Comprehensive Analysis of ISO 1518: The Core International Standard for Coating Scratch Resistance Testing
In fields such as automotive coating, industrial anti-corrosion, home appliance finishing, and wood coatings, the scratch resistance of coatings is a key indicator for measuring product durability, appearance quality, and service life. Fine scratches generated during daily use, hard abrasion during handling, and coating damage caused by environmental friction will directly affect the aesthetic appearance and protective performance of products.As the authoritative international standard for scratch resistance testing of paints and varnishes, ISO 1518 provides a unified, reproducible, and comparable testing method for various industries, serving as an indispensable technical basis for material research and development, quality control, and import/export compliance. This article systematically analyzes the framework, principles, testing methods, version iterations, and engineering application key points of ISO 1518.
1. Basic Positioning and Core Definitions of the Standard
1.1 Full Name and Standard Jurisdiction
ISO 1518, fully entitled Paints and varnishes — Determination of scratch resistance, is formulated and issued by ISO/TC 35 (Technical Committee for Paints, Varnishes and Related Pigments). It specifies standardized test methods for the penetration and scratch resistance of organic coatings (single-layer or multi-layer composite coating systems), acting as a fundamental general standard in the field of coating physical performance testing.
1.2 Scope of Application
This standard is applicable to all types of organic coatings, including paints, vernissen, and functional coatings applied on metal, plastic, and wood substrates. It can test both single-layer coatings and evaluate multi-layer composite coating systems. Its core testing objectives are divided into two categories: first, to determine whether the scratch needle penetrates the coating to reach the substrate; second, to identify whether the scratch needle penetrates the intermediate coating in multi-layer systems, so as to accurately distinguish the damage resistance of different coating layers.
1.3 Core Differences from Similar Standards
Many practitioners confuse ISO 1518 with ISO 12137. The core differences are clear: ISO 1518 adopts a hard pointed scratch needle and focuses on testing the penetration resistance of coatings; while ISO 12137 uses a curved scratch needle, mainly evaluating surface shallow scratches and apparent damage resistance without penetration judgment, leading to completely different application scenarios.
2. Standard Framework of ISO 1518: Two Core Parts
ISO 1518 consists of two independent parts with complementary testing principles, loading modes and application scenarios, forming a complete scratch resistance test system that cannot replace each other.
2.1 ISO 1518-1: Constant Load Method (Commonly Used for Industry)
The latest version is ISO 1518-1:2023 (3rd Edition), superseding the 2019 En 2011 versions. It is the most widely used method for industrial quality inspection and factory acceptance.
•Test Principle: A constant vertical load is applied to the scratch needle, which slides across the coating surface at a specified speed to determine whether the needle penetrates the coating to reach the substrate or the intermediate layer of a multi-layer system.
•Test Modes: Two practical modes are defined:
a.Pass/Fail Mode: Test with a single specified load to directly judge whether the sample meets specification requirements, suitable for mass production quality inspection and incoming material verification;
b.Critical Load Mode: Conduct tests with gradually adjusted constant loads to determine the minimum critical load that causes coating penetration, applicable to new material R&D and formula comparison.
•Core Features: High data repeatability, simple equipment, convenient operation, suitable for batch testing and industry benchmarking.
2.2 ISO 1518-2: Progressive Load Method (Dedicated for Scientific Research & Comparison)
The current valid version is ISO 1518-2:2011 with no updated revision, mainly used for laboratory research and performance comparison.
•Test Principle: The vertical load increases linearly and continuously as the scratch needle moves, rising from low to high load, and the corresponding relationship between load and scratch damage is recorded throughout the test;
•Scope of Application: Mainly used for testing single-layer coatings or the topcoat of multi-layer systems, not for penetration judgment of inner coating layers;
•Core Features: Full-range damage data can be obtained in a single test to accurately distinguish performance differences between coatings with different formulas, not suitable for rapid mass production inspection.
3. Core Test Elements and Practical Key Requirements
The accuracy of ISO 1518 test results highly depends on equipment parameters, sample status and operational specifications. De 2023 edition has refined key requirements, which are mandatory for practical testing.
3.1 Core Test Equipment: Scratch Needle and Tester
•Scratch Needle Material: Cemented carbide is uniformly adopted to avoid data deviation caused by wear of ordinary steel needles;
•Scratch Needle Specifications (New in 2023 Edition): 0.75mm and 3.0mm tip diameters are added. Combined with the original standard tip, it covers thin-film coatings and heavy-duty thick coatings for diverse scenarios;
•Equipment Requirements: The tester shall precisely control vertical load and scratching speed, with no lateral deviation or load fluctuation of the needle during testing.
Mandatory Requirement: The scratch needle tip must be inspected before each test to ensure it is unworn, contamination-free and smooth. A damaged needle will directly invalidate test data (new mandatory clause in ISO 1518-1:2023).
3.2 Test Samples and Environmental Conditions
•Test Panel Requirements: Substrate material, surface roughness and coating thickness shall be consistent with actual products. Panels shall be flat, distortion-free and free of surface defects; the new edition adds detailed specifications for panel preparation and conditioning;
•Environmental Conditions: Tests are normally conducted under standard laboratory conditions (23℃±2℃, 50%±5% RH). Coatings shall be fully cured to avoid false resistance data caused by uncured films.
3.3 Core Result Judgment Rules
The core judgment criterion of ISO 1518 is penetration verification, rather than surface scratch depth:
1.Single-layer coating: The test is deemed failed if the needle tip contacts the substrate (penetration occurs);
2.Multi-layer coating: Penetration is confirmed if the needle breaks through the topcoat to reach the intermediate coat, primer or direct substrate;
3.Auxiliary Evaluation: De 2023 edition introduces surface scratch appearance scoring, which quantifies minor surface damage in addition to penetration judgment, optimizing the performance evaluation dimension.
