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D2197-16 – Standard Test Method Technical Guide
📋 Scope and Significance
This standard, D2197‑16 (Reapproved 2022), covers the determination of adhesion of organic coatings such as paint, varnish, and lacquer when applied to smooth, flat panel surfaces. It is approved for use by agencies of the U.S. Department of Defense. The values stated in SI units are standard, and the method is vital for assessing coating performance.
Significance and Use: Adhesion is critical for coating durability. This test method provides relative ratings for coated panels, making it useful for comparing adhesion levels across different coatings or substrates.
⚙️ Apparatus and Test Procedure
The primary apparatus is a Balanced Beam Scrape Adhesion Tester, featuring a balanced beam with a weight platform and a rod at 45° holding a scraping loop of 1.6‑mm (1/16‑in.) diameter. Additional equipment includes application tools per Practices D823 and film‑thickness measurement devices per Test Method D1005 or Practice D7091.
Procedure: Apply the coating at uniform thickness to flat panels, typically sheet metal. After drying, push the panel beneath the loaded stylus with increasing load until the coating is removed. The loop contacts the surface directly below the weights.
| 🟦 Component | 📏 Specification |
|---|---|
| Application Equipment | As per Practices D823 |
| Film‑Thickness Apparatus | Per D1005 or D7091 |
| Balanced Beam Tester | With weight platform and 45° rod |
| Scraping Loop | 1.6 mm (1/16 in.) diameter |
📊 Interpretation and Limitations
This test method excels at differentiating adhesion among coatings. However, per Section 4.2, it is not applicable when solvent‑based coatings require 10‑20 kg loads to break the surface, as the chrome‑plated loop stylus chatters and skips. Similarly, powder coatings needing more than 10 kg yield meaningless data.
| ⚠️ Condition | 📝 Guideline |
|---|---|
| Solvent‑Based Coatings | Not applicable if 10‑20 kg load required |
| Powder Coatings | Not applicable if load >10 kg required |
⚠️ Important Note: The loop stylus may chatter under high loads, causing unreliable adhesion data. Avoid testing coatings that require significant force to breach the surface.
💡 Best Practice: Measure film thickness using D1005 or D7091 to ensure consistent coating application before proceeding with the adhesion test.
❓ Frequently Asked Questions
🔍 What organic coatings are covered by D2197?
This test method covers organic coatings like paint, varnish, and lacquer applied to smooth, flat panels.
💡 How is adhesion determined in this test?
Adhesion is measured by increasing the load on a 1.6‑mm stylus until the coating is scraped off the substrate.
⚡ What is the critical dimension of the scraping loop?
The scraping loop must have a diameter of 1.6 mm (1/16 in.) as specified in the standard.
📌 When is this test method not recommended?
It is not recommended for solvent‑based coatings needing 10‑20 kg loads or powder coatings requiring more than 10 kg to break the surface.