When selecting instruments for corrosive media, the core principles are material matching, adaptation of measuring principles, and sealing protection. Non-contact types are preferred; if contact types must be used, the wetted materials must be strictly controlled. A complete selection scheme is provided below by medium type and instrument type.
I. Quick Matching Table of Common Corrosive Media and Materials
| Medium Type |
Typical Media |
Recommended Wetted Materials (in order of priority) |
Taboo Materials |
| Strong Oxidizing Acids |
Concentrated nitric acid, fuming nitric acid, chromic acid |
316L, Titanium, Hastelloy C-276, Tantalum |
Carbon steel, ordinary stainless steel |
| Strong Reducing Acids |
Concentrated hydrochloric acid, dilute sulfuric acid (<80%) |
Hastelloy B-2, Tantalum, PTFE |
304/316L, Titanium |
| Strong Alkalis |
NaOH, KOH (normal temperature ≤50%) |
316L, Hastelloy C, Titanium |
Aluminum, zinc, ordinary carbon steel |
| Chloride-Containing Media |
Seawater, NaCl, wet chlorine gas |
Hastelloy C-276, Titanium, Tantalum |
304/316L (prone to pitting corrosion) |
| Organic Acids |
Acetic acid, formic acid, citric acid |
316L, Titanium, Hastelloy C, PTFE |
Carbon steel, ordinary rubber |
| Highly Corrosive Mixed Liquids |
Aqua regia, mixed acids |
Tantalum, Platinum, PFA lining |
Almost all ordinary metals |
| Corrosive Gases |
Chlorine gas, ammonia gas, hydrogen sulfide |
Hastelloy C, 316L, PTFE |
Carbon steel, ordinary seals |
II. Selection Guide for Various Instruments
1. Flow Measurement
Electromagnetic Flowmeter: First choice for conductive corrosive liquids
- Application: Acid-base solutions, salt solutions, sewage (conductivity ≥5μS/cm)
- Linings: PTFE (≤180℃), PFA (≤260℃), rubber (weak corrosion)
Clamp-on Ultrasonic Flowmeter (First Choice for Non-Contact)
- Application: Highly corrosive, toxic, particle-containing, high-viscosity, non-conductive media
- Advantages: Non-contact, zero corrosion, maintenance-free, installable without shutdown
- Limitations: Sensitive to pipe material/wall thickness and medium purity
Coriolis Mass Flowmeter (High Precision for Strong Corrosion)
- Application: Strong corrosion, high precision, small flow rate
- Materials: Measuring tube made of Hastelloy C-276, Titanium, Tantalum
Metal Tube Rotameter / Glass Rotameter (Intuitive Small Flow)
- Application: Small flow, normal pressure, weak/medium corrosion
- Materials: PTFE lining, Hastelloy alloy, Titanium; all-plastic (PVC/PP)
- Taboo: Particle-containing, easy to crystallize, high viscosity
2. Pressure / Differential Pressure Measurement
Diaphragm Pressure Gauge / Transmitter (First Choice for Strong Corrosion)
- Application: Strong acids, strong alkalis, particle-containing, viscous, crystallizing media
- Diaphragm materials: Tantalum (aqua regia/concentrated acids), Hastelloy C, Titanium, 316L, PTFE coating
3. Level Measurement
Radar / Ultrasonic Level Meter (First Choice for Non-Contact)
- Application: Strong acids, strong alkalis, toxic, volatile, foam/dust-containing media
- Advantages: Non-contact, zero corrosion, suitable for normal pressure/closed/ex-proof environments
- Selection: High-frequency radar (strong corrosion/steam), ultrasonic (normal temperature and pressure)
Magnetostrictive Level Meter (High Precision Contact Type)
- Application: Closed tanks, ex-proof, high-precision corrosive media (pharmaceutical/fine chemicals)
- Materials: Float/probe rod 316L, Hastelloy C, Titanium, PTFE coating
III. Common Misconceptions and Pitfalls to Avoid
- ❌ Using only 316L for all corrosive scenarios (especially pitting corrosion occurs rapidly in chloride-containing/concentrated hydrochloric acid)
- ❌ Using ordinary pressure gauges/transmitters for strong corrosion (leakage inevitable without diaphragm)
- ❌ Choosing electromagnetic flowmeters for non-conductive media (no signal)
- ❌ Using ordinary rubber for seals (aging and leakage within a few days)
With the development of the chemical process industry and the improvement of automation, instruments play a key role in the reliable operation of plants and production efficiency.
Selecting the right corrosion-resistant materials ensures longer instrument service life, lower maintenance costs, higher measurement accuracy, higher plant availability and economic benefits.
Corrosion cannot be completely eliminated, but reasonable material selection and correct product matching can significantly reduce failure risks and protect the operational investment of production plants.
Contact Information
Website: https://www.radar-leveltransmitter.com/
Email: lijunrong@china-nyjy.com
Whatsapp: +8615901050329
