MEDIA GUIDE
Sulfuric Acid Valves (93–98%)
Concentrated acid passivates carbon steel — with strict conditions attached.
Concentrated acid passivates carbon steel at ambient temperature — the industry-standard material for 93–98% acid (velocity < 0.6 m/s, no dilution). Stainless grades are borderline (Grundfos rates 316 not resistant at 98%); Alloy 20 / Hastelloy or fluoroplastic linings for severe duty. Never use titanium.
Materials at a glance
| Material | Rating | Up to |
|---|---|---|
| Carbon steel (ASTM A216 WCB) | Excellent | 40 °C |
| Stainless steel 304 (ASTM A351 CF8) | Conditional | 30 °C |
| Stainless steel 316 (ASTM A351 CF8M) | Conditional | 40 °C |
| Alloy 20 (ASTM A351 CN7M) | Excellent | 80 °C |
| Hastelloy C-276 (ASTM A494 CW6M) | Excellent | 90 °C |
| Titanium Gr.2 (ASTM B367 C2) | Not recommended | — |
| PTFE/PFA-lined ductile iron | Excellent | 150 °C |
Ratings: Excellent / Good / Conditional / Not recommended, from this site's boundary-and-medium data set. The manufacturer's data sheet for the specific product governs.
What drives the choice
- Carbon steel is the industry standard for 93–98% acid at ambient temperature — velocity under 0.6 m/s, no dilution, no aeration
- Stainless grades are borderline; Alloy 20, Hastelloy or fluoroplastic linings for severe duty
- Never titanium
Where the boundaries sit
- Mid-concentration acid (50–80%) is MORE aggressive to stainless than the concentrated acid — concentration belongs in the enquiry
Related reading
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