I. 304 Stainless Steel (Most Versatile, Cheapest)

Applicable Scenarios:

- Ordinary corrosive wastewater, low salinity

- Temperature not exceeding 80°C

- Food, beverages, general waste liquids

- Usage environment without strong acids, strong alkalis, or chloride ions

Typical Advantages:

- Low cost

- Good processability

- Sufficient for neutral and weakly corrosive working conditions

Limitations:

- Prone to pitting corrosion when chloride ions exceed 200 ppm

- Not resistant to high temperatures, strong acids, or strong alkalis

- Not suitable for high-salt, high-chloride industrial wastewater

II. 316L Stainless Steel (Preferred for Medium to High Corrosion Conditions)

Applicable Scenarios:

- High-salt wastewater, electroplating waste liquid, printing and dyeing wastewater

- Relatively high chloride ion concentration (several hundred to several thousand ppm)

- Temperature ≤ 120°C

- Codes, fine chemicals, high-requirement food scenarios

Typical Advantages:

- 3-5 times stronger corrosion resistance than 304

- Resistant to chlorine, sulfur, and weak acids

- Moderate cost, covering most industrial waste liquids

Limitations:

- May still have issues under extremely strong corrosion (strong acids, strong chlorine, high temperatures)

- Not suitable for high-concentration hydrofluoric acid or strong oxidizing environments

III. Titanium / Titanium Alloys (Extremely Corrosion-Resistant, High-End Scenarios)

Applicable Scenarios:

- Wastewater with high chlorine, high salt, and extremely strong corrosiveness

- Seawater desalination, desulfurization wastewater, strongly corrosive chemical systems

- Chloride ions can reach tens of thousands of ppm

- High temperature, long-term operation

Typical Advantages:

- Strongest resistance to chlorine corrosion

- High temperature resistance, oxidation stability

- Long service life, low maintenance

Limitations:

- Highest price

- Cannot be used in strong reducing environments (such as strong hydrochloric acid)

IV. Teflon (PTFE, PFA, etc.) Non-Metallic Corrosion-Resistant Materials

Applicable Scenarios:

- Strong corrosion: strong acids, strong alkalis, strong oxidants

- Extremely high chlorine content

- Temperature ≤ 180°C (PTFE generally ≤ 120°C)

- Amorphous, easily scaling materials (such as electroplating waste liquid, hydrofluoric acid systems)

Typical Advantages:

- Almost unbeatable corrosion resistance

- Non-conductive, non-adhesive, not easy to scale

- Suitable for the harshest working conditions

Limitations:

- Low thermal conductivity → requires larger heat exchange area

- Low mechanical strength → cannot be used for high-pressure shells

- High cost, complex processing

V. Comprehensive Summary (Direct Conclusion for Material Selection)

Select materials based on corrosiveness:

- Ordinary, weak corrosion → 304

- Medium to high corrosion, high salt → 316L (most versatile)

- Extremely high corrosion, high chlorine, strong oxidation → Titanium

- Strong acids, strong alkalis, strong corrosion, hydrofluoric acid → Teflon

Select based on temperature:

- ≤ 80°C → 304/316L

- ≤ 120°C → 316L

- High-temperature strong corrosion → Titanium

- Ultra-high temperature (within 180°C) → Teflon

Final one-sentence summary:

- Use 304 for ordinary working conditions

- Use 316L for most industrial wastewater

- Use titanium for high chlorine and high salt

- Use Teflon for extreme corrosion (strong acids and alkalis)