VW PV 3.3.3 Paints and Varnishes - Testing of Scratch Resistance of Clear Coatings

The standard "VW PV 3.3.3 Paints and varnishes - Testing the scratch resistance of clear coats," developed by the Volkswagen Automobile Company, describes a method for testing the car wash resistance of clear coats, top coats, and plastic surfaces using laboratory wash equipment. This standard includes additional specifications that must be adhered to when performing scratch resistance testing according to DIN EN ISO 20566. Unlike DIN EN ISO 20566, the test in this standard only measures and documents the change in gloss level.

The test is carried out using laboratory wash equipment according to the standard "DIN EN ISO 20566 Paints and varnishes - Determination of the scratch resistance of a coating system using a laboratory-scale car wash." It should be noted that this method cannot be used for any definitive determination, as the age of the brushes has a decisive influence on the scratching effect and the results. It can only be used to report results compared to a reference tested at the same time. Furthermore, the following specifications that deviate from DIN EN ISO 20566 must be adhered to. Deviations from the specifications in this standard are possible, and changes are indicated, as required for the specific task.

• Washing suspension (part of DIN EN ISO 20566 standard washing suspension): Washing suspension, per litre d₅₀ = 1,5 g of quartz powder with an average grain size of 19 μm. The water temperature should be between 18°C ​​and 28°C. For example, a constant temperature of 25°C provides better reproducibility. If instrumental comparison is not available, tap water can be used instead of demineralized water.
• Test panels (Test panels section of DIN EN ISO 20566): Unless otherwise agreed, test panels and reference panels must be made of sheet steel or sheet aluminium with dimensions of 100 mm x 100 mm x 0,8 mm, with original paint finish. Solid black is preferred. Samples must be conditioned according to the technical supply specifications TL 211 or TL 218. Alternatively, conditioning at room temperature of 22°C plus/minus 2°C for 2 days is possible. When testing plastic parts, a plastic support can alternatively be used as a substrate. If geometrically feasible, parts cut from finished parts can be used. The same applies to testing plastics with moulded colours. The gloss level can only be reliably determined in solid colours. Test panels can be ordered from the purchaser.
• Test procedure and evaluation (procedure and evaluation sections of the DIN EN ISO 20566 standard):
  • For high-gloss materials: Before testing, the initial gloss properties at 20 degrees are recorded according to DIN EN ISO 2813. The average value of at least 5 measured values ​​measured perpendicular to the expected scratch direction is stated.
  • For matt and semi-gloss materials: Before testing, the initial gloss properties are determined at the following measuring angle: 60° tool geometry for medium-gloss surfaces and 85° tool geometry for matt surfaces. The tool geometry to be used is determined separately for each gloss area according to DIN EN ISO 2813.

A test run of 10 pairs of impacts is performed without the sheet test panels. Then, 10 pairs of impacts are performed on each sheet test panel. After applying the load, the sheet test panels are rinsed with cold demineralized water to remove any quartz dust residue. The sheet test panels are then wiped with a non-scratching paper towel or dried with compressed air, then cleaned with a microfiber cloth moistened with mineral spirits to remove any abrasions from the brushing process. The residual gloss is measured within 2 hours at 20 degrees perpendicular to the scratch direction according to DIN EN ISO 2813. The average value of five measurements in a homogeneous area is determined.

At least two sheet test panels per sample should be tested in separate runs. To assess reflux behavior, samples are aged at 60°C for 2 hours. After cooling the sheet test panels to room temperature, the residual gloss is determined again.

• Test report (test report section of the DIN EN ISO 20566 standard): In order to take into account the wear of the brushes, in addition to the gloss and residual gloss values ​​after loading and reflow, the final and original measurement data of the reference sheet test panels must be stated in the test report.
• Monitoring of washing equipment (Addendum to DIN EN ISO 20566 standard for verification and calibration of washing equipment): In each test, a reference sheet test panel must be loaded simultaneously to monitor the washing brushes. The reference sheet test panel must always be placed in the same location on the washing table. The brush must be replaced after 50 hours of loading. The gloss level curve of the reference sheet test panels tested simultaneously must be documented to assess the consistency of the results and to influence any influences. Any deviations must be documented in the test report.

In short, the VW PV 3.3.3 standard outlines the procedure for assessing the scratch resistance of automotive clear coats, focusing specifically on damage caused by automatic car washes. This standard is crucial for ensuring the durability and aesthetic longevity of vehicle paint coatings under real-world conditions. Compliance with this standard is crucial for manufacturers and suppliers aiming to meet quality standards. It ensures that vehicle exterior surfaces maintain their appearance over time, even after repeated exposure to automatic car washes. Compliance with this standard is often a prerequisite for parts suppliers in the VW supply chain.

Our organization, which has been supporting businesses across all sectors for years through a wide range of testing, measurement, analysis, and evaluation activities, has a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services in accordance with the "VW PV 3.3.3 Paints and varnishes - Testing the scratch resistance of clear coatings" standard.