Standard polypropylene filter cloth handles 95% of industrial slurries fine. The other 5% — concentrated acids above 50%, strong oxidizers, hot organic solvents, high-temperature alkalis — kills PP within hours to days. For those duties, a properly-specified corrosion-resistant filter cloth can multiply life from days to years.
The Chemistry → Material Decision Matrix
| Chemistry | Avoid | Choose |
| Strong acid (HCl, H₂SO₄ to 80%) | Nylon, cotton | PP, PVDF, PTFE |
| Strong alkali (NaOH 50% hot) | Polyester, cotton | PP, PTFE |
| Hot organic solvent (above 60°C) | PP | Polyester, PTFE |
| Hot oil (above 100°C) | PP | PTFE, polyester |
| Strong oxidizer (HNO₃, chromate) | PP, polyester, nylon | PTFE (PVDF for HNO₃ under 30%) |
| Cold acid mix (50/50 HNO₃/HCl, “aqua regia”) | Anything except PTFE | PTFE only |
| Bleach / hypochlorite solution | Polyester, nylon | PP, PTFE |
| Concentrated chloride (above 20%) | Carbon steel plates | PP cloth + duplex frame |
Material Strengths Summary
- Polypropylene (PP) — best general acid/alkali tolerance, but limited to 95°C and incompatible with hot organics
- Polyester (PET) — better high-temperature (120°C) and abrasion, but hydrolyzes in hot alkali pH > 10
- PVDF — hot acid and chlorinated solvents to 130°C
- PTFE — universal chemistry, 250°C continuous, but $100-300/m² vs $10-30 for PP
- Polypropylene with PTFE coating — hybrid; PP backbone with thin PTFE coating gives 80% of PTFE chemistry at 40% of the price
Common Corrosive Applications
- Chemical & fine chemicals — acid intermediates, dye precursors, pharma APIs
- Hydrometallurgy — leach pulp filtration, cobalt and nickel chemistry
- Battery recycling — sulfuric acid leach
- Pickling line filtrate — HCl and HNO₃ + HF mixture
- FGD wastewater — chloride-laden gypsum slurry
- Electroplating — chromic acid and cyanide solutions
Specifications & Customization Options
- Materials: PP, polyester, PVDF, PTFE, PP/PTFE laminate
- Operating temperature: 95°C PP, 120°C polyester, 130°C PVDF, 250°C PTFE
- pH range: PP 0-14, polyester 2-10, PTFE 0-14 + all common solvents
- Weave options: All standard weaves available in all chemistries
- Edge construction: Heat-bonded (chemistry-safe), sewn (cheaper)
- Stitching thread: Match the cloth material — PP cloth needs PP thread, not nylon
FAQs
How do I test compatibility before specifying? Submerge a 100 cm² sample in your actual slurry at operating temperature for 7-14 days. Measure weight change (>3% loss indicates degradation) and visual inspection. Senjie can do this for you with a few hundred mL of your slurry.
Why does the stitching thread matter? The thread runs around the cloth edge and through hanger loops. If thread degrades faster than the cloth, the edges unravel and the cloth blows out. Always match thread chemistry to cloth chemistry.
Is PTFE always overkill? Often yes. PTFE is only needed when no other material works (strong oxidizers, hot mixed solvents, aqua regia). For most “corrosive” duty, PVDF or PP-with-PTFE-coating gives 90% of the performance at 25-40% of the cost.
Need a corrosive-duty cloth spec? Send Senjie your full chemistry breakdown (all components + concentration + temperature) and we’ll recommend the most economical material that survives.