet-chemical duties.
Why is PVDF rated worse than PP for acetone?
PVDF is attacked by ketones, esters and amines: the Euromixers published table rates acetone D for PVDF while polypropylene stays A. Fluorine chemistry does not make a material universally solvent-proof.
Which static mixer material handles the highest temperature?
Metals — our SK series is rated −50 °C to +300 °C in metallic construction versus −10 °C to +80 °C for plastics. Published continuous ceilings put PP near 54 °C and PVDF and 316 SS near 80 °C.
When should I choose a lined steel mixer instead of all-plastic?
When the duty needs corrosion resistance and pressure at the same time: a steel shell with PP, PVC or PTFE liner gives the plastic's chemical barrier with the shell's pressure rating.
Sources: STC Valve chemical compatibility chart (A–F ratings, 48 h exposure); Euromixers/SD Pack chemical compatibility table (A–D ratings, 20 °C ambient); Indco drum-pump chemical resistance guide (temperature ceilings); NYS OGS master specification 464117 inline static mixers (ASTM material grades).