ASTM D 2197 มาตรฐาน: Authoritative Test Guide for Scratch Adhesion of Organic Coatings

In the field of industrial coatings, adhesion is one of the core indicators for measuring coating quality, directly determining the durability, protectiveness, and service life of coatings. As an authoritative standard developed by the American Society for Testing and Materials (มาตรฐาน ASTM), ASTM D 2197 is specifically designed for the scratch adhesion testing of organic coatings, providing a unified and scientific testing basis for the coating industry, สถาบันทดสอบ, and manufacturing enterprises. This article will comprehensively dissect the core content, testing procedures, ขอบเขตการใช้งาน, and application value of the ASTM D 2197 มาตรฐาน, helping relevant practitioners deeply understand and standardize the application of this standard.

I. Core Definition and Version Iteration of ASTM D 2197 มาตรฐาน

ASTM D 2197 is fully titled “Standard Test Method for Adhesion of Organic Coatings by Scrape Adhesion”. Its core purpose is to quantitatively determine the adhesion strength of organic coatings (เช่นสี, เคลือบเงา, ฯลฯ) on the substrate surface through scratch tests, judge the bonding ability between coatings and substrates, and between coatings and coatings, and provide quantitative data for coating quality control and performance evaluation.
Since its release, the standard has undergone multiple revisions. The current mainstream version is ASTM D 2197-16 (Revised 2022). Compared with the old version, the new version has been optimized in terms of test accuracy, environmental control, and result determination, which is more in line with the current application needs of industrial coatings. It should be noted that the values expressed in SI units in the standard are legal standards, and the values given in parentheses are for reference only.
นอกจากนี้, ASTM D 2197 clearly stipulates that this standard is not intended to address all safety issues related to its use. Users shall establish appropriate safety, สุขภาพ, and environmental practices on their own and confirm the applicability of regulatory restrictions before use, which is a common requirement of all ASTM standards.

ครั้งที่สอง. Scope of Application and Core Test Objects of ASTM D 2197

The scope of application of ASTM D 2197 is clearly targeted, mainly covering the adhesion determination of various organic coatings on smooth and flat substrate surfaces, which can be specifically divided into the following aspects:
(1) Coating Types
It is applicable to various organic coatings such as paints, เคลือบเงา, and enamels, including single-layer coating systems (thickness ≥ 50μm) and multi-layer composite coating systems (total thickness ≤ 5mm). Whether it is a decorative coating, anti-corrosion coating, or functional coating, adhesion testing can be carried out through this standard. Common applicable coatings include epoxy coatings, polyurethane coatings, powder coatings, electrophoretic paints, insulating varnishes, ฯลฯ, which are widely used in various industrial fields.
(2) Substrate Types
The standard requires that the substrate surface be smooth, flat, and sufficiently hard to avoid damage by scratch tools. Common applicable substrates include metal alloys (cold-rolled steel plates, aluminum plates, magnesium alloys, ฯลฯ), พลาสติกวิศวกรรม (เอบีเอส, พีซี, PEEK, ฯลฯ), and composite materials (CFRP, GFRP). If no substrate is specified, the standard recommends the use of 0.8mm cold-rolled carbon steel plates, which shall be surface-treated in accordance with ASTM D 609 Method B or C.
(3) Application Scenarios
This standard is mainly used for the performance testing of coatings in laboratory environments and is not applicable to on-site testing. It can be widely used in quality control and product research and development in fields such as the automotive industry (body electrophoretic paint, topcoat), การบินและอวกาศ (thermal barrier coatings, radar absorbing coatings), marine engineering (hull anti-corrosion coatings), electronic devices (encapsulation coatings, conformal coatings), and architectural decoration (ceramic coatings, metal claddings).

