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D6189-97 – Standard Test Method Technical Guide
ASTM D6189-97 (Reapproved 2022) provides a standardized practice for evaluating the efficiency of chemical removers designed for organic coatings on wood and metal substrates. The practice is essential for assessing product performance prior to use in recoating operations, as outlined in its scope and significance sections.
🪵 Substrate Specifications and Coating Materials
The standard specifies distinct dimensions for wood and steel panels. Steel panels must measure 150 mm by 300 mm with a thickness of 0.8 mm. Wood panels must be a minimum of 300 mm by 300 mm and at least 8 mm thick. Suitable woods include birch plywood, fir, pine, oak, and walnut. The coatings tested must be applied in accordance with Practices D823 for producing films of uniform thickness.
| 🟦 Substrate | 📏 Minimum Dimensions | 🎯 Specified Thickness |
|---|---|---|
| Cold-Rolled Steel | 150 mm × 300 mm | 0.8 mm (0.032 in) |
| Solid Wood or Wood Laminate | 300 mm × 300 mm | 8 mm (5/16 in) |
⚙️ Apparatus and Test Procedure
The required apparatus includes a forced-draft oven (Type IB per Specification E145), a nylon/polyester bristle paint brush, a plastic paint scraper, very fine garnet sandpaper (220 to 240 grade), and a stopwatch. The procedure involves applying the remover, allowing it to dwell for a specified time, and then lifting the loosened coating with the plastic scraper to assess efficiency.
💡 Key Procedural Detail: The use of a plastic scraper is mandatory to prevent damage to the substrate, ensuring the rating reflects only the chemical removal efficiency and not mechanical scraping action.
📊 Evaluation and Rating System
After the specified dwell period, the efficiency of the coating removal is determined and recorded using a rating scheme from 5 to 0. As per the standard summary, a high rating indicates effective and complete removal, while a low rating indicates poor or no removal action. This allows for quantitative comparison of different chemical remover formulations on finishes such as latex enamel, alkyd enamel, and polyurethane.
⚠️ Important Consideration: The standard recommends testing a range of finishes. The rating can vary significantly between alkyd enamels, polyurethane, and nitrocellulose lacquer. Multiple substrate tests yield the most reliable data.
❓ Frequently Asked Questions
🔍 What is the specific designation of this standard?
The standard is designated as D6189-97 (Reapproved 2022), titled “Standard Practice for Evaluating the Efficiency of Chemical Removers for Organic Coatings.”
💡 What types of finishes are recommended for testing?
The standard recommends testing removers on a variety of finishes including latex enamel, alkyd enamel, polyurethane, varnish, shellac, and nitrocellulose lacquer.
⚡ Why is the forced-draft oven specified as Type IB?
This specific oven type, per Specification E145, ensures consistent and controlled forced-ventilation drying conditions for the coated test panels, which is critical for maintaining reproducibility across tests.
📌 What is the correct grit range for the required sandpaper?
The standard calls for “Very Fine Garnet Abrasive-Type Sandpaper” with a grade of 220 to 240 for surface preparation needs.