Volvo STD 1024-2523 Bending Test, Cylindrical Mandrel - Paints and Enamels

The “Volvo STD 1024-2523 Bending test, cylindrical mandrel - Paints and enamels” standard, developed by Volvo, describes an experimental test procedure to evaluate the resistance of a paint and enamel coating or substrate to cracking or material degradation when subjected to bending around a cylindrical mandrel under standard conditions. For a multi-layer system, each layer can be tested individually, or the entire system can be tested.

To define the requirements for compliance with this standard, the following are necessary:

• The mandrel diameter must be specified.
• Test piece data must be specified, e.g., material (panel, paint), thickness, preparation method (drying, heating, aging), etc.
• The temperature at the time of testing should be specified, unless it is between 0 plus/minus 2 degrees, -10 plus/minus 2 degrees, or -30 plus/minus 5 degrees.

Test panels should be made of plastic, polished steel, polished tinplate, or mild aluminum. Test panels must be flat and undamaged, and free from any visible protrusions or cracks on their surface. Unless otherwise specified, test panels should be rectangular and approximately 200 mm x 30 mm plus/minus 3 mm in size. After coating and drying, test panels can be cut to the desired size, provided there is no deformation. In aluminum panels, the long edge should be parallel to the longitudinal direction of the metallurgical rolling. Panel edges should be smooth to avoid cracking. Test panels should be coated using the method specified for the product being tested. The thickness of the dry coating should be specified in micrometers.

Coated test panels must be dried (or baked and aged) and conditioned in accordance with Volvo STD 1021-0001 standard. The appropriate test procedure should be carried out as soon as possible. Unless otherwise specified, tests should be performed at test temperatures of 0 ± 2 degrees, -10 ± 2 degrees and -30 ± 5 degrees.

A mandrel with a diameter corresponding to 15x the test piece thickness plus/minus 2 mm is selected. The apparatus with the appropriate mandrel attached is opened, and the panel is positioned so that it can be bent with the coated side facing outwards. The apparatus containing the panel is placed in the test chamber set to the pre-specified temperature. After 2 hours, while the panels are still in the chamber at the specified temperature, the device is turned off 90 degrees evenly and without shaking for 1-2 seconds. Wait 3-5 seconds.

The test panel coating is inspected immediately after the bending process. Using a lens with 10x magnification, according to normal corrected vision or agreement, the coating and substrate are examined for cracks or material damage. If a lens is used, this should be noted in the test report.

The appearance of cracks should be observed. These may include the following:

• Edge-to-edge propagating cracks, also known as brittle fracture cracks.
• Stagnant cracks, also known as microcracks.

In the high-risk automotive manufacturing world, where vehicles must withstand harsh conditions ranging from scorching sunlight to relentless road debris, ensuring the integrity of surface coatings is paramount. Among the standards developed by Volvo, a world leader in commercial vehicles, trucks, buses, and construction equipment, the Volvo STD 1024-2523 standard stands out as a specialized test method designed to evaluate the adhesion properties of paint films on various surfaces. This standard plays a critical role in maintaining the durability, aesthetics, and safety of manufactured vehicles, preventing issues such as peeling or cracking that could negatively impact vehicle performance or lead to costly recalls.

With the automotive industry increasingly focusing on sustainable and durable materials, Volvo STD 1024-2523 and similar standards remain indispensable for suppliers and manufacturers navigating changing regulations and material innovations.

This standard essentially includes a method for determining the adhesion of paint films to surfaces, particularly after accelerated aging or exposure to harsh conditions. Unlike general adhesion tests (e.g., cross-screening methods under the ISO 2409 standard), this standard tailors the assessment to automotive-grade coatings, emphasizing the criteria for the absence of crack formation after testing.

This standard covers the following:

• Surfaces: Primarily metals and plastics used on vehicle exterior surfaces, such as body panels or interior trim.
• Coatings: Multi-layer paint systems including primers, base coats, and varnishes.
• Test conditions: After exposure to UV light, chemicals, or temperature cycles to simulate real-world degradation.

The Volvo STD 1024-2523 standard, by requiring "no cracks" as a fit criterion, ensures that the coatings not only adhere but also flex without cracking. This is vital for vehicles that can withstand vibrations on rough terrain or thermal expansion in varying climates.

Volvo standards are renowned for their rigor and repeatability. Testing is often integrated with environmental simulations, as detailed in standards such as Volvo STD 1024-7132 (cold stone chip resistance). The testing process generally involves the following steps:

• Sample preparation: Test panels are prepared with the coating system being evaluated (e.g., thickness of at least 50 µm for durable paints). If necessary, protective measures such as UV or chemical protection are applied before the final painting process, according to Volvo STD 121-0002 standard.
• Environmental exposure: Samples are exposed to controlled conditions such as a standard black temperature of 80 degrees (STD 1027-337 standard) or cold chambers of plus/minus 20 degrees. Duration varies, but is generally consistent with accelerated weathering exposure protocols (e.g., 1.000 hours of xenon arc exposure).
• Adhesion assessment: After exposure, a mechanical test (possibly tensile or tape-on method) is performed to measure bond strength. Visual and microscopic inspection is carried out for cracks, delamination, or flaking. Success/failure depends on the presence of visible cracks or loss of adhesion exceeding specified thresholds (e.g., less than 5% detachment in tape tests).
• Reporting and compliance: Results are documented using Volvo's failure mode and effects analysis forms (Volvo STD 105-0005 standard). Compliance is ensured by comparing them to the parent samples.

As the industry rapidly moves towards net-zero emissions, such standards play a crucial role in striking a balance between performance and global responsibility.

For many years, our organization, with its competent and experienced staff, has been understanding the needs of its customers, providing the advanced testing services they require, and assisting in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services to businesses in accordance with the "Volvo STD 1024-2523 Bending test, cylindrical mandrel - Paints and enamels" standard.