III. Core Testing Procedures and Technical Requirements of ASTM D 2197

The ASTM D 2197 standard has strict regulations on testing procedures, equipment, environment, and operating steps to ensure the accuracy, การทำซ้ำ, and comparability of test results. The core process can be divided into four links: การเตรียมตัวอย่าง, equipment preparation, test operation, and result determination.
(1) Sample Preparation
Sample preparation is the basis of the test, which directly affects the reliability of the test results and must be strictly in accordance with the following requirements:
1.Substrate Treatment: The substrate surface shall be cleaned, degreased, derusted, ฯลฯ, to ensure no impurities or oxide layers. For metal substrates, Sa2.5 grade sandblasting (in accordance with ISO 8501-1 มาตรฐาน) can be adopted to enhance the bonding force between the coating and the substrate.
2.Coating Application: Apply an organic coating of uniform thickness in accordance with ASTM D 823, and retain a 13mm uncoated area at one end of the panel for the scratch starting position; the drying or baking conditions of the coating shall be agreed upon by both parties of the test to ensure complete curing of the coating.
3.Sample Conditioning: Condition the prepared samples in an environment of 23±2℃ and 50±5% relative humidity for at least 48 ชั่วโมง. Prepare at least 2 duplicate samples for each material to ensure the coating performance is stable before testing.
4.Film Thickness Measurement: Measure the dry film thickness using ASTM D 1005 (micrometer method) or ASTM D 7091 (non-destructive measurement method), and record the relevant data as an important part of the test report.
(2) Equipment Preparation
The test equipment shall meet the technical parameters specified in the standard, and the core equipment is the scratch adhesion tester, with specific requirements as follows:
1.Scratch Adhesion Tester: Adopt a balanced beam structure, equipped with a counterweight platform and a 45° angle scratch ring support rod, which can test samples with thickness ≤ 12mm and width ≥ 12mm; the scratch ring is U-shaped, with an outer radius of 3.25±0.05mm, made of hardened steel (เหล็กแผ่นรีดร้อน 56-58), and the surface shall be smooth to avoid affecting the test results due to wear of the scratch tool.
2.Auxiliary Equipment: Including film thickness gauge, environmental control equipment (to ensure the test environment temperature and humidity meet the requirements), counterweight blocks (adjustable load range, maximum load not exceeding 10kg), ฯลฯ. All equipment shall be calibrated regularly to ensure accuracy.
(3) Test Operation
Test operation shall be carried out in strict accordance with the standard steps, with core steps as follows:
1.Instrument Leveling: Level the scratch adhesion tester so that when the scratch ring lightly touches the sample surface, the balance beam is in a horizontal position to ensure uniform load application.
2.Initial Load Selection: Select the initial load according to the estimated adhesion of the coating. If the coating is scratched off, gradually reduce the load (in 0.5kg steps); if not scratched off, gradually increase the load (in 0.5kg steps) until the coating is scratched off or the maximum load (10กิโลกรัม) is reached.
3.Scratch Operation: Use a new area on the sample for each scratch, control the scratch speed at 1–2 seconds per inch, and the scratch length shall be at least 75mm. Ignore the 13mm uncoated area at the start of the scratch to avoid interference of this area on the test results.
4.Repeat Testing: After initially determining the critical load, perform 5 repeated tests at three levels above, below, and equal to the critical load, using duplicate samples and applying loads randomly to avoid using the same load continuously, ensuring the repeatability of the test results.
5.Equipment Inspection: Regularly check whether the surface of the scratch ring is worn during the test. If wear occurs, turn over or replace the scratch ring in a timely manner to prevent affecting the test accuracy.
(4) Result Determination and Report
ASTM D 2197 adopts a combination of quantitative and qualitative methods to determine test results, with core requirements as follows:
1.Determination of Adhesion Endpoint: Record the number of times the coating is “scratched off” หรือ “not scratched off” under each load. The adhesion endpoint is defined as the load at which the coating changes from “mainly not scratched off” ถึง “mainly scratched off”. This load value is the scratch adhesion value of the coating, and the larger the value, the stronger the coating adhesion.
2.Failure Mode Analysis: Synchronously determine the failure mode of the coating, which is divided into interfacial failure (separation between coating and substrate) and cohesive failure (separation within the coating). The analysis of failure mode can provide a basis for coating formula optimization and construction process improvement.
3.Test Report: The test report shall include the following core contents: sample information (coating type, substrate type, film thickness), test environment (อุณหภูมิและความชื้น), test equipment parameters, load gradient, number of tests, critical load value, failure mode, referenced standard (ASTM D 2197-16(2022)), ฯลฯ, to ensure the completeness and traceability of the report.

IV. Referenced Standards and Precautions of ASTM D 2197

(1) Core Referenced Standards
The implementation of ASTM D 2197 needs to be combined with a series of relevant ASTM standards to ensure the standardization of the test process. The core referenced standards include:
•ASTM D 609: Practice for Preparation of Cold-Rolled Steel Panels for Testing Paint, Varnish, Conversion Coatings, and Related Coating Products;
•ASTM D 823: Practice for Preparation of Uniform Thickness Films of Paint, Varnish, and Related Products on Test Panels;
•ASTM D 1005: Test Method for Measurement of Dry Film Thickness of Organic Coatings Using Micrometers;
•ASTM D 7091: Test Method for Nondestructive Measurement of Dry Film Thickness of Nonmagnetic Coatings on Ferrous Metals and Nonmagnetic Nonconductive Coatings on Nonferrous Metals;
•ASTM E 177: Practice for Use of the Terms Precision and Bias in ASTM Test Methods;
•ASTM E 691: Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method.
(2) Key Precautions
1.Load Control: ในระหว่างการทดสอบ, strictly control the application speed and gradient of the load to avoid meaningless test data caused by excessive load and ensure the accuracy of the test results;
2.Environmental Control: Temperature and humidity have a great impact on coating performance. Strictly control the temperature and humidity of the test environment (23±2℃, 50±5%RH) to avoid interference of environmental factors on the test results;
3.Sample Consistency: Ensure that all test samples have the same coating thickness, curing conditions, and substrate treatment methods to avoid incomparable test results due to sample differences;
4.Equipment Calibration: Scratch rings, counterweight blocks, film thickness gauges, and other equipment shall be calibrated regularly to ensure that the accuracy meets the standard requirements, and calibration records shall be properly kept;
5.Safe Operation: Wear protective equipment during the test to avoid scratches on operators by scratch tools. ในเวลาเดียวกัน, properly handle the tested samples and waste coatings in accordance with environmental protection requirements.

