ASTM C868 – 02: Chemical Resistance Test for Protective Linings

Introduction

ASTM C868 – 02 is a standard test method used to evaluate the chemical resistance of protective linings under immersion service conditions. This method closely simulates real industrial environments by creating a temperature differential between the exposed and unexposed sides of a coated panel — accelerating potential permeation, blistering, delamination, and substrate corrosion.

It is widely used in oil & gas, petrochemical plants, water treatment facilities, and industrial storage tanks where corrosion-resistant coatings are critical.

What Is ASTM C868?

ASTM C868 specifies laboratory procedures for assessing the durability and chemical resistance of polymer-based protective linings when exposed to corrosive media under controlled conditions.

The test helps determine:

• Resistance to corrosive chemicals
• Lining adhesion performance
• Blistering and permeation behavior
• Surface degradation and hardness changes
• Substrate corrosion protection

This method is intended as a qualitative evaluation tool, not the sole basis for material selection.

Scope of ASTM C868

The test method:

• Simulates immersion service conditions
• Applies temperature control (±2°C)
• Evaluates coating performance over 1 to 6 months (or longer)
• Uses steel test panels prepared to White Metal standard

The substrate preparation follows:

NACE No. 1/SSPC-SP-5 — White Metal Blast Cleaning.

Apparatus Used in ASTM C868

The primary equipment includes:

1️⃣ Four-Neck Borosilicate Glass Test Cell

• Cylindrical chemical-resistant glass cell
• Allows heater, thermometer, condenser, and gas bubbler installation

2️⃣ Heating Equipment

• Electrical immersion heater
• External heating tape (must not contact test panel)
• Controlled to ±4°F (±2°C)

3️⃣ Reflux Water Condenser

Maintains constant solution concentration and prevents evaporation loss.

4️⃣ Air or Gas Bubbler

• Used for agitation and temperature uniformity
• Nitrogen for oxygen-depleted simulations
• Air bubbling for aerated service conditions

ASTM B571 – Standard Practice for Qualitative Adhesion Testing of Metallic Coatings

Test Specimen Requirements

Substrate

• 1/4 in. carbon steel panels
• Prepared to White Metal condition
• Profile depth measured per ASTM D4417

Lining Application

• Applied as per manufacturer’s field method (spray, roller, etc.)
• Thickness within ±10% of nominal
• Opposite side remains unlined

Conditioning

• 7 days at 23 ± 2°C
• Additional curing if specified

Test Procedure Overview

1. Clamp coated panel to glass cell
2. Fill 2/3–3/4 with specified chemical solution
3. Maintain required temperature
4. Inspect at monthly intervals
5. Refill fresh solution after each inspection
6. Continue exposure for 6 months or until failure

Evaluation Criteria

Interim Inspection

• Color change
• Gloss reduction
• Surface erosion
• Blistering (per ASTM D714)
• Media changes

Final Inspection (After 6 Months)

• Hardness testing (D785, D1474, D2583, D3363)
• Adhesion testing (D4541 pull-off method)
• Substrate corrosion check
• Microscopic examination (if required)

⚠ High-voltage holiday testing is not permitted after exposure.

Significance in Oil & Gas & Industrial Coating Inspection

For coating inspectors like you, Pritam, this test is extremely relevant when selecting:

• Tank linings
• Chemical process equipment coatings
• Wastewater treatment linings
• Acid storage protective systems
• FRP lining systems

The results help verify long-term durability under aggressive chemical environments.

For official purchase or latest revision updates, visit:
👉 https://www.astm.org/

Advantages of ASTM C868

✔ Simulates real immersion service
✔ Accelerates permeation effects
✔ Evaluates adhesion & blister formation
✔ Applicable to multiple substrates
✔ Long-term durability assessment

Limitations

• Qualitative evaluation
• Subjective visual assessment
• Long exposure period required
• Requires strict temperature control

✅ Frequently Asked Questions (FAQ)