3.4 Mandatory Contents of Test Reports
The standard stipulates that official test reports must include: standard number & version, sample information, scratch needle specification, loading method, testmodus, penetration judgment result, critical load value, test environment, and needle status, ensuring full data traceability and reproducibility.
4. Core Changes in ISO 1518-1 Version Iteration (2011→2019→2023)
Understanding version differences avoids data comparison errors between old and new equipment/standards. The core optimizations of three iterations are summarized below:
| Version | Core Updates | Engineering Impact |
| 2011 Edition | Established basic framework, defined the division between constant and progressive load methods, without dedicated terminology chapter | Widely used in early industries with relatively low data accuracy |
| 2019 Edition | Added terminology definition and test panel specifications, refined scratch needle inspection requirements | Unified term definitions and reduced human operational errors |
| 2023 Edition (Latest Valid) | Added 0.75/3.0mm scratch needles and surface appearance scoring, optimized precision clauses, integrated appendices for legacy needle specification alignment | Compatible with more coating types, higher data rigor, becoming the global mandatory benchmark version |
5. Industrial Application Scenarios and Practical Value
5.1 Automotive Coating Industry (Core Application Field)
OEM body coatings, component topcoats and interior plastic coatings all adopt ISO 1518-1 constant load method as the factory acceptance standard. Bijvoorbeeld, automotive topcoats shall resist substrate penetration under specified loads, and interior parts shall withstand daily hard object abrasion. This standard is a mandatory test item for supplier access of mainstream automakers.
5.2 Home Appliance & 3C Products
Coatings on refrigerator/washing machine casings, mobile phone and computer plastic substrates use ISO 1518 to distinguish high scratch-resistance formulas from conventional ones, balancing appearance quality and manufacturing costs and preventing irreversible scratches during end-user daily use.
5.3 Industrial Anti-corrosion & Wood Coatings
Steel structure anti-corrosion coatings use critical load tests to evaluate long-term mechanical damage resistance; wood furniture varnishes apply this standard to determine hard object scratch resistance, maintaining the long-term appearance integrity of furniture products.
5.4 Import & Export Trade Compliance
Product access requirements for coatings and finished coated products in most countries worldwide recognize ISO 1518 test reports. The unified test method eliminates barriers of regional standards and serves as a core technical certificate for mutual quality recognition in cross-border trade.
6. Common Misconceptions and Troubleshooting Guidelines
•Misconception 1: Use ISO 1518 to test shallow surface scratch resistance.
✅ Correction: Shallow scratch testing shall adopt ISO 12137; ISO 1518 is only for penetration resistance testing, and the two standards are not interchangeable;
•Misconception 2: The scratch needle can be reused long-term without inspection.
✅ Correction: De 2023 edition mandates pre-test inspection for the needle tip; a worn needle causes artificially low load readings and invalid test data;
•Misconception 3: Only substrate penetration needs to be judged for multi-layer coatings.
✅ Correction: Intermediate layer penetration shall be identified for multi-layer systems, which is critical for evaluating primer and mid-coat protective performance;
•Misconception 4: 2011 edition data can be directly compared with 2023 edition data.
✅ Correction: Updates in needle specifications and evaluation dimensions make data from different versions not directly equivalent for benchmarking.
7. Conclusie
As the cornerstone international standard for coating scratch resistance testing, ISO 1518 establishes a unified performance evaluation system via the combined framework of ISO 1518-1 constant load method (for quality inspection) + ISO 1518-2 progressive load method (for R&D). De 2023 revision further refines equipment, sample and evaluation rules, delivering higher data accuracy and broader application coverage.
For industry practitioners, mastering the version differences, test principles and judgment rules of ISO 1518 enables accurate quality inspection and formula development. It also helps break down trade barriers via international standards, achieving dual improvement in product performance and regulatory compliance.
Our Product GA-6037 Automatic Scratch Tester Meets this standard.
Automatische krastester
Test standard :
ISO 1518, BS 3900, IN 61558, GB 4943, GB 4760.1, IEC 60335
Purpose:
Scratch tester is mainly used to evaluate the scratch performance of single layer insulation coated board. Scratch resistance of the coating can be determined by evaluating whether the coating is scratched by a certain weight of tungsten carbide hemispherical contacts or the maximum load of the coating cannot be scratched. Mainly used in product surface coating, such as coil coating, can ink, 3C ink, uv ink, enz.
Characteristic :
1. Touch screen display, you can directly set parameters on the screen, makkelijk te besturen.
2. The test results can be displayed on the screen in real time, with OK or NG displayed directly.
3. Adjustable working platform – more convenient
4. Display the test result on the conductive substrate
5. High hardness markers — more durable
6. Special sample clip design, makkelijk te besturen
technische parameters :
Scratch speed :0~40mm/s(configurable)
Moving distance :0~65mm (configurable)
Tip pressure: 10±0.5N
Gewicht: 50g~2500g(optioneel)
Scratch pen material: tungsten carbide hemispherical, radius 0.25±0.02mm (or customized)
Metal test plate size :100×150×0.2mm(lengte * breedte * hoogte)
Machine size: 500*400*450mm
Machine gewicht: about 22KG
Stroomvoorziening :220v / 50hz or 110v/60hz
Product link:
https://www.gonoava.com/product/ga-6037-automatic-scratch-tester/
Contact:
E-mail: [email protected]
WhatsAppen: 0086 18670728798(We chat)
If you have any questions you can send me a message or email.