Understanding PEEK's Resistance to Organic and Inorganic Acids

Is PEEK Material Acid-Resistant?

PEEK (Polyether Ether Ketone) is a high-performance specialty engineering plastic renowned for its excellent chemical resistance. Its acid resistance is outstanding in most cases, but its corrosion resistance must be evaluated considering factors like the type of acid, concentration, temperature, and exposure time.

1. Resistance to Common Acids

• Inorganic Acids (Low Concentration, Room Temperature):

For inorganic acids like hydrochloric acid, sulfuric acid, and nitric acid in low concentrations (e.g., ≤50% sulfuric acid, ≤37% hydrochloric acid), PEEK shows good corrosion resistance at room temperature. Long-term exposure does not lead to dissolution, swelling, or degradation of properties.

• Example: PEEK can be used to manufacture chemical pipelines, valve linings, and other components in environments with low-concentration hydrochloric acid at room temperature.

• Inorganic Acids (High Concentration, High Temperature):

Strong oxidizing acids at high concentrations (such as 98% concentrated sulfuric acid and concentrated nitric acid) may cause some corrosion to PEEK at high temperatures, especially when temperatures exceed 100°C. This could lead to slow degradation or surface damage.

• Note: The strong oxidizing nature of concentrated nitric acid significantly affects PEEK. Long-term exposure can lead to a decline in material properties.

• Organic Acids:

PEEK shows stable and excellent corrosion resistance in common organic acids, including acetic acid, citric acid, and formic acid, at room temperature to moderate temperatures (≤150°C), regardless of concentration. This makes it suitable for use in acidic environments in food, pharmaceuticals, and other sectors.

2. Key Factors Affecting Acid Resistance

• Temperature: PEEK exhibits the best acid resistance at room temperature. As temperature increases (e.g., exceeding 200°C), the reaction between PEEK and strongly corrosive acids may accelerate, reducing its corrosion resistance.

• Concentration: Low concentrations of acids have minimal impact on PEEK. However, high concentrations (especially strong oxidizing acids) may cause slow corrosion.

• Time: Short-term contact with high concentrations of acids may not show significant changes, but prolonged exposure can cause cumulative damage.

3. Application Scenarios

Thanks to its excellent acid resistance, PEEK is widely used in industries such as chemicals, pharmaceuticals, and environmental protection. Examples include:

• Seals and bearings for acid waste treatment equipment.

• Linings for reaction vessels in pharmaceutical processes that contact organic acids.

• Components of downhole tools in oilfield exploration that come into contact with acidic media.

Summary:

PEEK has excellent corrosion resistance to most low-concentration acids (including inorganic and organic acids) at room temperature. However, caution is needed when using it with highly concentrated oxidizing acids (such as concentrated nitric acid or high-temperature concentrated sulfuric acid). In practical applications, it is necessary to assess its suitability based on the specific type of acid, concentration, temperature, and exposure time.