วี. Differences Between ASTM D 2197 and Other Coating Adhesion Test Standards

In the field of coating adhesion testing, in addition to ASTM D 2197 (scratch method), there are many commonly used standards. The core differences lie in the test method, ขอบเขตการใช้งาน, and result expression, as detailed below:
1.ASTM D 3359 (Cross-Cut Method): It is a qualitative test method. By scribing a grid on the coating, pasting adhesive tape and tearing it off, the adhesion grade (0-5) is determined according to the degree of coating peeling. It is simple to operate and low in cost, suitable for on-site rapid detection. In contrast, ASTM D 2197 is a quantitative test that can provide specific load values with higher accuracy and is only applicable to laboratory testing;
2.ASTM D 4541 (Pull-Off Method): It measures the peel strength between the coating and the substrate by applying tensile stress perpendicular to the coating surface, which can be used for both laboratory and on-site testing and is suitable for evaluating single-layer or multi-layer coating systems. In contrast, ASTM D 2197 applies shear stress through horizontal scratching, focusing on the scratch adhesion testing of organic coatings;
3.ไอเอสโอ 2409 (Cross-Cut Method): Similar to ASTM D 3359, it is a qualitative test mainly used for coating adhesion evaluation under the international standard system. ASTM D 2197 is an American standard, which is more widely used in the North American market and related export enterprises.

VI. Application Value and Industry Significance of ASTM D 2197

As an authoritative standard for scratch adhesion testing of organic coatings, ASTM D 2197 has irreplaceable value in industrial production and quality control, mainly reflected in the following aspects:
1.Quality Control: Provide a quantitative adhesion test basis for coating manufacturers, effectively screen qualified products, avoid product failure caused by insufficient coating adhesion, and improve product quality and market competitiveness;
2.Process Optimization: Through test results and failure mode analysis, identify problems in coating formulation, construction process, substrate treatment, and other links, and provide scientific support for process improvement and formulation optimization;
3.Compliance Guarantee: For coating products exported to the North American market, testing in accordance with the ASTM D 2197 standard can meet customer and local regulatory requirements, ensuring that products enter the market in compliance;
4.ร&D Support: Provide a performance evaluation method for the research and development of new organic coatings, accelerate the R&D process of new products, and promote the technological upgrading of the coating industry;
5.Risk Avoidance: Through accurate adhesion testing, the durability of the coating in the use process can be predicted in advance, avoiding equipment corrosion, appearance damage, and other problems caused by coating peeling, and reducing use risks and maintenance costs.

VII. บทสรุป

As the core standard for scratch adhesion testing of organic coatings, ASTM D 2197-16(2022) provides a unified quality evaluation basis for the coating industry with scientific and rigorous test procedures and quantitative result determination. Its core advantage is that it can accurately quantify the scratch adhesion of coatings, clarify the bonding ability between coatings and substrates, and provide reliable support for quality control, process optimization, and product R&ดี.
For coating manufacturers, สถาบันทดสอบ, and relevant practitioners, deeply understanding the scope of application, test procedures, and technical requirements of ASTM D 2197, and strictly implementing tests in accordance with the standard can not only ensure the accuracy and comparability of test results but also improve product quality, avoid use risks, and promote the standardized development of the industry. In the future, with the continuous upgrading of coating technology, the ASTM D 2197 standard will also be continuously optimized to better adapt to the testing needs of new organic coatings and provide stronger support for industrial development.

Our Product GA-6001 Automatic Scratch Tester meets this standard.

เครื่องทดสอบรอยขีดข่วนอัตโนมัติ

Testing standard
กิกะไบต์/ที 9279-2007 การทดสอบรอยขีดข่วนของสีและสารเคลือบเงา
ไอเอสโอ 1518
ASTM D 2197, ดี 5178

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