PEEK Acid Resistance Explained

Is PEEK Acid Resistant? A Complete Guide to PEEK’s Acid Corrosion Performance

Introduction

PEEK (Polyether Ether Ketone) is a high-performance engineering thermoplastic known for its outstanding chemical resistance, mechanical strength, and thermal stability. One of the most common questions from industries such as chemical processing, pharmaceuticals, and oil & gas is: How does PEEK perform in acidic environments? This blog provides a detailed analysis of PEEK’s acid resistance, key influencing factors, and real-world application scenarios.

1. PEEK’s Acid Resistance Overview

PEEK exhibits excellent corrosion resistance against a wide range of acids, but its performance depends on the type of acid, concentration, temperature, and exposure duration.

• Inorganic Acids (Low Concentration, Ambient Temperature):
  PEEK performs very well in dilute inorganic acids such as hydrochloric acid (≤37%), sulfuric acid (≤50%), and nitric acid under ambient conditions. It does not easily dissolve, swell, or degrade, making it suitable for long-term contact.

  Example: PEEK is widely used for chemical pipelines and valve linings exposed to dilute acid solutions.

• Inorganic Acids (High Concentration, High Temperature):
  Highly concentrated and strong oxidizing acids like 98% sulfuric acid or concentrated nitric acid can slowly attack PEEK, especially at elevated temperatures (>100°C). Prolonged exposure may cause surface degradation or gradual loss of mechanical properties.

  Note: Concentrated nitric acid has strong oxidizing power and requires careful evaluation before use.

• Organic Acids:
  PEEK demonstrates exceptional stability against organic acids such as acetic acid, citric acid, and formic acid across a wide concentration range. Even at medium temperatures (≤150°C), it remains chemically stable and is widely applied in food, pharmaceutical, and biotech industries.

2. Key Factors Affecting PEEK’s Acid Resistance

• Temperature:
  PEEK performs best at ambient temperatures. As temperature increases (especially beyond 200°C), the risk of acid-induced degradation rises.

• Concentration:
  Lower acid concentrations typically have minimal impact on PEEK. Higher concentrations of strong oxidizing acids can cause slow corrosion.

• Exposure Time:
  Short-term exposure to strong acids may not cause visible damage, but long-term immersion can lead to cumulative degradation.

3. Applications of Acid-Resistant PEEK

Due to its superior acid resistance, PEEK is extensively used in industries requiring long-term exposure to acidic media:

• Chemical Processing: Seals, gaskets, and bearings in acid waste treatment systems.

• Pharmaceutical Manufacturing: Reactor vessel linings and components exposed to organic acids.

• Oil & Gas: Downhole tools and components in acidizing operations.

• Environmental Equipment: Acidic wastewater handling systems and filtration devices.

Conclusion

PEEK is an excellent material for acidic environments, especially for dilute inorganic acids and almost all organic acids at ambient to moderate temperatures. However, its performance with highly concentrated and strong oxidizing acids at high temperatures should be carefully evaluated. For any real-world application, always consider acid type, concentration, temperature, and exposure duration to ensure optimal material performance.